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Sample records for azotobacter

  1. Impact of Azotobacter exopolysaccharides on sustainable agriculture.

    Science.gov (United States)

    Gauri, Samiran S; Mandal, Santi M; Pati, Bikas R

    2012-07-01

    Recently, increasing attention have lead to search other avenue of biofertilizers with multipurpose activities as a manner of sustainable soil health to improve the plant productivity. Azotobacter have been universally accepted as a major inoculum used in biofertilizer to restore the nitrogen level into cultivated field. Azotobacter is well characterized for their profuse production of exopolysaccharides (EPS). Several reviews on biogenesis and multifunctional role of Azotobacter EPS have been documented with special emphasis on industrial applications. But the impact of Azotobacter EPS in plant growth promotion has not received adequate attention. This review outlines the evidence that demonstrates not only the contribution of Azotobacter EPS in global nutrient cycle but also help to compete successfully in different adverse ecological and edaphic conditions. This also focuses on new insights and concepts of Azotobacter EPS which have positive effects caused by the biofilm formation on overall plant growth promotion with other PGPRs. In addition, their potentials in agricultural improvement are also discussed. Recent data realized that Azotobacter EPS have an immense agro-economical importance including the survivability and maintenance of microbial community in their habitat. This leads us to confirm that the next generation Azotobacter inoculum with high yielding EPS and high nitrogen fixing ability can be utilized to satisfy the future demand of augmented crop production attributed to increase plant growth promoting agents.

  2. Multiple chromosomes of Azotobacter vinelandii.

    OpenAIRE

    1989-01-01

    The number of copies of the genes leuB, nifH, nifD, and nifK per cell of Azotobacter vinelandii has been determined to be about 80. A beta-lactamase gene was integrated into the A. vinelandii chromosome by single-point crossover. Subsequently, we have been able to detect nearly 80 copies of this beta-lactamase gene per cell of A. vinelandii when cultured for a large number of generations in the presence of ampicillin. The multiple copies of the beta-lactamase gene do not seem to be present on...

  3. Pyruvate dehydrogenase complex from Azotobacter vinelandii

    NARCIS (Netherlands)

    Bresters, T.W.

    1975-01-01

    The isolation and some alternatives for purification of PDC from Azotobacter vinelandii are described (CHAPTER 3). Ultimate extent and recovery seem to be limited by the lability of the enzyme: sensitivity to shearing forces. Moreover, sedimentation-velocity runs and light-scattering experiments sho

  4. Distribution of azotobacter in rhizosphere of maize

    International Nuclear Information System (INIS)

    Azotobacter distribution and species composition were studied under maize rhizosphere at four growth stages and in the uncropped soil (control). The study was conducted in the glazed pots with 10 kg soil in each pot. Soil in the pots was enriched with 20 mg N/kg and 15 mg/P/kg in the form of urea and single super phosphate, respectively. Six plants of maize variety Akbar were grown in 32 pots. Four pots were used as control (check). Sampling was done at four growth stages of 20, 40, 60 and 80 days after the germination of the crop. Results indicated that Azotobacter population increased as the plant growth progressed, reached maximum (1320) cells g/sup -1/ of soil at flowering stage and then declined. A chroococcum was found to be the dominant species in the main rhizosphere. (author)

  5. Phosphate solubilization characteristics of efficient nitrogen fixing soil Azotobacter strains.

    Directory of Open Access Journals (Sweden)

    Rahim Nosrati

    2014-08-01

    Full Text Available Azotobacter is a diazotroph bacterium reported to possess various plant growth-promoting characteristics.The aim of this study was to isolate Azotobacter strains capable of fixing nitrogen and effectively hydrolyzing both organic and inorganic Pi compounds.In this study, soil samples collected from a diverse range of slightly alkaline soil types were screened for Azotobacter isolates. The inorganic and organic phosphate solubilization potentials of twenty competent phosphate solubilizing Azotobacter isolates were assessed.Variations were noted in the solubilization potentials.Three isolates, identified as Azotobacter vinelandii strains O2, O4 and O6, were able to fix atmospheric N2 effectively. The nitrogenase activity of these isolates ranged between 158.6 and 326.4 C2H4h(-1vial(-1 (ethylene. Bacterial growth rates and phosphate solubilization activities were measured quantitatively under various environmental conditions. A close association was evident between phosphate solubilizing ability and growth rate as an indicator of active metabolism. All three phosphate solubilizing bacteria (PSB were able to withstand temperature as high as 45°C, high concentration of NaCl (upto 5% and a wide range of initial pH from 5 to 10 while hydrolyzing phosphate compounds actively.Azotobacter vinelandii strains O2, O4 and O6 are superior candidates for biofertilizers that may result in the reduction of chemical nitrogen and phosphate fertilizers leading to increase crop production.

  6. Chromosomal nif Genes Transfer by Conjugation in Nitrogen Fixing Azotobacter chroococcum to Lactobacillus plantarium

    OpenAIRE

    Adel Kamal Khider; Aras Muhammad Khidher

    2011-01-01

    To determine the possibility of transferring chromosomal nitrogen fixation genes (nif genes) from Azotobacter chroococcum to Lactobacillus planetarium, a total of 72 Azotobacter chroococcum isolated from Erbil governorate, Iraq were culturally, morphologically and biochemically characterized. Genes for atmospheric nitrogen fixation, located on the chromosome of Azotobacter chroococcum isolates were transferred by conjugation process to a recipient Lactobacillus plantarium isolated from Erbil ...

  7. Bioremediation of crude oil waste contaminated soil using petrophilic consortium and Azotobacter sp.

    Directory of Open Access Journals (Sweden)

    M. Fauzi

    2016-01-01

    Full Text Available This study was aimed to determine the effect Petrophilic and Azotobacter sp. consortium on the rate of degradation of hydrocarbons, Azotobacter growth, and Petrophilic fungi growth in an Inceptisol contaminated with crude oil waste originating from Balongan refinery, one of Pertamina (Indonesia’s largest state-owned oil and gas company units in Indramayu – West Java. This study was conducted from March to April 2014 in the glasshouse of research station of the Faculty of Agriculture, Padjadjaran University at Ciparanje, Jatinangor District, Sumedang Regency of West Java. This study used a factorial completely randomized design with two treatments. The first treatment factor was Petrophilic microbes (A consisting of four levels (without treatment, 2% Petrophilic fungi, 2% Petrophilic bacteria, and the 2% Petrophilic consortium, and Azotobacter sp. The second treatment factor was Azotobacter sp. (B consisting of four levels (without treatment, 0.5%, Azotobacter sp., 1% Azotobacter sp., and 1.5% Azotobacter sp. The results demonstrated interaction between Petrophilic microbes and Azotobacter sp. towards hydrocarbon degradation rate, but no interaction was found towards the growth rate of Azotobacter sp. and Petrophilic fungi. Treatments of a1b3 (2% consortium of Petrophilic fungi with 1.5% Azotobacter sp. and a3b3 (2% Petrophilic consortium and 1.5% Azotobacter sp. had hydrocarbon degradation rate at 0.22 ppm/day for each treatment, showing the highest hydrocarbon degradation rate.

  8. Studies on 2-oxoacid dehydrogenase multienzyme complexes of Azotobacter vinelandii

    NARCIS (Netherlands)

    Bosma, H.J.

    1984-01-01

    In this thesis, some studies on the pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase multienzyme complexes of Azotobacter vinelandii are described; the emphasis strongly lies on the pyruvate dehydrogenase complex.A survey of the literature on 2-oxoacid dehydrogenase complexes is given in chap

  9. Iron-molybdenum cofactor synthesis in Azotobacter vinelandii Nif- mutants.

    OpenAIRE

    Imperial, J; Shah, V K; Ugalde, R A; Ludden, P W; Brill, W J

    1987-01-01

    Nif- mutants of Azotobacter vinelandii defective in dinitrogenase activity synthesized iron-molybdenum cofactor (FeMo-co) and accumulated it in two protein-bound forms: inactive dinitrogenase and a possible intermediate involved in the FeMo-co biosynthetic pathway. FeMo-co from both these proteins could activate apo-dinitrogenase from FeMo-co-deficient mutants.

  10. Protons and pleomorphs: aerobic hydrogen production in Azotobacters.

    Science.gov (United States)

    Noar, Jesse D; Bruno-Bárcena, José M

    2016-02-01

    As obligate aerobic soil organisms, the ability of Azotobacter species to fix nitrogen is unusual given that the nitrogenase complex requires a reduced cellular environment. Molecular hydrogen is an unavoidable byproduct of the reduction of dinitrogen; at least one molecule of H2 is produced for each molecule of N2 fixed. This could be considered a fault in nitrogenase efficiency, essentially a waste of energy and reducing equivalents. Wild-type Azotobacter captures this hydrogen and oxidizes it with its membrane-bound uptake hydrogenase complex. Strains lacking an active hydrogenase complex have been investigated for their hydrogen production capacities. What is the role of H2 in the energy metabolism of nitrogen-fixing Azotobacter? Is hydrogen production involved in Azotobacter species' protection from or tolerance to oxygen, or vice versa? What yields of hydrogen can be expected from hydrogen-evolving strains? Can the yield of hydrogen be controlled or increased by changing genetic, environmental, or physiological conditions? We will address these questions in the following mini-review.

  11. Hydrogen-mediated enhancement of hydrogenase expression in Azotobacter vinelandii.

    OpenAIRE

    Prosser, J; Graham, L; Maier, R J

    1988-01-01

    Azotobacter vinelandii cultures express more H2 uptake hydrogenase activity when fixing N2 than when provided with fixed N. Hydrogen, a product of the nitrogenase reaction, is at least partly responsible for this increase. The addition of H2 to NH4+-grown wild-type cultures caused increased whole-cell H2 uptake activity, methylene blue-dependent H2 uptake activity of membranes, and accumulation of hydrogenase protein (large subunit as detected immunologically) in membranes. Both rifampin and ...

  12. Presence of a Vanadium Nitrogenase in Azotobacter paspali

    OpenAIRE

    Fallik, Elazar; Hartel, Peter G.; Robson, Robert L.

    1993-01-01

    There have been no previous studies on the genetics of Azotobacter paspali, an aerobic bacterium which forms a highly specific diazotrophic association with Bahia grass (Paspalum notatum). We constructed A. paspali strains defective in the molybdenum nitrogenase so that alternative N2ases could be studied. The cosmid vector pTBE and genomic DNA fragments (∼50 kb) of A. paspali ATCC 23367 were used to construct a gene library in Escherichia coli. Recombinant cosmids containing sequences homolo...

  13. Evidence for an alternative nitrogen fixation system in Azotobacter vinelandii.

    OpenAIRE

    Bishop, P E; Jarlenski, D M; Hetherington, D R

    1980-01-01

    Two Azotobacter vinelandii strains capable of growing on N2(Nif+) were isolated from two different mutant strains that lacked dinitrogenase activity (Nif-). Extracts of N2-grown cells of the two Nif+ strains lacked significant amounts of the "conventional" dinitrogenase protein subunits, as determined by two-dimensional gel electrophoresis. Instead, the extracts contained at least four new proteins that appeared to be ammonia-repressible (i.e., they were not detected in extracts of ammonia-gr...

  14. Expression of an alternative nitrogen fixation system in Azotobacter vinelandii.

    OpenAIRE

    Bishop, P E; Jarlenski, D M; Hetherington, D R

    1982-01-01

    Nitrogenase activities were determined from maximum acetylene reduction rates for mutant strains of Azotobacter vinelandii which are unable to fix N2 in the presence of molybdenum (Nif-) but undergo phenotypic reversal to Nif+ under conditions of Mo deficiency. The system responsible for N2 fixation under these conditions is thought to be an alternative N2 fixation system (Bishop et al., Proc. Natl. Acad. Sci. U.S.A. 77:7342-7346, 1980). Phenotypic reversal of Nif- strains to Nif+ strains was...

  15. Transcriptional regulation of nitrogen fixation by molybdenum in Azotobacter vinelandii.

    OpenAIRE

    Jacobson, M R; Premakumar, R; Bishop, P E

    1986-01-01

    Multiple genomic regions homologous to nifH were found in the diazotroph Azotobacter vinelandii. The nifHDK gene cluster, located on a 12.8-kilobase (kb) XhoI fragment and two additional XhoI fragments (7.4 and 8.4 kb) hybridized to a nifH-specific DNA template but the 7.4- and 8.4-kb fragments did not hybridize to nifD- or nifK-specific DNA probes. In vivo transcription of the nifHDK gene cluster was ammonia-repressible and required the presence of at least 50 nM molybdenum in the derepressi...

  16. Molecular cloning of nif DNA from Azotobacter vinelandii.

    OpenAIRE

    Bishop, P E; Rizzo, T M; Bott, K F

    1985-01-01

    Two clones which contained nif DNA were isolated from a clone bank of total EcoRI-digested Azotobacter vinelandii DNA. The clones carrying the recombinant plasmids were identified by use of the 32P-labeled 6.2-kilobase (kb) nif insert from pSA30 (which contains the Klebsiella pneumoniae nifK, nifD, and nifH genes) as a hybridization probe. Hybridization analysis with fragments derived from the nif insert of pSA30 showed that the 2.6-kb insert from one of the plasmids (pLB1) contains nifK wher...

  17. A new method of recovering polyhydroxyalkanoate from Azotobacter

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    After polyhydroxyalkanoate (PHA) fermentation for 42-48 h by the Azotobacter chroococcum G-3, the PHA content reached more than 75% of the dry weight. Biomass was isolated from culture by centrifugation and pretreated with freezing to release PHA pellet, then was treated with 10 g/L sodium dodecyl sulfate (SDS) for 15 min to effectively solubilize lipid and protein. Subsequently, it was further purified by digesting with 30% sodium hypochlorite (NaClO) for 3 min to remove peptidoglycan and non-PHA biomass. Finally, 98% PHA was obtained by diluting and rinsing with water, and the PHA recovered was suitable for processing.

  18. Efecto de diferentes plaguicidas sobre el crecimiento de Azotobacter chroococcum

    Directory of Open Access Journals (Sweden)

    Diego Rivera

    2010-06-01

    dichlorovinyl-2,2-dimethylcyclopropane carboxylate (RS-cyano-3-phenoxybenzyl; S-metolachlor:(S-2-chloro-N-(2-ethyl-6-methyl-phenyl-N-(2-methoxy-1-methyl-ethyl-acetamide; Fluometuron: 1,1-dimethyl-3 (alpha, alpha, alpha-trifluoro-m-tolyl urea and Glyphosate: (N-(phosphonomethyl glycine on the viability of biological inoculant Monibac ® - Corpoica whose active ingredient is based on non-symbiotic diazotrophic bacteria Azotobacter chroococcum AC1, applying the minimum inhibitory concentration and compatibility techniques. The results demonstrated the susceptibility of the organism Cypermethrin 50% and when it is mixed with other pesticides in the rate used in the field regularly. It was found that there were no significant effects (P< 0,05 of pesticides (Carboxin, Thiram, Imidacloprid, S-metolachlor, Fluometuron and Glyphosate under the different concentrations tested suggesting that this bacterium is able to tolerate these chemicals by different physiological mechanisms without affecting their growth in laboratory level. Key words: Azotobacter chroococcum, agrochemicals, bacteria, biofertilizer, inhibition

  19. A study on the NAD(P)+ transhydrogenase from Azotobacter vinelandii

    NARCIS (Netherlands)

    Krul, J.

    1975-01-01

    Azotobacter vinelandii transhydrogenase shows a pronounced polymerizing depolymerizing character (Chapter 3 and 5). Several factors seem to influence this phenomenon. With purified enzyme, obtained by a new purification method (Chapter 3), several parameters influencing the association-dissociation

  20. Azotobacter vinelandii NADPH:ferredoxin reductase cloning, sequencing, and overexpression.

    Science.gov (United States)

    Isas, J M; Yannone, S M; Burgess, B K

    1995-09-01

    Azotobacter vinelandii ferredoxin I (AvFdI) controls the expression of another protein that was originally designated Protein X. Recently we reported that Protein X is a NADPH-specific flavoprotein that binds specifically to FdI (Isas, J.M., and Burgess, B.K. (1994) J. Biol. Chem. 269, 19404-19409). The gene encoding this protein has now been cloned and sequenced. Protein X is 33% identical and has an overall 53% similarity with the fpr gene product from Escherichia coli that encodes NADPH:ferredoxin reductase. On the basis of this similarity and the similarity of the physical properties of the two proteins, we now designate Protein X as A. vinelandii NADPH:ferredoxin reductase and its gene as the fpr gene. The protein has been overexpressed in its native background in A. vinelandii by using the broad host range multicopy plasmid, pKT230. In addition to being regulated by FdI, the fpr gene product is overexpressed when A. vinelandii is grown under N2-fixing conditions even though the fpr gene is not preceded by a nif specific promoter. By analogy to what is known about fpr expression in E. coli, we propose that FdI may exert its regulatory effect on fpr by interacting with the SoxRS regulon. PMID:7673160

  1. Transcriptional profiling of nitrogen fixation in Azotobacter vinelandii.

    Science.gov (United States)

    Hamilton, Trinity L; Ludwig, Marcus; Dixon, Ray; Boyd, Eric S; Dos Santos, Patricia C; Setubal, João C; Bryant, Donald A; Dean, Dennis R; Peters, John W

    2011-09-01

    Most biological nitrogen (N(2)) fixation results from the activity of a molybdenum-dependent nitrogenase, a complex iron-sulfur enzyme found associated with a diversity of bacteria and some methanogenic archaea. Azotobacter vinelandii, an obligate aerobe, fixes nitrogen via the oxygen-sensitive Mo nitrogenase but is also able to fix nitrogen through the activities of genetically distinct alternative forms of nitrogenase designated the Vnf and Anf systems when Mo is limiting. The Vnf system appears to replace Mo with V, and the Anf system is thought to contain Fe as the only transition metal within the respective active site metallocofactors. Prior genetic analyses suggest that a number of nif-encoded components are involved in the Vnf and Anf systems. Genome-wide transcription profiling of A. vinelandii cultured under nitrogen-fixing conditions under various metal amendments (e.g., Mo or V) revealed the discrete complement of genes associated with each nitrogenase system and the extent of cross talk between the systems. In addition, changes in transcript levels of genes not directly involved in N(2) fixation provided insight into the integration of central metabolic processes and the oxygen-sensitive process of N(2) fixation in this obligate aerobe. The results underscored significant differences between Mo-dependent and Mo-independent diazotrophic growth that highlight the significant advantages of diazotrophic growth in the presence of Mo. PMID:21724999

  2. Presence of a Vanadium Nitrogenase in Azotobacter paspali.

    Science.gov (United States)

    Fallik, E; Hartel, P G; Robson, R L

    1993-06-01

    There have been no previous studies on the genetics of Azotobacter paspali, an aerobic bacterium which forms a highly specific diazotrophic association with Bahia grass (Paspalum notatum). We constructed A. paspali strains defective in the molybdenum nitrogenase so that alternative N(2)ases could be studied. The cosmid vector pTBE and genomic DNA fragments ( approximately 50 kb) of A. paspali ATCC 23367 were used to construct a gene library in Escherichia coli. Recombinant cosmids containing sequences homologous to molybdenum nitrogenase nifDK structural genes were identified by hybridization. A 2.9-kb fragment bearing the putative nifDK genes of A. paspali was subcloned and mutagenized in vitro by the insertion of a kanamycin resistance gene cassette. The mutation was recombined into the chromosome of A. paspali with the suicide vector pCU101. One resultant mutant strain, AP2, was incapable of diazotrophic growth in a molybdenum-containing medium (Nif) without vanadium but grew well in a molybdenum-deficient medium with vanadium. The nitrogenase system in AP2 reduced acetylene to ethylene and produced ethane as 2.4% of the total products. Molybdenum levels as low as 10 nM prevented the diazotrophic growth of AP2, even in the presence of vanadium at levels up to 10 muM. These results are consistent with the existence of a vanadium nitrogenase system in A. paspali. PMID:16348965

  3. Screening of Azotobacter isolates for PGP properties and antifungal activity

    Directory of Open Access Journals (Sweden)

    Bjelić Dragana Đ.

    2015-01-01

    Full Text Available Аmong 50 bacterial isolates obtained from maize rhizospherе, 13 isolates belonged to the genus Azotobacter. Isolates were biochemically characterized and estimated for pH and halo tolerance ability and antibiotic resistance. According to characterization, the six representative isolates were selected and further screened in vitro for plant growth promoting properties: production of indole-3-acetic acid (IAA, siderophores, hydrogen cyanide (HCN, exopolysaccharides, phosphate solubilization and antifungal activity (vs. Helminthosporium sp., Macrophomina sp., Fusarium sp.. Beside HCN production, PGP properties were detected for all isolates except Azt7. All isolates produced IAA in the medium without L-tryptophan and the amount of produced IAA increased with concentration of precursor in medium. The highest amount of IAA was produced by isolates Azt4 (37.69 and 45.86 μg ml-1 and Azt5 (29.44 and 50.38 μg ml-1 in the medium with addition of L-tryptophan (2.5 and 5 mM. The isolates showed the highest antifungal activity against Helminthosporium sp. and the smallest antagonistic effect on Macrophomina sp. Radial Growth Inhibition (RGI obtained by the confrontation of isolates with tested phytopathogenic fungi, ranged from 10 to 48%. [Projekat Ministarstva nauke Republike Srbije, br. TR 31073

  4. Defining the Pseudomonas Genus: Where Do We Draw the Line with Azotobacter?

    DEFF Research Database (Denmark)

    Özen, Asli Ismihan; Ussery, David

    2012-01-01

    The genus Pseudomonas has gone through many taxonomic revisions over the past 100 years, going from a very large and diverse group of bacteria to a smaller, more refined and ordered list having specific properties. The relationship of the Pseudomonas genus to Azotobacter vinelandii is examined us...... to that of Pseudomonas species with each other. The results of these different methods point to a high similarity between A. vinelandii and the Pseudomonas genus, suggesting that Azotobacter might actually be a Pseudomonas.......The genus Pseudomonas has gone through many taxonomic revisions over the past 100 years, going from a very large and diverse group of bacteria to a smaller, more refined and ordered list having specific properties. The relationship of the Pseudomonas genus to Azotobacter vinelandii is examined...

  5. Effect of Fym, Urea and Azotobacter on Growth, Yield and Quality of Strawberry Cv. Chandler

    Directory of Open Access Journals (Sweden)

    Iqbal UMAR

    2009-06-01

    Full Text Available The present investigation was carried out in the Research orchard of Division of Fruit Science, Faculty of Agriculture, SKUAST-J , Udheywalla, Jammu during 2005-06 and 2006-07 to study the effect of organics FYM integrated with urea and Azotobacter on growth, yield and quality of strawberry cv. Chandler. The strawberry plants attained the height of 21.24cm with 28.16cm plant spread , 74.95cm2 leaf area and fruit size (37.62 x 28.01mm and fruit weight (15.87gwith the application of 25 per cent nitrogen through FYM augmented with Azotobacter and was at par with the plants supplied with cent per cent nitrogen in the form of urea in combination with Azotobacter. The fruit quality viz. total soluble solids, total sugars, ascorbic acid and anthocyanin content was highest in fruits obtained from plants supplied with 25 per cent nitrogen through FYM + 75 per cent nitrogen in the form of urea + Azotobacter recording 6.81 oBrix, 4.73 per cent, 73.71mg/100g fresh berries and 0.191 OD respectively. Maximum yield of 372.89g per plant was obtained with the application of cent per cent nitrogen in the form of urea along with Azotobacter whereas 358.43g fruits per plant were recorded with the application of 25 per cent nitrogen in the form of FYM + 75 per cent through urea + Azotobacter and were at par with each other.

  6. The role of alginate in Azotobacter vinelandii aggregation in submerged culture Papel del alginato en la agregación de Azotobacter vinelandii en cultivo sumergido

    Directory of Open Access Journals (Sweden)

    Peña Carlos

    2008-07-01

    Full Text Available The culture of strain LA21, a non-mucoid strain of Azotobacter vinelandii derivative of ATCC 9046, revealed that alginate is not necessary for aggregate formation. In fact, the non-mucoid strain LA21 developed aggregates significantly larger than those of the mucoid strain (ATCC 9046, which suggests that alginate has a detrimental effect on the aggregate size, due to its properties as a surface active agent. Treating the aggregates with a protease caused a decrease in the equivalent diameter of the structures, suggesting the participation of extracellular proteins in the aggregation. Key words: Aggregation; Azotobacter vinelandii; alginate; mutant strain; mucoid.El cultivo de la cepa LA21, una cepa no-mucoide de Azotobacter vinelandii, derivada de la cepa parental ATCC9046, reveló que el alginato no es necesario para la formación de los agregados celulares. De hecho, la cepa mutante desarrolló agregados significativamente más grandes que los generados por la cepa parental mucoide (ATCC9046, lo cual sugiere que el alginato ejerce un efecto negativo sobre el tamaño de agregación debido a sus propiedades como agente tensoactivo. Al tratar los agregados con proteasas se produjo una disminución en el diámetro equivalente de las estructuras, sugiriendo la participación de proteínas extracelulares en el proceso de agregación de la bacteria. Palabras clave: agregación; Azotobacter vinelandii; alginato; cepa mutante; mucoide.

  7. Indole Acetic Acid Production by the Indigenous Isolates of Azotobacter and Fluorescent Pseudomonas in the Presence and Absence of Tryptophan

    OpenAIRE

    Ahmad, Farah; Ahmad, Iqbal; KHAN, Mohd Saghir

    2005-01-01

    A total of 21 bacterial isolates (Azotobacter sp., 10 and fluorescent Pseudomonas sp., 11) were isolated from different rhizospheric soils in the vicinity of Aligarh city and characterized as per standard methods. These isolates were further tested for the production of indole acetic acid (IAA) in a medium with 0, 1, 2 and 5 mg/ml of tryptophan. A low amount (2.68-10.80 mg/ml) of IAA production was recorded by Azotobacter strains without tryptophan addition. Seven Azotobacter isolates showed ...

  8. Differential accumulation of nif structural gene mRNA in Azotobacter vinelandii.

    Science.gov (United States)

    Hamilton, Trinity L; Jacobson, Marty; Ludwig, Marcus; Boyd, Eric S; Bryant, Donald A; Dean, Dennis R; Peters, John W

    2011-09-01

    Northern analysis was employed to investigate mRNA produced by mutant strains of Azotobacter vinelandii with defined deletions in the nif structural genes and in the intergenic noncoding regions. The results indicate that intergenic RNA secondary structures effect the differential accumulation of transcripts, supporting the high Fe protein-to-MoFe protein ratio required for optimal diazotrophic growth.

  9. Formation of on- and off-pathway intermediates in the folding kinetics of Azotobacter vinelandii apoflavodoxin.

    NARCIS (Netherlands)

    Bollen, Y.J.M.; Sanchez, I.E.; Mierlo, van C.P.M.

    2004-01-01

    The folding kinetics of the 179-residue Azotobacter vinelandii apoflavodoxin, which has an alpha-beta parallel topology, have been followed by stopped-flow experiments monitored by fluorescence intensity and anisotropy. Single-jump and interrupted refolding experiments show that the refolding kineti

  10. Differential accumulation of nif structural gene mRNA in Azotobacter vinelandii.

    Science.gov (United States)

    Hamilton, Trinity L; Jacobson, Marty; Ludwig, Marcus; Boyd, Eric S; Bryant, Donald A; Dean, Dennis R; Peters, John W

    2011-09-01

    Northern analysis was employed to investigate mRNA produced by mutant strains of Azotobacter vinelandii with defined deletions in the nif structural genes and in the intergenic noncoding regions. The results indicate that intergenic RNA secondary structures effect the differential accumulation of transcripts, supporting the high Fe protein-to-MoFe protein ratio required for optimal diazotrophic growth. PMID:21725008

  11. Differential Accumulation of nifStructural Gene mRNA in Azotobacter vinelandii ▿

    OpenAIRE

    Hamilton, Trinity L.; Jacobson, Marty; Ludwig, Marcus; Boyd, Eric S.; Bryant, Donald A.; Dean, Dennis R.; Peters, John W.

    2011-01-01

    Northern analysis was employed to investigate mRNA produced by mutant strains of Azotobacter vinelandiiwith defined deletions in the nifstructural genes and in the intergenic noncoding regions. The results indicate that intergenic RNA secondary structures effect the differential accumulation of transcripts, supporting the high Fe protein-to-MoFe protein ratio required for optimal diazotrophic growth.

  12. THE CONFORMATIONAL STABILITY OF THE REDOX STATES OF LIPOAMIDE DEHYDROGENASE FROM AZOTOBACTER-VINELANDII

    NARCIS (Netherlands)

    VANBERKEL, WJH; REGELINK, AG; BEINTEMA, JJ; KOK, A

    1991-01-01

    The conformational stability of holo-lipoamide and apo-lipoamide dehydrogenase from Azotobacter vinelandii was studied by thermoinactivation, unfolding and limited proteolysis. The oxidized holoenzyme is thermostable, showing a melting temperature, t(m) = 80-degrees-C. The thermal stability of the h

  13. Isolation, screening, and molecular characterization of plant growth promoting rhizobacteria isolates of Azotobacter and Trichoderma and their beneficial activities

    OpenAIRE

    Kasa, Parameswari; Modugapalem, Hemalatha; Battini, Kishori

    2015-01-01

    Objectives: The present study was conducted for isolation, screening, and identification of Azotobacter and Trichoderma from different soil samples. Methods: A total of 10 isolates of Azotobacter and Trichoderma were isolated from rhizospheric soils. The test isolates were biochemically characterized and screened in in-vitro conditions for their plant growth promoting properties. DNA polymorphism of isolates was studied using randomly amplified polymorphic DNA analysis. Results: A total of 41...

  14. SOME PROPERTIES OF MELANIN PRODUCED BY AZOTOBACTER CHROOCOCCUM AND ITS POSSIBLE APPLICATION IN BIOTECHNOLOGY

    OpenAIRE

    Gospodaryov, D.; Lushchak, V.

    2011-01-01

    The strain of bacteria Azotobacter chroococcum, producing and excreting melanin, was isolated. Melanin excretion was observed only on Ashby medium with benzoic acid, but not on the medium with mannitol as carbon source. Some properties of bacterial melanin (absorption spectrum, reduction of permanganates to manganates, rate of bleaching by hydrogen peroxide, coprecipitation with calcium ions) and conditions of its production (dependence on copper ion concentration) were described. A scheme of...

  15. The Basis of Ammonium Release in nifL Mutants of Azotobacter vinelandii

    OpenAIRE

    Brewin, Brett; Woodley, Paul; DRUMMOND, MARTIN

    1999-01-01

    In Azotobacter vinelandii, nitrogen fixation is regulated at the transcriptional level by an unusual two-component system encoded by nifLA. Certain mutations in nifL result in the bacterium releasing large quantities of ammonium into the medium, and earlier work suggested that this occurs by a mechanism that does not involve NifA, the activator of nif gene transcription. We have investigated a number of possible alternative mechanisms and find no evidence for their involvement in ammonium rel...

  16. Azotobacter vinelandii nifD- and nifE-encoded polypeptides share structural homology

    OpenAIRE

    Dean, Dennis R.; Brigle, Kevin E.

    1985-01-01

    The Azotobacter vinelandii nifE gene was isolated and its complete nucleotide sequence was determined. The amino acid sequences deduced from the A. vinelandii nifE and nifD gene sequences were compared and found to share striking primary sequence homology. This homology implies a functional and possibly an evolutionary relationship between these two gene products. The structural homology is discussed with regard to the potential FeMo cofactor binding properties of these polypeptides and the p...

  17. Physical and genetic map of the major nif gene cluster from Azotobacter vinelandii.

    OpenAIRE

    Jacobson, M R; Brigle, K E; Bennett, L T; Setterquist, R. A.; Wilson, M S; Cash, V L; Beynon, J; Newton, W E; Dean, D R

    1989-01-01

    Determination of a 28,793-base-pair DNA sequence of a region from the Azotobacter vinelandii genome that includes and flanks the nitrogenase structural gene region was completed. This information was used to revise the previously proposed organization of the major nif cluster. The major nif cluster from A. vinelandii encodes 15 nif-specific genes whose products bear significant structural identity to the corresponding nif-specific gene products from Klebsiella pneumoniae. These genes include ...

  18. Catalytic mechanism of hydrogenase from Azotobacter vinelandii. Final technical report, August 1, 1994--July 31, 1997

    Energy Technology Data Exchange (ETDEWEB)

    Arp, D.J.

    1997-10-01

    This project is focused on investigations of the catalytic mechanism of the hydrogenase found in the aerobic, N{sub 2}-fixing microorganism Azotobacter vinelandii. This report summarizes the progress during the first two years of the current project and include the anticipated course of the research for the remaining year of the current project. Because the current proposal represents a change in direction, the authors also include a brief progress report of prior DOE-sponsored research dealing with hydrogenases.

  19. Characterization and site-directed mutagenesis of NifU from Azotobacter vinelandii

    OpenAIRE

    Jack, Richard F.

    1995-01-01

    In order to elucidate the function of the nifU gene product in nitrogenase maturation in Azotobacter vinelandii. the gene product has been hyperexpressed in Escherichia coli and characterized by various biophysical techniques. Following the initial characterization, site-directed mutagenesis of conserved cysteinyl residues was performed in order to gain further insight into the structure/function relationship of NifU. Both the Fe protein and the MoFe protein of nitrogena...

  20. Chromosomal nif Genes Transfer by Conjugation in Nitrogen Fixing Azotobacter chroococcum to Lactobacillus plantarium

    Directory of Open Access Journals (Sweden)

    Adel Kamal Khider

    2011-03-01

    Full Text Available To determine the possibility of transferring chromosomal nitrogen fixation genes (nif genes from Azotobacter chroococcum to Lactobacillus planetarium, a total of 72 Azotobacter chroococcum isolated from Erbil governorate, Iraq were culturally, morphologically and biochemically characterized. Genes for atmospheric nitrogen fixation, located on the chromosome of Azotobacter chroococcum isolates were transferred by conjugation process to a recipient Lactobacillus plantarium isolated from Erbil city soils. The chromosomal genes transferred were verified by analysis of the genomes of donor, recipient and putative transconjugants, by polymorphism of DNA bands obtained through amplification of nifH1, nifH2, nifH3, nifU and nifV genes by PCR technique. The transconjugant cells promote an efficient fixation of nitrogen in liquid cultures fixed 0.2% nitrogen, and in the soil as inoculums of wheat plants, fixed 0.31% nitrogen and solublized 11.71 ppm phosphorus, beside all advantages of Lactic acid bacteria, and probably to be used as inoculums for both nitrogen fixation and solublizing insoluble phosphorus components, and used as biofertilizers

  1. Protein Quantity and Quality of Safflower Seed Improved by NP Fertilizer and Rhizobacteria (Azospirillum and Azotobacter spp.)

    Science.gov (United States)

    Nosheen, Asia; Bano, Asghari; Yasmin, Humaira; Keyani, Rumana; Habib, Rabia; Shah, Syed T. A.; Naz, Rabia

    2016-01-01

    HIGHLIGHTS Rhizobacteria (Azotobacter spp.) have improved the quality and quantity of safflower seed protein.Protein quality was confirmed by SDS-PAGE and new bands were found in response to different combinations of rhizobacteria and lower doses of fertilizers.The PGPR application has reduced the use of fertilizers upto 50%. Protein is an essential part of the human diet. The aim of this present study was to improve the protein quality of safflower seed by the application of plant growth promoting rhizobacteria (PGPR) in combination with conventional nitrogen and phosphate (NP) fertilizers. The seeds of two safflower cultivars Thori and Saif-32, were inoculated with Azospirillum and Azotobacter and grown under field conditions. Protein content and quality was assessed by crude protein, amino acid analysis, and SDS-PAGE. Seed crude protein and amino acids (methionine, phenylalanine, and glutamic acid) showed significant improvements (55–1250%) by Azotobacter supplemented with a quarter dose of fertilizers (BTQ) at P ≤ 0.05. Additional protein bands were induced in Thori and Saif-32 by BTQ and BTH (Azotobacter supplemented with a half dose of fertilizer) respectively. The Azospirillum in combination with half dose of fertilizer (SPH) and BTQ enhanced both indole acetic acid (IAA) (90%) and gibberellic acid (GA) (23–27%) content in safflower leaf. Taken together, these data suggest that Azospirillum and Azotobacter along with significantly reduced (up to 75%) use of NP fertilizers could improve the quality and quantity of safflower seed protein. PMID:26941744

  2. Relative efficiency of Azotobacter and Azospirillum on yield and P utilization by wheat (Triticum Aestivum) with various N levels

    International Nuclear Information System (INIS)

    Efficiency of 32P labelled single superphosphate along with N levels (0, 60, 80 and 120 kg/ha) and biofertilizers (Azotobacter and Azospirillum) was studied on wheat in Typic ustifluvent (saline phase) soil. Average grain and straw yield, total P uptake, per cent P derived by crop from applied phosphorus and its utilization in grain and straw increased either with Azospirillum or Azotobacter inoculation. However, the magnitude of increase in these attributes was of higher extent in presence of Azotobacter as compared to Azospirillum. The yield, uptake and utilization of P increased with increasing levels of N. Per cent Pdff was higher with all levels of N over control, whereas, it was at par with their successive levels. Interaction effect between levels of nitrogen and biofertilizers were also positive and significant at all levels of N with respect to yield and uptake of P, while per cent Pdff and its utilization by wheat was more pronounced at 60 and 80 kg N ha-1 in the presence of Azotobacter. Azospirillum was more effective at 60 kg of N than the other levels. Generally, Azotobacter performed better than the Azospirillum with respect to all parameters. (author)

  3. Nucleotide sequence and mutational analysis of the structural genes (anfHDGK) for the second alternative nitrogenase from Azotobacter vinelandii.

    OpenAIRE

    Joerger, R D; Jacobson, M R; Premakumar, R; Wolfinger, E D; Bishop, P E

    1989-01-01

    The nucleotide sequence of a region of the Azotobacter vinelandii genome exhibiting sequence similarity to nifH has been determined. The order of open reading frames within this 6.1-kilobase-pair region was found to be anfH (alternative nitrogen fixation, nifH-like gene), anfD (nifD-like gene), anfG (potentially encoding a protein similar to the product of vnfG from Azotobacter chroococcum), anfK (nifK-like gene), followed by two additional open reading frames. The 5'-flanking region of anfH ...

  4. ACCUMULATION OF POLYHYDROXYALKANOIC ACIDS BY AZOTOBACTER CHROOCOCCUM MAL-201 FROM ORGANIC WASTE

    OpenAIRE

    Soma Pal Saha; A. Patra; P. B. Ghosh; A.K. Paul

    2013-01-01

    Azotobacter chroococcum MAL-201 (MTCC 3853), a free-living nitrogen-fixing bacterium accumulated intracellular poly(3-hydroxybutyric acid) [P(3HB)] accounting 69% of cell dry weight (CDW) when grown in nitrogrn-free Stockdale medium containing 2% (w/v) glucose. It also produced copolymer of poly(3-hydroxybutyrate co-3-hydroxyvalerate) [P(3HB-co-3HV)] using glucose as primary carbon source and valerate cas cosubstrate. To make the polymer production cost effective four types of waste material ...

  5. Nucleotide sequence and mutational analysis of the vnfENX region of Azotobacter vinelandii.

    OpenAIRE

    Wolfinger, E D; Bishop, P E

    1991-01-01

    The nucleotide sequence (3,600 bp) of a second copy of nifENX-like genes in Azotobacter vinelandii has been determined. These genes are located immediately downstream from vnfA and have been designated vnfENX. The vnfENX genes appear to be organized as a single transcriptional unit that is preceded by a potential RpoN-dependent promoter. While the nifEN genes are thought to be evolutionarily related to nifDK, the vnfEN genes appear to be more closely related to nifEN than to either nifDK, vnf...

  6. Genes required for rapid expression of nitrogenase activity in Azotobacter vinelandii

    OpenAIRE

    Curatti, Leonardo; Brown, Carolyn S.; Ludden, Paul W.; Rubio, Luis M.

    2005-01-01

    Rnf proteins are proposed to form membrane-protein complexes involved in the reduction of target proteins such as the transcriptional regulator SoxR or the dinitrogenase reductase component of nitrogenase. In this work, we investigate the role of rnf genes in the nitrogen-fixing bacterium Azotobacter vinelandii. We show that A. vinelandii has two clusters of rnf-like genes: rnf1, whose expression is nif-regulated, and rnf2, which is expressed independently of the nitrogen source in the medium...

  7. Spectroscopic and Functional Characterization of Iron-Bound Forms of Azotobacter vinelandiiNifIscA†

    OpenAIRE

    Mapolelo, Daphne T.; Zhang, Bo; Naik, Sunil G.; Huynh, Boi Hanh; Johnson, Michael K.

    2012-01-01

    The ability of Azotobacter vinelandii NifIscA to bind Fe has been investigated to assess the role of Fe-bound forms in NIF-specific Fe-S cluster biogenesis. NifIscA is shown to bind one Fe(III) or one Fe(II) per homodimer and the spectroscopic and redox properties of both the Fe(III)- and Fe(II)-bound forms have been characterized using the UV-visible absorption, CD and VTMCD, EPR, Mössbauer and resonance Raman spectroscopies. The results reveal a rhombic intermediate-spin (S = 3/2) Fe(III...

  8. Nucleotide sequence and genetic analysis of the nifB-nifQ region from Azotobacter vinelandii.

    OpenAIRE

    Joerger, R D; Bishop, P E

    1988-01-01

    A 3.8-kilobase-pair EcoRI fragment which corrects the mutations carried by the NifB- Azotobacter vinelandii strains CA30 and UW45 was cloned, and its nucleotide sequence was determined. Four complete open reading frames (ORFs) and two partial ORFs were found. The translation product of the first partial ORF is the carboxy-terminal end of a protein homologous to the nifA gene product from Klebsiella pneumoniae. A 285-base-pair sequence containing a potential nif promoter and nif regulatory sit...

  9. Mutagenesis of nifE and nifN from Azotobacter vinelandii

    OpenAIRE

    Wilson, Mark Steven Michael

    1988-01-01

    The products of nifE and nifN from Azotobacter vinelandii, which are involved in the biosynthesis of the iron-molybdenum cofactor (FeMo-co) co) from nitrogenase, have been analyzed using a variety of mutagenic techniques. NifE was the object of several site-specific, amino acid substitutions that were designed to elicit information regarding metal cluster ligands, subunit-subunit interactions, and the proposed transfer of FeMo-co.from a nifEN-products complex to the apo-MoFe pr...

  10. Two nifA-like genes required for expression of alternative nitrogenases by Azotobacter vinelandii.

    OpenAIRE

    Joerger, R D; Jacobson, M R; Bishop, P E

    1989-01-01

    Two nifA-like genes, designated anfA and vnfA, have been identified in Azotobacter vinelandii. The anfA gene is located upstream from the nitrogenase-3 structural gene cluster (anfHDGK) and is preceded by a sequence that is potentially part of a ntrA-dependent promoter. The product of anfA appears to be required for expression of nitrogenase-3, since cells of the anfA deletion strain CA66 were unable to synthesize this nitrogenase when derepressed in N-free, Mo- and V-deficient medium. The vn...

  11. Excretion of ammonium by a nifL mutant of Azotobacter vinelandii fixing nitrogen.

    OpenAIRE

    Bali, A.; Blanco, G.; Hill, S.; Kennedy, C

    1992-01-01

    A mutation in the gene upstream of nifA in Azotobacter vinelandii was introduced into the chromosome to replace the corresponding wild-type region. The resulting mutant, MV376, produced nitrogenase constitutively in the presence of 15 mM ammonium. When introduced into a nifH-lacZ fusion strain, the mutation permitted beta-galactosidase production in the presence of ammonium. The gene upstream of nifA is therefore designated nifL because of its similarity to the Klebsiella pneumoniae nifL gene...

  12. Purification of the Azotobacter vinelandii nifV-encoded homocitrate synthase.

    OpenAIRE

    Zheng, L; White, R H; Dean, D R

    1997-01-01

    The nifV gene product (NifV) from Azotobacter vinelandii was recombinantly expressed at high levels in Escherichia coli and purified. NifV is a homodimer that catalyzes the condensation of acetyl coenzyme A (acetyl-CoA) and alpha-ketoglutarate. Although alpha-ketoglutarate supports the highest level of activity, NifV will also catalyze the condensation of acetyl-CoA and certain other keto acids. E. coli cells in which a high level of nifV expression is induced excrete homocitrate into the gro...

  13. Investigation on Strain Development of Azotobacter chroococcum through Chemical Mutagenesis for Indole Acetic Acid Production

    International Nuclear Information System (INIS)

    Two wild strains of Azotobacter chroococcum were mutagenized by various concentration of NTG (.005% , .0075% and .01%) for 1 hour. The IAA producing activity of 12 effective mutagenized strains were quantitatively measured by UV spectroscopic method. Mutagenized strains M1 and M2 from W1, and M8 and M9 from W2 were selected. Their IAA productivities were 300.498, 216.290, 238.436 and 190.856 ppm, respectively. M1and M9 were higher IAA productivity with greater quality. In germination, M1, M8 and M9 can promote the plant growth compare with commercial IAA.

  14. Protein quantity and quality of safflower seed improved by NP fertilizer and rhizobacteria (Azospirillum and Azotobacter spp.

    Directory of Open Access Journals (Sweden)

    Asia eNosheen

    2016-02-01

    Full Text Available Protein is an essential part of human diet. The aim of present study was to improve the protein quality of safflower seed by the application of plant growth promoting rhizobacteria (PGPR in combination with conventional nitrogen and phosphate (NP fertilizers. The seeds of two safflower cultivar Thori and Saif-32, were inoculated with Azospirillum and Azotobacter and grown under field conditions. Protein content and quality was assessed by crude protein, amino acid analysis and SDS-PAGE. Seed crude protein and amino acids (metheonine, phenylanine and glutamic acid showed significant improvement (55%–1250% by Azotobacter supplemented with quarter dose of fertilizers (BTQ at P≤0.05. Additional protein bands were induced in Thori and Saif-32 by BTQ and BTH (Azotobacter supplemented with half dose of fertilizers respectively. The Azospirillum in combination with half dose of fertilizers (SPH and BTQ enhanced the indole acetic acid (90% and gibberellic acid (23%–27% contents in safflower leaf. Taken together, these data suggest that Azospirillum and Azotobacter along with significantly reduced (up to 75% use of NP fertilizers improved the quality and quantity of safflower seed protein.

  15. The involvement of the fixABCX genes and the respiratory chain in electron transport to nitrogenase in Azotobacter vinelandii.

    NARCIS (Netherlands)

    Wientjens, M.J.C.

    1993-01-01

    Introduction.The work in this thesis is mainly focused on the electron transport route to nitrogenase in the free-living, obligate aerobic, nitrogen fixing organism Azotobacter vinelandii. For many years now, this topic has been the subject of research. Several hypotheses, which would explain the me

  16. Melanin from the nitrogen-fixing bacterium Azotobacter chroococcum: a spectroscopic characterization.

    Directory of Open Access Journals (Sweden)

    Aulie Banerjee

    Full Text Available Melanins, the ubiquitous hetero-polymer pigments found widely dispersed among various life forms, are usually dark brown/black in colour. Although melanins have variety of biological functions, including protection against ultraviolet radiation of sunlight and are used in medicine, cosmetics, extraction of melanin from the animal and plant kingdoms is not an easy task. Using complementary physicochemical techniques (i.e. MALDI-TOF, FTIR absorption and cross-polarization magic angle spinning solid-state (13C NMR, we report here the characterization of melanins extracted from the nitrogen-fixing non-virulent bacterium Azotobacter chroococcum, a safe viable source. Moreover, considering dihydroxyindole moiety as the main constituent, an effort is made to propose the putative molecular structure of the melanin hetero-polymer extracted from the bacterium. Characterization of the melanin obtained from Azotobacter chroococcum would provide an inspiration in extending research activities on these hetero-polymers and their use as protective agent against UV radiation.

  17. Maize responds to Azotobacter sp and Burkholderia sp inoculation at reduced dose of nitrogen fertilizer

    Directory of Open Access Journals (Sweden)

    Juan Manuel Sánchez-Yáñez

    2014-03-01

    Full Text Available The positive maize response to inoculation with plant growth promoting bacteria (PGPB as Azotobacter sp and Burkholderia sp an endophytic type, are an alternative to reduced and optimize nitrogen fertilizer (NF dose, recommended for this plant, without adversely affect its growth. The aim of this study was to analyze maize respond to inoculation with Azotobacter sp and Burkholderia sp at the dose 50% of FN. Used an experimental design of randomized blocks. By response variables: percent germination (%, the shoot and root phenology: plant height (PH, root length (RL and biomass: shoot fresh weight (SFW and root fresh weight (RFW, the shoot dry weight (SDW and root dry weight (RDW. The results indicated a positive maize respond to PGPB inoculation at germination, seedling and flowering level, reached a RDW of 7.03 g, statistically significant value compared with 2.60 g of RDW non inoculated maize feed with NF dose recommended regard as relative control (RC. This suggests a synergistic interaction among these PGPB in synthesis of plant growth promoting substances (PGPS on maize, to optimize the reduced NF dose.

  18. The use of lacZ marker in enumeration of Azotobacter chroococcum in carrier based inoculants

    Directory of Open Access Journals (Sweden)

    Manu Solanki

    2014-06-01

    Full Text Available A transconjugant of Azotobacter chroococcum Mac 27 tagged with lac Z(A. chroococcum Mac27 L was found to possess high levels of β-galactosidase activity constitutively.Further, the lac Z marker was found to be stably integrated into the chromosome of the A. chroococcum Mac 27 and did not have any adverse effect on growth, nitrogen fixation and excretion of ammonia. A quick method to determine the viable cell number in broth culture and carrier based inoculants has been developed on the basis of β-galactosidase assay. It was found that there was a direct relationship between the number of cell as determined by standard plate count and intensity of colour that developed upon degradation of ONPG due to β-galactosidase activity .The method was found to be sensitive enough to determine 1.7 x 10(6 CFU mL-1 in broth culture as well as carrier based Azotobacter inoculants. Further, it was observed that when A. chroococcum Mac27 L was inoculated on Brassica campestris, it could be detected in the presence of other bacteria capable of growing on Burks agar medium containing X-gal on the basis of lac Z genetic marker.

  19. Producción de un biofertilizante a partir de un aislamiento de Azotobacter nigricans obtenido en un cultivo de Stevia rebaudiana Bert

    OpenAIRE

    Daniel Borda-Molina; Juan Manuel Pardo-García; María Mercedes Martínez-Salgado; José Salvador Montaña-Lara

    2009-01-01

    Bio-fertilizer production from an isolate of Azotobacter nigricans obtained from a plantation of Stevia rebaudiana Bert. Objective.To isolate nitrogen fixing bacteria to be used in a fertilization regime of an organic agriculture program. Materials and methods. Theisolation of nitrogen fixing bacteria was done in an Ashby-benzoate medium from soil of a Stevia rebaudiana plantation. Isolates identifiedas Azotobacter nigricans were evaluated by their growth kinetics and the strain with the fast...

  20. Isolation and characterization of nifDK::kanamycin and nitrogen fixation proficient Azotobacter vinelandii strain, and its implication on the status of multiple chromosomes in Azotobacter.

    Science.gov (United States)

    Suh, M H; Pulakat, L; Gavini, N

    2000-01-01

    Several lines of experimental analyses on the ploidy status of Azotobacter vinelandii genome lead to the conclusion that it contains more than 40 copies of its chromosome and therefore it is a polyploid organism. The genetic evidence argues against the existence of polyploidy in these cells since the segregation pattern of genetic markers under lack of selection pressure mimic that of haploids. However, when A. vinelandii was made Nif- by inserting a kanamycin resistance marker gene in the nifDK sequence and the cells were selected for kanamycin resistance and Nif+ phenotype, we were able to score colonies that are both kanamycin resistant and Nif+. Therefore, when the cells were subjected to forced double selection of the same locus, they behaved as if they carried at least two chromosomes, one carrying the kanamycin resistance marker in the nifDK genes and the other carrying the intact nifDK genes. These analyses suggested that at least a diploidy status can be induced in these cells under selection pressure. PMID:11678500

  1. Benefits of inoculation with azotobacter in the growth and production of tomato and peppers

    Directory of Open Access Journals (Sweden)

    Jarak Mirjana N.

    2010-01-01

    Full Text Available The aim of this research was to investigate the effects of Azotobacter chroococcum in tomato and pepper growth and production by using two types of inoculation - seed inoculation and seedling inoculation. The effect of inoculation was observed thirty days after sowing, thirty days after transplanting, and in the phase of technological maturity. The following were measured: height of the plants, dry matter of the plants and number and the weight of the fruits. Inoculation had a positive effect on these in both plants. With tomato, better results were achieved when seedlings were inoculated. With pepper, the length of the plant and the dry matter were greater with seedling inoculation, whereas the number and the weight of the fruits were greater with seed inoculation.

  2. PRODUCTION AND RECOVERY OF POLY-Β-HYDROXYBUTYRATE FROM WHEY DEGRADATION BY AZOTOBACTER

    Directory of Open Access Journals (Sweden)

    A. Khanafari , A. Akhavan Sepahei, M. Mogharab

    2006-07-01

    Full Text Available Three strains of Azotobacter chroococcum were studied to produce poly-β hydroxybutyrate as a inclusion body by whey degradation. Optimum degradation whey results were obtained when using whey broth as a fermentation medium without extra salt, temperature at 35 °C and pH 7 (P<0.05. Lambda max for whey broth medium was determined probably about 400 nm. The effect of different nitrogenous rich compounds (NH4NO3, Bactopeptone, Casein, Yeast extract, Meat extract, Protease peptone and Tryptone on whey degradation showed that incorporation of nitrogenous compounds into the medium did not increase whey degradation by Azotobacter chroococcum 1723 (P<0.05. But poly-β hydroxyl-butyrate production was increased in presence Meat extract up to 75% of the cell dry weight after 48h. The addition of nitrogenous sourced (except ammonium nitrate had a positive effect on poly-β hydroxyl-butyrate production as it peaked in the presence of Meat extract and 4.43 g/L was accumulated in comparison to 0.5g at diazotrophically growing cells. Increasing the O2 values resulted by shaking at 122 rpm in decreased poly-β hydroxyl-butyrate yield form 4.43 to 0.04 g/L. The results show that this medium supports the growth of strain 1735 and also that this waste could be utilized as a carbon and nitrogen source. Production of poly-β hydroxyl-butyrate by using whey as a medium looks promising, since the use of inexpensive feed-stocks for poly-β hydroxyl-butyrate is essential if bioplastics are to become competitive products.

  3. Biochemical and genetic analysis of the nifUSVWZM cluster from Azotobacter vinelandii.

    Science.gov (United States)

    Jacobson, M R; Cash, V L; Weiss, M C; Laird, N F; Newton, W E; Dean, D R

    1989-10-01

    Azotobacter vinelandii genes contained within the major nif-cluster and designated orf6, nifU, nifS, nifV, orf7, orf8, nifW, nifZ, nifM, and orf9 are organized into at least two overlapping transcriptional units. Nitrogenase derepressed crude extracts of Azotobacter vinelandii mutant strains having individual deletions located within nifU, nifS, nifV, nifW, nifZ, or nifM were examined for nitrogenase component protein activities. The results of these experiments indicated that, in A. vinelandii, the nifU, nifS and nifM gene products are required for the full activation or the catalytic stability of the nitrogenase Fe protein. Deletion of the nifV gene resulted in lower MoFe protein activity, probably resulting from the accumulation of an altered FeMo-cofactor. The nifW and nifZ gene products were required for the full activation or catalytic stability of the MoFe protein. Deletion of nifZ alone or nifM alone did not appear to affect FeMo-cofactor biosynthesis. However, deletion of both nifZ and nifM eleminated either FeMo-cofactor biosynthesis or the insertion of FeMo-cofactor into the apo-MoFe protein. Other genes contained within the nifUSVWZM gene cluster (orf6, orf7, orf8, and orf9) were not required for Mo-dependent diazotrophic growth. PMID:2615765

  4. EFECTIVIDAD DE CEPAS DE Azotobacter sp. Y Bacillus sp. PARA EL CONTROL DE ESPECIES FÚNGICAS ASOCIADAS A HORTALIZAS

    Directory of Open Access Journals (Sweden)

    Janet Rodríguez Sánchez

    2016-01-01

    Full Text Available Los géneros Azotobacter y Bacillus tienen la potencialidad de fijar nitrógeno atmosférico, solubilizar elementos minerales y producir un grupo de sustancias estimuladoras del crecimiento vegetal. Bacillus se reconoce, además, por su actividad antagonista. Estas razones justifican su selección como principios activos de productos biofertilizantes. La presencia de enfermedades causadas por hongos en los cultivos hortícolas, constituye un problema en la agricultura cubana. El objetivo del presente trabajo fue evaluar la actividad antagonista de cepas de los géneros Azotobacter y Bacillus contra hongos que causan enfermedades a cultivos hortícolas. Para ello se emplearon las especies Fusarium chlamydosporum, Corynespora cassiicola y Cladosporium oxysporum . Todas las cepas pertenecen a las colecciones del INIFAT. Para desarrollar este trabajo se utilizó el Método de “Enfrentamiento de Cultivos Duales”, que permitió seleccionar aquellas que poseen dicha actividad y describir, a la vez, las principales afectaciones que provocan a las estructuras fúngicas. Los resultados arrojaron que dentro de los dos géneros hay cepas que logran inhibir el crecimiento micelial. Dentro de las cepas de Azotobacter cinco resultaron promisorias contra Cladosporium oxysporum, dos responden frente a Fusarium chlamydosporum y una sola resultó efectiva contra Corynespora cassiicola. La actividad mostrada por el género Bacillus fue mayor. En este caso, dos cepas muestran efectividad contra Corynespora casiicola; seis contra Cladosporium oxysporum y ocho contra Fusarium chlamydosporum. Se comprobó que existen cepas de Azotobacter capaces de inhibir a más de una especie fúngica, lo que resulta novedoso por encontrarse poco citada la actividad del género contra patógenos de hortalizas

  5. Response of Sunflower Yield and Phytohormonal Changes to Azotobacter,Azospirillum,Pseudomonas and Animal Manure in a Chemical Free Agroecosystem

    OpenAIRE

    Maziyar, Mehran; M. Reza, Ardakani; Hamid, Madani; Mohammad , Zahedi; Mohsen, Amirabadi; Saeed, Mafakheri

    2011-01-01

    There are new trends in agriculture to move toward the low input systems with the lower application of chemical fertilizers. To reach this goal, different methods, such as the application of biofertilizers, may be used. So this experiment was conducted in 2010 at a research farm in Arak, Iran, in factorial in the form of a randomized complete block design with three replications and four factors: animal manure (M), Pseudomonas putida (P), Azotobacter chroococcum (A)and Azospirillum lipoferum ...

  6. Effects of homocitrate, homocitrate lactone, and fluorohomocitrate on nitrogenase in NifV- mutants of Azotobacter vinelandii.

    OpenAIRE

    Madden, M S; Paustian, T D; Ludden, P W; Shah, V K

    1991-01-01

    Azotobacter vinelandii DJ71, which contains a mutation in the nifV gene, was derepressed for nitrogenase in the presence of homocitrate. When dinitrogenase was isolated from this culture, it was found to be identical to the wild-type dinitrogenase. However, when the same NifV- strain was derepressed in the presence of erythrofluorohomocitrate, a homocitrate analog which produces a nitrogenase with wild-type properties in vitro, the isolated dinitrogenase was characteristic of the NifV- enzyme...

  7. Flavodoxin 1 of Azotobacter vinelandii: characterization and role in electron donation to purified assimilatory nitrate reductase.

    Science.gov (United States)

    Gangeswaran, R; Eady, R R

    1996-07-01

    Flavodoxins synthesized by Azotobacter vinelandii strain UW 36 during growth on nitrate as nitrogen source were separated by FPLC on a Mono Q column into two species, flavodoxin 1 (AvFld 1) and flavodoxin 2 (AvFld 2). Both proteins migrated as single bands on SDS/PAGE. AvFld 1 was approx. 5-fold more abundant than AvFld 2 in the unresolved flavodoxin mixture. N-terminal amino acid analysis showed the sequence of AvFld 2 to correspond to the nif F gene product, an electron donor to nitrogenase. The sequences also show that these species corresponded to the flavodoxins Fld A and Fld B isolated from N2-grown cultures of the closely related organism Azotobacter throococcum [Bagby, Barker, Hill, Eady and Thorneley (1991) Biochem.J.277, 313-319]. Electrospray mass spectrometry gave M, values for the polypeptides of 19430 +/- 3 and 19533 +/- 5 respectively. 31P-NMR measurements showed that in addition to the phosphate associated with the FMN (delta = -136.3 p.p.m. and -135.48 p.p.m.), AvFld 1 had a signal at delta = -142.1 p.p.m. and AvFld 2 at delta = -138.59 p.p.m. present in substoichiometric amounts with FMN. These appeared to arise from unstable species since they were readily lost on further manipulation of the proteins. The mid-point potentials of the semiquinone hydroquinone redox couples were -330 mV and -493 mV for AvFld 1 and AvFld 2 respectively, but only AvFld 1 was competent in donating electrons to the purified assimilatory nitrate reductase of A. vinelandii to catalyse the reduction of nitrate to nitrite. Flavodoxin isolated from NH4(+)-grown cells (Fld 3) also functioned as electron donor at half the rate of AvFld 1, but ferredoxin 1 from A. chroococcum did not. PMID:8694750

  8. Production of polyhydroxybutyrate and alginate from glycerol by Azotobacter vinelandii under nitrogen-free conditions.

    Science.gov (United States)

    Yoneyama, Fuminori; Yamamoto, Mayumi; Hashimoto, Wataru; Murata, Kousaku

    2015-01-01

    Glycerol is an interesting feedstock for biomaterials such as biofuels and bioplastics because of its abundance as a by-product during biodiesel production. Here we demonstrate glycerol metabolism in the nitrogen-fixing species Azotobacter vinelandii through metabolomics and nitrogen-free bacterial production of biopolymers, such as poly-d-3-hydroxybutyrate (PHB) and alginate, from glycerol. Glycerol-3-phosphate was accumulated in A. vinelandii cells grown on glycerol to the exponential phase, and its level drastically decreased in the cells grown to the stationary growth phase. A. vinelandii also overexpressed the glycerol-3-phosphate dehydrogenase gene when it was grown on glycerol. These results indicate that glycerol was first converted to glycerol-3-phosphate by glycerol kinase. Other molecules with industrial interests, such as lactic acid and amino acids including γ-aminobutyric acid, have also been accumulated in the bacterial cells grown on glycerol. Transmission electron microscopy revealed that glycerol-grown A. vinelandii stored PHB within the cells. The PHB production level reached 33% per dry cell weight in nitrogen-free glycerol medium. When grown on glycerol, alginate-overproducing mutants generated through chemical mutagenesis produced 2-fold the amount of alginate from glycerol than the parental wild-type strain. To the best of our knowledge, this is the first report on bacterial production of biopolymers from glycerol without addition of any nitrogen source. PMID:25880041

  9. Manipulation and Characterization of Alginate Exo polysaccharides produced by Azotobacter Vinelandii

    International Nuclear Information System (INIS)

    Exo polysaccharides (EPS) have been found in a wide range of applications in food industry and in the biomedical field. In the present study, the effect of nutritional factors (carbon and nitrogen sources) and gamma irradiations on alginate production by Azotobacter vinelandii was investigated. To understand the direct and indirect relations among these variables, a two way factorial design experiment was set up. At low concentration of carbon source (≤ 20 g/l), the alginate yield was influenced by the type of nitrogen substrate and C/N ratio, whereas the role of these factors on alginate production was minimized at high concentration of carbon source (> 20 g/l). Batch fermentation of alginate exo polysaccharides was manipulated by maintaining the ph value of the cultures at 7 along the incubation period and reducing the agitation speed to 100 rpm after 24 h at the time of inoculation. This process succeeded to increase the alginate yield exponentially with time by 50%. Exposing A. vinelandii cells to gamma irradiation at dose level 0.5 kGy decreased their activity to synthesis alginate by 44%. The produced alginate was characterized by gel permeation chromatography (GPC), nuclear magnetic resonance (NMR) and differential scanning calorimeter (DSC).

  10. Flagella-Mediated Differences in Deposition Dynamics for Azotobacter vinelandii in Porous Media

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Nanxi; Bevard, Tara; Massoudieh, Arash; Zhang, Changyong; Dohnalkova, Alice; Zilles, Julie L.; Nguyen, Thanh H.

    2013-05-21

    A multi-scale approach was designed to investigate deposition of flagellated and non-flagellated strains of Azotobacter vinelandii in porous media. In a radial stagnation point flow cell (RSPF), the deposition rate of the flagellated strain (DJ77) on quartz was higher than that of the non-flagellated (Fla-) strain. In contrast, deposition of the Fla- strain exceeded that of DJ77 in two-dimensional silicon microfluidic models (micromodels) and in columns packed with glass beads. Direct cell counts in micromodel experiments showed decreasing values of clean collector removal efficiencies over time, suggesting that approaching cells were blocked from deposition by cells already attached to the collector surface. Column breakthrough curves for both strains also showed a decrease in deposition rates with time. Modeling results showed that blocking becomes effective for DJ77 strain at lower ionic strengths (1mM and 10mM), while for Fla- strain blocking was similar at all ionic strengths. In later stages of micromodel experiments, a ripening effect was also observed, where cells preferentially attached to already attached cells. Ripening happened earlier with the Fla- strain, which suggested that flagella interfered with ripening. Different mechanisms dominate at different stages of bacteria transport in porous media.

  11. Dual symbiosis between Piriformospora indica and Azotobacter chroococcum enhances the artemisinin content in Artemisia annua L.

    Science.gov (United States)

    Arora, Monika; Saxena, Parul; Choudhary, Devendra Kumar; Abdin, Malik Zainul; Varma, Ajit

    2016-02-01

    At present, Artemisia annua L. is the major source of artemisinin production. To control the outbreaks of malaria, artemisinin combination therapies (ACTs) are recommended, and hence an ample amount of artemisinin is required for ACTs manufacture to save millions of lives. The low yield of this antimalarial drug in A. annua L. plants (0.01-1.1%) ensues its short supply and high cost, thus making it a topic of scrutiny worldwide. In this study, the effects of root endophyte, Piriformospora indica strain DSM 11827 and nitrogen fixing bacterium, Azotobacter chroococcum strain W-5, either singly and/or in combination for artemisinin production in A. annua L. plants have been studied under poly house conditions. The plant growth was monitored by measuring parameters like height of plant, total dry weight and leaf yield with an increase of 63.51, 52.61 and 79.70% respectively, for treatment with dual biological consortium, as compared to that of control plants. This significant improvement in biomass was associated with higher total chlorophyll content (59.29%) and enhanced nutrition (especially nitrogen and phosphorus, 55.75 and 86.21% respectively). The concentration of artemisinin along with expression patterns of artemisinin biosynthesis genes were appreciably higher in dual treatment, which showed positive correlation. The study suggested the potential use of the consortium P. indica strain DSM 11827 and A. chroococcum strain W-5 in A. annua L. plants for increased overall productivity and sustainable agriculture. PMID:26745979

  12. N2O reduction by Azotobacter vinelandii with emphasis on kinetic nitrogen isotope effects

    International Nuclear Information System (INIS)

    A nitrogen-fixing bacterium Azotobacter vinelandii was successfully grown in a specially designed system with constant partial pressures of N2O (0.2 atm) and O2 (0.2 atm) in a nitrogen-free liquid medium. Reduction of N2O proceeded with the evolution of N2 in the gas phage. Large nitrogen isotope fractionation was found for both processes, reduction of N2O to N2 and N2O-fixation. The kinetic isotope fractionation factors of these reactions were at most 1.039 and 1.034, respectively. Furthermore, an unexpected inverse isotope effect (organic-N, the end-product, is more enriched in 15N than N2, the intermediate) strongly suggested that N2O was directly assimilated within the bacterial cells. Simultaneous assimilation of N2O and N2 was also confirmed by using a 15N tracer technique. Three independent pathways were demonstrated for the nitrogen fixing system investigated in this study: (1) a direct reduction of N2O to ammonium (apparently 8-electron reduction), (2) reduction of N2 to ammonium (6-electron reduction) and (3) N2O reduction to N2 (2-electron reduction). (author)

  13. Purification and characterization of the vnf-encoded apodinitrogenase from Azotobacter vinelandii.

    Science.gov (United States)

    Chatterjee, R; Allen, R M; Ludden, P W; Shah, V K

    1996-03-22

    The vnf-encoded apodinitrogenase (apodinitrogenase 2) has been purified from Azotobacter vinelandii strain CA117.30 (DeltanifKDB), and is an alpha2beta2delta2 hexamer. Apodinitrogenase 2 can be activated in vitro by the addition of the iron-vanadium cofactor (FeV-co) to form holodinitrogenase 2, which functions in C2H2, H+, and N2 reduction. Under certain conditions, the alpha2beta2delta2 hexamer dissociates to yield the free delta subunit (the VNFG protein) and a form of apodinitrogenase 2 that exhibits no C2H2, H+, or N2 reduction activities in the in vitro FeV-co activation assay; however, these activities can be restored upon addition of VNFG to the FeV-co activation assay system. No other vnf-, nif-, or non-nif-encoded proteins were able to replace the function of VNFG in the in vitro processing of alpha2beta2 apodinitrogenase 2 (in the presence of FeV-co) to a form capable of substrate reduction. Apodinitrogenase 2 is also activable in vitro by the iron-molybdenum cofactor to form a hybrid enzyme with unique properties, most notably the inability to reduce N2 and insensitivity to CO inhibition of C2H2 reduction. PMID:8636105

  14. Activation of vanadium nitrogenase expression in Azotobacter vinelandii DJ54 revertant in the presence of molybdenum.

    Science.gov (United States)

    Lei, S; Pulakat, L; Gavini, N

    2000-09-29

    Azotobacter vinelandii carries three different and genetically distinct nitrogenase systems on its chromosome. Expression of all three nitrogenases is repressed by high concentrations of fixed nitrogen. Expression of individual nitrogenase systems is under the control of specific metal availability. We have isolated a novel type of A. vinelandii DJ54 revertant, designated A. vinelandii BG54, which carries a defined deletion in the nifH gene and is capable of diazotrophic growth in the presence of molybdenum. Inactivation of nifDK has no effect on growth of this mutant strain in nitrogen-free medium suggesting that products of the nif system are not involved in supporting diazotrophic growth of A. vinelandii BG54. Similar to the wild type, A. vinelandii BG54 is also sensitive to 1 mM tungsten. Tn5-B21 mutagenesis to inactivate the genes specific to individual systems revealed that the structural genes for vnf nitrogenase are required for diazotrophic growth of A. vinelandii BG54. Analysis of promoter activity of different nif systems revealed that the vnf promoter is activated in A. vinelandii BG54 in the presence of molybdenum. Based on these data we conclude that A. vinelandii BG54 strain utilizes vnf nitrogenase proteins to support its diazotrophic growth. PMID:11018539

  15. The basis of ammonium release in nifL mutants of Azotobacter vinelandii.

    Science.gov (United States)

    Brewin, B; Woodley, P; Drummond, M

    1999-12-01

    In Azotobacter vinelandii, nitrogen fixation is regulated at the transcriptional level by an unusual two-component system encoded by nifLA. Certain mutations in nifL result in the bacterium releasing large quantities of ammonium into the medium, and earlier work suggested that this occurs by a mechanism that does not involve NifA, the activator of nif gene transcription. We have investigated a number of possible alternative mechanisms and find no evidence for their involvement in ammonium release. Enhancement of NifA-mediated transcription, on the other hand, by either elimination of nifL or overexpression of nifA, resulted in ammonium release, correlating with enhanced levels of nifH mRNA, raised levels of nitrogenase and acetylene-reducing activity, and increased concentrations of intracellular ammonium. Up to 35 mM ammonium can accumulate in the medium. Where measured, intracellular levels exceeded extracellular levels, indicating that rather than being actively transported, ammonium is lost from the cell passively, possibly by reversal of an NH(4)(+) uptake system. The data also indicate that in the wild type the bulk of NifA is inactivated by NifL during steady-state growth on dinitrogen. PMID:10572141

  16. Characterization of the glnK-amtB operon of Azotobacter vinelandii.

    Science.gov (United States)

    Meletzus, D; Rudnick, P; Doetsch, N; Green, A; Kennedy, C

    1998-06-01

    To determine whether in Azotobacter vinelandii the PII protein influences the regulation of nif gene expression in response to fluxes in the ammonium supply, the gene encoding PII was isolated and characterized. Its deduced translation product was highly similar to PII proteins from other organisms, with the greatest degree of relatedness being exhibited to the Escherichia coli glnK gene product. A gene designated amtB was found downstream of and was contranscribed with glnK as in E. coli. The AmtB protein is similar to functionally characterized ammonium transport proteins from a few other eukaryotes and one other prokaryote. glnK and amtB comprise an operon. Attempts to isolate a stable glnK mutant strain were unsuccessful, suggesting that glnK, like glnA, is an essential gene in A. vinelandii. amtB mutants were isolated, and although growth on limiting amounts of ammonium was similar in the mutant and wild-type strains, the mutants were unable to transport [14C]methylammonium. PMID:9620984

  17. Excretion of ammonium by a nifL mutant of Azotobacter vinelandii fixing nitrogen.

    Science.gov (United States)

    Bali, A; Blanco, G; Hill, S; Kennedy, C

    1992-05-01

    A mutation in the gene upstream of nifA in Azotobacter vinelandii was introduced into the chromosome to replace the corresponding wild-type region. The resulting mutant, MV376, produced nitrogenase constitutively in the presence of 15 mM ammonium. When introduced into a nifH-lacZ fusion strain, the mutation permitted beta-galactosidase production in the presence of ammonium. The gene upstream of nifA is therefore designated nifL because of its similarity to the Klebsiella pneumoniae nifL gene in proximity to nifA, in mutant phenotype, and in amino acid sequence of the gene product. The A. vinelandii nifL mutant MV376 excreted significant quantities of ammonium (approximately 10 mM) during diazotrophic growth. In contrast, ammonium excretion during diazotrophy was much lower in a K. pneumoniae nifL deletion mutant (maximum, 0.15 mM) but significantly higher than in NifL+ K. pneumoniae. The expression of the A. vinelandii nifA gene, unlike that of K. pneumoniae, was not repressed by ammonium. PMID:1622243

  18. Noncoupled NADH:Ubiquinone Oxidoreductase of Azotobacter vinelandii Is Required for Diazotrophic Growth at High Oxygen Concentrations

    OpenAIRE

    Bertsova, Yulia V.; Alexander V. Bogachev; Skulachev, Vladimir P.

    2001-01-01

    The gene encoding the noncoupled NADH:ubiquinone oxidoreductase (NDH II) from Azotobacter vinelandii was cloned, sequenced, and used to construct an NDH II-deficient mutant strain. Compared to the wild type, this strain showed a marked decrease in respiratory activity. It was unable to grow diazotrophically at high aeration, while it was fully capable of growth at low aeration or in the presence of NH4+. This result suggests that the role of NDH II is as a vital component of the respiratory p...

  19. Mutational analysis of genes of the mod locus involved in molybdenum transport, homeostasis, and processing in Azotobacter vinelandii.

    OpenAIRE

    Mouncey, N J; Mitchenall, L A; Pau, R N

    1995-01-01

    DNA sequencing of the region upstream from the Azotobacter vinelandii operon (modEABC) that contains genes for the molybdenum transport system revealed an open reading frame (modG) encoding a hypothetical 14-kDa protein. It consists of a tandem repeat of an approximately 65-amino-acid sequence that is homologous to Mop, a 7-kDa molybdopterin-binding protein of Clostridium pasteurianum. The tandem repeat is similar to the C-terminal half of the product of modE. The effects of mutations in the ...

  20. Papel del Mn (II) como regulador del metabolismo del nitrógeno inorgánico en Azotobacter

    OpenAIRE

    Ruiz Pérez, María Teresa

    1989-01-01

    En este trabajo hemos estudiado el efecto que diversos metales divalentes, especialmente manganeso, ejercen sobre la asimilación de nitrato y la fijación de nitrógeno en Azotobacter chrococcum, un área de investigación que no gabía sido abordad ... a hasta ahora. Los resultados que se describen sugieren que el Mn (II) puede actuar como una señal regulatoria del metabolismo nitrogenado, siendo la glutamina sintetasa su blanco de acción.La hipótesis de trabajo formuladas para explicar estos res...

  1. Expression of the nifBfdxNnifOQ region of Azotobacter vinelandii and its role in nitrogenase activity.

    OpenAIRE

    Rodríguez-Quiñones, F; Bosch, R.; Imperial, J

    1993-01-01

    The nifBQ transcriptional unit of Azotobacter vinelandii has been previously shown to be required for activity of the three nitrogenase systems, Mo nitrogenase, V nitrogenase, and Fe nitrogenase, present in this organism. We studied regulation of expression and the role of the nifBQ region by means of translational beta-galactosidase fusions to each of the five open reading frames: nifB, orf2 (fdxN), orf3 (nifO), nifQ, and orf5. Expression of the first three open reading frames was observed u...

  2. Tn5-induced mutants of Azotobacter vinelandii affected in nitrogen fixation under Mo-deficient and Mo-sufficient conditions.

    OpenAIRE

    Joerger, R D; Premakumar, R; Bishop, P E

    1986-01-01

    Mutants of Azotobacter vinelandii affected in N2 fixation in the presence of 1 microM Na2MoO4 (conventional system), 50 nM V2O5, or under Mo deficiency (alternative system) have been isolated after Tn5 mutagenesis with the suicide plasmid pSUP1011. These mutants can be grouped into at least four broad phenotypic classes. Mutants in the first class are Nif- under Mo sufficiency but Nif+ under Mo deficiency or in the presence of V2O5. A nifk mutant and a mutant apparently affected in regulation...

  3. Identification of a Positive Transcription Regulatory Element within the Coding Region of the nifLA Operon in Azotobacter vinelandii

    OpenAIRE

    Mitra, Ranjana; Das, Hirendra K.; Dixit, Aparna

    2005-01-01

    Nitrogen fixation in Azotobacter vinelandii is regulated by the nifLA operon. NifA activates the transcription of nif genes, while NifL antagonizes the transcriptional activator NifA in response to fixed nitrogen and molecular oxygen levels. However, transcriptional regulation of the nifLA operon of A. vinelandii itself is not fully understood. Using the S1 nuclease assay, we mapped the transcription start site of the nifLA operon, showing it to be similar to the σ54-dependent promoters. We a...

  4. Role of GlnK in NifL-Mediated Regulation of NifA Activity in Azotobacter vinelandii

    OpenAIRE

    Rudnick, Paul; Kunz, Christopher; Gunatilaka, Malkanthi K.; Hines, Eric R.; Kennedy, Christina

    2002-01-01

    In several diazotrophic species of Proteobacteria, PII signal transduction proteins have been implicated in the regulation of nitrogen fixation in response to NH4+ by several mechanisms. In Azotobacter vinelandii, expression of nifA, encoding the nif-specific activator, is constitutive, and thus, regulation of NifA activity by the flavoprotein NifL appears to be the primary level of nitrogen control. In vitro and genetic evidence suggests that the nitrogen response involves the PII-like GlnK ...

  5. A Proposed Role for the Azotobacter vinelandii NfuA Protein as an Intermediate Iron-Sulfur Cluster Carrier*

    OpenAIRE

    Bandyopadhyay, Sibali; Naik, Sunil G.; O'Carroll, Ina P.; Huynh, Boi-Hanh; Dean, Dennis R.; Johnson, Michael K.; Dos Santos, Patricia C.

    2008-01-01

    Iron-sulfur clusters ([Fe-S] clusters) are assembled on molecular scaffolds and subsequently used for maturation of proteins that require [Fe-S] clusters for their functions. Previous studies have shown that Azotobacter vinelandii produces at least two [Fe-S] cluster assembly scaffolds: NifU, required for the maturation of nitrogenase, and IscU, required for the general maturation of other [Fe-S] proteins. A. vinelandii also encodes a protein designated NfuA, which shares amino acid sequence ...

  6. Crystallization and preliminary crystallographic data of the PAS domain of the NifL protein from Azotobacter vinelandii.

    OpenAIRE

    Hefti, M.H.; Hendle, J.; Enroth, C.; Vervoort, J.J.M.; Tucker, P A

    2001-01-01

    The Azotobacter vinelandii NifL protein is a redox-sensing flavoprotein which inhibits the activity of the nitrogen-specific transcriptional activator NifA. The N-terminal PAS domain has been overexpressed in Escherichia coli and crystallized by the hanging-drop vapour-diffusion method. The crystal belongs to the rhombohedral space group R32, with unit-cell parameters a = b = 65.0, c = 157.3 Å, and has one molecule in the asymmetric unit. Native data were collected to 3.0 Å on the BW7B synchr...

  7. Analysis of Azotobacter vinelandii strains containing defined deletions in the nifD and nifK genes.

    OpenAIRE

    J. G. LI; Tal, S; Robinson, A. C.; Dang, V; Burgess, B. K.

    1990-01-01

    Strains of Azotobacter vinelandii which contain defined deletions within the nifD and nifK genes which encode, respectively, the alpha and beta subunits of the MoFe protein of nitrogenase were analyzed. When synthesized without its partner, the beta subunit accumulated as a soluble beta 4 tetramer. In contrast, when the alpha subunit was present without its partner, it accumulated primarily as an insoluble aggregate. The solubility of this protein was increased by the presence of a form of th...

  8. NifEN-B complex of Azotobacter vinelandii is fully functional in nitrogenase FeMo cofactor assembly

    OpenAIRE

    Wiig, Jared A.; Hu, Yilin; Ribbe, Markus W.

    2011-01-01

    Assembly of nitrogenase FeMoco is one of the key processes in bioinorganic chemistry. NifB and NifEN are two essential elements immediately adjacent to each other along the biosynthetic pathway of FeMoco. Previously, an 8Fe-precursor of FeMoco was identified on NifEN; however, the identity of the biosynthetic intermediate on NifB has remained elusive to date. Here, we present a combined biochemical and spectroscopic investigation of a His-tagged NifEN-B fusion protein of Azotobacter vinelandi...

  9. Spectroscopic and Functional Characterization of Iron-Sulfur Cluster-Bound Forms of Azotobacter vinelandii NifIscA†

    OpenAIRE

    Mapolelo, Daphne T.; Zhang, Bo; Naik, Sunil G.; Huynh, Boi Hanh; Johnson, Michael K.

    2012-01-01

    The mechanism of [4Fe-4S] cluster assembly on A-type Fe-S cluster assembly proteins, in general, and the specific role of NifIscA in the maturation of nitrogen fixation proteins are currently unknown. To address these questions, in vitro spectroscopic studies (UV–visible absorption/CD, resonance Raman and Mössbauer) have been used to investigate the mechanism of [4Fe-4S] cluster assembly on Azotobacter vinelandii NifIscA, and the ability of NifIscA to accept clusters from NifU and to donat...

  10. VnfY Is Required for Full Activity of the Vanadium-Containing Dinitrogenase in Azotobacter vinelandii

    OpenAIRE

    Rüttimann-Johnson, Carmen; Rubio, Luis M.; Dean, Dennis R.; Ludden, Paul W.

    2003-01-01

    A gene from Azotobacter vinelandii whose product exhibits primary sequence similarity to the NifY, NafY, NifX, and VnfX family of proteins, and which is required for effective V-dependent diazotrophic growth, was identified. Because this gene is located downstream from vnfK in an arrangement similar to the relative organization of the nifK and nifY genes, it was designated vnfY. A mutant strain having an insertion mutation in vnfY has 10-fold less vnf dinitrogenase activity and exhibits a gre...

  11. Growth and cyanide degradation of Azotobacter vinelandii in cyanide-containing wastewater system.

    Science.gov (United States)

    Koksunan, Sarawut; Vichitphan, Sukanda; Laopaiboon, Lakkana; Vichitphan, Kanit; Han, Jaehong

    2013-04-01

    Azotobacter vinelandii, a strict aerobic nitrogen-fixing bacterium, has been extensively studied with regard to the ability of N2-fixation due to its high expression of nitrogenase and fast growth. Because nitrogenase can also reduce cyanide to ammonia and methane, cyanide degradation by A. vinelandii has been studied for the application in the bioremediation of cyanide-contaminated wastewater. Cyanide degradation by A. vinelandii in NFS (nitrogen-free sucrose) medium was examined in terms of cell growth and cyanide reduction, and the results were applied for cyanide-contaminated cassava mill wastewater. From the NFS medium study in the 300 ml flask, it was found that A. vinelandii in the early stationary growth phase could reduce cyanide more rapidly than the cells in the exponential growth phase, and 84.4% of cyanide was degraded in 66 h incubation upon addition of 3.0 mM of NaCN. The resting cells of A. vinelandii could also reduce cyanide concentration by 90.4% with 3.0 mM of NaCN in the large-scale (3 L) fermentation with the same incubation time. Finally, the optimized conditions were applied to the cassava mill wastewater bioremediation, and A. vinelandii was able to reduce the cyanide concentration by 69.7% after 66 h in the cassava mill wastewater containing 4.0 mM of NaCN in the 3 L fermenter. Related to cyanide degradation in the cassava mill wastewater, nitrogenase was the responsible enzyme, which was confirmed by methane production. These findings would be helpful to design a practical bioremediation system for the treatment of cyanide-contaminated wastewater. PMID:23568214

  12. Physical and genetic map of the major nif gene cluster from Azotobacter vinelandii.

    Science.gov (United States)

    Jacobson, M R; Brigle, K E; Bennett, L T; Setterquist, R A; Wilson, M S; Cash, V L; Beynon, J; Newton, W E; Dean, D R

    1989-02-01

    Determination of a 28,793-base-pair DNA sequence of a region from the Azotobacter vinelandii genome that includes and flanks the nitrogenase structural gene region was completed. This information was used to revise the previously proposed organization of the major nif cluster. The major nif cluster from A. vinelandii encodes 15 nif-specific genes whose products bear significant structural identity to the corresponding nif-specific gene products from Klebsiella pneumoniae. These genes include nifH, nifD, nifK, nifT, nifY, nifE, nifN, nifX, nifU, nifS, nifV, nifW, nifZ, nifM, and nifF. Although there are significant spatial differences, the identified A. vinelandii nif-specific genes have the same sequential arrangement as the corresponding nif-specific genes from K. pneumoniae. Twelve other potential genes whose expression could be subject to nif-specific regulation were also found interspersed among the identified nif-specific genes. These potential genes do not encode products that are structurally related to the identified nif-specific gene products. Eleven potential nif-specific promoters were identified within the major nif cluster, and nine of these are preceded by an appropriate upstream activator sequence. A + T-rich regions were identified between 8 of the 11 proposed nif promoter sequences and their upstream activator sequences. Site-directed deletion-and-insertion mutagenesis was used to establish a genetic map of the major nif cluster.

  13. ACCUMULATION OF POLYHYDROXYALKANOIC ACIDS BY AZOTOBACTER CHROOCOCCUM MAL-201 FROM ORGANIC WASTE

    Directory of Open Access Journals (Sweden)

    Soma Pal Saha

    2013-08-01

    Full Text Available Azotobacter chroococcum MAL-201 (MTCC 3853, a free-living nitrogen-fixing bacterium accumulated intracellular poly(3-hydroxybutyric acid [P(3HB] accounting 69% of cell dry weight (CDW when grown in nitrogrn-free Stockdale medium containing 2% (w/v glucose. It also produced copolymer of poly(3-hydroxybutyrate co-3-hydroxyvalerate [P(3HB-co-3HV] using glucose as primary carbon source and valerate cas cosubstrate. To make the polymer production cost effective four types of waste material of different origin were tested for growth and polymer production. Stockdale medium supplemented with 1% (w/v waste materials failed to yield good growth and polymer accumulation. Two–step cultivation was adopted for better growth and enhanced polymer accumulation. The candy factory waste was most suitable for synthesis of P(3HB accounting 17.8 and 40.58% using single and two-step cultivation conditions respectively. Wastes of domestic and poultry origin produced P(3HB-co-3HV with 3HV content 28.8 and 21.5 mol% respectively in two-step cultivation. Increase concentration of these wastes resulted in further upliftment of 3HV content of polymer with reduced growth and polymer accumulation. However, at optimum incubation the strain MAL-201 cells accumulated P(3HB 48.5% of CDW (at 40h from candy factory waste and P(3HB-co-3HV 24.75 % of CDW with 3HV 34.65 mol % from domestic waste. Intrinsic viscosity, molecular weight and thermal degradation of the polymers accumulated in the cells grown in glucose, glucose with valerate and glucose with waste were compared.

  14. The "Gln-Type" Thiol Dioxygenase from Azotobacter vinelandii is a 3-Mercaptopropionic Acid Dioxygenase.

    Science.gov (United States)

    Pierce, Brad S; Subedi, Bishnu P; Sardar, Sinjinee; Crowell, Joshua K

    2015-12-29

    Cysteine dioxygenase (CDO) is a non-heme iron enzyme that catalyzes the O2-dependent oxidation of l-cysteine to produce cysteinesulfinic acid. Bacterial CDOs have been subdivided as either "Arg-type" or "Gln-type" on the basis of the identity of conserved active site residues. To date, "Gln-type" enzymes remain largely uncharacterized. It was recently noted that the "Gln-type" enzymes are more homologous with another thiol dioxygenase [3-mercaptopropionate dioxygenase (MDO)] identified in Variovorax paradoxus, suggesting that enzymes of the "Gln-type" subclass are in fact MDOs. In this work, a putative "Gln-type" thiol dioxygenase from Azotobacter vinelandii (Av) was purified to homogeneity and characterized. Steady-state assays were performed using three substrates [3-mercaptopropionic acid (3mpa), l-cysteine (cys), and cysteamine (ca)]. Despite comparable maximal velocities, the "Gln-type" Av enzyme exhibited a specificity for 3mpa (kcat/KM = 72000 M(-1) s(-1)) nearly 2 orders of magnitude greater than those for cys (110 M(-1) s(-1)) and ca (11 M(-1) s(-1)). Supporting X-band electron paramagnetic resonance (EPR) studies were performed using nitric oxide (NO) as a surrogate for O2 binding to confirm obligate-ordered addition of substrate prior to NO. Stoichimetric addition of NO to solutions of 3mpa-bound enzyme quantitatively yields an iron-nitrosyl species (Av ES-NO) with EPR features consistent with a mononuclear (S = (3)/2) {FeNO}(7) site. Conversely, two distinct substrate-bound conformations were observed in Av ES-NO samples prepared with cys and ca, suggesting heterogeneous binding within the enzymatic active site. Analytical EPR simulations are provided to establish the relative binding affinity for each substrate (3map > cys > ca). Both kinetic and spectroscopic results presented here are consistent with 3mpa being the preferred substrate for this enzyme. PMID:26624219

  15. Physical and genetic map of the major nif gene cluster from Azotobacter vinelandii.

    Science.gov (United States)

    Jacobson, M R; Brigle, K E; Bennett, L T; Setterquist, R A; Wilson, M S; Cash, V L; Beynon, J; Newton, W E; Dean, D R

    1989-02-01

    Determination of a 28,793-base-pair DNA sequence of a region from the Azotobacter vinelandii genome that includes and flanks the nitrogenase structural gene region was completed. This information was used to revise the previously proposed organization of the major nif cluster. The major nif cluster from A. vinelandii encodes 15 nif-specific genes whose products bear significant structural identity to the corresponding nif-specific gene products from Klebsiella pneumoniae. These genes include nifH, nifD, nifK, nifT, nifY, nifE, nifN, nifX, nifU, nifS, nifV, nifW, nifZ, nifM, and nifF. Although there are significant spatial differences, the identified A. vinelandii nif-specific genes have the same sequential arrangement as the corresponding nif-specific genes from K. pneumoniae. Twelve other potential genes whose expression could be subject to nif-specific regulation were also found interspersed among the identified nif-specific genes. These potential genes do not encode products that are structurally related to the identified nif-specific gene products. Eleven potential nif-specific promoters were identified within the major nif cluster, and nine of these are preceded by an appropriate upstream activator sequence. A + T-rich regions were identified between 8 of the 11 proposed nif promoter sequences and their upstream activator sequences. Site-directed deletion-and-insertion mutagenesis was used to establish a genetic map of the major nif cluster. PMID:2644218

  16. Sequence and molecular analysis of the nifL gene of Azotobacter vinelandii.

    Science.gov (United States)

    Blanco, G; Drummond, M; Woodley, P; Kennedy, C

    1993-08-01

    In both Klebsiella pneumoniae and Azotobacter vinelandii the nifL gene, which encodes a negative regulator of nitrogen fixation, lies immediately upstream of nifA. We have sequenced the A. vinelandii nifL gene and found that it is more homologous in its C-terminal domain to the histidine protein kinases (HPKs) than is K. pneumoniae NifL. In particular A. vinelandii NifL contains a conserved histidine at a position shown to be phosphorylated in other systems. Both NifL proteins are homologous in their N-termini to a part of the Halobacterium halobium bat gene product; Bat is involved in regulation of bacterio-opsin, the expression of which is oxygen sensitive. The same region showed homology to the haem-binding N-terminal domain of the Rhizobium meliloti fixL gene product, an oxygen-sensing protein. Like K. pneumoniae NifL, A. vinelandii NifL is shown here to prevent expression of nif genes in the presence of NH+4 or oxygen. The sequences found homologous in the C-terminal regions of NifL, FixL and Bat might therefore be involved in oxygen binding or sensing. An in-frame deletion mutation in the nifL coding region resulted in loss of repression by NH+4 and the mutant excreted high amounts of ammonia during nitrogen fixation, thus confirming a phenotype reported earlier for an insertion mutation. In addition, nifLA are cotranscribed in A. vinelandii as in K. pneumoniae, but expression from the A. vinelandii promoter requires neither RpoN nor NtrC. PMID:8231815

  17. Genes required for rapid expression of nitrogenase activity in Azotobacter vinelandii.

    Science.gov (United States)

    Curatti, Leonardo; Brown, Carolyn S; Ludden, Paul W; Rubio, Luis M

    2005-05-01

    Rnf proteins are proposed to form membrane-protein complexes involved in the reduction of target proteins such as the transcriptional regulator SoxR or the dinitrogenase reductase component of nitrogenase. In this work, we investigate the role of rnf genes in the nitrogen-fixing bacterium Azotobacter vinelandii. We show that A. vinelandii has two clusters of rnf-like genes: rnf1, whose expression is nif-regulated, and rnf2, which is expressed independently of the nitrogen source in the medium. Deletion of each of these gene clusters produces a time delay in nitrogen-fixing capacity and, consequently, in diazotrophic growth. Deltarnf mutations cause two distinguishable effects on the nitrogenase system: (i), slower nifHDK gene expression and (ii), impairment of nitrogenase function. In these mutants, dinitrogenase reductase activity is lowered, whereas dinitrogenase activity remains essentially unaltered. Further analysis indicates that deltarnf mutants accumulate an inactive and iron-deficient form of NifH because they have lower rates of incorporation of [4Fe-4S] into NifH. Deltarnf mutations also cause a noticeable decrease in aconitase activity; however, they do not produce general oxidative stress or modification of Fe metabolism in A. vinelandii. Our results suggest the existence of a redox regulatory mechanism in A. vinelandii that controls the rate of expression and maturation of nitrogenase by the activity of the Rnf protein complexes. rnf1 plays a major and more specific role in this scheme, but the additive effects of mutations in rnf1 and rnf2 indicate the existence of functional complementation between the two homologous systems. PMID:15845763

  18. Bioflocculant exopolysaccharide production by Azotobacter indicus using flower extract of Madhuca latifolia L.

    Science.gov (United States)

    Patil, Satish V; Salunkhe, Rahul B; Patil, Chandrashekhar D; Patil, Deepak M; Salunke, Bipinchandra K

    2010-10-01

    Efficacy of Azotobacter indicus ATCC 9540 strain for production exopolysaccharide (EPS) bioflocculant was investigated. Mahua flower extract (Madhuca latifolia L), a natural substrate at the concentration of 20 g L(-1), gave maximum recovery of EPS followed by sucrose and mannitol as compared to other carbon sources after 172 h. Yeast extract was found to be the most effective nitrogen source as compared to beef extract, sodium nitrate, ammonium sulfate, casein hydrolysate, and urea for the production of EPS. EPS production was increased in presence of nitrogen (5.51 g L(-1)) as compared to nitrogen-free medium (3.51 g L(-1)), and fermentation time was also reduced by 28 h. Maximum EPS production (6.10 g L(-1)) was found in the presence of 20 g L(-1) flower extract and 0.5 g L(-1) yeast extract containing Ashby's media with 180 rpm at 30 degrees C at 144 h, under controlled conditions in 2.5 L fermenter using optimized medium. The isolated EPS showed cation-dependent flocculating activity. Concentration of EPS played an important role in bioflocculating activity which increased in a concentration-dependent manner up to a certain limit, with the maximum flocculation of 72% at 500 mg L(-1) concentration but remained almost static after this concentration. Extracted polymer was characterized by different chemical tests, FT-IR spectroscopy, and TLC which showed presence of uronic acids, O-acetyl groups, and Orcinol with suggestive indication of alginate like polymer. This study suggests that use of M. latifolia L. flowers can be a potential alternative bioresource for production of exopolysaccharide. PMID:19921493

  19. Cloning of nifHD from Nostoc commune UTEX 584 and of a flanking region homologous to part of the Azotobacter vinelandii nifU gene.

    OpenAIRE

    Defrancesco, N; Potts, M

    1988-01-01

    The heterocystous cyanobacterium Nostoc commune UTEX 584 contains two nifH-like sequences (nifH1 and nifH2) in addition to nifHD. A region of DNA 1 kilobase upstream from the 5' end of nifH showed considerable sequence similarity to part of the published nifU sequences of Azotobacter vinelandii and Klebsiella pneumoniae.

  20. Studies on the incorporation of a covalently bound disubstituted phosphate residue into Azotobacter vinelandii flavodoxin in vivo.

    Science.gov (United States)

    Boylan, M H; Edmondson, D E

    1990-06-15

    Previous studies have shown the flavodoxin from Azotobacter vinelandii (strain OP, Berkeley) to contain a covalently bound disubstituted phosphate residue [Edmondson & James (1979) Proc. Natl. Acad. Sci. U.S.A. 76, 3786-3789]. Phosphorylation of the protein in vivo was investigated by the addition of [32P]phosphate to cells grown under N2-fixing conditions, under conditions of nif-gene repression and under conditions of nif-gene de-repression. Rocket immunoelectrophoresis of cell extracts showed an approx. 5-fold decrease in the concentration of flavodoxin expressed in cells grown in the presence of NH4+ as compared with those grown under N2-fixing conditions. A similar increase in flavodoxin concentration was observed on nif-gene de-repression. Incorporation of [32P]phosphate occurs only into newly synthesized flavodoxin, as observed on SDS/PAGE of immunoprecipitates of cell extracts. Western blots demonstrated no observable precursor forms of flavodoxin. These data provide conclusive evidence for the phosphorylation of Azotobacter strain OP flavodoxin in vivo and suggest that the covalently bound phosphate residue does not exchange with cellular phosphate pools. Thus the role of this phosphodiester cross-link is proposed to be structural rather than regulatory. PMID:2363708

  1. Complementation of a pleiotropic Nif-Gln regulatory mutant of Rhodospirillum rubrum by a previously unrecognized Azotobacter vinelandii regulatory locus.

    Science.gov (United States)

    Hu, C Z; Yoch, D C

    1990-01-01

    A spontaneous pleiotropic Nif- mutation in Rhodospirillum rubrum has been partially characterized biochemically and by complementation analysis with recombinant plasmids carrying Azotobacter vinelandii DNA in the vicinity of ORF12 [Jacobson et al. (1989) J. Bacteriol 171: 1017-1027]. In addition to being unable to grow on N2 as a nitrogen source the phenotypic characterization of this and other metronidazole enriched spontaneous mutants showed (a) no nitrogenase activity, (b) the absence of NifHDK polypeptides, (c) a slower growth rate on NH4+, (d) approximately 50% higher glutamine synthetase (GS) activity than the wild-type, which was repressible, (e) an inability to switch-off GS activity in response to an NH4+ up-shift, and (f) an inability to modify (32P-label) the GS polypeptide. The apparent relationship between the absence of nifHDK expression and the absence of GS adenylylation cannot be explained in terms of the current model for nif gene regulation. However, R. rubrum transconjugants receiving A. vinelandii DNA which originated immediately upstream from nifH, restored all aspects of the wild-type phenotype. These data suggest a here-to-fore unrecognized relationship between nif expression and GS switch-off (adenylylation) activity, and the existence of a previously unidentified regulatory locus in Azotobacter that complements this mutation. PMID:1980582

  2. Spectroscopic and functional characterization of iron-bound forms of Azotobacter vinelandii (Nif)IscA.

    Science.gov (United States)

    Mapolelo, Daphne T; Zhang, Bo; Naik, Sunil G; Huynh, Boi Hanh; Johnson, Michael K

    2012-10-16

    The ability of Azotobacter vinelandii(Nif)IscA to bind Fe has been investigated to assess the role of Fe-bound forms in NIF-specific Fe-S cluster biogenesis. (Nif)IscA is shown to bind one Fe(III) or one Fe(II) per homodimer and the spectroscopic and redox properties of both the Fe(III)- and Fe(II)-bound forms have been characterized using the UV-visible absorption, circular dichroism, and variable-temperature magnetic circular dichroism, electron paramagnetic resonance, Mössbauer and resonance Raman spectroscopies. The results reveal a rhombic intermediate-spin (S = 3/2) Fe(III) center (E/D = 0.33, D = 3.5 ± 1.5 cm(-1)) that is most likely 5-coordinate with two or three cysteinate ligands and a rhombic high spin (S = 2) Fe(II) center (E/D = 0.28, D = 7.6 cm(-1)) with properties similar to reduced rubredoxins or rubredoxin variants with three cysteinate and one or two oxygenic ligands. Iron-bound (Nif)IscA undergoes reversible redox cycling between the Fe(III)/Fe(II) forms with a midpoint potential of +36 ± 15 mV at pH 7.8 (versus NHE). l-Cysteine is effective in mediating release of free Fe(II) from both the Fe(II)- and Fe(III)-bound forms of (Nif)IscA. Fe(III)-bound (Nif)IscA was also shown to be a competent iron source for in vitro NifS-mediated [2Fe-2S] cluster assembly on the N-terminal domain of NifU, but the reaction occurs via cysteine-mediated release of free Fe(II) rather than direct iron transfer. The proposed roles of A-type proteins in storing Fe under aerobic growth conditions and serving as iron donors for cluster assembly on U-type scaffold proteins or maturation of biological [4Fe-4S] centers are discussed in light of these results.

  3. Nif- phenotype of Azotobacter vinelandii UW97. Characterization and mutational analysis.

    Science.gov (United States)

    Pulakat, L; Hausman, B S; Lei, S; Gavini, N

    1996-01-26

    We have identified the molecular basis for the nitrogenase negative phenotype exhibited by Azotobacter vinelandii UW97. This strain was initially isolated following nitrosoguanidine mutagenesis. Recently, it was shown that this strain lacks the Fe protein activity, which results in the synthesis of a FeMo cofactor-deficient apodinitrogenase. Activation of this apodinitrogenase requires the addition of both MgATP and wild-type Fe protein to the crude extracts made by A. vinelandii UW97 (Allen, R.M., Homer, M.J., Chatterjee R., Ludden, P.W., Roberts, G.P., and Shah, V.K. (1993) J. Biol. Chem. 268 23670-23674). Earlier, we proposed the sequence of events in the MoFe protein assembly based on the biochemical and spectroscopic analysis of the purified apodinitrogenase from A. vinelandii DJ54 (Gavini, N., Ma, L., Watt, G., and Burgess, B.K. (1994) Biochemistry 33, 11842-11849). Taken together, these results imply that the assembly process of apodinitrogenase is arrested at the same step in both of these strains. Since A. vinelandii DJ54 is a delta nifH strain, this strain is not useful in identifying the features of the Fe protein involved in the MoFe protein assembly. Here, we report a systematic analysis of an A. vinelandii UW97 mutant and show that, unlike A. vinelandii DJ54, the nifH gene of A. vinelandii UW97 has no deletion in either coding sequence or the surrounding sequences. The specific mutation responsible for the Nif- phenotype of A. vinelandii UW97 is the substitution of a non-conserved serine at position 44 of the Fe protein by a phenylalanine as shown by DNA sequencing. Furthermore, oligonucleotide site-directed mutagenesis was employed to confirm that the Nif- phenotype in A. vinelandii UW97 is exclusively due to the substitution of the Fe protein residue serine 44 by phenylalanine. By contrast, replacing Ser-44 with alanine did not affect the Nif phenotype of A. vinelandii. Therefore, it seems that the Nif- phenotype of A. vinelandii UW97 is caused by a

  4. Spectroscopic and functional characterization of iron-bound forms of Azotobacter vinelandii (Nif)IscA.

    Science.gov (United States)

    Mapolelo, Daphne T; Zhang, Bo; Naik, Sunil G; Huynh, Boi Hanh; Johnson, Michael K

    2012-10-16

    The ability of Azotobacter vinelandii(Nif)IscA to bind Fe has been investigated to assess the role of Fe-bound forms in NIF-specific Fe-S cluster biogenesis. (Nif)IscA is shown to bind one Fe(III) or one Fe(II) per homodimer and the spectroscopic and redox properties of both the Fe(III)- and Fe(II)-bound forms have been characterized using the UV-visible absorption, circular dichroism, and variable-temperature magnetic circular dichroism, electron paramagnetic resonance, Mössbauer and resonance Raman spectroscopies. The results reveal a rhombic intermediate-spin (S = 3/2) Fe(III) center (E/D = 0.33, D = 3.5 ± 1.5 cm(-1)) that is most likely 5-coordinate with two or three cysteinate ligands and a rhombic high spin (S = 2) Fe(II) center (E/D = 0.28, D = 7.6 cm(-1)) with properties similar to reduced rubredoxins or rubredoxin variants with three cysteinate and one or two oxygenic ligands. Iron-bound (Nif)IscA undergoes reversible redox cycling between the Fe(III)/Fe(II) forms with a midpoint potential of +36 ± 15 mV at pH 7.8 (versus NHE). l-Cysteine is effective in mediating release of free Fe(II) from both the Fe(II)- and Fe(III)-bound forms of (Nif)IscA. Fe(III)-bound (Nif)IscA was also shown to be a competent iron source for in vitro NifS-mediated [2Fe-2S] cluster assembly on the N-terminal domain of NifU, but the reaction occurs via cysteine-mediated release of free Fe(II) rather than direct iron transfer. The proposed roles of A-type proteins in storing Fe under aerobic growth conditions and serving as iron donors for cluster assembly on U-type scaffold proteins or maturation of biological [4Fe-4S] centers are discussed in light of these results. PMID:23003563

  5. Molecular Study of nifH1, nifH2, nifH3, nifU, nifV, VF Genes and Classical Approach Cared out to Identification of Azotobacter chrococcum from Soil

    OpenAIRE

    Adel Kamal Khider

    2012-01-01

    The present study aimed to compare classical approach with molecular based method for identification of Azotobacter chrococcum from soil samples. A. chrococcum was isolated from soil source in Erbil city, Iraq. They were cultivated under laboratory conditions using Nitrogen free Azotobacter specific medium. A. chrococcum was present in all soil samples. result shows that A. chrococcum were rod shape, motility occur through the use of peritrichous flagella, cysts-forming, positive to oxidase, ...

  6. APLICACIÓN DE AZOTOBACTER CHROOCOCCUM EN LA PRODUCCIÓN DE PLÁNTULAS DE TABACO NEGRO

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    Yarilis León González

    2012-01-01

    en la producción de plántulas de tabaco. Los resultados mostraron que con la aplicación de Azotobacter chroococcum, se lograron mejorar las características morfológicas de las plántulas, como el diámetro y longitud del tallo y la masa fresca y seca total. Además se redujo el ciclo del semillero en siete días. La variante biofertilizada tuvo el mejor comportamiento económico en comparación con la testigo, con valores de utilidades por hectárea de $ 23 344,9, rentabilidad de 127,05 % y costos de $ 0,44 por cada peso recibido.

  7. Peptidyl-prolyl cis/trans isomerase-independent functional NifH mutant of Azotobacter vinelandii.

    Science.gov (United States)

    Gavini, Nara; Tungtur, Sudheer; Pulakat, Lakshmi

    2006-08-01

    Peptidyl-prolyl cis/trans isomerases (PPIases) play a pivotal role in catalyzing the correct folding of many prokaryotic and eukaryotic proteins that are implicated in a variety of biological functions, ranging from cell cycle regulation to bacterial infection. The nif accessory protein NifM, which is essential for the biogenesis of a functional NifH component of nitrogenase, is a PPIase. To understand the nature of the molecular signature that defines the NifM dependence of NifH, we screened a library of nifH mutants in the nitrogen-fixing bacterium Azotobacter vinelandii for mutants that acquired NifM independence. Here, we report that NifH can acquire NifM independence when the conserved Pro258 located in the C-terminal region of NifH, which wraps around the other subunit in the NifH dimer, is replaced by serine. PMID:16885471

  8. STUDY OF CATECHOL SIDEROPHORE FROM A NEWLY ISOLATED Azotobacter sp. SUP-III FOR ITS ANTIMICROBIAL PROPERTY

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    Shirishkumar Supanekar

    2013-12-01

    Full Text Available In present study, the isolate SUP III showed maximum siderophore production in Burk’s medium with maximum 43% decolorization of CAS reagent in liquid CAS assay. Optimum yield of siderophore was obtained at pH 7.2. The culture was identified as Azotobacter sp. based on 16S rRNA gene sequencing and phylogenetic studies using MEGA 4. The siderophore extraction and purification was achieved using XAD2 column. Colorimetric reactions prove that purified siderophore is of catecholate type. Fourier – transform infrared (FTIR analysis showed peaks at 3402 cm-1, 1652 cm-1, 1032 cm-1, and 1112 cm-1 which supported the colorimetric results. Antimicrobial activity of the purified siderophore showed significant zones of inhibition for some pathogens. This type of study has not been previously reported in this area.

  9. Nucleotide sequence and mutational analysis of the structural genes (anfHDGK) for the second alternative nitrogenase from Azotobacter vinelandii.

    Science.gov (United States)

    Joerger, R D; Jacobson, M R; Premakumar, R; Wolfinger, E D; Bishop, P E

    1989-02-01

    The nucleotide sequence of a region of the Azotobacter vinelandii genome exhibiting sequence similarity to nifH has been determined. The order of open reading frames within this 6.1-kilobase-pair region was found to be anfH (alternative nitrogen fixation, nifH-like gene), anfD (nifD-like gene), anfG (potentially encoding a protein similar to the product of vnfG from Azotobacter chroococcum), anfK (nifK-like gene), followed by two additional open reading frames. The 5'-flanking region of anfH contains a nif promoter similar to that found in the A. vinelandii nifHDK gene cluster. The presumed products of anfH, anfD, and anfK are similar in predicted Mr and pI to the previously described subunits of nitrogenase 3. Deletion plus insertion mutations introduced into the anfHDGK region of wild-type strain A. vinelandii CA resulted in mutant strains that were unable to grow in Mo-deficient, N-free medium but grew in the presence of 1 microM Na2MoO4 or V2O5. Introduction of the same mutations into the nifHDK deletion strain CA11 resulted in strains that grew under diazotrophic conditions only in the presence of vanadium. The lack of nitrogenase 3 subunits in these mutant strains was demonstrated through two-dimensional gel analysis of protein extracts from cells derepressed for nitrogenase under Mo and V deficiency. These results indicate that anfH, anfD, and anfK encode structural proteins for nitrogenase 3. PMID:2644222

  10. Regulated expression of the nifM of Azotobacter vinelandii in response to molybdenum and vanadium supplements in Burk's nitrogen-free growth medium.

    Science.gov (United States)

    Lei, S; Pulakat, L; Gavini, N

    1999-10-14

    Azotobacter is a diazotrophic bacterium that harbors three genetically distinct nitrogenases referred to as nif, vnf, and anf systems. The nifM is an accessory gene located in the nif gene cluster and is transcriptionally regulated by the NifA. However, Azotobacter mutants that lack NifA are known to synthesize functional NifM and this accessory protein is known to be needed for the activity of nitrogenase-2 and nitrogenase-3. To determine how the transcription of nifM is regulated when Azotobacter is grown under conditions in which nitrogenase-2 or nitrogenase-3 is expressed, we generated an Azotobacter vinelandii strain that carries a nifM:lacZ-kanamycin resistance gene cassette in its chromosome. In this strain the nifM open reading frame was disrupted by the presence of a lacZ-kanamycin resistance gene cassette so that it could not produce active NifM. Moreover, the lacZ gene was placed under the transcriptional control elements of the nifM gene so that the lacZ expression could be used as a marker to determine the extent of expression of the nifM gene under different growth conditions. Our results show that this strain was unable to grow in Burk's nitrogen-free medium supplemented with either molybdenum or vanadium or lacking both metals suggesting that in the absence of functional NifM none of the nitrogenases were active. It was also found that the nifM expression was differentially regulated when the A. vinelandii cells were grown under conditions that activate nitrogenase-2 and nitrogenase-3, as determined by liquid beta-galactosidase activity measurements. These results suggest that the transcriptional activators, VnfA and AnfA, may regulate the nifM expression. PMID:10527862

  11. mRNA Extraction and Reverse Transcription-PCR Protocol for Detection of nifH Gene Expression by Azotobacter vinelandii in Soil

    OpenAIRE

    Bürgmann, Helmut; Widmer, Franco; Sigler, William V.; Zeyer, Josef

    2003-01-01

    The study of free-living nitrogen-fixing organisms in bulk soil is hampered by the great diversity of soil microbial communities and the difficulty of relating nitrogen fixation activities to individual members of the diazotroph populations. We developed a molecular method that allows analysis of nifH mRNA expression in soil in parallel with determinations of nitrogen-fixing activity and bacterial growth. In this study, Azotobacter vinelandii growing in sterile soil and liquid culture served ...

  12. Azotobacter vinelandii NIFL is a flavoprotein that modulates transcriptional activation of nitrogen-fixation genes via a redox-sensitive switch.

    OpenAIRE

    Hill, S.; Austin, S; Eydmann, T.; Jones, T.; Dixon, R

    1996-01-01

    The NIFL regulatory protein controls transcriptional activation of nitrogen fixation (nif) genes in Azotobacter vinelandii by direct interaction with the enhancer binding protein NIFA. Modulation of NIFA activity by NIFL, in vivo occurs in response to external oxygen concentration or the level of fixed nitrogen. Spectral features of purified NIFL and chromatographic analysis indicate that it is a flavoprotein with FAD as the prosthetic group, which undergoes reduction in the presence of sodiu...

  13. Comparative organization of nitrogen fixation-specific genes from Azotobacter vinelandii and Klebsiella pneumoniae: DNA sequence of the nifUSV genes.

    OpenAIRE

    Beynon, J; Ally, A; Cannon, M; Cannon, F.; Jacobson, M.; Cash, V; Dean, D.

    1987-01-01

    In the facultative anaerobe Klebsiella pneumoniae 17 nitrogen fixation-specific genes (nif genes) have been identified. Homologs to 12 of these genes have now been isolated from the aerobic diazotroph Azotobacter vinelandii. Comparative studies have indicated that these diverse microorganisms share striking similarities in the genetic organization of their nif genes and in the primary structure of their individual nif gene products. In this study the complete nucleotide sequence of the nifUSV...

  14. Genetic analysis of nifF and nifA and site-directed mutagenesis of nifE in Azotobacter vinelandii

    OpenAIRE

    Bennett, Lisa Tracy

    1989-01-01

    Nitrogenase-catalyzed nitrogen fixation is a biochemically and genetically complex process requiring the participation of a number of different nif (nitrogen fixation) gene products. The nifF (electron transport), nifA (nif gene regulation) and nifE (FeMo-cofactor biosynthesis) genes from Azotobacter vinelandii were genetically analyzed. The nucleotide sequence of the nifF gene, which encodes a flavodoxin, was determined. Specific mutation strains indicated that in A vineland...

  15. Evaluación de la estabilidad de Trichoderma sp. y Azotobacter sp. conservados por diferentes métodos

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    Yvonne Sarmiento Rangel

    2013-06-01

    Full Text Available Título en ingles: Evaluation of the stability of Trichoderma sp. and Azotobacter sp.  preserved by different methods Resumen En el Laboratorio de Microbiología Aplicada de la Universidad Francisco de Paula Santander (Cúcuta, Colombia constantemente ingresan al Banco de Cepas, cultivos microbianos de interés biotecnológico, especialmente del sector agrícola, los cuales son utilizados en las actividades de docencia e investigación.  Por esta razón, existe el interés de mantener viables a través del tiempo estos cultivos microbianos, para lo cual se realizó en esta investigación, la evaluación de la estabilidad de los aislados de Trichoderma sp. y Azotobacter sp., utilizando  las técnicas de conservación  en viales con solución salina estéril (0,85% NaCl en refrigeración (4°C y temperatura ambiente (30°C, suelo estéril en refrigeración (4°C, comparados con la metodología de repiques sucesivos como tratamiento control.  Los resultados no mostraron diferencias significativas según el Test de Duncan (P≤0,05 en  la tasa de supervivencia microbiana entre los métodos de conservación. Sin embargo, se observó en las técnicas de viales con solución salina  estéril y suelo estéril mantenidos en refrigeración, mayor estabilidad en la concentración celular durante los cuatros meses de evaluación, sin registrar contaminación en los cultivos.  Así mismo, se registró un óptimo crecimiento macroscópico de los cultivos microbianos y sus características microscópicas se mantuvieron estables en estos dos métodos de conservación.  Por esta razón, se seleccionaron como técnicas de conservación de estos microorganismos, teniendo en cuenta además, ventajas como la facilidad de la técnica, disponibilidad de equipos, materiales y personal con los que se cuenta en el laboratorio.  Palabras clave: banco de cepas, conservación de microorganismos, viabilidad celular, Trichoderma sp., Azotobacter sp. Abstract In the

  16. Evaluation of three methods for preservation of Azotobacter: freeze-drying, cryopreservation, and immobilization in dry polymers

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    Daniel Fernando Rojas Tapias

    2013-04-01

    Full Text Available Because the use of bacteria for biotechnological processes requires maintaining their viability and geneticstability, preserving them becomes essential. Here, we evaluated three preservation methods for A.chroococcum C26 and A. vinelandii C27; preservation methods: cryopreservation and immobilization in drypolymers for 60 days, and freeze-drying for 30. We evaluated their efficiency by counting viable cells andmeasuring nitrogen fixation activity. Additionally, we assessed the effect of three protective agents forfreeze-drying, three for cryopreservation, and four polymers. Freeze-drying proved the best technique tomaintain viability and activity, followed by immobilization and cryopreservation. Bacterial nitrogen fixingability remained unchanged using the freeze-drying method, and bacterial survival exceeded 80%; S/BSAwas the best protective agent. Immobilization maintained bacterial survival over 80%, but nitrogen fixationwas decreased by 20%. Lastly, cryopreservation resulted in a dramatic loss of viability for C26 (BSRapprox. 70%, whereas C27 was well preserved. Nitrogen fixation for both strains decreased regardless ofthe cryoprotective agent used (P < 0.05. In conclusion, the success of Azotobacter preservation methodsdepend on the technique, the protective agent, and the strain used. Our results also indicated that freezedryingusing S/BSA is the best technique to preserve bacteria of this genus.

  17. Characterization of a spontaneous mutant of Azotobacter vinelandii in which vanadium-dependent nitrogen fixation is not inhibited by molybdenum.

    Science.gov (United States)

    Bageshwar, U K; Raina, R; Das, H K

    1998-05-01

    A spontaneous mutant derivative of Azotobacter vinelandii CA12 (delta nif HDK), which vanadium-dependent nitrogen fixation is not inhibited by molybdenum (A. vinelandii CARR), grows profusely on BNF-agar containing 1 microM Na2MoO4, alone or supplemented with 1 microM V2O5. The expression of A. vinelandii vnfH::lacZ and vnfA::lacZ fusions in A. vinelandii CARR was not inhibited by 1 mM Na2MoO4, whereas molybdenum at much lower concentration inhibited the expression of vnfH::lacZ and vnfA::lacZ fusions in A. vinlandii CA12. The mutant also exhibited normal acetylene reduction activity in the presence of 1 microM Na2MoO4. The expression of A. vinelandii nifH::lacZ fusion in A. vinelandii CARR was low even though the cells were cultured under non-repressing conditions with urea as nitrogen source in the presence of Na2MoO4. The molybdenum content of A. vinelandii CARR cells was found to be about one-fourth that of A. vinelandii CA12. No nitrate reductase activity could be detected in A. vinelandii CARR when the cells were cultured in the presence of 10 microM Na2MoO4, whereas A. vinelandii CA12 exhibited some activity even with 100 pM Na2MoO4. PMID:9595678

  18. A new type of metalloprotein: The Mo storage protein from azotobacter vinelandii contains a polynuclear molybdenum-oxide cluster.

    Science.gov (United States)

    Fenske, Dirk; Gnida, Manuel; Schneider, Klaus; Meyer-Klaucke, Wolfram; Schemberg, Jörg; Henschel, Volker; Meyer, Anne-Katrin; Knöchel, Arndt; Müller, Achim

    2005-02-01

    Azotobacter vinelandii is a diazotrophic bacterium characterized by the outstanding capability of storing Mo in a special storage protein, which guarantees Mo-dependent nitrogen fixation even under growth conditions of extreme Mo starvation. The Mo storage protein is constitutively synthesized with respect to the nitrogen source and is regulated by molybdenum at an extremely low concentration level (0-50 nM). This protein was isolated as an alpha4beta4 octamer with a total molecular mass of about 240 kg mol(-1) and its shape was determined by small-angle X-ray scattering. The genes of the alpha and beta subunits were unequivocally identified; the amino acid sequences thereby determined reveal that the Mo storage protein is not related to any other known molybdoprotein. Each protein molecule can store at least 90 Mo atoms. Extended X-ray absorption fine-structure spectroscopy identified a metal-oxygen cluster bound to the Mo storage protein. The binding of Mo (biosynthesis and incorporation of the cluster) is dependent on adenosine triphosphate (ATP); Mo release is ATP-independent but pH-regulated, occurring only above pH 7.1. This Mo storage protein is the only known noniron metal storage system in the biosphere containing a metal-oxygen cluster.

  19. Roles of RpoS and PsrA in cyst formation and alkylresorcinol synthesis in Azotobacter vinelandii.

    Science.gov (United States)

    Cocotl-Yañez, Miguel; Sampieri, Arístides; Moreno, Soledad; Núñez, Cinthia; Castañeda, Miguel; Segura, Daniel; Espín, Guadalupe

    2011-06-01

    Azotobacter vinelandii is a soil bacterium that undergoes differentiation to form cysts that are resistant to desiccation. Upon induction of cyst formation, the bacterium synthesizes alkylresorcinols that are present in cysts but not in vegetative cells. Alternative sigma factors play important roles in differentiation. In A. vinelandii, AlgU (sigma E) is involved in controlling the loss of flagella upon induction of encystment. We investigated the involvement of the sigma factor RpoS in cyst formation in A. vinelandii. We analysed the transcriptional regulation of the rpoS gene by PsrA, the main regulator of rpoS in Pseudomonas species, which are closely related to A. vinelandii. Inactivation of rpoS resulted in the inability to form cysts resistant to desiccation and to produce cyst-specific alkylresorcinols, whereas inactivation of psrA reduced by 50 % both production of alkylresorcinols and formation of cysts resistant to desiccation. Electrophoretic mobility shift assays revealed specific binding of PsrA to the rpoS promoter region and that inactivation of psrA reduced rpoS transcription by 60 %. These results indicate that RpoS and PsrA are involved in regulation of encystment and alkylresorcinol synthesis in A. vinelandii.

  20. SMALL SCALE PRODUCTION AND CHARACTERIZATION OF ALGINATE FROM AZOTOBACTER CHROOCOCCUM USING DIFFERENT SUBSTRATES UNDER VARIOUS STRESS CONDITIONS

    Directory of Open Access Journals (Sweden)

    Gayathri Pandurangan

    2013-03-01

    Full Text Available Alginates form an important family of biopolymers. These are linear polysaccharides composed of variable amounts of (1–4-β-D-mannuronic acid and its epimer, α-L-guluronic acid. Currently, commercial alginates are extracted from marine brown algae. Considering the merits of bacterial alginates, optimal fermentation conditions aiming at the maximization of alginate using bacterium Azotobacter chroococcum from different substrates were examined. Whey, molasses, ammonium nitrate, starch, yeast extract, butanol, mannitol, and glucose have been used. The alginate obtained from whey (45.15%, ammonium nitrate (46.02% and butanol (47.3% varied. Among the physical stress conditions, the production of alginate was maximum at heat shock 50 0C for 30min (42.96% followed by 41.29% on UV radiation for 10 min. At pH 7 and 8 the alginate produced was 44.63% and 46.64% respectively. Carbazole reagent was used to recognize alginate; it was lyophilized and quantitated by gas chromatography.

  1. PERFORMANCE AND PERSISTENCE OF GREEN FLUORESCENT PROTEIN (gfp) MARKED AZOTOBACTER CHROOCOCCUM IN STERILIZED AND UNSTERILIZED WHEAT RHIZOSPHERIC SOIL

    Institute of Scientific and Technical Information of China (English)

    SINGH R; KUMAR V; SHARMA S; BEHL RK; SINGH BP; NARULA N

    2005-01-01

    The persistence and performance (growth promoting potential) of green fluorescent protein (gfp) marked Azotobacter chroococcum strain ABR 4G were studied in sterilized and unsterilized wheat rhizospheric soil. The gfp was integrated via Tn 5 transposition into A. chroococcum chromosome and the resultant gfp marked colonies were identified by green fluorescent emission under UV light. The gfp was stably maintained in A. chroococcum and the gfp insertion had no apparent adverse effect on the growth promoting properties of the marked soil isolate ABR 4G. The growth promoting properties ( nitrogen fixation, ammonia excretion, phosphate solubilization and IAA production) of the parent soil isolate and the gfp marked strain were found to be almost the same. All the quantitative wheat plant traits were significantly influenced by inoculation of A. chroococcum ABR 4G strain in sterilized and unsterilized soil. Inoculated bacterial counts increased gradually in wheat rhizosphere, reached maximum on 60th d and declined on 80th d. Fertility levels also affected survival of marked strain and the survival was comparable in sterilized and unsterilized soil. The growth promoting properties were also determined from the marked strain reisolated from wheat rhizosphere in both types of soil. Fig 1, Tab 2, Ref 22

  2. Mutant Forms of the Azotobacter vinelandii Transcriptional Activator NifA Resistant to Inhibition by the NifL Regulatory Protein

    OpenAIRE

    Reyes-Ramirez, Francisca; Little, Richard; Dixon, Ray

    2002-01-01

    The Azotobacter vinelandii σ54-dependent transcriptional activator protein NifA is regulated by the NifL protein in response to redox, carbon, and nitrogen status. Under conditions inappropriate for nitrogen fixation, NifL inhibits transcription activation by NifA through the formation of the NifL-NifA protein complex. NifL inhibits the ATPase activity of the central AAA+ domain of NifA required to drive open complex formation by σ54-RNA polymerase and may also inhibit the activator-polymeras...

  3. Activity, reconstitution, and accumulation of nitrogenase components in Azotobacter vinelandii mutant strains containing defined deletions within the nitrogenase structural gene cluster.

    OpenAIRE

    Robinson, A. C.; Burgess, B. K.; Dean, D R

    1986-01-01

    The Azotobacter vinelandii genes encoding the nitrogenase structural components are clustered and ordered: nifH (Fe protein)-nifD (MoFe protein alpha subunit)-nifK (MoFe protein beta subunit). In this study various A. vinelandii mutant strains which contain defined deletions within the nitrogenase structural genes were isolated and studied. Mutants deleted for the nifD or nifK genes were still able to accumulate significant amounts of the unaltered MoFe protein subunit as well as active Fe pr...

  4. A crucial arginine residue is required for a conformational switch in NifL to regulate nitrogen fixation in Azotobacter vinelandii

    OpenAIRE

    Martinez-Argudo, Isabel; Little, Richard; Dixon, Ray

    2004-01-01

    NifL is an antiactivator that tightly regulates transcription of genes required for nitrogen fixation in Azotobacter vinelandii by controlling the activity of its partner protein NifA, a member of the family of σ54-dependent transcriptional activators. Although the C-terminal region of A. vinelandii NifL shows homology to the transmitter domains of histidine protein kinases, signal transduction between NifL and NifA is conveyed by means of protein-protein interactions rather than by phosphory...

  5. Nucleotide sequence and genetic analysis of the Azotobacter chroococcum nifUSVWZM gene cluster, including a new gene (nifP) which encodes a serine acetyltransferase.

    OpenAIRE

    Evans, D J; Jones, R; Woodley, P R; Wilborn, J R; Robson, R.L.

    1991-01-01

    Nucleotide sequence was obtained for a region of 7,099 bp spanning the nifU, nifS, nifV, nifW, nifZ, and nifM genes from Azotobacter chroococcum. Chromosomal mutations constructed at several sites within the locus confirmed a requirement for this region for expression of the molybdenum nitrogenase in this organism. The genes are tightly clustered and ordered as in Klebsiella pneumoniae except for two additional open reading frames (ORFs) between nifV and nifW. The arrangement of genes in A. c...

  6. Expression from the nifB promoter of Azotobacter vinelandii can be activated by NifA, VnfA, or AnfA transcriptional activators.

    OpenAIRE

    Drummond, M; Walmsley, J.; Kennedy, C

    1996-01-01

    In Azotobacter vinelandii, nifB is required for the activity of all three nitrogenases. Expression of a nifB-lacZ fusion was examined to determine which regulatory gene products are important for nifB expression and how its transcription is regulated in response to metals. In all conditions, expression in A. vinelandii was eliminated by an rpoN mutation, confirming the absolute requirement for sigma N. In the wild type, nifB-lacZ expression was approximately twofold higher in cells grown with...

  7. Second gene (nifH*) coding for a nitrogenase iron protein in Azotobacter chroococcum is adjacent to a gene coding for a ferredoxin-like protein

    OpenAIRE

    Robson, Robert; Woodley, Paul; Jones, Robert

    1986-01-01

    Azotobacter chroococcum MCD1 contains a cluster of nitrogen fixation (nif) genes coding for the structural polypeptides for nitrogenase (nifH for the Fe-protein and nifD and nifK for the MoFe protein) and a second sequence in the genome homologous to nifH. DNA fragments bearing this second nifH-like sequence were cloned and the DNA sequence around the homologous region determined. Two open reading frames were identified in this region. One codes for a protein of 289 amino acid residues and is...

  8. Role of Escherichia coli Nitrogen Regulatory Genes in the Nitrogen Response of the Azotobacter vinelandii NifL-NifA Complex

    OpenAIRE

    Reyes-Ramirez, Francisca; Little, Richard; Dixon, Ray

    2001-01-01

    The redox-sensing flavoprotein NifL inhibits the activity of the nitrogen fixation (nif)-specific transcriptional activator NifA in Azotobacter vinelandii in response to molecular oxygen and fixed nitrogen. Although the mechanism whereby the A. vinelandii NifL-NifA system responds to fixed nitrogen in vivo is unknown, the glnK gene, which encodes a PII-like signal transduction protein, has been implicated in nitrogen control. However, the precise function of A. vinelandii glnK in this respons...

  9. Transformation of Azotobacter vinelandii OP with a broad host range plasmid containing a cloned chromosomal nif-DNA marker.

    Science.gov (United States)

    Bingle, W H

    1988-05-01

    The non-nitrogen-fixing (Nif-) strain UW10 of Azotobacter vinelandii OP (UW) was naturally induced to competence and transformed with broad host range plasmid pKT210 containing the cloned wild-type nif-10 locus from A. vinelandii UW (Nif+); this marker was unable to complement the nif-10 mutation in trans, but could through recombination with the chromosome. The most frequent type of transformation event observed was recombination between the homologous regions of the plasmid and chromosome (producing Nif+ transformants) with loss of the plasmid vector. At a substantially lower frequency, transformants expressing the plasmid-encoded antibiotic resistance determinants were isolated which were phenotypically Nif-. Agarose gel electrophoresis showed that these transformants contained a plasmid migrating with the same mobility as the original donor plasmid. During culture these transformants acquired a Nif+ phenotype without the loss of the plasmid, as judged by the use of a hybridization probe specific for the cloned nif-DNA fragment. These data indicate that plasmids carrying sequences homologous to chromosomal sequences could be maintained in recombination-proficient A. vinelandii UW. The introduction of plasmids containing sequences homologous to chromosomal sequences was facilitated by prelinearization of the plasmid using a restriction endonuclease generating cohesive ends. Because the site of linearization could be chosen outside the region of shared homology, it was unlikely that the route of plasmid establishment occurred via a homology-facilitated transformation mechanism. The data also indicated that A. vinelandii UW could harbor broad host range cloning vectors based on plasmid RSF1010 without significant impairment of its nitrogen-fixation ability.

  10. Modeling and Re-Engineering of Azotobacter vinelandii Alginate Lyase to Enhance Its Catalytic Efficiency for Accelerating Biofilm Degradation.

    Directory of Open Access Journals (Sweden)

    Chul Ho Jang

    Full Text Available Alginate is known to prevent elimination of Pseudomonas aeruginosa biofilms. Alginate lyase (AlgL might therefore facilitate treatment of Pseudomonas aeruginosa-infected cystic fibrosis patients. However, the catalytic activity of wild-type AlgL is not sufficiently high. Therefore, molecular modeling and site-directed mutagenesis of AlgL might assist in enzyme engineering for therapeutic development. AlgL, isolated from Azotobacter vinelandii, catalyzes depolymerization of alginate via a β-elimination reaction. AlgL was modeled based on the crystal structure template of Sphingomonas AlgL species A1-III. Based on this computational analysis, AlgL was subjected to site-directed mutagenesis to improve its catalytic activity. The kcat/Km of the K194E mutant showed a nearly 5-fold increase against the acetylated alginate substrate, as compared to the wild-type. Double and triple mutants (K194E/K245D, K245D/K319A, K194E/K245D/E312D, and K194E/K245D/K319A were also prepared. The most potent mutant was observed to be K194E/K245D/K319A, which has a 10-fold improved kcat value (against acetylated alginate compared to the wild-type enzyme. The antibiofilm effect of both AlgL forms was identified in combination with piperacillin/tazobactam (PT and the disruption effect was significantly higher in mutant AlgL combined with PT than wild-type AlgL. However, for both the wild-type and K194E/K245D/K319A mutant, the use of the AlgL enzyme alone did not show significant antibiofilm effect.

  11. Identification of a positive transcription regulatory element within the coding region of the nifLA operon in Azotobacter vinelandii.

    Science.gov (United States)

    Mitra, Ranjana; Das, Hirendra K; Dixit, Aparna

    2005-07-01

    Nitrogen fixation in Azotobacter vinelandii is regulated by the nifLA operon. NifA activates the transcription of nif genes, while NifL antagonizes the transcriptional activator NifA in response to fixed nitrogen and molecular oxygen levels. However, transcriptional regulation of the nifLA operon of A. vinelandii itself is not fully understood. Using the S1 nuclease assay, we mapped the transcription start site of the nifLA operon, showing it to be similar to the sigma54-dependent promoters. We also identified a positive cis-acting regulatory element (+134 to +790) of the nifLA operon within the coding region of the nifL gene of A. vinelandii. Deletion of this element results in complete loss of promoter activity. Several protein factors bind to this region, and the specific binding sites have been mapped by DNase I foot printing. Two of these sites, namely dR1 (+134 to +204) and dR2 (+745 to +765), are involved in regulating the nifLA promoter activity. The absence of NtrC-like binding sites in the upstream region of the nifLA operon in A. vinelandii makes the identification of these downstream elements a highly significant finding. The interaction of the promoter with the proteins binding to the dR2 region spanning +745 to +765 appears to be dependent on the face of the helix as introduction of 4 bases just before this region completely disrupts promoter activity. Thus, the positive regulatory element present within the BglII-BglII fragment may play, in part; an important role in nifLA regulation in A. vinelandii. PMID:16000781

  12. Lethality of glnD null mutations in Azotobacter vinelandii is suppressible by prevention of glutamine synthetase adenylylation.

    Science.gov (United States)

    Colnaghi, R; Rudnick, P; He, L; Green, A; Yan, D; Larson, E; Kennedy, C

    2001-05-01

    GlnD is a pivotal protein in sensing intracellular levels of fixed nitrogen and has been best studied in enteric bacteria, where it reversibly uridylylates two related proteins, PII and GlnK. The uridylylation state of these proteins determines the activities of glutamine synthetase (GS) and NtrC. Results presented here demonstrate that glnD is an essential gene in Azotobacter vinelandii. Null glnD mutations were introduced into the A. vinelandii genome, but none could be stably maintained unless a second mutation was present that resulted in unregulated activity of GS. One mutation, gln-71, occurred spontaneously to give strain MV71, which failed to uridylylate the GlnK protein. The second, created by design, was glnAY407F (MV75), altering the adenylylation site of GS. The gln-71 mutation is probably located in glnE, encoding adenylyltransferase, because introducing the Escherichia coli glnE gene into MV72, a glnD(+) derivative of MV71, restored the regulation of GS activity. GlnK-UMP is therefore apparently required for GS to be sufficiently deadenylylated in A. vinelandii for growth to occur. The DeltaglnD GS(c) isolates were Nif(-), which could be corrected by introducing a nifL mutation, confirming a role for GlnD in mediating nif gene regulation via some aspect of the NifL/NifA interaction. MV71 was unexpectedly NtrC(+), suggesting that A. vinelandii NtrC activity might be regulated differently than in enteric organisms. PMID:11320130

  13. Assessment of free-living nitrogen fixing microorganisms for commercial nitrogen fixation. [Klebsiella penumoniae and Azotobacter vinelandii

    Energy Technology Data Exchange (ETDEWEB)

    Stokes, B.O.; Wallace, C.J.

    1978-08-01

    This economic assessment indicates that ammonia production by Klebsiella penumoniae is not economical with present strains; and improving nitrogen fixation to its theoretical limits in this organism is not sufficient to achieve economic viability. Contamination and reversion of the mutant are major technical problems. This leads to sterilization requirements which are economically prohibitive. Ammonia is a low value product and has been obtained only in dilute solutions with biological systems. Since the value of both the hydrogen produced by this organism and the methane value of the carbon source required greatly exceed the value of the ammonia formed, ammonia (fixed nitrogen) should be considered the by-product and attention should be focused on other products. The production of hydrogen by Klebsiella or other anaerobic nitrogen fixers should receive additional study, since the value of hydrogen produced by Klebsiella greatly exceeds the value of the nitrogen fixed and since the activity of nitrogenase offers a significant improvement in hydrogen production. At observed efficiencies, the production of fixed nitrogen in the form of cell mass by Azotobacter is also uneconomical and the methane value of the carbon substrate exceeds the value of the nitrogen fixed. Parametric studies indicate that as efficiencies approach the theoretical limits the economics may become competititve under the assumptions of the economic model employed. The use of nif-derepressed microorganisms, particularly blue--green algae, may have significant potential for in situ fertilization in the environment. Additional work is required to determine: (1) the extent of in situ nitrogen fixation when nif-derepressed strains are added to the environment and; (2) how effective these strains are in increasing crop yields through the production of substances, other than fixed nitrogen, which may enhance plant growth.

  14. Modeling and Re-Engineering of Azotobacter vinelandii Alginate Lyase to Enhance Its Catalytic Efficiency for Accelerating Biofilm Degradation

    Science.gov (United States)

    Jang, Chul Ho; Piao, Yu Lan; Huang, Xiaoqin; Yoon, Eun Jeong; Park, So Hee; Lee, Kyoung; Zhan, Chang-Guo; Cho, Hoon

    2016-01-01

    Alginate is known to prevent elimination of Pseudomonas aeruginosa biofilms. Alginate lyase (AlgL) might therefore facilitate treatment of Pseudomonas aeruginosa-infected cystic fibrosis patients. However, the catalytic activity of wild-type AlgL is not sufficiently high. Therefore, molecular modeling and site-directed mutagenesis of AlgL might assist in enzyme engineering for therapeutic development. AlgL, isolated from Azotobacter vinelandii, catalyzes depolymerization of alginate via a β-elimination reaction. AlgL was modeled based on the crystal structure template of Sphingomonas AlgL species A1-III. Based on this computational analysis, AlgL was subjected to site-directed mutagenesis to improve its catalytic activity. The kcat/Km of the K194E mutant showed a nearly 5-fold increase against the acetylated alginate substrate, as compared to the wild-type. Double and triple mutants (K194E/K245D, K245D/K319A, K194E/K245D/E312D, and K194E/K245D/K319A) were also prepared. The most potent mutant was observed to be K194E/K245D/K319A, which has a 10-fold improved kcat value (against acetylated alginate) compared to the wild-type enzyme. The antibiofilm effect of both AlgL forms was identified in combination with piperacillin/tazobactam (PT) and the disruption effect was significantly higher in mutant AlgL combined with PT than wild-type AlgL. However, for both the wild-type and K194E/K245D/K319A mutant, the use of the AlgL enzyme alone did not show significant antibiofilm effect. PMID:27253324

  15. Molecular Study of nifH1, nifH2, nifH3, nifU, nifV, VF Genes and Classical Approach Cared out to Identification of Azotobacter chrococcum from Soil

    Directory of Open Access Journals (Sweden)

    Adel Kamal Khider

    2012-09-01

    Full Text Available The present study aimed to compare classical approach with molecular based method for identification of Azotobacter chrococcum from soil samples. A. chrococcum was isolated from soil source in Erbil city, Iraq. They were cultivated under laboratory conditions using Nitrogen free Azotobacter specific medium. A. chrococcum was present in all soil samples. result shows that A. chrococcum were rod shape, motility occur through the use of peritrichous flagella, cysts-forming, positive to oxidase, catalase and tryptophanase test, unable to liquefy gelatin, with insoluble brown or brown-black pigmentation and darken with age. Utilized starch, sucrose, mannitol and moloanat, but not rhamnose. molecular method based on detection of nifgenes have been successfully applied to describe A. chrococcum isolated from soil. The PCR products for nifH1 1102bp, nifH2 246bp, nifH3 128bp, nifU 930bp, nifV 1146bp and VF gene 594bp were detected on gel electrophoresis, while no bands observed for negative control. The isolated bacteria considered Azotobacte chrococcum belonging to Genus Azotobacter.

  16. Producción de un biofertilizante a partir de un aislamiento de Azotobacter nigricans obtenido en un cultivo de Stevia rebaudiana Bert

    Directory of Open Access Journals (Sweden)

    Daniel Borda-Molina

    2009-04-01

    Full Text Available Bio-fertilizer production from an isolate of Azotobacter nigricans obtained from a plantation of Stevia rebaudiana Bert. Objective.To isolate nitrogen fixing bacteria to be used in a fertilization regime of an organic agriculture program. Materials and methods. Theisolation of nitrogen fixing bacteria was done in an Ashby-benzoate medium from soil of a Stevia rebaudiana plantation. Isolates identifiedas Azotobacter nigricans were evaluated by their growth kinetics and the strain with the fastest growth was used for the production of abiofertilizer by discontinuous fermentation. The preliminary evaluation of the biofertilizer was done by its inoculation into t hree ridges ofa plantation of S. rebaudiana and yield determination was based upon biomass production and glycoside concentration. Results. Twoisolates (A5 and A6 were identified as A. nigricans based on their phenotypic and genotypic characterization. Isolate A5 was selected forpreparing the biofertilizer because it showed a better stability, pigmentation, a faster growth rate (0.1405 h-1 exponential phase of 18 hoursand an average IAA production of 38.4 mg/ml after 150 hours. The bio-fertilizer was obtained in milk medium with a cell concentration of4x1012 CFU/ml. Conclusions. The preliminary field evaluation showed a positive correlation between the increase of the glycosideconcentration in the leaves of S. rebaudiana and a higher production of biomass in response to the bio-fertilizer application.

  17. Spectroscopic and functional characterization of iron-sulfur cluster-bound forms of Azotobacter vinelandii (Nif)IscA.

    Science.gov (United States)

    Mapolelo, Daphne T; Zhang, Bo; Naik, Sunil G; Huynh, Boi Hanh; Johnson, Michael K

    2012-10-16

    The mechanism of [4Fe-4S] cluster assembly on A-type Fe-S cluster assembly proteins, in general, and the specific role of (Nif)IscA in the maturation of nitrogen fixation proteins are currently unknown. To address these questions, in vitro spectroscopic studies (UV-visible absorption/CD, resonance Raman and Mössbauer) have been used to investigate the mechanism of [4Fe-4S] cluster assembly on Azotobacter vinelandii(Nif)IscA, and the ability of (Nif)IscA to accept clusters from NifU and to donate clusters to the apo form of the nitrogenase Fe-protein. The results show that (Nif)IscA can rapidly and reversibly cycle between forms containing one [2Fe-2S](2+) and one [4Fe-4S](2+) cluster per homodimer via DTT-induced two-electron reductive coupling of two [2Fe-2S](2+) clusters and O(2)-induced [4Fe-4S](2+) oxidative cleavage. This unique type of cluster interconversion in response to cellular redox status and oxygen levels is likely to be important for the specific role of A-type proteins in the maturation of [4Fe-4S] cluster-containing proteins under aerobic growth or oxidative stress conditions. Only the [4Fe-4S](2+)-(Nif)IscA was competent for rapid activation of apo-nitrogenase Fe protein under anaerobic conditions. Apo-(Nif)IscA was shown to accept clusters from [4Fe-4S] cluster-bound NifU via rapid intact cluster transfer, indicating a potential role as a cluster carrier for delivery of clusters assembled on NifU. Overall the results support the proposal that A-type proteins can function as carrier proteins for clusters assembled on U-type proteins and suggest that they are likely to supply [2Fe-2S] clusters rather than [4Fe-4S] for the maturation of [4Fe-4S] cluster-containing proteins under aerobic or oxidative stress growth conditions.

  18. Role of GlnK in NifL-mediated regulation of NifA activity in Azotobacter vinelandii.

    Science.gov (United States)

    Rudnick, Paul; Kunz, Christopher; Gunatilaka, Malkanthi K; Hines, Eric R; Kennedy, Christina

    2002-02-01

    In several diazotrophic species of Proteobacteria, P(II) signal transduction proteins have been implicated in the regulation of nitrogen fixation in response to NH(4)(+) by several mechanisms. In Azotobacter vinelandii, expression of nifA, encoding the nif-specific activator, is constitutive, and thus, regulation of NifA activity by the flavoprotein NifL appears to be the primary level of nitrogen control. In vitro and genetic evidence suggests that the nitrogen response involves the P(II)-like GlnK protein and GlnD (uridylyltransferase/uridylyl-removing enzyme), which reversibly uridylylates GlnK in response to nitrogen limitation. Here, the roles of GlnK and GlnK-UMP in A. vinelandii were studied to determine whether the Nif (-) phenotype of glnD strains was due to an inability to modify GlnK, an effort previously hampered because glnK is an essential gene in this organism. A glnKY51F mutation, encoding an unuridylylatable form of the protein, was stable only in a strain in which glutamine synthetase activity is not inhibited by NH(4)(+), suggesting that GlnK-UMP is required to signal adenylyltransferase/adenylyl-removing enzyme-mediated deadenylylation. glnKY51F strains were significantly impaired for diazotrophic growth and expression of a nifH-lacZ fusion. NifL interacted with GlnK and GlnKY51F in a yeast two-hybrid system. Together, these data are consistent with those obtained from in vitro experiments (Little et al., EMBO J., 19:6041-6050, 2000) and support a model for regulation of NifA activity in which unmodified GlnK stimulates NifL inhibition and uridylylation of GlnK in response to nitrogen limitation prevents this function. This model is distinct from one proposed for the related bacterium Klebsiella pneumoniae, in which unmodified GlnK relieves NifL inhibition instead of stimulating it. PMID:11790752

  19. Tn5-induced mutants of Azotobacter vinelandii affected in nitrogen fixation under Mo-deficient and Mo-sufficient conditions

    Energy Technology Data Exchange (ETDEWEB)

    Joerger, R.D.; Premakumar, R.; Bishop, P.E.

    1986-11-01

    Mutants of Azotobacter vinelandii affected in N/sub 2/ fixation in the presence of 1 ..mu..M Na/sub 2/MoO/sub 4/ (conventional system), 50 nM V/sub 2/O/sub 5/, or under Mo deficiency (alternative system) have been isolated after Tn5 mutagenesis with the suicide plasmid pSUP1011. These mutants are grouped into four broad phenotypic classes. Mutants in the first class are Nif/sup -/ under Mo sufficiency but Nif/sup +/ under Mo deficiency or in the presence of V/sub 2/O/sub 5/. Mutants in the second class are Nif/sup -/ under all conditions. An FeMo-cofactor-negative mutant (NifB/sup -/) belongs to this class. The third mutant class consists of mutants incapable of N/sub 2/-dependent growth under Mo deficiency. Most of the mutants of this class are also affected in N/sub 2/ fixation in the presence of 1 ..mu..M Na/sub 2/MoO/sub 4/, with acetylene reduction rates ranging from 28 to 51% of the rates of the wild type. Strains constructed by genetic transfer of the Kan/sup r/ marker of mutants from this class into nifHDK or nifK deletion mutants showed N/sub 2/-dependent growth only in the presence of V/sup 2/O/sub 5/. The only mutant in the fourth class shows wild-type nitrogenase activity under Mo sufficiency, but only 10% of the acetylene reduction activity of the wild type in the presence of 50 nM V/sub 2/O/sub 5/. The acetylene reduction rates of whole cells of this mutant are identical in Mo-deficient medium and in medium containing V/sub 2/O/sub 5/. The conventional nitrogenase subunits are expressed in this mutant even under Mo deficiency or in the presence of V/sub 2/O/sub 5/; however, the NH/sub 4//sup +/-and Mo-repressible proteins normally seen under these conditions could not be detected on two-dimensional gels.

  20. Spectroscopic and functional characterization of iron-sulfur cluster-bound forms of Azotobacter vinelandii (Nif)IscA.

    Science.gov (United States)

    Mapolelo, Daphne T; Zhang, Bo; Naik, Sunil G; Huynh, Boi Hanh; Johnson, Michael K

    2012-10-16

    The mechanism of [4Fe-4S] cluster assembly on A-type Fe-S cluster assembly proteins, in general, and the specific role of (Nif)IscA in the maturation of nitrogen fixation proteins are currently unknown. To address these questions, in vitro spectroscopic studies (UV-visible absorption/CD, resonance Raman and Mössbauer) have been used to investigate the mechanism of [4Fe-4S] cluster assembly on Azotobacter vinelandii(Nif)IscA, and the ability of (Nif)IscA to accept clusters from NifU and to donate clusters to the apo form of the nitrogenase Fe-protein. The results show that (Nif)IscA can rapidly and reversibly cycle between forms containing one [2Fe-2S](2+) and one [4Fe-4S](2+) cluster per homodimer via DTT-induced two-electron reductive coupling of two [2Fe-2S](2+) clusters and O(2)-induced [4Fe-4S](2+) oxidative cleavage. This unique type of cluster interconversion in response to cellular redox status and oxygen levels is likely to be important for the specific role of A-type proteins in the maturation of [4Fe-4S] cluster-containing proteins under aerobic growth or oxidative stress conditions. Only the [4Fe-4S](2+)-(Nif)IscA was competent for rapid activation of apo-nitrogenase Fe protein under anaerobic conditions. Apo-(Nif)IscA was shown to accept clusters from [4Fe-4S] cluster-bound NifU via rapid intact cluster transfer, indicating a potential role as a cluster carrier for delivery of clusters assembled on NifU. Overall the results support the proposal that A-type proteins can function as carrier proteins for clusters assembled on U-type proteins and suggest that they are likely to supply [2Fe-2S] clusters rather than [4Fe-4S] for the maturation of [4Fe-4S] cluster-containing proteins under aerobic or oxidative stress growth conditions. PMID:23003323

  1. NifU and NifS are required for the maturation of nitrogenase and cannot replace the function of isc-gene products in Azotobacter vinelandii.

    Science.gov (United States)

    Johnson, D C; Dos Santos, P C; Dean, D R

    2005-02-01

    In recent years, it has become evident that [Fe-S] proteins, such as hydrogenase, nitrogenase and aconitase, require a complex machinery to assemble and insert their associated [Fe-S] clusters. So far, three different types of [Fe-S] cluster biosynthetic systems have been identified and these have been designated nif, isc and suf. In the present work, we show that the nif-specific [Fe-S] cluster biosynthetic system from Azotobacter vinelandii, which is required for nitrogenase maturation, cannot functionally replace the isc [Fe-S] cluster system used for the maturation of other [Fe-S] proteins, such as aconitase. The results indicate that, in certain cases, [Fe-S] cluster biosynthetic machineries have evolved to perform only specialized functions. PMID:15667274

  2. The FeMoco-deficient MoFe Protein Produced by a nifH Deletion Strain of Azotobacter vinelandii Shows Unusual P-cluster Features

    OpenAIRE

    Ribbe, Markus W.; Hu, Yilin; Guo, Maolin; Schmidt, Benedikt; Burgess, Barbara K.

    2002-01-01

    The His-tag MoFe protein expressed by the nifH deletion strain Azotobacter vinelandii DJ1165 (Delta nifH MoFe protein) was purified in large quantity. The alpha 2beta 2 tetrameric Delta nifH MoFe protein is FeMoco-deficient based on metal analysis and the absence of the S = 3/2 EPR signal, which arises from the FeMo cofactor center in wild-type MoFe protein. The Delta nifH MoFe protein contains 18.6 mol Fe/mol and, upon reduction with dithionite, exhibits an unusually strong S = 1/2 EPR signa...

  3. Nucleotide sequence and genetic analysis of the Azotobacter chroococcum nifUSVWZM gene cluster, including a new gene (nifP) which encodes a serine acetyltransferase.

    Science.gov (United States)

    Evans, D J; Jones, R; Woodley, P R; Wilborn, J R; Robson, R L

    1991-09-01

    Nucleotide sequence was obtained for a region of 7,099 bp spanning the nifU, nifS, nifV, nifW, nifZ, and nifM genes from Azotobacter chroococcum. Chromosomal mutations constructed at several sites within the locus confirmed a requirement for this region for expression of the molybdenum nitrogenase in this organism. The genes are tightly clustered and ordered as in Klebsiella pneumoniae except for two additional open reading frames (ORFs) between nifV and nifW. The arrangement of genes in A. chroococcum closely matches that described for Azotobacter vinelandii. The polypeptide encoded by ORF4 immediately downstream from nifV is 41% identical over 186 amino acids to the product of the cysE gene from Escherichia coli, which encodes serine acetyltransferase (SAT), a key enzyme in cysteine biosynthesis. Plasmids which potentially express ORF4 complemented E. coli JM39, a cysteine auxotroph which lacks SAT. SAT activity was detected in crude extracts of one such complemented strain. A strain of A. chroococcum carrying a chromosomal disruption of ORF4 grew normally with ammonium as the N source but more slowly than the parental strain when N2 was the sole N source. These data suggest that ORF4 encodes a nif-specific SAT required for optimizing expression of nitrogenase activity. ORF4 was assigned the name nifP. nifP may be required to boost rates of synthesis or intracellular concentrations of cysteine or methionine. Sequence identity between nifV and leuA gene products suggests that nifV may catalyze a condensation reaction analogous to that carried out by isopropylmalate synthase (LEUA) but in which acetyl coenzyme and alpha-ketoglutarate are substrates for the formation of homocitrate, the proposed product of NIFV activity. PMID:1885524

  4. Inoculation two azotobacter enhancing osmotic stress resistance and growth in wheat seedling%接种两种固氮菌增强小麦幼苗抗渗透胁迫及生长能力

    Institute of Scientific and Technical Information of China (English)

    刘华伟; 林晓军; 孙超; 李强; 杨呼; 郭蔼光

    2013-01-01

    Aims The seedling stage is the key stage of matter and energy accumulation in the wheat life cycle. Therefore, drought during the seedling stage affects population formation in late stages. In this study, wheat seedlings were inoculated with azotobacters Azorhizobium caulinodans 'ORS571' and Azospirillum brasilense 'Yu62'. Methods Wheat seedlings germination was screened in normal conditions and with PEG 6000 osmotic stress using seedlings inoculated with azotobacters. Root volume, relative water content (RWC), proline content and soluble protein content of seedling laminas were determined under PEG drought stress using seedlings inoculated with azotobacters on laminas. Important findings The germination rate of wheat seedlings was significantly increased under drought stress when inoculated with azotobacters. Moreover, wheat seedlings inoculated with mixed azotobacters have more obvious growth promotion than when inoculated with a single azotobacter. The former laminas proline content, relative water content, proline content and soluble protein content had increased. The results showed that drought resistance of wheat seedlings was improved when inoculated with mixed azotobacters, which provided the foundation for further study of azotobacter-wheat interaction under drought stress.%苗期是小麦(Triticum aestivum)物质和能量积累的关键时期,苗期干旱影响小麦的后期群体建成.利用田菁茎瘤固氮根瘤菌(Azorhizobium caulinodans)‘ORS571’与巴西固氮螺菌(Azospirillum brasilense)‘Yu62’浸种侵染小麦和聚乙二醇(PEG)模拟渗透胁迫,研究渗透胁迫下接菌小麦种子的发芽状况;利用固氮菌涂抹小麦幼苗叶部,测定PEG模拟渗透胁迫下小麦幼苗根体积、叶片相对含水量、脯氨酸含量及可溶性蛋白含量,探究固氮菌增强小麦幼苗抗渗透胁迫的能力.结果表明,接种混合固氮菌后在渗透胁迫下小麦种子的发芽率明显提高;在渗透胁迫下叶部

  5. Biopolymers by Azotobacter Vinelandii

    OpenAIRE

    Silva, Adriana Navarro da; Garcia-Cruz, Crispin Humberto

    2010-01-01

    The highest PHB yield (100 mg g cell-1 h-1) using sugar cane molasses occurred in the incubation time of 10 h, 60.0 ºC and the soluble solids concentrations between 14.0 – 25.0%. To alginate yield was observed that, using molasses, yield was greater (250 mg g cell-1 h-1) also in the incubation time of 10 h, temperature of 60.0 ºC and the soluble solids concentration between 4.0 - 6.0%. The PHB purity was between 93.0 to 97.5%. Thus, Cane sugar molasses was very promising for the alginate ...

  6. Final Report: The Rhizosphere Association of the Nitrogen Fixing Bacterial Species Azotobacter Paspali with the Tropical Grass Paspalum Notatum: Specificity of Colonization and Contribution to Plant Nutrition, July 1, 1995 - February 14, 1997

    Energy Technology Data Exchange (ETDEWEB)

    Kennedy, Christina K.

    1997-02-14

    The nitrogen fixing bacterium azotobacter paspali was first isolated from the roots of the sub-tropical grass, palpium notatum, and added to the clenus in 1996, by Dr. J. Dobereiner (Brazil). It is mentioned that this root association bacteria shows remarkable signs of host-plant specificity to one eco-type of this grass. This specificity is rare in non-symbiotic plant microbe interactions so far identified.

  7. Assembly of iron-sulfur clusters. Identification of an iscSUA-hscBA-fdx gene cluster from Azotobacter vinelandii.

    Science.gov (United States)

    Zheng, L; Cash, V L; Flint, D H; Dean, D R

    1998-05-22

    An enzyme having the same L-cysteine desulfurization activity previously described for the NifS protein was purified from a strain of Azotobacter vinelandii deleted for the nifS gene. This protein was designated IscS to indicate its proposed role in iron-sulfur cluster assembly. Like NifS, IscS is a pyridoxal-phosphate containing homodimer. Information gained from microsequencing of oligopeptides obtained by tryptic digestion of purified IscS was used to design a strategy for isolation and DNA sequence analysis of a 7,886-base pair A. vinelandii genomic segment that includes the iscS gene. The iscS gene is contained within a gene cluster that includes homologs to nifU and another gene contained within the major nif cluster of A. vinelandii previously designated orf6. These genes have been designated iscU and iscA, respectively. Information available from complete genome sequences of Escherichia coli and Hemophilus influenzae reveals that they also encode iscSUA gene clusters. A wide conservation of iscSUA genes in nature and evidence that NifU and NifS participate in the mobilization of iron and sulfur for nitrogenase-specific iron-sulfur cluster formation suggest that the products of the iscSUA genes could play a general role in the formation or repair of iron-sulfur clusters. The proposal that IscS is involved in mobilization of sulfur for iron-sulfur cluster formation in A. vinelandii is supported by the presence of a cysE-like homolog in another gene cluster located immediately upstream from the one containing the iscSUA genes. O-Acetylserine synthase is the product of the cysE gene, and it catalyzes the rate-limiting step in cysteine biosynthesis. A similar cysE-like gene is also located within the nif gene cluster of A. vinelandii. The likely role of such cysE-like gene products is to increase the cysteine pool needed for iron-sulfur cluster formation. Another feature of the iscSUA gene cluster region from A. vinelandii is that E. coli genes previously

  8. Non-chemical proton-dependent steps prior to O2-activation limit Azotobacter vinelandii 3-mercaptopropionic acid dioxygenase (MDO) catalysis.

    Science.gov (United States)

    Crowell, Joshua K; Sardar, Sinjinee; Hossain, Mohammad S; Foss, Frank W; Pierce, Brad S

    2016-08-15

    3-mercaptopropionate dioxygenase from Azotobacter vinelandii (Av MDO) is a non-heme mononuclear iron enzyme that catalyzes the O2-dependent oxidation of 3-mercaptopropionate (3mpa) to produce 3-sulfinopropionic acid (3spa). With one exception, the active site residues of MDO are identical to bacterial cysteine dioxygenase (CDO). Specifically, the CDO Arg-residue (R50) is replaced by Gln (Q67) in MDO. Despite this minor active site perturbation, substrate-specificity of Av MDO is more relaxed as compared to CDO. In order to investigate the relative timing of chemical and non-chemical events in Av MDO catalysis, the pH/D-dependence of steady-state kinetic parameters (kcat and kcat/KM) and viscosity effects are measured using two different substrates [3mpa and l-cysteine (cys)]. The pL-dependent activity of Av MDO in these reactions can be rationalized assuming a diprotic enzyme model in which three ionic forms of the enzyme are present [cationic, E((z+1)); neutral, E(z); and anionic, E((z-1))]. The activities observed for each substrate appear to be dominated by electrostatic interactions within the enzymatic active site. Given the similarity between MDO and the more extensively characterized mammalian CDO, a tentative model for the role of the conserved 'catalytic triad' is proposed. PMID:27311613

  9. Establishment of phosphate-solubilizing strains of Azotobacter chroococcum in the rhizosphere and their effect on wheat cultivars under green house conditions.

    Science.gov (United States)

    Kumar, V; Behl, R K; Narula, N

    2001-01-01

    A pot experiment was conducted in the green house to investigate the establishment of phosphate solubilizing strains of Azotobacter chroococcum, including soil isolates and their mutants, in the rhizosphere and their effect on growth parameters and root biomass of three genetically divergent wheat cultivars (Triticum aestivum L.). Five fertilizer treatments were performed: Control, 90 kg N ha(-1), 90 kg N + 60 kg P2O5 ha(-1), 120 kg N ha(-1) and 120 kg N + 60 kg P2O5 ha(-1). Phosphate solubilizing and phytohormone producing parent soil isolates and mutant strains of A. chroococcum were isolated and selected by an enrichment method. In vitro phosphate solubilization and growth hormone production by mutant strains was increased compared with soil isolates. Seed inoculation of wheat varieties with P solubilizing and phytohormone producing A. chroococcum showed better response compared with controls. Mutant strains of A. chroococcum showed higher increase in grain (12.6%) and straw (11.4%) yield over control and their survival (12-14%) in the rhizosphere as compared to their parent soil isolate (P4). Mutant strain M37 performed better in all three varieties in terms of increase in grain yield (14.0%) and root biomass (11.4%) over control.

  10. Purification and Characterization of a New Heme-Binding Protein (HBP59) from the Mutant Strain DJ35 of Azotobacter vinelandii

    Institute of Scientific and Technical Information of China (English)

    Shao-Min Bian; Huang-Ping Wang; Hui-Na Zhou; Ying Zhao; Jian-Feng Zhao; Ju-Fu Huang

    2007-01-01

    A new protein, an approximately 59-kDa monomer containing iron atoms, was first isolated from the mutant strain DJ35 of Azotobacter vinelandli Lipmann. After analysis by matrix-assisted laser desorptlon ionization time-offlight mass spectrometry, the protein was identified as the product of a predicted gene. Thus, the protein was tentatively called HBP59. Its absorption spectra (ABS) in the reduced state exhibited three peaks at 421,517, and 556nm and the maximal peak was shifted from 421 to 413 nm after exposure of HBP59 to air. The Soret circular dichroism (CD) spectrum of HBP59 in the reduced state displayed four positive peaks at 364, 382, 406, and 418 nm and two negative peaks at 398 and 433 nm; the Δε (CD extinction coefficient) values of these peaks were found to be 0.92, 0.58, 0.87, 0.72, -0.65 and -1.12 L/mol per cm, respectively. Titration with heme showed that the protein has 0.1 heme molecules/protein molecule. After HBP59 had fully interacted with heme, its maximal ABS value and Soret CD intensity were increased by approximately 10-fold compared with values before interaction. Therefore, it seems that one molecule of HBP59 can be interacted with only one heme. These results indicate that HBP59 contains heme with iow spin and may be involved in heme utilization or adhesion.

  11. The genes encoding the delta subunits of dinitrogenases 2 and 3 are required for mo-independent diazotrophic growth by Azotobacter vinelandii.

    Science.gov (United States)

    Waugh, S I; Paulsen, D M; Mylona, P V; Maynard, R H; Premakumar, R; Bishop, P E

    1995-03-01

    vnfG and anfG encode the delta subunits of alternative nitrogenases 2 and 3 in Azotobacter vinelandii, respectively. As a first step towards elucidating the role of these subunits, diazotrophic growth and acetylene reduction studies were conducted on mutants containing alterations in the genes encoding these subunits. Mutants containing a stop codon (C36stop) or an in-frame deletion in anfG were unable to grow in N-free, Mo-deficient medium (Anf-). Mutants in which cysteine 36 of AnfG (a residue conserved between VnfG and AnfG) was changed to Ala or Ser were Anf+. Thus, this conserved cysteine is not essential for the function of AnfG in dinitrogenase 3. A mutant with a stop codon in vnfG (C17stop) grew after a lag of 25 h in N-free, Mo-deficient medium containing V2O5. However, a Nif- Anf- strain with this mutation was unable to grow under these conditions. This shows that the vnfG gene product is required for nitrogenase 2-dependent growth. Strains with mutations in vnfG and anfG reduced acetylene to different degrees. This indicates that the delta subunits are not required for acetylene reduction by nitrogenases 2 and 3. PMID:7883707

  12. NifB and NifEN protein levels are regulated by ClpX2 under nitrogen fixation conditions in Azotobacter vinelandii.

    Science.gov (United States)

    Martínez-Noël, Giselle; Curatti, Leonardo; Hernandez, Jose A; Rubio, Luis M

    2011-03-01

    The major part of biological nitrogen fixation is catalysed by the molybdenum nitrogenase that carries at its active site the iron and molybdenum cofactor (FeMo-co). The nitrogen fixation (nif) genes required for the biosynthesis of FeMo-co are derepressed in the absence of a source of fixed nitrogen. The nifB gene product is remarkable because it assembles NifB-co, a complex cluster proposed to comprise a [6Fe-9S-X] cluster, from simpler [Fe-S] clusters common to other metabolic pathways. NifB-co is a common intermediate of the biosyntheses of the cofactors present in the molybdenum, vanadium and iron nitrogenases. In this work, the expression of the Azotobacter vinelandii nifB gene was uncoupled from its natural nif regulation to show that NifB protein levels are lower in cells growing diazotrophically than in cells growing at the expense of ammonium. A. vinelandii carries a duplicated copy of the ATPase component of the ubiquitous ClpXP protease (ClpX2), which is induced under nitrogen fixing conditions. Inactivation of clpX2 resulted in the accumulation of NifB and NifEN and a defect in diazotrophic growth, especially when iron was in short supply. Mutations in nifE, nifN and nifX or in nifA also affected NifB accumulation, suggesting that NifB susceptibility to degradation might vary during its catalytic cycle. PMID:21231969

  13. Redundancy of the conserved His residue in Azotobacter vinelandii NifL, a histidine autokinase homologue which regulates transcription of nitrogen fixation genes.

    Science.gov (United States)

    Woodley, P; Drummond, M

    1994-08-01

    The NifL protein of Azotobacter vinelandii inhibits NifA, the activator of nif (nitrogen fixation) transcription, in response to oxygen and fixed nitrogen. NifL shows strong homology in its C-terminal domain to the histidine autokinase domains of the canonical two-component sensor proteins, including the region around His-304, which corresponds to the residue known to be phosphorylated in other systems. To examine the mechanism of sensory transduction by NifL, mutations encoding 10 substitutions for His-304 were introduced into the A. vinelandii chromosome. Regulation of nif transcription was measured using acetylene reduction and RNA blots. The substitutions His-304-->Arg and His-304-->Pro impaired regulation by both fixed nitrogen and oxygen, but substitution of Ala, Phe, Ile, Lys, Asn, Ser, Thr, Val had no effect. None of the mutants, including His-304-->Arg and His-304-->Pro, excreted ammonium during diazotrophy, a phenotype of nifL deletion mutants, suggesting that the molecular basis of this effect differs from that responsible for the inhibition of nif transcription. The data show conclusively that phosphorylation of His-304 is not essential for any of the known functions of A. vinelandii NifL. Homology to the family of histidine autokinases is therefore inadequate evidence for a mechanism of sensory transduction involving phosphorylation of the conserved histidine residue. PMID:7997174

  14. Purification of a NifEN protein complex that contains bound molybdenum and a FeMo-Co precursor from an Azotobacter vinelandii DeltanifHDK strain.

    Science.gov (United States)

    Soboh, Basem; Igarashi, Robert Y; Hernandez, Jose A; Rubio, Luis M

    2006-12-01

    The NifEN protein complex serves as a molecular scaffold where some of the steps for the assembly of the iron-molybdenum cofactor (FeMo-co) of nitrogenase take place. A His-tagged version of the NifEN complex has been previously purified and shown to carry two identical [4Fe-4S] clusters of unknown function and a [Fe-S]-containing FeMo-co precursor. We have improved the purification of the his-NifEN protein from a DeltanifHDK strain of Azotobacter vinelandii and have found that the amounts of iron and molybdenum within NifEN were significantly higher than those reported previously. In an in vitro FeMo-co synthesis system with purified components, the NifEN protein served as a source of both molybdenum and a [Fe-S]-containing FeMo-co precursor, showing significant FeMo-co synthesis activity in the absence of externally added molybdate. Thus, the NifEN scaffold protein, purified from DeltanifHDK background, contained the Nif-Bco-derived Fe-S cluster and molybdenum, although these FeMo-co constituents were present at different levels within the protein complex. PMID:17012743

  15. Azotobacter vinelandii NIFL is a flavoprotein that modulates transcriptional activation of nitrogen-fixation genes via a redox-sensitive switch.

    Science.gov (United States)

    Hill, S; Austin, S; Eydmann, T; Jones, T; Dixon, R

    1996-03-01

    The NIFL regulatory protein controls transcriptional activation of nitrogen fixation (nif) genes in Azotobacter vinelandii by direct interaction with the enhancer binding protein NIFA. Modulation of NIFA activity by NIFL, in vivo occurs in response to external oxygen concentration or the level of fixed nitrogen. Spectral features of purified NIFL and chromatographic analysis indicate that it is a flavoprotein with FAD as the prosthetic group, which undergoes reduction in the presence of sodium dithionite. Under anaerobic conditions, the oxidized form of NIFL inhibits transcriptional activation by NIFA in vitro, and this inhibition is reversed when NIFL is in the reduced form. Hence NIFL is a redox-sensitive regulatory protein and may represent a type of flavoprotein in which electron transfer is not coupled to an obvious catalytic activity. In addition to its ability to act as a redox sensor, the activity of NIFL is also responsive to adenosine nucleotides, particularly ADP. This response overrides the influence of redox status on NIFL and is also observed with refolded NIFL apoprotein, which lacks the flavin moiety. These observations suggest that both energy and redox status are important determinants of nif gene regulation in vivo. PMID:8700899

  16. Evidence of reduced poly-B-hydroxybutyrate biosynthesis in free-living nitrogen-fixing bacteria, Azotobacter chroococcum, following acquired resistance to the fungicide captan.

    Science.gov (United States)

    Miclaus, N; Vannini, C; Celano, G; Piccolo, A; Simoncini, S

    1992-08-12

    Some biological activities of Azotobacter chroococcum, strain Azcap 1, (spontaneous mutant, captan resistant up to 300 micrograms/ml) were assayed on RM medium with and without the presence of the fungicide. Comparisons were also carried out with Az. chroococcum sensitive strains Azwt, Azcan 10 and 14. The hydrolysis of captan, incorporated in agar plates of RM at 100 micrograms/ml, was rapid, since on 4-day plates, no effect was found on the strain Azwt, while on freshly prepared ones its growth was completely blocked. As for Azcap 1, grown on RM only, the behaviour was similar to that of sensitive strains, whereas when grown on captan the results of experiments showed: (i) a lag of approximately 12 h to reach the maximum nitrogen-fixing activity; (ii) delay of 12-24 h in the full consumption of glucose present in the medium, although the invertase activity did not present differences; (iii) high ATP culture content during the 50 h of the experiment; (iv) approximately 6-10-fold lower production of PHB (poly-B-hydroxybutyrate); (v) lack of typical encystment phase, for the tested 96 h and reduced viability in developing colonies on agar RM medium. In contrast, when captan was added to cultural medium at sublethal concentration, 50 micrograms/ml for sensitive strain Azwt and 200 micrograms/ml for Azcap 1, the amount of glutathione produced (to remove the fungicide toxicity) was several times higher for the former.

  17. Characterization of a FeMo cofactor-deficient MoFe protein from a nifE-deleted strain (DJ35) of Azotobacter vinelandii

    Institute of Scientific and Technical Information of China (English)

    ZHAO Ying; BIAN Shaomin; ZHANG Chunxi; ZHOU Huina; WANG Huangping; ZHAO Jianfeng; HUANG Jufu

    2005-01-01

    A MoFe protein (ΔnifE Av1) with a purity of ~80% was purified from a nifE-deleted mutant of Azotobacter vinelandii DJ35. Compared with MoFe protein purified from wild-type strain OP (OP Av1), ΔnifE Av1 had the same subunits composition, and had immune reaction with antibody to OP Av1, but its relative mobility in anaerobic native polyacrylamide gel electrophoresis (PAGE) was a little larger than that of OP Av1. Metal analysis showed that Mo and Fe contents of ΔnifE Av1 both apparently decreased. When complemented with OP Fe protein, ΔnifE Av1 had no C2H2-reduction activity, but it could be in vitro activated by FeMoco extracted from OP Av1. The circular dichroism (CD) spectrum of ΔnifE Av1 at ~450 nm was similar to that of OP Av1, while the EPR signal at g≈3.7 was absolutely silent, and the signal intensities at g≈4.3 and 2.0 decreased by 75% and 50%, respectively. The results indicated that ΔnifE Av1 purified from DJ35 was a FeMoco-deficient but P-cluster-con- taining MoFe protein.

  18. EFECTO DE LA INOCULACIÓN DE azotobacter chroococcum Y glomus intraradices EN EL CRECIMIENTO Y NUTRICIÓN DE PLÁNTULAS DE PAPAYA EN FASE DE VIVERO

    OpenAIRE

    Maricela Constantino; Regino Gómez; José David Álvarez; Juan Manuel Pat; Elda Guadalupe Espín

    2011-01-01

    En el presente estudio se evaluó la etapa y el número de aplicaciones de los biofertilizantes (Azotobacter chroococcum y Glomus intraradices), sobre el crecimiento, biomasa y nutrición de papaya en fase de vivero. También se estudió el efecto de la materia orgánica y su interacción con los biofertilizantes aplicados. Se realizaron 2 experimentos; en el primero se aplicaron 2 inoculaciones, en semillas y después en plántulas, 30 días después de la emergencia. En el segundo se aplicó una inocul...

  19. The product of the nitrogen fixation regulatory gene nfrX of Azotobacter vinelandii is functionally and structurally homologous to the uridylyltransferase encoded by glnD in enteric bacteria.

    OpenAIRE

    Contreras, A; Drummond, M; Bali, A.; Blanco, G.; Garcia, E.; Bush, G; Kennedy, C; Merrick, M.

    1991-01-01

    We sequenced the nitrogen fixation regulatory gene nfrX from Azotobacter vinelandii, mutations in which cause a Nif- phenotype, and found that it encodes a 105-kDa protein (NfrX), the N terminus of which is highly homologous to that of the uridylyltransferase-uridylyl-removing enzyme encoded by glnD in Escherichia coli. In vivo complementation experiments demonstrate that the glnD and nfrX products are functionally interchangeable. A vinelandii nfrX thus appears to encode a uridylyltransferas...

  20. The GacS/A-RsmA Signal Transduction Pathway Controls the Synthesis of Alkylresorcinol Lipids that Replace Membrane Phospholipids during Encystment of Azotobacter vinelandii SW136

    Science.gov (United States)

    Romero, Yanet; Guzmán, Josefina; Moreno, Soledad; Cocotl-Yañez, Miguel; Vences-Guzmán, Miguel Ángel; Castañeda, Miguel; Espín, Guadalupe; Segura, Daniel

    2016-01-01

    Azotobacter vinelandii is a soil bacterium that undergoes a differentiation process that forms cysts resistant to desiccation. During encystment, a family of alkylresorcinols lipids (ARs) are synthesized and become part of the membrane and are also components of the outer layer covering the cyst, where they play a structural role. The synthesis of ARs in A. vinelandii has been shown to occur by the activity of enzymes encoded in the arsABCD operon. The expression of this operon is activated by ArpR, a LysR-type transcriptional regulator whose transcription occurs during encystment and is dependent on the alternative sigma factor RpoS. In this study, we show that the two component response regulator GacA, the small RNA RsmZ1 and the translational repressor protein RsmA, implicated in the control of the synthesis of other cysts components (i.e., alginate and poly-ß-hydroxybutyrate), are also controlling alkylresorcinol synthesis. This control affects the expression of arsABCD and is exerted through the regulation of arpR expression. We show that RsmA negatively regulates arpR expression by binding its mRNA, repressing its translation. GacA in turn, positively regulates arpR expression through the activation of transcription of RsmZ1, that binds RsmA, counteracting its repressor activity. This regulatory cascade is independent of RpoS. We also show evidence suggesting that GacA exerts an additional regulation on arsABCD expression through an ArpR independent route. PMID:27055016

  1. The production, molecular weight and viscosifying power of alginate produced by Azotobacter vinelandii is affected by the carbon source in submerged cultures

    Directory of Open Access Journals (Sweden)

    Mauricio A. Trujillo-Roldán

    2015-01-01

    Full Text Available El alginato es un polímero lineal compuesto por ácidos 1,4 manurónico y su epímero, -L- gulurónico y con frecuencia se extrae de algas marinas, como también de bacterias como Azotobacter y Pseudomonas. En este trabajo, se presenta el impacto de diferentes fuentes de carbono convencionales y no convencionales en el crecimiento de A. vinelandii, producción de alginato, su peso molecular promedio (PMP y su capacidad viscosificante. Todos los experimentos se iniciaron con 20 g/L de azúcares totales, donde la más alta concentración de biomasa se obtuvo utilizando suero de leche hidrolizado y desproteinizado (6.67±0.72 g/L, y jugo de caña de azúcar (6.68±0.45 g/L. Sin embargo, la producción máxima de alginato se logró utilizando sacarosa (5.11±0.37 g/L, así como el más alto rendimiento de alginato y productividad específica. Por otra parte, el mayor PMP de alginato se obtuvo con jugo de caña de azúcar (1203±120 kDa. Además, la capacidad viscosificante más alta se obtuvo utilizando suero de leche desproteinizado e hidrolizado (23.8±2.6 cpsL/galg. Esta información sugiere que es posible manipular la productividad y las características moleculares de alginatos como función de la fuente de carbono utilizada. En conjunto con el conocimiento de los efectos de las condiciones ambientales se lograrían altos rendimientos de biopolímeros de alto valor agregado.

  2. Functional expression of the FeMo-cofactor-specific biosynthetic genes nifEN as a NifE-N fusion protein synthesizing unit in Azotobacter vinelandii.

    Science.gov (United States)

    Suh, Man Hee; Pulakat, Lakshmi; Gavini, Nara

    2002-11-29

    The nifEN encodes an E2N2 tetrameric metalloprotein complex that serves as scaffold for assembly of the FeMo cofactor of nitrogenase. In most diazotrophs, the NifE and NifN are translated as separate polypeptides and then assembled into tetrameric E2N2 complex. However, in Anabaena variabilis which has two nif clusters that encode two different NifEN complexes, the NifEN2 is encoded by a single nifE-N like gene, which has high homology to the NifE at amino-terminus and to the NifN at the carboxy-terminus. These observations implied that a metalloprotein like NifEN can accommodate large variations in their amino acid composition and also in the way they are synthesized (as two separate proteins or as a single protein) and yet remain functional. In Azotobacter vinelandii NifE and NifN are synthesized separately. To test whether NifEN could retain its functionality when encoded by a single gene, we generated a translational fusion of the nifE and nifN genes of A. vinelandii that could encode a large NifE-N fusion protein. When expressed in the nifEN-minus strain of A. vinelandii, the nifE-N gene fusion could complement the NifEN function. Western blot analysis by using polyclonal NifEN antibodies revealed that the complementing nifEN product is a large NifE-N fusion protein unit. The fact that the gene fusion of nifE-N specifies a functional NifE-N fusion protein reflects that these metalloproteins can accommodate a wide range of flexibility in their gene organization, structure, and assembly. PMID:12437975

  3. Cloning and mutational analysis of the gamma gene from Azotobacter vinelandii defines a new family of proteins capable of metallocluster binding and protein stabilization.

    Science.gov (United States)

    Rubio, Luis M; Rangaraj, Priya; Homer, Mary J; Roberts, Gary P; Ludden, Paul W

    2002-04-19

    Dinitrogenase is a heterotetrameric (alpha(2)beta(2)) enzyme that catalyzes the reduction of dinitrogen to ammonium and contains the iron-molybdenum cofactor (FeMo-co) at its active site. Certain Azotobacter vinelandii mutant strains unable to synthesize FeMo-co accumulate an apo form of dinitrogenase (lacking FeMo-co), with a subunit composition alpha(2)beta(2)gamma(2), which can be activated in vitro by the addition of FeMo-co. The gamma protein is able to bind FeMo-co or apodinitrogenase independently, leading to the suggestion that it facilitates FeMo-co insertion into the apoenzyme. In this work, the non-nif gene encoding the gamma subunit (nafY) has been cloned, sequenced, and found to encode a NifY-like protein. This finding, together with a wealth of knowledge on the biochemistry of proteins involved in FeMo-co and FeV-co biosyntheses, allows us to define a new family of iron and molybdenum (or vanadium) cluster-binding proteins that includes NifY, NifX, VnfX, and now gamma. In vitro FeMo-co insertion experiments presented in this work demonstrate that gamma stabilizes apodinitrogenase in the conformation required to be fully activable by the cofactor. Supporting this conclusion, we show that strains containing mutations in both nafY and nifX are severely affected in diazotrophic growth and extractable dinitrogenase activity when cultured under conditions that are likely to occur in natural environments. This finding reveals the physiological importance of the apodinitrogenase-stabilizing role of which both proteins are capable. The relationship between the metal cluster binding capabilities of this new family of proteins and the ability of some of them to stabilize an apoenzyme is still an open matter. PMID:11823455

  4. The amino-terminal GAF domain of Azotobacter vinelandii NifA binds 2-oxoglutarate to resist inhibition by NifL under nitrogen-limiting conditions.

    Science.gov (United States)

    Little, Richard; Dixon, Ray

    2003-08-01

    The expression of genes required for the synthesis of molybdenum nitrogenase in Azotobacter vinelandii is controlled by the NifL-NifA transcriptional regulatory complex in response to nitrogen, carbon, and redox status. Activation of nif gene expression by the transcriptional activator NifA is inhibited by direct protein-protein interaction with NifL under conditions unfavorable for nitrogen fixation. We have recently shown that the NifL-NifA system responds directly to physiological concentrations of 2-oxoglutarate, resulting in relief of NifA activity from inhibition by NifL under conditions when fixed nitrogen is limiting. The inhibitory activity of NifL is restored under conditions of excess combined nitrogen through the binding of the signal transduction protein Av GlnK to the carboxyl-terminal domain of NifL. The amino-terminal domain of NifA comprises a GAF domain implicated in the regulatory response to NifL. A truncated form of NifA lacking this domain is not responsive to 2-oxoglutarate in the presence of NifL, suggesting that the GAF domain is required for the response to this ligand. Using isothermal titration calorimetry, we demonstrate stoichiometric binding of 2-oxoglutarate to both the isolated GAF domain and the full-length A. vinelandii NifA protein with a dissociation constant of approximately 60 microm. Limited proteolysis experiments indicate that the binding of 2-oxoglutarate increases the susceptibility of the GAF domain to trypsin digestion and also prevents NifL from protecting these cleavage sites. However, protection by NifL is restored when the non-modified (non-uridylylated) form of Av GlnK is also present. Our results suggest that the binding of 2-oxoglutarate to the GAF domain of NifA may induce a conformational change that prevents inhibition by NifL under conditions when fixed nitrogen is limiting. PMID:12759352

  5. MgATP-induced conformational changes in the iron protein from Azotobacter vinelandii, as studied by small-angle x-ray scattering.

    Science.gov (United States)

    Chen, L; Gavini, N; Tsuruta, H; Eliezer, D; Burgess, B K; Doniach, S; Hodgson, K O

    1994-02-01

    Small angle x-ray scattering experiments have been carried out on the purified iron proteins of nitrogenase from wild-type Azotobacter vinelandii and from a Nif- mutant strain, A. vinelandii UW91 (which has an A157S mutation). This study was designed to investigate the influence of MgATP and MgADP binding on the protein structure in solution. For the wild-type protein, the binding of MgATP induces a significant conformational change that is observed as a decrease of about 2.0 A in the radius of gyration. In contrast, the binding of MgADP to the wild-type iron protein does not detectably affect the radius of gyration. In the absence of nucleotides, the radius of gyration for the UW91 mutant is indistinguishable from that of the wild-type. However, unlike for the wild-type protein, the radius of gyration of the UW91 iron protein is unaffected by the addition of MgATP. We have previously shown that the UW91 iron protein has a normal [4Fe-4S] cluster and MgATP binding ability but that it is completely blocked for electron transfer and MgATP hydrolysis (Gavini, N., and Burgess, B. K. (1992) J. Biol. Chem. 267, 21179-21186). These x-ray scattering measurements suggest that a conformation different from that of the native state is therefore required for the iron protein to perform electron transfer to the MoFe protein. These results also support the hypothesis that Ala-157 is crucial for the iron protein to establish the electron-transfer-favored conformation induced by MgATP binding. PMID:8106367

  6. The [2Fe-2S] protein I (Shetna protein I) from Azotobacter vinelandii is homologous to the [2Fe-2S] ferredoxin from Clostridium pasteurianum.

    Science.gov (United States)

    Chatelet, C; Meyer, J

    1999-06-01

    The [2Fe-2S] protein from Azotobacter vinelandii that was previously known as iron-sulfur protein I, or Shethna protein I, has been shown to be encoded by a gene belonging to the major nif gene cluster. Overexpression of this gene in Escherichia coli yielded a dimeric protein of which each subunit comprises 106 residues and contains one [2Fe-2S] cluster. The sequence of this protein is very similar to that of the [2Fe-2S] ferredoxin from Clostridium pasteurianum (2FeCpFd), and the four cysteine ligands of the [2Fe-2S] cluster occur in the same positions. The A. vinelandii protein differs from the C. pasteurianum one by the absence of the N-terminal methionine, the presence of a five-residue C-terminal extension, and a lesser number of acidic and polar residues. The UV-visible absorption and EPR spectra, as well as the redox potentials of the two proteins, are nearly identical. These data show that the A. vinelandii FeS protein I, which is therefore proposed to be designated 2FeAvFdI, is the counterpart of the [2Fe-2S] ferredoxin from C. pasteurianum. The occurrence of the 2FeAvFdI-encoding gene in the nif gene cluster, together with the previous demonstration of a specific interaction between the 2FeCpFd and the nitrogenase MoFe protein, suggest that both proteins might be involved in nitrogen fixation, with possibly similar roles. PMID:10439076

  7. An investigation of agitation speed as a factor affecting the quantity and monomer distribution of alginate from Azotobacter vinelandii ATCC(®) 9046.

    Science.gov (United States)

    Kıvılcımdan Moral, C; Sanin, F D

    2012-03-01

    Alginate is a copolymer of β-D: -mannuronic and α-L: -guluronic acids. Distribution of these monomers in the alginate structure is one of the important characteristics that affect the commercial value of the polymer. In the present work, the effect of agitation speed in the range of 200-700 rpm on alginate production by Azotobacter vinelandii ATCC(®) 9046 was investigated at a dissolved oxygen tension of 5% of air saturation. Experiments were conducted in a fermentor operated in batch mode for 72 h while the production of biomass and alginate, the consumption of substrate and the change in culture broth viscosity and monomer distribution of the polymer were monitored. Results showed that the growth rate of the bacteria increased from 0.165 to 0.239 h(-1) by the increase of mixing speed from 200 to 400 rpm. On the other hand, alginate production was found to be the most efficient at 400 rpm with the highest value of 4.51 g/l achieved at the end of fermentation. The viscosity of culture broth showed similar trends to alginate production. Viscosity was recorded as 24.61 cP at 400 rpm while it was only 4.26 cP at 700 rpm. The MM- and GG-block contents were almost equal in most of the culture times at 400 rpm. On the other hand, GG-blocks dominated at both low and high mixing speeds. Knowing that GG-blocks make rigid and protective gels with divalent cations, due to the higher GG-block content, the gel formation potential is higher at 200 rpm as well at 700 rpm, which might originate from the unfavorable environmental conditions that the bacteria were exposed to. PMID:22009058

  8. The role of regulatory genes nifA, vnfA, anfA, nfrX, ntrC, and rpoN in expression of genes encoding the three nitrogenases of Azotobacter vinelandii.

    Science.gov (United States)

    Walmsley, J; Toukdarian, A; Kennedy, C

    1994-01-01

    Several regulatory gene mutants of Azotobacter vinelandii were tested for ability to synthesize functional nitrogenase-1 (Nif phenotype), nitrogenase-2 (Vnf), or nitrogenase-3 (Anf). While nifA mutants were Nif-, Vnf+, and Anf+/-, and ntrC mutants were Nif+, Vnf+, and Anf+, nifA ntrC double mutants were Nif-, Vnf-, and Anf-. A vnfA mutant was Nif+, Vnf+/-, and Anf+/-, and an anfA strain was Nif+, Vnf+, and Anf-. lacZ fusions in the nifH, vnfH, vnfD, anfH, and nifM genes of Azotobacter vinelandii were constructed and introduced into wild-type and regulatory mutants of A. vinelandii. Expression of these operons correlated with the growth phenotype of the regulatory mutants. Apparently either NifA or NtrC can activate expression of nifM. Also, expression of the anf operon required the NifA transcriptional activator, although there are no NifA binding sites at appropriate locations upstream of anfH (or anfA). The results confirm previous reports that VnfA and AnfA are required for expression of vnf and anf genes, respectively, and that VnfA is involved in repression of the nifHDK operon in the absence of molybdenum and of the anfHDGK operon in the presence of vanadium. PMID:7872838

  9. The composition and distribution of metal clusters in the MoFe protein from a nifZ deletion strain (DJ 194) of Azotobacter vinelandii

    Institute of Scientific and Technical Information of China (English)

    ZHOU Huina; ZHANG Chunxi; ZHAO Ying; BIAN Shaomin; REN Fei; WANG Huangping; HUANG Jufu

    2005-01-01

    Through the anaerobic chromatography on the columns of DEAE 52, Q-Sepharose and Sephacryl S-200, a nitrogenase MoFe protein (ΔnifZ Av1) was obtained from a nifZ deleted mutant of Azotobacter vinelandii (stain DJ194). The results of Western blotting after anoxic native electrophoresis and SDS-PAGE showed that ΔnifZ Av1 was similar to wild type MoFe protein (OP Av1) at the electrophoretic mobility, molecular weight and subunit composition. Furthermore, ΔnifZ Av1 was also similar to OP Av1 at the molybdenum content, EPR signal (g≈4.3, 3.65 and 2.01), and the molar extinction coefficient (Δε) of circular dichroism (CD) at 660 nm region. All of these indicated that, besides having the same α2β2 composition as OP Av1, the ΔnifZ Av1 also contained equal amount of reductive FeMoco in the spin state of S=3/2 to OP Av1. However, the iron content and substrate (C2H2, H+ and N2)-reduction activity of ΔnifZ Av1 were 74% and 46%―50% of those of OP Av1, respectively. Furthermore, the Δε at around 450 nm, which reflects P-cluster in Av1, was obviously lower than that of OP Av1. It suggested that the difference between ΔnifZ Av1 and OP Av1 resulted from P-cluster rather than FeMoco, and from the half number of P-cluster in ΔnifZ Av1, but the composition or redox state of P-cluster in ΔnifZ Av1 were not changed. Thus it could propose that ΔnifZ Av1 is composed of two different αβ subunit pairs. One is a FeMoco- and P-cluster-containing pair, and the other is a P-cluster-deficient but FeMoco-con- taining pair. Since the deletion of nifZ gene leads to the deficiency of only one of two P-clusters in a α2β2 tetramer, the assembly of P-cluster may not simply depend on one gene product, and so a possible mechanism of NifZ is supposed here.

  10. Characterization of a nitrogenase CrFe protein from a mutant UW3 of Azotobacter vinelandii grown on a Cr-containing medium

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhigang; ZHAO Ying; ZHANG Chunxi; BIAN Shaomin; ZHOU Huina; WANG Huangping; YIN Hong; HUANG Jufu

    2006-01-01

    Through the anoxic chromatography on the columns of DEAE-52, Q-Sepharose and Sephacryl S-200, a CrFe protein preparation was obtained from UW3, a mutant of Azotobacter vinelandii, which grew well on the Cr-containing medium. Compared with MoFe protein (OP Av1) from wild-type strain OP,-50% protein in the preparation had similar subunits composition and had immune reaction with antibody of OP Av1. The preparation had ~40% of C2H2-, H+-and N2 (expressed by the difference in H+-reduction activity between under Ar and under N2) -reduction activity of OP Av1 and similar electron pairs to those of OP Av1. And metal analysis showed that the preparation contained Fe, Cr and Mo. The circular dichroism (CD) spectrum in the preparation at ~450 nm was similar to that of OP Av1, while the relative intensities of three EPR signals appearing at the same g values (g≈4.3, 3.7 and 2.0) were different.The EPR-based calculated results showed that (1)the ratios of Mo to Cr and of Fe to (Cr+Mo) of the CrFe protein preparation were 0.41 and 15, respectively, indicating that in the preparation, a ratio of Cr-containing protein to MoFe protein was about 2.5;(2) the ratios of activity to Fe and to Cr of the preparation were close to the ratios of activity to Fe and to Mo of OP Av1, respectively; (3) the ratios of the EPR signal intensities at the above three g values to Cr of CrFe protein were about ~83%, 0% and ~40% of those to Mo of OP Av1, respectively. The results indicate further that CrFe protein might be a new nitrogenase component Ⅰ protein with a similar function and structure including metallocluster to those of MoFe protein instead of simple replacement of Mo by Mn in the cofactor.

  11. Kinetic Studies of Iron Deposition Catalyzed by Recombinant Human Liver Heavy, and Light Ferritins and Azotobacter Vinelandii Bacterioferritin Using O2 and H2O2 as Oxidants

    Science.gov (United States)

    Bunker, Jared; Lowry, Thomas; Davis, Garrett; Zhang, Bo; Brosnahan, David; Lindsay, Stuart; Costen, Robert; Choi, Sang; Arosio, Paolo; Watt, Gerald D.

    2005-01-01

    The discrepancy between predicted and measured H2O2 formation during iron deposition with recombinant heavy human liver ferritin (rHF) was attributed to reaction with the iron protein complex [Biochemistry 40 (2001) 10832-10838]. This proposal was examined by stopped-flow kinetic studies and analysis for H2O2 production using (1) rHF, and Azotobacter vinelandii bacterial ferritin (AvBF), each containing 24 identical subunits with ferroxidase centers; (2) site-altered rHF mutants with functional and dysfunctional ferroxidase centers; and (3) rccombinant human liver light ferritin (rLF), containing 110 ferroxidase center. For rHF, nearly identical pseudo-first-order rate constants of 0.18 per second at pH 7.5 were measured for Fe(2+) oxidation by both O2 and H2O2, but for rLF, the rate with O2 was 200-fold slower than that for H2O2 (k-0.22 per second). A Fe(2+)/O2 stoichiometry near 2.4 was measured for rHF and its site altered forms, suggesting formation of H2O2. Direct measurements revealed no H2O2 free in solution 0.5-10 min after all Fe(2+) was oxidized at pH 6.5 or 7.5. These results are consistent with initial H2O2 formation, which rapidly reacts in a secondary reaction with unidentified solution components. Using measured rate constants for rHF, simulations showed that steady-state H2O2 concentrations peaked at 14 pM at approx. 600 ms and decreased to zero at 10-30 s. rLF did not produce measurable H2O2 but apparently conducted the secondary reaction with H2O2. Fe(2+)/O2 values of 4.0 were measured for AvBF. Stopped-flow measurements with AvBF showed that both H2O2 and O2 react at the same rate (k=0.34 per second), that is faster than the reactions with rHF. Simulations suggest that AvBF reduces O2 directly to H2O without intermediate H2O2 formation.

  12. Functional NifD-K fusion protein in Azotobacter vinelandii is a homodimeric complex equivalent to the native heterotetrameric MoFe protein

    International Nuclear Information System (INIS)

    The MoFe protein of the complex metalloenzyme nitrogenase folds as a heterotetramer containing two copies each of the homologous α and β subunits, encoded by the nifD and the nifK genes respectively. Recently, the functional expression of a fusion NifD-K protein of nitrogenase was demonstrated in Azotobacter vinelandii, strongly implying that the MoFe protein is flexible as it could accommodate major structural changes, yet remain functional [M.H. Suh, L. Pulakat, N. Gavini, J. Biol. Chem. 278 (2003) 5353-5360]. This finding led us to further explore the type of interaction between the fused MoFe protein units. We aimed to determine whether an interaction exists between the two fusion MoFe proteins to form a homodimer that is equivalent to native heterotetrameric MoFe protein. Using the Bacteriomatch Two-Hybrid System, translationally fused constructs of NifD-K (fusion) with the full-length λCI of the pBT bait vector and also NifD-K (fusion) with the N-terminal α-RNAP of the pTRG target vector were made. To compare the extent of interaction between the fused NifD-K proteins to that of the β-β interactions in the native MoFe protein, we proceeded to generate translationally fused constructs of NifK with the α-RNAP of the pTRG vector and λCI protein of the pBT vector. The strength of the interaction between the proteins in study was determined by measuring the β-galactosidase activity and extent of ampicillin resistance of the colonies expressing these proteins. This analysis demonstrated that direct protein-protein interaction exists between NifD-K fusion proteins, suggesting that they exist as homodimers. As the interaction takes place at the β-interfaces of the NifD-K fusion proteins, we propose that these homodimers of NifD-K fusion protein may function in a similar manner as that of the heterotetrameric native MoFe protein. The observation that the extent of protein-protein interaction between the β-subunits of the native MoFe protein in Bacterio

  13. Role of Escherichia coli nitrogen regulatory genes in the nitrogen response of the Azotobacter vinelandii NifL-NifA complex.

    Science.gov (United States)

    Reyes-Ramirez, F; Little, R; Dixon, R

    2001-05-01

    The redox-sensing flavoprotein NifL inhibits the activity of the nitrogen fixation (nif)-specific transcriptional activator NifA in Azotobacter vinelandii in response to molecular oxygen and fixed nitrogen. Although the mechanism whereby the A. vinelandii NifL-NifA system responds to fixed nitrogen in vivo is unknown, the glnK gene, which encodes a PII-like signal transduction protein, has been implicated in nitrogen control. However, the precise function of A. vinelandii glnK in this response is difficult to establish because of the essential nature of this gene. We have shown previously that A. vinelandii NifL is able to respond to fixed nitrogen to control NifA activity when expressed in Escherichia coli. In this study, we investigated the role of the E. coli PII-like signal transduction proteins in nitrogen control of the A. vinelandii NifL-NifA regulatory system in vivo. In contrast to recent findings with Klebsiella pneumoniae NifL, our results indicate that neither the E. coli PII nor GlnK protein is required to relieve inhibition by A. vinelandii NifL under nitrogen-limiting conditions. Moreover, disruption of both the E. coli glnB and ntrC genes resulted in a complete loss of nitrogen regulation of NifA activity by NifL. We observe that glnB ntrC and glnB glnK ntrC mutant strains accumulate high levels of intracellular 2-oxoglutarate under conditions of nitrogen excess. These findings are in accord with our recent in vitro observations (R. Little, F. Reyes-Ramirez, Y. Zhang, W. Van Heeswijk, and R. Dixon, EMBO J. 19:6041-6050, 2000) and suggest a model in which nitrogen control of the A. vinelandii NifL-NifA system is achieved through the response to the level of 2-oxoglutarate and an interaction with PII-like proteins under conditions of nitrogen excess. PMID:11325935

  14. A metodologia de superfície de resposta como ferramenta para a avaliação da produção de alginato e poli-hidroxibutirato pela Azotobacter vinelandii = The response surface methodology as a tool for assessing the production of alginate and polyhydroxybutirate by Azotobacter vinelandii

    Directory of Open Access Journals (Sweden)

    Adriana Navarro da Silva

    2010-07-01

    Full Text Available O alginato é um polissacarídeo normalmente extraído de paredes celulares de algas marrons e utilizado nas indústrias de alimentos, farmacêuticas e biotecnológicas. A produção é concentrada no cultivo de algas marinhas marrons, mas várias bactérias do gênero Pseudomonas e Azotobacter produzem alginato. A estrutura química dos alginatosproduzidos por algas é similar a dos sintetizados pela A. vinelandii. Esta bactéria também produz polímeros intracelulares como o poli-hidroxibutirato (PHB, conhecido como bioplástico. Neste trabalho, estudou-se a produção simultânea do alginato e PHB pela A.vinelandii, utilizando-se sacarose e diferentes parâmetros de fermentação em agitador orbital rotatório. Os valores ótimos para produção destes compostos foram determinados pela MSR. O 1º experimento foi um planejamento fatorial fracionado 26-2. O 2º foi baseado nas variáveis significativas do 1º experimento, resultando em um planejamento fatorial completo 33-0. Verificou-se, do primeiro para o segundo, aumento na produtividade do PHB de 12 para 45 mg g-1 de célula h-1 e do alginato de 100 para 1.600 mg g-1 de célula h-1. Aprodutividade de ambos os compostos foi máxima na temperatura de incubação de 62ºC, no menor tempo de incubação (18h e na concentração de sacarose de 11 g L-1. Em ambos os experimentos, o PHB extraído apresentou pureza de 94%.Alginate is a polysaccharide extracted from cell walls of brown algae and used in the food, pharmaceuticals and biotech industries. Production is concentrated on the cultivation of brown seaweed, but several bacteria of the genus Pseudomonas and Azotobacter producealginate. The chemical structure of alginates produced by algae is similar to those synthesized by A. vinelandii. The bacteria also produce intracellular polymers such as polyhydroxybutyrate (PHB, known as bioplastic. This work studied the simultaneous alginate and PHB production by A. vinelandii using sucrose and

  15. Regulation of nitrogen fixation in Klebsiella pneumoniae and Azotobacter vinelandii: NifL, transducing two environmental signals to the nif transcriptional activator NifA.

    Science.gov (United States)

    Schmitz, Ruth A; Klopprogge, Kai; Grabbe, Roman

    2002-05-01

    The enzymatic reduction of molecular nitrogen to ammonia requires high amounts of energy, and the presence of oxygen causes the catalyzing nitrogenase complex to be irreversible inactivated. Thus nitrogen-fixing microorganisms tightly control both the synthesis and activity of nitrogenase to avoid the unnecessary consumption of energy. In the free-living diazotrophs Klebsiella pneumoniae and Azotobacter vinelandii, products of the nitrogen fixation nifLA operon regulate transcription of the other nifoperons. NifA activates transcription of nif genes by the alternative form of RNA-polymerase, sigma54-holoenzyme; NifL modulates the activity of the transcriptional activator NifA in response to the presence of combined nitrogen and molecular oxygen. The translationally-coupled synthesis of the two regulatory proteins, in addition to evidence from studies of NifL/NifA complex formation, imply that the inhibition of NifA activity by NifL occurs via direct protein-protein interaction in vivo. The inhibitory function of the negative regulator NifL appears to lie in the C-terminal domain, whereas the N-terminal domain binds FAD as a redox-sensitive cofactor, which is required for signal transduction of the internal oxygen status. Recently it was shown, that NifL acts as a redox-sensitive regulatory protein, which modulates NifA activity in response to the redox-state of its FAD cofactor, and allows NifA activity only in the absence of oxygen. In K. pneumoniae, the primary oxygen sensor appears to be Fnr (fumarate nitrate reduction regulator), which is presumed to transduce the signal of anaerobiosis towards NifL by activating the transcription of gene(s) whose product(s) function to relieve NifL inhibition through reduction of the FAD cofactor. In contrast, the reduction of A. vinelandii-NifL appears to occur unspecifically in response to the availability of reducing equivalents in the cell. Nitrogen status of the cells is transduced towards the NifL/NifA regulatory system

  16. HONGOS MICORRÍZICOS ARBUSCULARES, Azotobacter chroococcum, Bacillus megatherium Y FitoMas-E: UNA ALTERNATIVA EFICAZ PARA LA REDUCCIÓN DEL CONSUMO DE FERTILIZANTES MINERALES EN Psidium guajava, L. var. Enana Roja cubana

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    Leudiyanes Ramos Hernández

    2013-01-01

    Full Text Available El trabajo experimental se desarrolló en la Unidad Básica de Producción Cooperativa (UBPC «Batalla de Jobito» ubicada en el municipio «El Salvador», provincia Guantánamo en el período comprendido entre los años 2007-2009. El objetivo de la investigación fue definir una alternativa de manejo nutricional basada en el empleo de hongos micorrízicos arbusculares (HMA, Azotobacter chroococcum , Bacillus megatherium y el fitoestimulante FitoMas-E, como vía factible para la reducción de la fertilización mineral en el cultivo de la guayaba Enana Roja cubana, sin afectaciones a los rendimientos. Para el montaje del experimento se combinaron 10 g.planta -1 de micorriza (especie: Glomus intraradices ; 2 L.ha -1 de AZOMEG [producto comercial compuesto por Azotobacter chroococcum (2x10 11 ufc x mL -1 y Bacillus megatherium (3.2x10 11 ufc x mL -1 ] y 1 L.ha -1 de FitoMas-E con la reducción gradual de la fertilización mineral de N y P; utilizando el 100, 75, 50 y 25 % respectivamente. Como variable respuesta se midieron la altura de las plantas, los pares de hojas, el número de brindillas, el número de flores y frutos, el diámetro polar y ecuatorial y peso promedio de los frutos; también se calcularon la pérdida de peso postcosecha y el rendimiento. Los resultados experimentales demostraron que la combinación del 75 % de la fertilización mineral con los biofertilizantes y el FitoMas-E fue superior al resto de los tratamientos en estudio para las variables evaluadas, así como posibilitó la reducción del 25 % de la fertilización mineral y obtener una mejor respuesta económica.

  17. The product of the nitrogen fixation regulatory gene nfrX of Azotobacter vinelandii is functionally and structurally homologous to the uridylyltransferase encoded by glnD in enteric bacteria.

    Science.gov (United States)

    Contreras, A; Drummond, M; Bali, A; Blanco, G; Garcia, E; Bush, G; Kennedy, C; Merrick, M

    1991-12-01

    We sequenced the nitrogen fixation regulatory gene nfrX from Azotobacter vinelandii, mutations in which cause a Nif- phenotype, and found that it encodes a 105-kDa protein (NfrX), the N terminus of which is highly homologous to that of the uridylyltransferase-uridylyl-removing enzyme encoded by glnD in Escherichia coli. In vivo complementation experiments demonstrate that the glnD and nfrX products are functionally interchangeable. A vinelandii nfrX thus appears to encode a uridylyltransferase-uridylyl-removing enzyme, and in this paper we report the first sequence of such a protein. The Nif- phenotype of nfrX mutants can be suppressed by a second mutation in a recently identified nifL-like gene immediately upstream of nifA in A. vinelandii. NifL mediates nif regulation in response to the N status in A. vinelandii, presumably by inhibiting NifA activator function as occurs in Klebsiella pneumoniae; thus, one role of NfrX is to modify, either directly or indirectly, the activity of the nifL product. PMID:1683868

  18. Structure of C42D Azotobacter vinelandii FdI. A Cys-X-X-Asp-X-X-Cys motif ligates an air-stable [4Fe-4S]2+/+ cluster.

    Science.gov (United States)

    Jung, Y S; Bonagura, C A; Tilley, G J; Gao-Sheridan, H S; Armstrong, F A; Stout, C D; Burgess, B K

    2000-11-24

    All naturally occurring ferredoxins that have Cys-X-X-Asp-X-X-Cys motifs contain [4Fe-4S](2+/+) clusters that can be easily and reversibly converted to [3Fe-4S](+/0) clusters. In contrast, ferredoxins with unmodified Cys-X-X-Cys-X-X-Cys motifs assemble [4Fe-4S](2+/+) clusters that cannot be easily interconverted with [3Fe-4S](+/0) clusters. In this study we changed the central cysteine of the Cys(39)-X-X-Cys(42)-X-X-Cys(45) of Azotobacter vinelandii FdI, which coordinates its [4Fe-4S](2+/+) cluster, into an aspartate. UV-visible, EPR, and CD spectroscopies, metal analysis, and x-ray crystallography show that, like native FdI, aerobically purified C42D FdI is a seven-iron protein retaining its [4Fe-4S](2+/+) cluster with monodentate aspartate ligation to one iron. Unlike known clusters of this type the reduced [4Fe-4S](+) cluster of C42D FdI exhibits only an S = 1/2 EPR with no higher spin signals detected. The cluster shows only a minor change in reduction potential relative to the native protein. All attempts to convert the cluster to a 3Fe cluster using conventional methods of oxygen or ferricyanide oxidation or thiol exchange were not successful. The cluster conversion was ultimately accomplished using a new electrochemical method. Hydrophobic and electrostatic interaction and the lack of Gly residues adjacent to the Asp ligand explain the remarkable stability of this cluster.

  19. Transcriptional regulation of cytochrome d in nitrogen-fixing Azotobacter vinelandii. Evidence that up-regulation during N2 fixation is independent of nifA but dependent on ntrA.

    Science.gov (United States)

    Moshiri, F; Smith, E G; Taormino, J P; Maier, R J

    1991-12-01

    Cytochrome d has been postulated to be the "respiratory protection" oxidase of Azotobacter vinelandii, allowing this organism to fix nitrogen under aerobic growth conditions. We have previously cloned and characterized the structural genes for the A. vinelandii cytochrome d (cydA and cydB). The cyd genes are co-transcribed, yielding an mRNA of approximately 3.6 kilobase pairs. The level of the cyd message was 2-3-fold higher in cells that were fixing nitrogen, as compared with non-nitrogen-fixing cells. RNase protection analysis was used to determine the transcriptional start site at 275 bases upstream of the initiator ATG of cydA, and this start site was the same for nitrogen-fixing and non-nitrogen-fixing cells. The cyd promoter has sequence similarities to the canonical Escherichia coli promoters, which are transcribed by the major sigma 70 form of RNA polymerase. Plasmid-borne lacZ transcriptional fusions were constructed, using approximately 650 base pairs of 5'-upstream sequences of the cyd structural genes. This region had a strong promoter activity which was further up-regulated 1.5-2.5-fold upon the induction of nitrogen fixation. The cyd-lacZ fusions were characterized in a nifA- as well as an ntrA- background. Mutations in neither of these nif regulatory genes affected the constitutive expression of cyd under non-nitrogen-fixing conditions. However, the up-regulation of this promoter during the induction of nitrogen fixation was abolished only in the ntrA- background. Based on these results, the cytochrome d promoter of A. vinelandii belongs to a new class of nitrogen-regulated promoters which, unlike the authentic nif genes, does not require the ntrA gene product for its expression. The up-regulation of this promoter during nitrogen fixation, however, requires the ntrA gene product. PMID:1660468

  20. A T14C variant of Azotobacter vinelandii ferredoxin I undergoes facile [3Fe-4S]0 to [4Fe-4S]2+ conversion in vitro but not in vivo.

    Science.gov (United States)

    Gao-Sheridan, H S; Kemper, M A; Khayat, R; Tilley, G J; Armstrong, F A; Sridhar, V; Prasad, G S; Stout, C D; Burgess, B K

    1998-12-11

    [4Fe-4S]2+/+ clusters that are ligated by Cys-X-X-Cys-X-X-Cys sequence motifs share the general feature of being hard to convert to [3Fe-4S]+/0 clusters, whereas those that contain a Cys-X-X-Asp-X-X-Cys motif undergo facile and reversible cluster interconversion. Little is known about the factors that control the in vivo assembly and conversion of these clusters. In this study we have designed and constructed a 3Fe to 4Fe cluster conversion variant of Azotobacter vinelandii ferredoxin I (FdI) in which the sequence that ligates the [3Fe-4S] cluster in native FdI was altered by converting a nearby residue, Thr-14, to Cys. Spectroscopic and electrochemical characterization shows that when purified in the presence of dithionite, T14C FdI is an O2-sensitive 8Fe protein. Both the new and the indigenous clusters have reduction potentials that are significantly shifted compared with those in native FdI, strongly suggesting a significantly altered environment around the clusters. Interestingly, whole cell EPR have revealed that T14C FdI exists as a 7Fe protein in vivo. This 7Fe form of T14C FdI is extremely similar to native FdI in its spectroscopic, electrochemical, and structural features. However, unlike native FdI which does not undergo facile cluster conversion, the 7Fe form T14C FdI quickly converts to the 8Fe form with a high efficiency under reducing conditions.

  1. Kinetics of nitrogenase from Azotobacter vinelandii.

    NARCIS (Netherlands)

    Duyvis, M.G.

    1997-01-01

    Nitrogenase has been the subject of many investigations since the early 1960's. The catalytic mechanism of nitrogenase is unique because it couples the transfer of electrons with the hydrolysis of MgATP. The details of the mechanism are still to be revealed. The work described in this thesis aimed a

  2. 缺失nifH的棕色固氮菌突变种固氮酶钼铁蛋白的结晶%Crystallization of MoFe Protein (△nifH Av1) from a nifH Deleted Strain of Azotobacter vinelandii

    Institute of Scientific and Technical Information of China (English)

    边少敏; 赵剑峰; 吕玉兵; 赵颖; 周会娜; 王耀萍; 黄巨富

    2004-01-01

    A FeMoco-deficient △nifHAv1 was partially purified from a nifHdeleted mutant DJ54 of Azotobacter vinelandii Lipmann grown in NH3-limited medium. By using the same purification method, △nifE Av1 and NifB-Av1 were obtained from DJ35 and UW45, respectively. The latter two proteins were obviously much purer than △nifHAv1. Under a suitable condition for crystallization, dark brown short rhombohedron crystals could be obtained from the three proteins. Like NifB-Av1, the time for formation of △nifHAv1 crystal was longer than that of △nifEAv1. But the optimal concentrations of precipitant and buffer for crystallization of △nifH Av1 were similar to those of △nifE Av1. SDS-PAGE analysis showed that the crystalline △nifHAv1 was similar in the composition to OP Av1. It indicates that the crystal formed in △nifH Av1 solution could be the protein crystal.%从限氨固氮培养基中培养的缺失nif H的棕色固氮菌(Azotobacter vinelandii Lipmann)突变种DJ54中,分离纯化出部分纯的缺失FeMoco的钼铁蛋白(△nifH Av1).用相同纯化方法分别从DJ35和UW45突变种中纯化的△nifE Av1和NifB- Av1的纯度明显高于△nifH Av1的纯度.在合适的结晶条件下,可得到这三种蛋白的深棕色短斜四棱柱晶体.△nifH Av1与NifB- Av1一样,晶体形成所需的时间比△nifE Av1的长.而它结晶所需的沉淀剂和缓冲液最适浓度则与△nifE Av1的相同.SDS-PAGE鉴定表明,结晶的△nifH Av1与OP Av1的组成相似.这表明,在△nifH Av1溶液中形成的晶体可能就是该蛋白质的晶体.

  3. Purification and Activation In Vitro of MoFe Protein from a nifE Deleted Mutant Strain of Azotobacter vinelandii%缺失nifE的棕色固氮菌突变种MoFe蛋白的纯化及体外激活

    Institute of Scientific and Technical Information of China (English)

    赵剑峰; 赵颖; 汪志平; 吕玉兵; 潜中兴; 黄巨富

    2003-01-01

    The △ nif E MoFe protein ( △ nif EAv1) was obtained by a chromatography on DE52, SephacrylS-300 and Q-Sepharose columns from the unheated crude extract of nifE-deleted mutant strain (DJ35)of Azotobacter vinelandii Lipmann. The analysis by SDS-PAGE showed that the △ nifEAv1 was similar toOP MoFe protein (Av1) of A. vinelandii in the kinds and molecular weights of subunits (α and β subunit).When complemented with nitrogenase Fe protein (Av2), the △ nif EAv1 had hardly any proton-reductionactivity, but could be significantly activated by FeMoco extracted from OP Av1. After the △ nif E Av1 wastreated with an excess o-phenanthroline (o-phen) and chromatographied on Sephadex G-25 column underatmosphere of Ar, △ nif EAv1 was obtained. In the presence of both Av2 and MgATP regenerationsystem, the △ nif E Av1 , rather than △ nif E Av1, was significantly activated in vitro by a reconstituentsolution containing Mn which composed of KMnO4, ferric homocitrate, Na2S, Na2S2O4 (DT) and dithiothreitol(DTT). But in the absence of MgATP or Av2, the activation of △nifE Av1 did not happen. It indicates thatactivation of △ nif E Av1 by RS-Mn requires the pretreatment with o-phen and the simultaneous presenceof Av2 and MgATP.%经DEAE纤维素、Sephacryl S-300和Q-Sepharose柱层析分离纯化,从缺失nifE的棕色固氮菌(Azotobactervinelandii Lipmann)突变种(DJ35)的无细胞粗提物中得到△nifE MoFe蛋白(△nifE Av1).SDS凝胶电泳分析表明,△nifE Av1的亚单位种类和分子量分别与棕色固氮菌野生型(OP)MoFe蛋白(Av1)的α和β亚单位相似.当与固氮酶Fe蛋白(Av2)活性互补时,△nifE Av1不具有还原质子的能力,但从OP Av1中抽提的FeMoco却可使其激活.经过量的邻菲啰啉(o-phen)厌氧处理并经Sephadex G-25柱层析分离后,便得到△nifE Av1 .在同时存在Av2和MgATP发生系统的条件下,△nifE Av1 ,而不是△nifE Av1,可为由KMnO4、高柠檬酸铁、Na2S、Na2S2O4和二硫苏糖醇组成

  4. Electron transport through the nitrogenase enzyme complex of Azotobacter vinelandii

    OpenAIRE

    Braaksma, A.

    1985-01-01

    In Chapter VII (Discussion) the current thoughts as they were accepted in 1980 about the electron transport within the nitrogenase complex are summarized. The starting points and ideas about the subject of this thesis are also given. In this way, Chapter VII can be considered both as a summary and as a discussion for the scientific interested reader. For those, who are less familiar with this kind of research, the following summary gives the results of this study which emerge in the different...

  5. Electron transport through the nitrogenase enzyme complex of Azotobacter vinelandii

    NARCIS (Netherlands)

    Braaksma, A.

    1985-01-01

    In Chapter VII (Discussion) the current thoughts as they were accepted in 1980 about the electron transport within the nitrogenase complex are summarized. The starting points and ideas about the subject of this thesis are also given. In this way, Chapter VII can be considered both as a summary and a

  6. SYMBIOTIC EFFECTIVENESS OF RHIZOBIUM LEGUMINOSARUM BV. VICIAE WITH PEA PLANTS AS INFLUENCED BY AZOTOBACTER CHROOCOCCUM

    Directory of Open Access Journals (Sweden)

    Stefan Martyniuk

    2015-09-01

    Full Text Available The aim of this work was to examine the effects of A. chroococcum on the proliferation of R. leguminosarum bv. viciae (Rlv in a solid-carrier inoculant and on symbiotic effectiveness of Rlv with pea plants grown under laboratory and field conditions. In a laboratory experiment it was found that proliferation of both bacterial species, Rlv and A. chroococcum, in the dual-culture inoculants was efficient, and that A. chroococcum had no adverse effects on the development of the rhizobia (Rlv in the solid-carrier inoculant. In a pot experiment the highest number of nodules was detected on roots of pea plants inoculated with the dual-culture inoculant containing Rlv and A. chroococcum, slightly lower numbers on pea roots inoculated with the mono-culture inoculum of Rlv and almost no nodules were found on the roots of pea un-inoculated (control treatment with the bacteria. In the micro-plot experiment conducted in the years 2011–2012 pre-sowing inoculation of pea seeds with the mono-culture inoculant of Rlv or with the mixed inoculant of Rlv and A. chroococcum slightly increased nodule numbers/plant, pod numbers/plant and seed numbers/pod, as compared to the un-inoculated control, but these differences were not reflected in pea seed yields/m2, which were similar in all treatments.

  7. Characterization of transcripts expressed from nitrogenase-3 structural genes of Azotobacter vinelandii.

    Science.gov (United States)

    Premakumar, R; Jacobson, M R; Loveless, T M; Bishop, P E

    1992-09-01

    Five major anfH-hybridizing mRNA species accumulated in Azobacter vinelandii cells derepressed for nitrogenase-3 (an alternative nitrogenase, which appears to lack Mo and V). Using anfH-, anfD-, anfG-, anfK-, and orflorf2-specific probes and mutant strains of A. vinelandii these mRNA species have been identified as encoding anfHDGKorflorf2 (6.0 kb), anfHDGK (4.3 kb), anfHD (2.6 kb), vnfHorfFd (1.3 kb), and vnfH and (or) anfH (1.0 kb). A 0.6-kb mRNA species, which hybridized only to the orflorf2-specific probe, and a 3.5-kb mRNA species, which hybridized to anfD or anfK, also accumulated under these conditions. Northern blot analysis and S1 nuclease mapping indicate that transcription of the anf structural gene cluster initiates at a unique nif consensus promoter situated 127 base pairs upstream from the anfH coding region. Observation of anfH-hybridizing mRNA species that accumulate in strains derepressed for nitrogen fixation demonstrates that transcription of the anfHDGKorflorf2 cluster is normally repressed by Mo, V, and NH4+, whereas transcription of the vnfHorfFd cluster does not require the presence of V and is repressed only by Mo, but not NH4+. Analysis of the accumulation of mRNAs in a tungsten-tolerant strain revealed that Mo and V repression of anf transcription must occur by different mechanisms. PMID:1281443

  8. Analysis of respiratory activity and carbon usage of a mutant of Azotobacter vinelandii impaired in poly-β-hydroxybutyrate synthesis.

    Science.gov (United States)

    Jiménez, Lucero; Castillo, Tania; Flores, Celia; Segura, Daniel; Galindo, Enrique; Peña, Carlos

    2016-08-01

    In this study, the respiratory activity and carbon usage of the mutant strain of A. vinelandii AT6, impaired in poly-β-hydroxybutyrate (PHB) production, and their relationship with the synthesis of alginate were evaluated. The alginate yield and the specific oxygen uptake rate were higher (2.5-fold and 62 %, respectively) for the AT6 strain, compared to the control strain (ATCC 9046), both in shake flasks cultures and in bioreactor, under fixed dissolved oxygen tension (1 %). In contrast, the degree of acetylation was similar in both strains. These results, together with the analysis of carbon usage (% C-mol), suggest that in the case of the AT6 strain, the flux of acetyl-CoA (precursor molecule for PHB biosynthesis and alginate acetylation) was diverted to the respiratory chain passing through the tricarboxylic acids cycle, and an important % C-mol was directed through alginate biosynthesis, up to 25.9 % and to a lesser extent, to biomass production (19.7 %). PMID:27154760

  9. Characterization of an altered MoFe protein from a nifV- strain from Azotobacter vinelandii

    OpenAIRE

    Comaratta, Leonard M.

    1998-01-01

    ABSTRACT The site of substrate binding and reduction for the nitrogenase complex is located on the iron molybdenum cofactor (FeMo-co) which is contained within the a-subunit of the molybdenum iron protein. FeMo co consists of a metal sulfur core composed of an FeS cluster bridged by three inorganic sulfides to a MoFeS cluster. An organic acid, homocitrate, is coordinated to the Mo atom through its 2-carboxy and 2-hydroxy groups. Homocitrate is formed by the condensation of acetyl-CoA a...

  10. Purification and characterization of the nifN and nifE gene products from Azotobacter vinelandii mutant UW45.

    OpenAIRE

    Paustian, T D; Shah, V K; Roberts, G P

    1989-01-01

    The nifN and -E gene products are involved in the synthesis of the iron-molybdenum cofactor of dinitrogenase, the enzyme responsible for the reduction of dinitrogen to ammonia. By using the in vitro iron-molybdenum cofactor biosynthesis assay, we have followed the purification of these gene products 450-fold to greater than 95% purity. An overall recovery of 20% was obtained with the purified protein having a specific activity of 6900 units/mg of protein. The protein (hereafter referred to as...

  11. Peptidyl-Prolyl cis/trans Isomerase-Independent Functional NifH Mutant of Azotobacter vinelandii†

    OpenAIRE

    Gavini, Nara; Tungtur, Sudheer; Pulakat, Lakshmi

    2006-01-01

    Peptidyl-prolyl cis/trans isomerases (PPIases) play a pivotal role in catalyzing the correct folding of many prokaryotic and eukaryotic proteins that are implicated in a variety of biological functions, ranging from cell cycle regulation to bacterial infection. The nif accessory protein NifM, which is essential for the biogenesis of a functional NifH component of nitrogenase, is a PPIase. To understand the nature of the molecular signature that defines the NifM dependence of NifH, we screened...

  12. Evaluation of Gene Expression and Alginate Production in Response to Oxygen Transfer in Continuous Culture of Azotobacter vinelandii

    Science.gov (United States)

    Díaz-Barrera, Alvaro; Martínez, Fabiola; Guevara Pezoa, Felipe; Acevedo, Fernando

    2014-01-01

    Alginates are polysaccharides used as food additives and encapsulation agents in biotechnology, and their functional properties depend on its molecular weight. In this study, different steady-states in continuous cultures of A. vinelandii were established to determine the effect of the dilution rate (D) and the agitation rate on alginate production and expression of genes involved in alginate polymerization and depolymerization. Both, the agitation and dilution rates, determined the partitioning of the carbon utilization from sucrose into alginate and CO2 under oxygen-limiting conditions. A low D (0.07 h−1) and 500 rpm resulted in the highest carbon utilization into alginate (25%). Quantitative real-time polymerase chain reaction was used to determine the transcription level of six genes involved in alginate polymerization and depolymerization. In chemostat cultures at 0.07 h−1, the gene expression was affected by changes in the agitation rate. By increasing the agitation rate from 400 to 600 rpm, the algE7 gene expression decreased tenfold, whereas alyA1, algL and alyA2 gene expression increased between 1.5 and 2.8 times under similar conditions evaluated. Chemostat at 0.07 h−1 showed a highest alginate molecular weight (580 kDa) at 500 rpm whereas similar molecular weights (480 kDa) were obtained at 400 and 600 rpm. The highest molecular weight was not explained by changes in the expression of alg8 and alg44 (genes involved in alginate polymerization). Nonetheless, a different expression pattern observed for lyases could explain the highest alginate molecular weight obtained. Overall, the results suggest that the control of alginate molecular weight in A. vinelandii cells growing in continuous mode is determined by a balance between the gene expression of intracellular and extracellular lyases in response to oxygen availability. These findings better our understanding of the biosynthesis of bacterial alginate and help us progress toward obtain tailor-made alginates. PMID:25162704

  13. Evaluation of gene expression and alginate production in response to oxygen transfer in continuous culture of Azotobacter vinelandii.

    Directory of Open Access Journals (Sweden)

    Alvaro Díaz-Barrera

    Full Text Available Alginates are polysaccharides used as food additives and encapsulation agents in biotechnology, and their functional properties depend on its molecular weight. In this study, different steady-states in continuous cultures of A. vinelandii were established to determine the effect of the dilution rate (D and the agitation rate on alginate production and expression of genes involved in alginate polymerization and depolymerization. Both, the agitation and dilution rates, determined the partitioning of the carbon utilization from sucrose into alginate and CO2 under oxygen-limiting conditions. A low D (0.07 h(-1 and 500 rpm resulted in the highest carbon utilization into alginate (25%. Quantitative real-time polymerase chain reaction was used to determine the transcription level of six genes involved in alginate polymerization and depolymerization. In chemostat cultures at 0.07 h(-1, the gene expression was affected by changes in the agitation rate. By increasing the agitation rate from 400 to 600 rpm, the algE7 gene expression decreased tenfold, whereas alyA1, algL and alyA2 gene expression increased between 1.5 and 2.8 times under similar conditions evaluated. Chemostat at 0.07 h(-1 showed a highest alginate molecular weight (580 kDa at 500 rpm whereas similar molecular weights (480 kDa were obtained at 400 and 600 rpm. The highest molecular weight was not explained by changes in the expression of alg8 and alg44 (genes involved in alginate polymerization. Nonetheless, a different expression pattern observed for lyases could explain the highest alginate molecular weight obtained. Overall, the results suggest that the control of alginate molecular weight in A. vinelandii cells growing in continuous mode is determined by a balance between the gene expression of intracellular and extracellular lyases in response to oxygen availability. These findings better our understanding of the biosynthesis of bacterial alginate and help us progress toward obtain tailor-made alginates.

  14. The nifU, nifS and nifV gene products are required for activity of all three nitrogenases of Azotobacter vinelandii.

    Science.gov (United States)

    Kennedy, C; Dean, D

    1992-02-01

    Strains with mutations in 23 of the 30 genes and open reading frames in the major nif gene cluster of A. vinelandii were tested for ability to grow on N-free medium with molybdenum (Nif phenotype), with vanadium (Vnf phenotype), or with neither metal present (Anf phenotype). As reported previously, nifE, nifN, nifU, nifS and nifV mutants were Nif- (failed to grow on molybdenum) while nifM mutants were Nif-, Vnf- and Anf-. nifV, nifS, and nifU mutants were found to be unable to grow on medium with or without vanadium, i.e. were Vnf- Anf-. Therefore neither vnf nor anf analogoues of nifU, nifS, nifV or nifM are expected to be present in A. vinelandii. PMID:1538703

  15. NifB and NifEN protein levels are regulated by ClpX2 under nitrogen fixation conditions in Azotobacter vinelandii

    OpenAIRE

    Martínez-Noël, Giselle; Curatti, Leonardo; Hernandez, Jose A.; Rubio, Luis M.

    2011-01-01

    The major part of biological nitrogen fixation is catalyzed by the molybdenum nitrogenase that carries at its active site the iron and molybdenum cofactor (FeMo-co). The nitrogen fixation (nif) genes required for the biosynthesis of FeMo-co are derepressed in the absence of a source of fixed nitrogen. The nifB gene product is remarkable because it assembles NifB-co, a complex cluster proposed to have a [6Fe-9S-X] composition, from simpler [Fe-S] clusters common to other metabolic pathways. Ni...

  16. Biosynthesis of the Nitrogenase FeMo-cofactor from Azotobacter vinelandii: Involvement of the NifEN complex, NifX and the Fe protein

    OpenAIRE

    Goodwin, Paul Joshua

    1999-01-01

    The iron-molybdenum cofactor (FeMo-cofactor) of nitrogenase is the subject of one the most intensive biochemical/genetic detective cases of modern science. At the active site of nitrogenase, the FeMo-cofactor not only represents the heart of biological nitrogen fixation, but its synthesis also serves as a model for complex metallocluster biosynthesis. Research in the Dean Lab is focused on furthering the understanding of Fe-S cluster biosynthesis in the nitrogenase enzyme system. Through...

  17. Impact of seed coatings on diversity of soybean rhizospheric azotobacter%种衣剂对大豆根际固氮菌多样性的影响

    Institute of Scientific and Technical Information of China (English)

    韩雪; 孙龙; 仕相林; 尹晓玉; 文景芝

    2010-01-01

    利用变性梯度凝胶电泳(DGGE)技术研究宁南霉素、甲霜灵、多克福和咯菌腈4种种衣剂对大豆根际固氮菌多样性的影响.运用nif H基因的特异引物对,将大豆根际土壤总DNA进行PCR扩增后,通过DGGE技术对PCR产物进行分析.结果表明,种衣剂对固氮菌产生了不同程度的抑制作用.对大豆根际固氮菌抑制作用由强到弱的种衣剂品种依次是咯菌腈、甲霜灵、多克福和宁南霉素;种衣剂浓度对大豆根际固氮菌多样性的抑制程度不同,但没有明显规律.

  18. nasST, two genes involved in the induction of the assimilatory nitrite-nitrate reductase operon (nasAB) of Azotobacter vinelandii.

    Science.gov (United States)

    Gutierrez, J C; Ramos, F; Ortner, L; Tortolero, M

    1995-11-01

    An operon including two new genes (nasS and nasT) has been defined, cloned and sequenced. The deduced NASS protein is homologous to NRTA from Synechococcus sp. and to NASF from Klebsiella pneumoniae, two proteins involved in nitrate uptake. The predicted NAST polypeptide is homologous to the regulator proteins of the two-component regulatory systems. NASS plays a negative regulatory role in the synthesis of the nitrate and nitrite reductase. NAST is required for the expression of the nitrite-nitrate reductase operon (nasAB). Expression of the nasST operon is not under the control of the NTR system and is not regulated by the nitrogen source. A Phi(nasA-lacZ) fusion has been used to analyse expression of the nasAB operon in three different genetic backgrounds with altered nitrate reductase activity. Beta-galactosidase activity in two of them was independent of nitrate but in a mutant unable to reduce nitrate, nas-4, it was normally induced by nitrate. PMID:8748040

  19. Genetic Complementation Studies of Human Pin1 in Azotobacter vinelandii Revealed that it Requires Amino Terminus of the NifM to Deliver PPIase Effect to the Fe-protein of Nitrogenase

    OpenAIRE

    Kumaraguru Raja; Lakshmi Pulakat; Narayanan Gavini

    2006-01-01

    The NifM is a peptidyl prolyl cis-trans isomerase and is required for the maturation and activation of the Fe protein of Nitrogenase. Since the carboxyl terminus of NifM is similar to the Human Pin1, we expressed the Human Pin1 in A. vinelandii BG98, a nifM mutant strain containing a kanamycin insertion and found that it could not complement the function of nifM. It was hypothesized that the amino terminus of the NifM might be required for the Pin1 to bind to NifH similar to requirement of th...

  20. Genetic analysis on the NifW by utilizing the yeast two-hybrid system revealed that the NifW of Azotobacter vinelandii interacts with the NifZ to form higher-order complexes.

    Science.gov (United States)

    Lee, S H; Pulakat, L; Parker, K C; Gavini, N

    1998-03-17

    Nitrogenase is a complex metalloenzyme composed of two separately purified proteins designated the Fe-protein and the MoFe-protein. Apart from these two proteins, a number of accessory proteins are essential for the maturation and assembly of nitrogenase. Even though experimental evidence suggests that these accessory proteins are required for nitrogenase activity, the exact roles played by many of these proteins in the functions of nitrogenase are unclear. Our studies were directed to understand the role of two nif accessory proteins, the NifW and the NifZ in the biological nitrogen fixation. To accomplish this, we have utilized a genetic method, the Yeast based Two-Hybrid protein-protein interaction assay. This analysis showed that the NifW could interact with itself to make a multimeric complex. In contrast, the NifZ could not interact with itself. However, the NifZ could interact with the NifW. Previously it was shown that mutating either the NifW or the NifZ have similar effects on the activity of nitrogenase. This observation indicated that both these proteins may exert their regulation on the nitrogenase by a common pathway. Furthermore, it was suggested that the NifW plays a role in the oxygen-protection of the MoFe-protein by direct physical interaction. Our observation that the NifW can interact with itself as well as with the NifZ, suggests that the NifW and the NifZ may form a higher order complex and such a complex may be needed to exert the effects of the NifW or the NifZ on the nitrogenase activity. PMID:9514861

  1. Azotobacter vinelandii nitrogenase: “Kinetics of nif gene expression and insights into the roles of FdxN and NifQ in FeMo-co biosynthesis”

    OpenAIRE

    Jiménez Vicente, Emilio

    2014-01-01

    The Molybdenum-nitrogenase is responsible for most biological nitrogen fixation activity (BNF) in the biosphere. Due to its great agronomical importance, it has been the subject of profound genetic and biochemical studies. The Mo nitrogenase carries at its active site a unique iron-molybdenum cofactor (FeMoco) that consists of an inorganic 7 Fe, 1 Mo, 1 C, 9 S core coordinated to the organic acid homocitrate. Biosynthesis of FeMo-co occurs outside nitrogenase through a complex and highly regu...

  2. Effect of azotobacter,slurry and their combination on economic characters and yield of maize%菌剂、沼液及其复配对玉米经济性状和产量的影响

    Institute of Scientific and Technical Information of China (English)

    贺国强; 邓志平; 刘展志; 谢剑波; 李朋飞; 董仁杰; 庞昌乐; 陈三凤

    2011-01-01

    本试验旨在研究菌剂、沼液及其复配对玉米经济性状和产量的影响。用固氮芽孢杆菌W6、巴西固氮螺菌Yu62及固氮巨大芽孢杆菌C4这3种固氮菌分别接种,并与沼液复配后接种玉米,以及这3种固氮菌与解磷假单胞菌S20组成的的4种微生物复合菌剂单独或与沼液复配后接种玉米。结果表明:除百粒重外,单菌剂处理组、沼液处理组及二者复配处理组均较清水组在玉米经济性状及单产方面表现优良。各单菌剂处理组中,固氮巨大芽孢杆菌C4效果较佳,相对于清水处理组,干穗单产增产10.47%。沼液与菌剂配合使用处理玉米的效果要优于相应菌剂单独处理%The aim of this research was to study the effect of microbes,biogas slurry and their combination on the economic characters and yield of maize.The nitrogen-fixing bacteria Bacillus megaterium C4,Bacillus sp.W6,Azospirillum brasilense Yu62,the combination of nitrogen-fixing bacteria with Pseudomonas alealigenes S20 and the combination of bacteria with the biogas slurry were applied to maize in the field.Experimental results showed that the treatments of either single bacterium,biogas slurry or their combination gave a more excellent performance than water treatment in terms of maize yield and economic characteristics except kernel weight,Bacteria treatment groups,especially with C4,gave a 10% higher dry ear yield compared to the water treatment group.The combination of biogas slurry with these bacteria was superior to individual use on maize.In particular,the combined biogas slurry with microbial agent C4 had increases of 2.17% kernel weight,25.15% dry ear yield and 12.47% grain yield comparing to the water treatment.

  3. The gram-negative bacterium Azotobacter chroococcum NCIMB 8003 employs a new glycoside hydrolase family 70 4,6-α-glucanotransferase enzyme (GtfD) to synthesize a reuteran like polymer from maltodextrins and starch

    NARCIS (Netherlands)

    Gangoiti, Joana; van Leeuwen, Sander S; Vafiadi, Christina; Dijkhuizen, Lubbert

    2016-01-01

    BACKGROUND: Originally the glycoside hydrolase (GH) family 70 only comprised glucansucrases of lactic acid bacteria which synthesize α-glucan polymers from sucrose. Recently we have identified 2 novel subfamilies of GH70 enzymes represented by the Lactobacillus reuteri 121 GtfB and the Exiguobacteri

  4. NCBI nr-aa BLAST: CBRC-XTRO-01-0305 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-XTRO-01-0305 ref|ZP_00419399.1| Heavy metal efflux pump CzcA [Azotobacter vine...landii AvOP] gb|EAM04226.1| Heavy metal efflux pump CzcA [Azotobacter vinelandii AvOP] ZP_00419399.1 0.0 77% ...

  5. Alterations in seedling vigour and antioxidant enzyme activities in Catharanthus roseus under seed priming with native diazotrophs

    Science.gov (United States)

    Karthikeyan, B.; Jaleel, C.A.; Gopi, R.; Deiveekasundaram, M.

    2007-01-01

    An experiment was conducted on Catharanthus roseus to study the effect of seed treatments with native diazotrophs on its seedling growth and antioxidant enzyme activities. The treatments had significant influence on various seedling parameters. There is no significant influence on dry matter production with the diazotrophs, Azospirillum and Azotobacter. However, the vital seedling parameters such as germination percentage and vigour index were improved. Azotobacter treatment influenced maximum of 50% germination, whereas Azospirillum and Azotobacter were on par with C. roseus with respect to their vigour index. There was significant difference in the population of total diazotrophs. Azospirillum and Azotobacter between rhizosphere and non-rhizosphere soils of C. roseus had the same trend and were observed at various locations of the study. The activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POX) and catalase (CAT) were increased to a significant extent due to the treatment with diazotrophs. PMID:17610323

  6. The algT gene of Pseudomonas syringae pv. glycinea and new insights into the transcriptional organization of the algT-muc gene cluster.

    Science.gov (United States)

    The phytopathogenic bacterium Pseudomonas syringae pv. glycinea infects soybean plants and causes bacterial blight. In addition to P. syringae, the human pathogen Pseudomonas aeruginosa and the soil bacterium Azotobacter vinelandii produce the exopolysaccharide alginate, copolymer of D-mannuronic a...

  7. Alterations in seedling vigour and antioxidant enzyme activities in Catharanthus roseus under seed priming with native diazotrophs

    Institute of Scientific and Technical Information of China (English)

    KARTHIKEYAN B.; JALEEL C.A.; GOPI R.; DEIVEEKASUNDARAM M.

    2007-01-01

    An experiment was conducted on Catharanthus roseus to study the effect of seed treatments with native diazotrophs on its seedling growth and antioxidant enzyme activities. The treatments had significant influence on various seedling parameters.There is no significant influence on dry matter production with the diazotrophs, Azospirillum and Azotobacter. However, the vital seedling parameters such as germination percentage and vigour index were improved. Azotobacter treatment influenced maximum of 50% germination, whereas Azospirillum and Azotobacter were on par with C. roseus with respect to their vigour index. There was significant difference in the population of total diazotrophs. Azospirillum and Azotobacter between rhizosphere and non-rhizosphere soils of C. roseus had the same trend and were observed at various locations of the study. The activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POX) and catalase (CAT) were increased to a significant extent due to the treatment with diazotrophs.

  8. RESPONSE MICROORGANISMS TO SOIL CONTAMINATION WITH HEAVY METALS

    OpenAIRE

    Grazyna Kaczynska; Aneta Lipinska; Jadwiga Wyszkowska; Jan Kucharski

    2014-01-01

    The main aim of our work was to evaluate the effect that the soil contamination with zinc, copper and cadmium has on the number of (CFU)Azotobacter, organotrophic bacteria and Streptomyces. The results of the experiment revealed their role in the CFU modification and the impact on the level of soil contamination with heavy metals. Organotrophic bacteria have a similar tolerance to the heavy metals as Streptomyces, since the lowest resistance characterizes the Azotobacter. The toxicity of the ...

  9. Alterations in seedling vigour and antioxidant enzyme activities in Catharanthus roseus under seed priming with native diazotrophs

    OpenAIRE

    B.Karthikeyan; Jaleel, C.A.; Gopi, R.; Deiveekasundaram, M.

    2007-01-01

    An experiment was conducted on Catharanthus roseus to study the effect of seed treatments with native diazotrophs on its seedling growth and antioxidant enzyme activities. The treatments had significant influence on various seedling parameters. There is no significant influence on dry matter production with the diazotrophs, Azospirillum and Azotobacter. However, the vital seedling parameters such as germination percentage and vigour index were improved. Azotobacter treatment influenced maximu...

  10. Dicty_cDB: Contig-U14077-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available . 383 chromosome... 89 2e-16 CP000615_1478( CP000615 |pid:none) Burkholderia vietnamiensis G4 c... 89 2e-16 ...er koseri ATCC BAA-895... 47 0.001 AL939110_147( AL939110 |pid:none) Streptomyces coelicolor A3(2) co... 47 ...m... 188 2e-46 CP001157_3032( CP001157 |pid:none) Azotobacter vinelandii DJ, co...mple... 87 1e-15 CP000447_787( CP000447 |pid:none) Shewanella frigidimarina... str. AY... 67 9e-10 CP001157_4250( CP001157 |pid:none) Azotobacter vinelandii DJ, comp... 67 1e-0

  11. Evaluación de la asociación bacterias fijadoras de nitrógeno - líneas interespecíficas de arroz-nitrógeno, en Typic haplustalf. Ibagué, Colombia Evaluation of the association nitrogen fixing bacterias interspecific - rice lines - nitrogen, in typic haplustalf. Ibagué, Colombia

    Directory of Open Access Journals (Sweden)

    Margarita M Vallejo

    2008-01-01

    Full Text Available El estudio se llevó a cabo en la hacienda Cauchitos, municipio de Ibagué, departamento del Tolima (Norte 4° 23' 51" y Oeste 75° 9' 7", 979 msnm, 24.3°C, bosque seco tropical (bs-T, con el objetivo de evaluar las asociaciones entre bacterias fijadoras de nitrógeno con inóculo y sin él en diez líneas interespecíficas de arroz, con tres dosis de nitrógeno (0%, 50% y 100% de 250 kg/ha-1 y tres repeticiones por tratamiento. La inoculación se realizó con 1 cm³ de unidades formadoras de colonias por 250 g de semilla de cada cultivar. Se aislaron 2.260 bacterias de los géneros Azotobacter spp y Azospirillum spp, se identificaron las especies A. brasilense, A. lipoferum, A. amazonense y del género Azotobacter las especies A. chroococcum, A. vinelandii, A. paspali y A. beijerinckii. Respecto al inóculo no se encontraron diferencias significativas al realizar su aplicación, se determinó que Azotobacter spp y Azospirillum spp fueron géneros típicos de la flora bacteriana en el cultivo del arroz y en condiciones de campo hubo efecto de los tratamientos en la flora bacteriana, y Azotobacter spp fue el predominante en cada uno de los tratamientos.The study was carried out at the Cauchitos farm, Ibague municipality department of Tolima, with bounds: North 4°23'51" and west 75°9'7", 979 ansm, the average temperature is 24,3°C, tropical dry forest (bs-t in the Holdridge classification. The purpose of this study was to evaluate the association between the nitrogen fixation bacteries with and without inoculo in 10 interespecific rice lines with three nitrogen dosis (0, 50 and 100% de 250 kg/ ha-1 and three repetitions. The inoculation was realized with 10(8 former units of colonies per millimeter. 2.260 bacteries of the generums Azotobacter spp y Azospirrillum spp., and identification the species: Azospirillum brasilense, Azospirillum lipoferum, Azospirillum amazonense, were identified and from the genus Azotobacter were identified the

  12. Genotypic Characterization of Azotobacteria Isolated from Argentinean Soils and Plant-Growth-Promoting Traits of Selected Strains with Prospects for Biofertilizer Production

    Directory of Open Access Journals (Sweden)

    Esteban Julián Rubio

    2013-01-01

    Full Text Available The genetic diversity among 31 putative Azotobacter isolates obtained from agricultural and non-agricultural soils was assessed using rep-PCR genomic fingerprinting and identified to species level by ARDRA and partial 16S rRNA gene sequence analysis. High diversity was found among the isolates, identified as A. chroococcum, A. salinestris, and A. armeniacus. Selected isolates were characterized on the basis of phytohormone biosynthesis, nitrogenase activity, siderophore production, and phosphate solubilization. Indole-3 acetic-acid (IAA, gibberellin (GA3 and zeatin (Z biosynthesis, nitrogenase activity, and siderophore production were found in all evaluated strains, with variation among them, but no phosphate solubilization was detected. Phytohormones excreted to the culture medium ranged in the following concentrations: 2.2–18.2 μg IAA mL−1, 0.3–0.7 μg GA3 mL−1, and 0.5–1.2 μg Z mL−1. Seed inoculations with further selected Azotobacter strains and treatments with their cell-free cultures increased the number of seminal roots and root hairs in wheat seedlings. This latter effect was mimicked by treatments with IAA-pure solutions, but it was not related to bacterial root colonization. Our survey constitutes a first approach to the knowledge of Azotobacter species inhabiting Argentinean soils in three contrasting geographical regions. Moreover, this phenotypic characterization constitutes an important contribution to the selection of Azotobacter strains for biofertilizer formulations.

  13. The Nifl PAS domain: Insight into its structure and function

    NARCIS (Netherlands)

    Hefti, M.H.

    2003-01-01

    Azotobacter vinelandii is an aerobic soil-dwelling organism with a wide variety of metabolic capabilities which include the ability to fix atmospheric nitrogen by converting it to ammonia. The biosynthesis of ammonia is controlled by 15 to 20 different nif gene products. The activation of nif gene e

  14. Studies on the structure and function of pyruvate dehydrogenase complexes

    NARCIS (Netherlands)

    Abreu, de R.A.

    1978-01-01

    The aim of the present investigation was to obtain more information of the structure and function of the pyruvate dehydrogenase complexes from Azotobacter vinelandii and Escherichia coli.In chapter 2 a survey is given of the recent literature on pyruvate dehydrogenase complexes.In chapter 3 results

  15. 5-Fluorotryptophan as dual probe for ground-state heterogeneity and excited-state dynamics in apoflavodoxin

    NARCIS (Netherlands)

    Visser, N. V.; Westphal, A. H.; Nabuurs, S. M.; van Hoek, A.; Mierlo, C. P. M. van; Visser, A. J. W. G.; Broos, J.; van Amerongen, H.

    2009-01-01

    The apoflavodoxin protein from Azotobacter vinelandii harboring three tryptophan (Trp) residues, was biosynthetically labeled with 5-fluorotryptophan (5-FTrp). 5-FTrp has the advantage that chemical differences in its microenvironment can be sensitively visualized via (19)F NMR. Moreover, it shows s

  16. Isolation and characterization of bacteria from Waste Sugar Mill Arasoe-Kab.Bone As Raw Material Producing Bioplastics Degraded (Poly-??-hydroxybutyrate)

    OpenAIRE

    Haedar, Nur; Gobel, Risco B.; Umar, Muhammad Ruslan; Ambeng, Ambeng

    2014-01-01

    Beberapa genera bakteri seperti Alcaligenes, Pseudomonas, Azotobacter, Rhizobium, Azospirilum, dan Micrococcus dari beberapa spesies algae mampu mengakumulasi granula PHB yang diakumulasi oleh sel bakteri yang ditumbuhkan dalam medium yang mengandung konsentrasi karbon tinggi tetapi nitrogen dan fosfatnya terbatas, Salah satu upaya untuk menekan biaya produksi perlu dilakukan penelitian dari sudut pandang mikrobiologi, diantaranya ialah menemukan mikroba unggul baru penghasil PHB atau menemuk...

  17. Potential of plant growth promoting rhizobacteria and chemical fertilizers on soil enzymes and plant growth

    International Nuclear Information System (INIS)

    The present investigation deals with the role of Plant Growth Promoting Rhizobacteria and chemical fertilizers alone or in combination on urease, invertase and phosphatase activities of rhizospheric soil and also on general impact on growth of safflower cvv. Thori and Saif-32. The PGPR (Azospirillum brasilense and Azotobacter vinelandii) were applied at 10/sup 6/ cells/mL as seed inoculation prior to sowing. Chemical fertilizers were applied at full (Urea 60 Kg ha/sup -1/ and Diammonium phosphate (DAP) 30 Kg ha/sup -1/), half (Urea 30 Kg ha/sup -1/ and DAP 15 Kg ha/sup -1/) and quarter doses (Urea 15 Kg ha-1 and DAP 7.5 Kg ha/sup -1/) during sowing. The chemical fertilizers and PGPR enhanced urease and invertase activities of soil. Presence of PGPR in combination with quarter and half doses of chemical fertilizers further augmented their effect on soil enzymes activities. The soil phosphatase activity was greater in Azospirillum and Azotobacter in combination with half dose of chemical fertilizers. Maximum increase in leaf melondialdehyde content was recorded in full dose of chemical fertilizers whereas coinoculation treatment exhibited significant reduction in cv. Thori. Half and quarter dose of chemical fertilizers increased the shoot length of safflower whereas maximum increase in leaf protein was recorded in Azotobacter in combination with full dose of chemical fertilizers. Root length was improved by Azospirillum and Azotobacter in combination with quarter dose of chemical fertilizers. Leaf area and chlorophyll contents were significantly improved by Azotobacter in combination with half dose of chemical fertilizers. It is inferred that PGPR can supplement 50 % chemical fertilizers for better plant growth and soil health. (author)

  18. BIOFERTILIZANTES, UNA ALTERNATIVA PROMISORIA PARA LA PRODUCCIÓN HORTÍCOLA EN ORGANOPÓNICOS

    Directory of Open Access Journals (Sweden)

    Elein Terry

    2002-01-01

    Full Text Available Con el objetivo de evaluar el efecto agrobiológico de dos biofertilizantes, se estudió la influencia de la inoculación simple y combinada de Azotobacter chroococcum y hongos formadores de micorrizas arbusculares, en los cultivos hortícolas de tomate, lechuga, habichuela y rabanito, evaluándose la efectividad de estos bioproductos sobre el crecimiento, desarrollo y rendimiento de estas especies. Los resultados mostraron un efecto positivo de la inoculación de estos microorganismos en los diferentes parámetros evaluados, siendo la inoculación mixta (Glomus clarum-Azotobacter chroococcum la que brindó los resultados más efectivos, lo que demuestra que ambos microorganismos funcionaron de forma sinérgica cuando se añadieron simultáneamente.

  19. RESPONSE MICROORGANISMS TO SOIL CONTAMINATION WITH HEAVY METALS

    Directory of Open Access Journals (Sweden)

    Grazyna Kaczynska

    2014-09-01

    Full Text Available The main aim of our work was to evaluate the effect that the soil contamination with zinc, copper and cadmium has on the number of (CFUAzotobacter, organotrophic bacteria and Streptomyces. The results of the experiment revealed their role in the CFU modification and the impact on the level of soil contamination with heavy metals. Organotrophic bacteria have a similar tolerance to the heavy metals as Streptomyces, since the lowest resistance characterizes the Azotobacter. The toxicity of the examined heavy metals can be ranked as follows (from the most sensitive to the least: Azotobacter>organotrophic bacteria>Streptomyces. It can be concluded that the succession of the microorganuisms is determined by the soil fertility, which stimulates both the characteristics and biochemical transformations, that occur in it through the mechanisms involved in reducing the negative impact of the heavy metals on the number of microorganisms.

  20. Impact of bio-fertilizers and different levels of cadmium on the growth, biochemical contents and lipid peroxidation of Plantago ovata Forsk.

    Science.gov (United States)

    Haneef, Irfana; Faizan, Shahla; Perveen, Rubina; Kausar, Saima

    2014-09-01

    Plantago ovata Forsk. (isabgol) is a valuable medicinal plant; its seeds and shell have a significant role in pharmacy as a laxative compound. Increasing soil contamination with cadmium (Cd) is one of the major concerns and is responsible for toxic effects in plants. This investigation was aimed to analyze the role of biofertilizers in alleviation of cadmium stress, given at the rate of 0, 50, and 100 mg kg(-1) of soil. The plants of isabgol, were grown in pots with and without application of AM fungi and Azotobacter (alone and combination). Cadmium showed negative effect on growth and biochemical component whereas proline and MDA content increase with increasing cadmium concentration. Addition of bio-fertilizer showed better growth and higher pigment concentration under cadmium stress as compared to the control. The dual inoculation of AM fungi and Azotobacter was found to be the best in reduction of cadmium stress and promotion of growth parameters. PMID:25183940

  1. INFLUENCIA DE DIFERENTES VARIANTES DE FERTILIZACIÓN EN EL CRECIMIENTO Y DESARROLLO DE POSTURAS DE Coffea canephora Pierre

    OpenAIRE

    Pérez, A.; Bustamante, C; R. Rodríguez; Díaz, A.(Laboratori Nazionali di Frascati, INFN, Frascati, Italy); Y. Bertot; Maritza I. Rodríguez

    2002-01-01

    En áreas experimentales de la Estación Central de Investigaciones de Café y Cacao (ECICC), se desarrolló un experimento dirigido a evaluar la respuesta de Coffea canephora Pierre a la fertilización con hongos micorrízicos arbusculares (HMA), Azotobacter chroococcum y urea. La cepa de Azotobacter utilizada se aisló de la rizosfera del cafeto cultivado en suelo Pardo ócrico sin carbonatos. El inóculo se obtuvo en el medio DIMARGON y se aplicó con título de 1010UFC.mL-1. El inóculo micorrízico (...

  2. Bacterias fijadoras asimbióticas de nitrógeno de la zona agrícola de San Carlos. Córdoba, Colombia

    OpenAIRE

    Lara Mantilla Cecilia; Villalba Anaya Mara; Oviedo Zumaqué Luis Eliécer

    2007-01-01

    Se aislaron bacterias diazotróficas de los géneros Azotobacter sp y Azospirrillum sp a partir de la rizosfera de cultivos de plátano, pastos, maíz y de rastrojos (zonas sin cultivar) en el municipio de San Carlos (Valle del Sinú medio en el departamento de Córdoba, Colombia). Las poblaciones microbianas se identificaron mediante pruebas bioquímicas y observación macroscópica y microscópica con tinción de Gram en diferentes medios de cultivo: a) Burk´s, Asbhy y Jensen´s, (género Azotobacter sp...

  3. Increased root exudation of 14C-compounds by sorghum seedlings inoculated with nitrogen-fixing bacteria

    International Nuclear Information System (INIS)

    Organic components leaked from Sorghum bicolor seedlings ('root exudates') were examined by recovering 14C labelled compounds from root solutions of seedlings inoculated with Azospirillum brasilense, Azotobacter vinelandii or Klebsiella pneumoniae nif-. Up to 3.5% of the total 14C recovered from shoots, roots, and nutrient solutions was found in the root solutions. Inoculation with Azospirillum and Azotobacter increased the amounts of 14C and decreased the amounts of carbohydrates in the root solutions. When sucrose was added as a carbon source for the bacteria, the increase of 14C in the solutions did not occur. Quantities of 14C found in the root solutions were proportional to amounts of mineral nitrogen supplied to the plants. Bacterial growth also was proportional to nitrogen levels. When sorghum plants were grown in soil and labelled with 14CO2, about 15% of the total 14C recovered within 48 hours exposure was found in soil leachates. (orig.)

  4. A Designed A. vinelandii-S. elongatus Coculture for Chemical Photoproduction from Air, Water, Phosphate, and Trace Metals.

    Science.gov (United States)

    Smith, Matthew J; Francis, Matthew B

    2016-09-16

    Microbial mutualisms play critical roles in a diverse number of ecosystems and have the potential to improve the efficiency of bioproduction for desirable chemicals. We investigate the growth of a photosynthetic cyanobacterium, Synechococcus elongatus PCC 7942, and a diazotroph, Azotobacter vinelandii, in coculture. From initial studies of the coculture grown in media with glutamate, we proposed a model of cross-feeding between these organisms. We then engineer a new microbial mutualism between Azotobacter vinelandii AV3 and cscB Synechococcus elongatus that grows in the absence of fixed carbon or nitrogen. The coculture cannot grow in the absence of a sucrose-exporting S. elongatus, and neither organism can grow alone without fixed carbon or nitrogen. This new system has the potential to produce industrially relevant products, such as polyhydroxybutyrate (PHB) and alginate, from air, water, phosphate, trace metals, and sunlight. We demonstrate the ability of the coculture to produce PHB in this work. PMID:27232890

  5. Long-term effect of mineral fertilizers and amendments on microbial dynamics in an alfisol of Western Himalayas.

    Science.gov (United States)

    Mahajan, S; Kanwar, S S; Sharma, S P

    2007-03-01

    The microbial dynamics expressed in terms of culturable microbial populations i.e. bacteria, fungi, actinomycetes and Azotobacter were measured after 33 years of continuous application of mineral fertilizers and amendments to an acid alfisol. The bacterial, fungal and Azotobacter populations were maximum in plots treated with mineral fertilizers and FYM (100%NPK+FYM) while actinomycetes population was maximum in mineral fertilizes and lime treated plots (100%NPK+Lime). The bacterial population decreased and fungal population increased with increasing levels of NPK i.e. from 50% to 150%NPK. Bacillus species of bacteria and Gliocladium, Aspergillus and Rhizopus species of fungi were the main dominating culturable microorganisms in all the treatments. The FYM and lime amended plots sustained crop productivity and microbial populations at higher levels than rest of the mineral fertilizer treatments. The nitrogenous fertilizers alone had the most deleterious effect on crop productivity and the biological soil environment.

  6. Evaluation of the association nitrogen fixing bacterias interspecific – rice lines – nitrogen, in typic haplustalf. Ibagué, Colombia Evaluación de la asociación bacterias fijadoras de nitrógeno – líneas interespecíficas de arroz–nitrógeno, en Typic haplustalf. Ibagué, Colombia

    Directory of Open Access Journals (Sweden)

    Bonilla Correa Carmen Rosa

    2008-03-01

    Full Text Available The study was carried out at the Cauchitos farm, Ibague municipality department of Tolima, with bounds: North 4°23'51"; and west 75°9'7";, 979 ansm, the average temperature is 24,3°C, tropical dry forest (bs–t in the Holdridge classification. The purpose of this study was to evaluate the association between the nitrogen fixation bacteries with and without inoculo in 10 interespecific rice lines with three nitrogen dosis (0, 50 and 100% de 250 kg/ ha–1 and three repetitions. The inoculation was realized with 108 former units of colonies per millimeter. 2.260 bacteries of the generums Azotobacter spp y Azospirrillum spp., and identification the species: Azospirillum brasilense, Azospirillum lipoferum, Azospirillum amazonense, were identified and from the genus Azotobacter were identified the species: A. choroococcum, A. vinelandii, A. paspali and A. veijerinckii. Weren't found none significative differences after the inoculation. Azotobacter spp and Azospirillum spp. were typical generums of the bacterian flora in the rice plantation and in field conditions were effect of the treatment effects in the bacterian . The Azotobacter spp was the predominant in generum in each one of the treatments.El estudio se llevó a cabo en la hacienda Cauchitos, municipio de Ibagué, departamento del Tolima (Norte 4° 23' 51"; y Oeste 75° 9' 7";, 979 msnm, 24.3°C, bosque seco tropical (bs–T, con el objetivo de evaluar las asociaciones entre bacterias fijadoras de nitrógeno con inóculo y sin él en diez líneas interespecíficas de arroz, con tres dosis de nitrógeno (0%, 50% y 100% de 250 kg/ha–1 y tres repeticiones por tratamiento. La inoculación se

  7. A STUDY ON NITROGEN FIXING AND PHOSPHATE SOLUBILIZING MICROORGANISMS ON GROWTH AND PHYSIOLOGY OF PLUMBAGO ZEYLANICA.L

    OpenAIRE

    D.Haribabu Rao; T.Vijaya; B.V.Ramana naidu; Subramanyam, P.; D.Jayasimha Rayalu

    2012-01-01

    Organisms that are commonly used as biofertilizers component are nitrogen fixers (N-fixer), potassium solubilizer (K-solubilizer) and phosphorus solubilizer (P- solubilizer), or with the combination of molds or fungi. Most of the bacteria included in biofertilizer have close relationship with plant roots. In this work we have selected plumbago zeylanica.L plant to study the effect of Azotobacter on the growth of roots, stem, and leaves. Also biochemical characterization was done to identify t...

  8. Progress in Research of Bacteria Fertilizer Strengthening Resistance of Plants

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Bacteria fertilizer is used most widely among all kinds of microbial fertilizers. We summarize the research headway of bacteria fertilizer. It mainly focuses on bacteria fertilizer improving the stress resistance of plant. Then we can offer basis to research and exploit bacteria fertilizer. These bacteria include azotobacter, photosynthetic bacteria, Bacillus mucilaginosus siliceous, phosphorus bacteria, plant growth-promoting rhizobacteria(PGPR), effective microorganism(EM).

  9. CHARACTERIZATION, BIO-FORMULATION DEVELOPMENT AND SHELF-LIFE STUDIES OF LOCALLY ISOLATED BIO-FERTILIZER STRAINS

    OpenAIRE

    Vipin Kumar

    2014-01-01

    Nitrogen fixing, phosphate solubilizing and potash mobilizing bacterial strains were isolated from rhizosphere soil of agricultural land, the isolated bacterial strains were further characterized by a series of biochemical reactions and identified as genus Azotobacter, Bacillus and Pseudomonas respectively. A technology for their mass multiplication and their bio-formulation has been developed. Fly-ash was used as carrier materials for bio-formulation development of bio-fertilizer strains. Sh...

  10. Effect of plant growth promoting rhizobacteria on Ambrosia rtemisiifolia L. seed germination

    OpenAIRE

    Vrbničanin Sava; Božić Dragana; Sarić Marija; Pavlović Danijela; Raičević Vera

    2011-01-01

    Soil bacteria are able either to stimulate or inhibit seed germination. If seed germination is stimulated, the seedlings of weed species emerge more uniformly, so that they could be killed in the next step of weed control. This investigation focused on testing the germination of Ambrosia artemisiifolia L. on several media: Pseudomonas fluorescens (B1), Azotobacter chroococcum (B2), Bacillus licheniformis (B3), B. pumilus (B4), B. amyloliquefaciens (B5). In ...

  11. Effect of Plant Growth Promoting Rhizobacteria on Ambrosia artemisiifolia L. Seed Germination

    OpenAIRE

    Sava Vrbničanin; Dragana Božić; Marija Sarić; Danijela Pavlović; Vera Raičević

    2011-01-01

    Soil bacteria are able either to stimulate or inhibit seed germination. If seed germination is stimulated, the seedlings of weed species emerge more uniformly, so that they could be killed in the next step of weed control. This investigation focused on testing the germination of Ambrosia artemisiifolia L. on several media: Pseudomonas fluorescens (B1), Azotobacter chroococcum (B2), Bacillus licheniformis (B3), B. pumilus (B4), B. amyloliquefaciens (B5). In control, seeds germinated in water. ...

  12. GenBank blastx search result: AK061948 [KOME

    Lifescience Database Archive (English)

    Full Text Available AK061948 001-042-E07 AF267243.2 Azotobacter vinelandii PhbF (phbF), putative phasin protein PhbP (phb...P), putative transcription activator PhbR (phbR), acetoacetyl-CoA reductase (phbB), polyhy...droxybutyrate biosynthetic beta-ketothiolase (phbA), and PHB synthase (phbC) genes, complete cds.|BCT BCT 1e-56 +3 ...

  13. GenBank blastx search result: AK059654 [KOME

    Lifescience Database Archive (English)

    Full Text Available AK059654 001-031-C10 AF267243.2 Azotobacter vinelandii PhbF (phbF), putative phasin protein PhbP (phb...P), putative transcription activator PhbR (phbR), acetoacetyl-CoA reductase (phbB), polyhy...droxybutyrate biosynthetic beta-ketothiolase (phbA), and PHB synthase (phbC) genes, complete cds.|BCT BCT 3e-82 +1 ...

  14. Role of NifS in maturation of glutamine phosphoribosylpyrophosphate amidotransferase.

    OpenAIRE

    Chen, S.; Zheng, L; Dean, D R; Zalkin, H.

    1997-01-01

    Glutamine phosphoribosylpyrophosphate amidotransferase from Bacillus subtilis is synthesized as an inactive precursor that requires two maturation steps: incorporation of a [4Fe-4S] center and cleavage of an 11-residue NH2-terminal propeptide. Overproduction from a multicopy plasmid in Escherichia coli leads to the formation of soluble proenzyme and mature enzyme forms as well as a small fraction of insoluble proenzyme. Heterologous expression of Azotobacter vinelandii nifS from a compatible ...

  15. Controlled Expression of nif and isc Iron-Sulfur Protein Maturation Components Reveals Target Specificity and Limited Functional Replacement between the Two Systems▿ †

    OpenAIRE

    Dos Santos, Patricia C.; Johnson, Deborah C.; Ragle, Brook E.; Unciuleac, Mihaela-Carmen; Dean, Dennis R.

    2007-01-01

    The nitrogen-fixing organism Azotobacter vinelandii contains at least two systems that catalyze formation of [Fe-S] clusters. One of these systems is encoded by nif genes, whose products supply [Fe-S] clusters required for maturation of nitrogenase. The other system is encoded by isc genes, whose products are required for maturation of [Fe-S] proteins that participate in general metabolic processes. The two systems are similar in that they include an enzyme for the mobilization of sulfur (Nif...

  16. Quaternary structure changes in a second Per-Arnt-Sim domain mediate intramolecular redox signal relay in the NifL regulatory protein

    OpenAIRE

    Slavny, Peter; Little, Richard; Salinas Berná, Paloma; Clarke, Thomas A.; Dixon, Ray

    2009-01-01

    Per-Arnt-Sim (PAS) domains play a critical role in signal transduction in multidomain proteins by sensing diverse environmental signals and regulating the activity of output domains. Multiple PAS domains are often found within a single protein. The NifL regulatory protein from Azotobacter vinelandii contains tandem PAS domains, the most N-terminal of which, PAS1, contains a FAD cofactor and is responsible for redox sensing, whereas the second PAS domain, PAS2, has no apparent cofactor and its...

  17. Identification and characterization of functional homologs of nitrogenase cofactor biosynthesis protein NifB from methanogens

    OpenAIRE

    Fay, Aaron W.; Wiig, Jared A.; Lee, Chi Chung; Hu, Yilin

    2015-01-01

    Nitrogenase biosynthesis protein NifB catalyzes the radical S-adenosyl-L-methionine (SAM)-dependent insertion of carbide into the nitrogenase cofactor, M cluster, in a chemically unprecedented and biologically important reaction. The observation that two naturally “truncated” NifB homologs from Methanosarcina acetivorans (NifBMa) and Methanobacterium thermoautotrophicum (NifBMt) are functional equivalents of NifB from the diazotrophic organism, Azotobacter vinelandii, establishes the minimum ...

  18. Cysteine desulfurase activity indicates a role for NIFS in metallocluster biosynthesis.

    OpenAIRE

    Zheng, L; White, R H; Cash, V L; Jack, R F; Dean, D R

    1993-01-01

    Biological nitrogen fixation is catalyzed by nitrogenase, a complex metalloenzyme composed of two separately purifiable component proteins encoded by the structural genes nifH, nifD, and nifK. Deletion of the Azotobacter vinelandii nifS gene lowers the activities of both nitrogenase component proteins. Because both nitrogenase component proteins have metallocluster prosthetic groups that are composed of iron- and sulfur-containing cores, this result indicated that the nifS gene product could ...

  19. Nucleotide sequence of a cyanobacterial nifH gene coding for nitrogenase reductase

    OpenAIRE

    Mevarech, Moshe; Rice, Douglas; Haselkorn, Robert

    1980-01-01

    The nucleotide sequence of nifH, the structural gene for nitrogenase reductase (component II or Fe protein of nitrogenase) from the cyanobacterium Anabaena 7120 has been determined. Also reported are 194 bases of the 5′-flanking sequence and 170 bases of the 3′-flanking sequence. The predicted amino acid sequence was compared with that determined for the complete nitrogenase reductase of Clostridium pasteurianum and the cysteine-containing peptides of the protein from Azotobacter vinelandii. ...

  20. Kinetics of nif Gene Expression in a Nitrogen-Fixing Bacterium

    OpenAIRE

    C. Poza-Carrion; E. Jimenez-Vicente; M. Navarro-Rodriguez; C. Echavarri-Erasun; L. M. Rubio

    2014-01-01

    Nitrogen fixation is a tightly regulated trait. Switching from N2 fixation-repressing conditions to the N2-fixing state is carefully controlled in diazotrophic bacteria mainly because of the high energy demand that it imposes. By using quantitative real-time PCR and quantitative immunoblotting, we show here how nitrogen fixation (nif) gene expression develops in Azotobacter vinelandii upon derepression. Transient expression of the transcriptional activator-encoding gene, nifA, was followed by...

  1. The N-terminal and C-terminal portions of NifV are encoded by two different genes in Clostridium pasteurianum.

    OpenAIRE

    Wang, S Z; Dean, D R; Chen, J. S.; Johnson, J L

    1991-01-01

    The nifV gene products from Azotobacter vinelandii and Klebsiella pneumoniae share a high level of primary sequence identity and are proposed to catalyze the synthesis of homocitrate. While searching for potential nif (nitrogen fixation) genes within the genomic region located downstream from the nifN-B gene of Clostridium pasteurianum, we observed two open reading frames (ORFs) whose deduced amino acid sequences exhibit nonoverlapping sequence identity to different portions of the nifV gene ...

  2. History on the biological nitrogen fixation research in graminaceous plants: special emphasis on the Brazilian experience

    OpenAIRE

    José I. Baldani; Vera L.D. Baldani

    2005-01-01

    This review covers the history on Biological Nitrogen Fixation (BNF) in Graminaceous plants grown in Brazil, and describes research progress made over the last 40 years, most of whichwas coordinated by Johanna Döbereiner. One notable accomplishment during this period was the discovery of several nitrogen-fixing bacteria such as the rhizospheric (Beijerinckia fluminensis and Azotobacter paspali), associative (Azospirillum lipoferum, A. brasilense, A. amazonense) and the endophytic (Herbaspiril...

  3. Effect of Biofertilizers on Agronomic Criteria of Hyssop (Hyssopus officinalis)

    OpenAIRE

    Tabrizi, Leila; Alireza KOOCHEKI; Ghorbani, Reza

    2008-01-01

    An experiment was conducted under field conditions to evaluate the effects of pure or combinations of biofertilizers on agronomic and quality criteria of Hyssop (Hyssopus officinalis), a medicinal and aromatic plant from Labiateae family at the Research Station of the Faculty of Agriculture, Ferdowsi University of Mashhad, during 2006 and 2007. A complete randomized block design with three replications was used. Treatments containing Azospirillum/Azotobacter(Nitroxin), Azospirillum/Bacillus s...

  4. Changes in the ecological and biological properties of ordinary chernozems polluted by heavy metals of the second hazard class (Mo, Co, Cr, and Ni)

    Science.gov (United States)

    Kolesnikov, S. I.; Evreinova, A. V.; Kazeev, K. Sh.; Val'Kov, V. F.

    2009-08-01

    The pollution of ordinary chernozems by heavy metals of the second hazard class (Mo, Co, Cr, and Ni) results in a decrease in the numbers of saprotrophic bacteria and fungi and bacteria of the Azotobacter genus; the catalase and invertase activities and the rates of the cellulose and urea decomposition also decrease. The soil phytotoxicity becomes higher. With respect to their ecological hazard, the studied heavy metals may be arranged into the following sequence: Cr > Co ≥ Ni > Mo.

  5. Genotypic Characterization of Azotobacteria Isolated from Argentinean Soils and Plant-Growth-Promoting Traits of Selected Strains with Prospects for Biofertilizer Production

    OpenAIRE

    Esteban Julián Rubio; Marcela Susana Montecchia; Micaela Tosi; Fabricio Darío Cassán; Alejandro Perticari; Olga Susana Correa

    2013-01-01

    The genetic diversity among 31 putative Azotobacter isolates obtained from agricultural and non-agricultural soils was assessed using rep-PCR genomic fingerprinting and identified to species level by ARDRA and partial 16S rRNA gene sequence analysis. High diversity was found among the isolates, identified as A. chroococcum, A. salinestris, and A. armeniacus. Selected isolates were characterized on the basis of phytohormone biosynthesis, nitrogenase activity, siderophore production, and phosph...

  6. Influence of Organic Manures (Biofertilizers on Soil Microbial Population in the Rhizosphere of Mulberry (Morus Indica L.

    Directory of Open Access Journals (Sweden)

    L. Christilda Louis Mary

    2015-03-01

    Full Text Available The effect of different kinds of organic manures on soil microbial population and mulberry production was assessed. A field experiment wascarried out at Periyar EVR College, Tamil Nadu, India in basic soil to study the influence of organic manures on soil bacterial population andmulberry production. The 4 groups of mulberry plants of MR2 variety were biofertilized with FYM, Azospirillum, Phosphobacteria andVermicompost respectively. The biofertilizers lodged bacteria on the rhizosphere of mulberry plants. When the root microorganism areanalyzed Farm yard manure biofertilized mulberry plant root tips had Gluconacobacter diazotrophicus, Bacillus pumilus, Pseudomonas putida,Bacillus coagulans, Bacillus sonorensis, Azotobacter chrococcum; Azospirillum biofertilized mulberry plants root tips had Bacillus coaculans,Azotobactor chrococcum, Azotobactor vinelandii, Bacillus subtilis and Azospirillum brasilense. Phosphobacteria biofertilized mulberry plantroot tips had Pseudomonas putida, Bacillus stearothermophilus, Brevibacillus borslelansis and Streptomycies thermonitrificans andvermicompost biofertilized mulberry plant root tips had lodged bacterias like Bacillus megaterium, Bacillus subtilis, Gluconacobacterdiazotrophicus, Pseudomonas putida, Azotobacter chrococcum, Azotobacter vinelandi, Bacillus stearothermophilus, Brevibacillus borslelansisand Bacillus sonorensis. Microbiology work reveals luxuriant growth of bacteria in all the biofertizer treated rhizosphere in the order FYM

  7. Response Of Guava Trees (Psidium Guajava To Soil Applications Of Mineral And Organic Fertilisers And Biofertilisers Under Conditions Of Low Fertile Soil

    Directory of Open Access Journals (Sweden)

    Shukla Sushil Kumar

    2014-12-01

    Full Text Available The goal of this study was to assess the influence of different organic fertilisers - vermicompost, mulching, Azotobacter, phosphate solubilising microbes (PSM and Trichoderma harzianum added each year to mineral fertilisers containing NPK and to farmyard manure (FYM on leaf nutrient status, tree growth, fruit yield and quality of guava grown in low fertile soil. The results revealed that vermicompost, bio-fertilisers and organic mulching resulted in yield and fruit quality boosters, as compared to application of NPK and FYM as the only organic fertiliser. Significant differences in plant height, canopy spread and stem girth of guava plants were obtained in combination, where Azotobacter, T. harzianum, PSM and organic mulching were applied. The leaf nutrient contents (N, P, K, Ca, Mg, Fe, Cu, Mn and Zn were within sufficient ranges. Fruit yields and quality were highest in combination, where vermicompost, Azotobacter, T. harzianum, PSM and organic mulching was applied. Fruit quality parameters viz. soluble solid concentration, titratable acidity, total sugars and ascorbic acid showed positive correlation with the available macro- and micronutrients in the soil.

  8. Selección y caracterización de rizobacterias promotoras de crecimiento vegetal (RPCV asociadas al cultivo de algodón (Gossypium hirsutum

    Directory of Open Access Journals (Sweden)

    Andrés Guzmán

    2012-04-01

    Full Text Available Normal 0 21 false false false ES-CO X-NONE X-NONE MicrosoftInternetExplorer4 Título en ingles: Selection and characterization of plant growth promoting rhizobacteria (PGPR’s associated with cotton crop (Gossypium hirsutum Resumen: Como parte de las estrategias de una agricultura sostenible, se hace necesario disminuir el uso de fertilizantes nitrogenados de síntesis, mediante la utilización de los biofertilizantes. En particular, los géneros Azotobacter y Azospirillum son utilizados como agentes promotores de crecimiento vegetal debido a su capacidad para fijar nitrógeno atmosférico y producir hormonas de tipo indólico. Por tal razón, en este estudio se aislaron bacterias diazotróficas de los géneros Azotobacter y Azospirillum a partir de la rizósfera de cultivos de algodón en el Espinal (Tolima. Las poblaciones microbianas se caracterizaron fenotípicamente en los medios de cultivo semiespecíficos: Ashby y LG (Azotobacter sp. y NFb, LGI y Batata (Azospirillum sp.. La promoción de crecimiento vegetal se determinó mediante la actividad de la enzima nitrogenasa por medio de la técnica de reducción de acetileno y producción de índoles por el método colorimétrico de Salkowsky. Se obtuvieron 9 aislamientos tentativos de Azotobacter sp. y 4 de Azospirillum sp. Se presentaron diferencias significativas en la prueba de reducción de acetileno con las cepas presuntivas de Azotobacter sp.: NAT 9 (206.43 nmol C2H2 mL-1.h-1, NAT 4, (292.77 nmol C2H2 mL-1.h-1, y NAT 6 (460.60 nmol C2H2 mL-1.h-1 y en la producción de índoles de las cepas NAT 19 (19.87 μg.mL-1 y NAT 13 (20.08 μg.mL-1. Por su eficiencia in vitro en la promoción de crecimiento vegetal se seleccionaron las cepas NAT9, NAT4, NAT6, NAT19 y NAT13 para ser evaluadas como principio activo en futuros inoculantes para el algodón en esta zona del departamento del Tolima. Palabras clave: fijación biológica de nitrógeno; producción de índoles; promoción del crecimiento

  9. LA BIOFERTILIZACIÓN CON RIZOBACTERIAS Y HONGOS MICORRÍZICOS ARBUSCULARES EN LA PRODUCCIÓN DE POSTURAS DE TOMATE (Lycopersicon esculentum Mill. Y CEBOLLA (Allium cepa L.. I. CRECIMIENTO VEGETATIVO

    Directory of Open Access Journals (Sweden)

    L. E. Pulido

    2003-01-01

    Full Text Available En áreas experimentales de la Universidad de Ciego de Ávila, sobre un suelo Ferralítico Rojo compactado eútrico y durante dos campañas hortícolas sucesivas, se estudió el efecto de la inoculación, simple y combinada, mediante recubrimiento de las semillas y prescindiendo de la fertilización mineral, con cuatro y cinco especies, respectivamente, de rizobacterias promotoras del crecimiento vegetal -RPCV- (Azospirillum brasilense, Azotobacter chroococcum, Burkholderia cepacia y Pseudomonas fluorescens y de hongos micorrízicos arbusculares -HMA- (Glomus clarum, G. fasciculatum, G. mosseae, G. agregatum y G. versiculiferum, sobre algunos indicadores del crecimiento de posturas de tomate y cebolla, tomando como criterio de evaluación la altura y la longitud radical de las plántulas. Los resultados mostraron que, para el tomate, la inoculación con Azospirillum brasilense, Azotobacter chroococcum y Burkholderia cepacia permitió obtener posturas de calidad equivalente a la alcanzada con la fertilización mineral, mientras que para la cebolla, solo Azospirillum brasilense y Azotobacter chroococcum lograron que las posturas tuvieran dicha calidad. En relación con la inoculación con HMA, las especies Glomus clarum, G. fasciculatum y G. mosseae, para ambos cultivos, produjeron posturas con valores de altura y longitud radical considerados óptimos. Con las coinoculaciones de RPCV + HMA se lograron posturas de calidad superior a la alcanzada con las mejores variantes de inoculación simple, destacándose las combinaciones de G. clarum y G. fasciculatum con A. brasilense para el tomate y de G. clarum y G. fasciculatum con A. chroococcum para la cebolla.

  10. Selection of rhizosphere local microbial as bioactive inoculant based on irradiated compost

    International Nuclear Information System (INIS)

    One of the main components of carrier based on irradiation compost for bio organic fertilizer is a potential microbial isolates role in nutrient supply and growth hormone. This research was conducted to obtain microbial isolates from plant root zone (rhizosphere), further isolation and selection in order to obtain potential isolates capable of nitrogen fixation (N2), resulting in growth hormone (Indole Acetic Acid), and phosphate solubilizing. Selected potential isolates used as bioactive microbial inoculants formulation in irradiation compost based. Forty eight (48) rhizosphere samples were collected from different areas of West and Central Java. One hundred sixteen (116) isolates have been characterized for their morphological, cultural, staining and biochemical characteristics. Isolates have been selected for further screening of PGPR traits. Parameters assessed were Indole Acetic Acid (IAA) content analysis with colorimetric methods, dinitrogen fixation using gas chromatography, phosphate solubility test qualitatively (in the media pikovskaya) and quantitative assay of dissolved phosphate (spectrophotometry). Evaluation of the ability of selected isolates on the growth of corn plants were done in pots. The isolates will be used as inoculant consortium base on compost irradiation. The selection obtained eight (8) bacterial isolates identified as Bacillus circulans (3 isolates), Bacillus stearothermophilus (1 isolate), Azotobacter sp (3 isolates), Pseudomonas diminuta (1 isolate). The highest phosphate released (91,21 mg/l) was by BD2 isolate (Bacillus circulan) with a holo zone size (1.32 cm) on Pikovskaya agar medium. Isolate of Pseudomonas diminuta (KACI) was capable to produce the highest IAA hormone (74.34 μg/ml). The highest nitrogen (N2) fixation activity was shown by Azotobacter sp isolates (KDB2) at a rate of 235.05 nmol/hour. The viability test showed that all selected isolates in compost irradiation carrier slightly decreased after 3 months of storage

  11. Efekt inokulacije korijena korijenovim bakterijama za poticanje rasta (PGPR) na rast biljke, sadržaj alkaloida i nutrijenata kod biljke Catharanthus roseus (L.) G. Don.

    OpenAIRE

    Karthikeyan, Balathandayutham; Joe, Manoharan Melvin; Jaleel, Cheruth Abdul; Deiveekasundaram, Muthukumar

    2010-01-01

    Testirani su učinci korijenovih bakterija za poticanje rasta, kao što su Azotobacter, Bacillus i Pseudomonas, zasebno ili u kombinaciji, na biljci Catharanthus roseus i to tijekom dviju godina (2005 i 2006). Kombinacije gorespomenutih PGPR sojeva značajno su povećale visinu biljaka, duljinu korijena, debljinu korijena i sadržaj alkaloida kod C. roseus u usporedbi s kontrolom. Uz to sadržaj svih nutrijenata (N, P, K, Ca i Mg) bio je značajno povišen u usporedbi s kontrolom. Maksimalni sadržaj ...

  12. Iron-sulfur proteins: spin-coupling model for three-iron clusters.

    OpenAIRE

    Kent, T A; Huynh, B H; Münck, E

    1980-01-01

    Recent Mössbauer and EPR studies of two ferredoxins and of aconitase have given evidence for a three-iron cluster, probably of a [3Fe-3S] type. The studies of the oxidized EPR-active centers have shown that the three iron sites are characterized by significantly different magnetic hyperfine coupling constants. For the ferredoxin from Azotobacter vinelandii, for instance, we have observed A1 = -41 MHz, A2 = +18 MHz, and [A3] = 5 MHz. We demonstrate here that the magnetic properties of the clus...

  13. Survival of microorganisms in smectite clays - Implications for Martian exobiology

    Science.gov (United States)

    Moll, Deborah M.; Vestal, J. R.

    1992-01-01

    The survival of Baccillus subtilis, Azotobacter chroococcum, and the enteric bacteriophage MS2 has been examined in clays representing terrestrial (Wyoming type montmorillonite) and Martian (Fe3+ montmorillonite) soils exposed to terrestrial and Martian environmental conditions of temperature and atmospheric composition and pressure. An important finding is that MS2 survived simulated Mars conditions better than the terrestrial environment, probably owing to stabilization of the virus caused by the cold and dry conditions of the simulated Mars environment. This finding, the first published indication that viruses may be able to survive in Mars-type soils, may have important implications for future missions to Mars.

  14. Dicty_cDB: Contig-U16436-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available :none) Burkholderia vietnamiensis G4 c... 271 8e-71 AM902716_277( AM902716 |pid:none) Bordetella petrii... synthase; ... 244 1e-62 CP000614_1059( CP000614 |pid:none) Burkholderia vietnami...6 0.007 1 ( CO013215 ) EST801550 Coccidioides posadasii spherule cDNA li... 56 0.007 1 ( AC117075 ) Dictyostelium discoid...001157_4095( CP001157 |pid:none) Azotobacter vinelandii DJ, comp... 253 2e-65 AL646053_1106( AL646053 |pid:none) Ralstonia solana...:none) Francisella tularensis subsp. ho... 38 1.5 AL939120_104( AL939120 |pid:none) Streptomyces coelico

  15. Dicty_cDB: Contig-U04114-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available :none) Burkholderia vietnamiensis G4 c... 49 1e-04 CP000774_1633( CP000774 |pid:none) Parvibaculu...:none) Streptomyces coelicolor A3(2) co... 47 3e-07 AE016958_1966( AE016958 |pid:none) Myco...:none) Streptomyces coelicolor A3(2) co... 37 0.72 CP000634_624( CP000634 |pid...re E Sequences producing significant alignments: (bits) Value N ( AU062051 ) Dictyostelium discoid...0.001 CP001157_4718( CP001157 |pid:none) Azotobacter vinelandii DJ, comp... 46 0.001 A83391( A83391 ) probable glutamin

  16. EFFECT OF INTEGRATED NUTRIENT MANAGEMENT ON VEGETATIVE GROWTH AND YIELD OF TRANSPLANTED HYBRID RICE (ORYZA SATIVA L. CROP

    Directory of Open Access Journals (Sweden)

    RAYEES A. SHAH* SANDEEP KUMAR

    2014-09-01

    Full Text Available The integrated use of organic and inorganic sources of plant nutrients can help in sustainable and environmentally sound nutrient management of soils that are low in organic matter. A study was conducted  during 2009- 10 & 2010-11, on sandy loam soils, low in organic carbon, medium in available phosphorus and potash with pH of 7.5 at Agricultural Research Farm of C.C.R.(P.G. College, Muzaffarnagar U.P. India, to investigate the comparative use of  integrated nutrient management on vegetative growth and yield of hybrid rice. The experiment was laid out with fifteen treatments in a RBD. The treatments were; Control (T1, NPK 100% RDF (T2, NPK 75% RDF (T3, NPK 50% RDF + FYM @ 10 tons  ha-1 (T4, NPK 50% RDF + FYM @15 tons ha-1 (T5, NPK 50% RDF + wheat cut straw @10 tons ha-1 (T6, NPK 50% RDF + wheat cut straw @15 tons ha-1 (T7, NPK 50% RDF + Neem cake @ 2.5 tones ha-1 (T8, NPK 50% RDF + Neem cake @ 5 tones ha-1 (T9, NPK 50% RDF + Vermicompost @ 2.5 tons ha-1 (T10, NPK 50% RDF + Vermicompost @ 2.5 tons ha-1 +Azotobacter (T11, NPK 50% RDF + Vermicompost @ 2.5 tones ha-1 +PSB @ 5Kg ha-1 (T12, NPK 50% RDF + Vermicompost @ 2.5 tones ha-1 + Azospirillum (T13, NPK 50% RDF  + Azotobacter + Azospirillum + PSB @ 5 Kg ha-1(T14, and NPK 50% RDF + Neem cake @ 2.5 tones ha-1 +FYM @5 tons  ha-1 + Azotobacter+PSB @ 5Kg ha-1 (T15. The maximum grain yield (63 and 67 q per hectare during 2009 and 2010, respectively was obtained with the integration of NPK 50% RDF + Neem cake @2.5 tonnes ha-1 + FYM @5 tonnes ha-1+Azotobacter+PSB @ 5kg ha-1.

  17. Structure of precursor bound NifEN: a nitrogenase FeMo cofactor maturase/insertase*

    OpenAIRE

    Kaiser, Jens T.; Hu, Yilin; Wiig, Jared A.; Rees, Douglas C.; Ribbe, Markus W.

    2011-01-01

    NifEN plays an essential role in the biosynthesis of the nitrogenase iron-molybdenum (FeMo) cofactor (M cluster). It is an α_2β_2 tetramer that is homologous to the catalytic molybdenum-iron (MoFe) protein (NifDK) component of nitrogenase. NifEN serves as a scaffold for the conversion of an iron-only precursor to a matured form of the M cluster before delivering the latter to its target location within NifDK. Here, we present the structure of the precursor-bound NifEN of Azotobacter vinelandi...

  18. nifV-dependent, low-molecular-weight factor required for in vitro synthesis of iron-molybdenum cofactor of nitrogenase.

    OpenAIRE

    Hoover, T R; Shah, V K; Roberts, G P; Ludden, P W

    1986-01-01

    The molybdate- and ATP-dependent in vitro synthesis of the iron-molybdenum cofactor of nitrogenase requires a low-molecular-weight factor. The factor is present in extracts of nitrogen fixation-derepressed cultures of Klebsiella pneumoniae and Azotobacter vinelandii, but not in extracts of repressed cultures of these bacteria. Analysis of K. pneumoniae Nif mutants has indicated that the nifV gene product is the only nif protein (besides nifA) necessary for the synthesis and accumulation of th...

  19. In vitro synthesis of the iron-molybdenum cofactor of nitrogenase.

    OpenAIRE

    Shah, V K; Imperial, J; Ugalde, R A; Ludden, P W; Brill, W J

    1986-01-01

    Molybdate- and ATP-dependent in vitro synthesis of the iron-molybdenum cofactor (FeMo-co) of nitrogenase requires the protein products of at least the nifB, nifN, and nifE genes. Extracts of FeMo-co-negative mutants of Klebsiella pneumoniae and Azotobacter vinelandii with lesions in different genes can be complemented for FeMo-co synthesis. Both K. pneumoniae and A. vinelandii dinitrogenase (component I) deficient in FeMo-co can be activated by FeMo-co synthesized in vitro. Properties of the ...

  20. EXAFS and NRVS Reveal that NifB-co, a FeMo-co Precursor, Comprises a 6Fe Core with an Interstitial Light Atom

    OpenAIRE

    George, Simon J.; Igarashi, Robert Y.; Xiao, Yuming; Hernandez, Jose A.; Demuez, Marie; Zhao, Dehua; Yoda, Yoshitaka; Ludden, Paul W.; Rubio, Luis M.; Cramer, Stephen P.

    2008-01-01

    NifB-co, a Fe-S cluster produced by the enzyme NifB, is an intermediate on the biosynthetic pathway for the iron molybdenum cofactor (FeMo-co) of nitrogenase. We have used Fe K-edge extended x-ray absorption fine structure (EXAFS) spectroscopy together with 57Fe nuclear resonance vibrational spectroscopy (NRVS) to probe the structure of NifB-co while bound to the NifX protein from Azotobacter vinelandii. EXAFS analysis of the NifX:NifB-co complex yields Fe-S distances of 2.26 Å and Fe-Fe dist...

  1. Structural insights into a protein-bound iron-molybdenum cofactor precursor

    OpenAIRE

    Corbett, Mary C.; Hu, Yilin; Fay, Aaron W.; Ribbe, Markus W.; Hedman, Britt; Hodgson, Keith O.

    2006-01-01

    The iron-molybdenum cofactor (FeMoco) of the nitrogenase MoFe protein is a highly complex metallocluster that provides the catalytically essential site for biological nitrogen fixation. FeMoco is assembled outside the MoFe protein in a stepwise process requiring several components, including NifB-co, an iron- and sulfur-containing FeMoco precursor, and NifEN, an intermediary assembly protein on which NifB-co is presumably converted to FeMoco. Through the comparison of Azotobacter vinelandii s...

  2. Identification of a nitrogenase FeMo cofactor precursor on NifEN complex

    OpenAIRE

    Hu, Yilin; Fay, Aaron W.; Ribbe, Markus W.

    2005-01-01

    The biosynthesis of the FeMo cofactor (FeMoco) of Azotobacter vinelandii nitrogenase presumably starts with the production of its Fe/S core by NifB (the nifB gene product). This core is subsequently processed on the α2β2 tetrameric NifEN complex (formed by the nifE and nifN gene products). In this article, we identify a NifEN-bound FeMoco precursor form that can be converted to fully assembled FeMoco in a so-called FeMoco-maturation assay containing only purified components. We also establish...

  3. Influence of PAS Domain Flanking Regions on Oligomerisation and Redox Signalling By NifL

    OpenAIRE

    Richard Little; Peter Slavny; Ray Dixon

    2012-01-01

    Per-ARNT-Sim (PAS) domains constitute a typically dimeric, conserved α/β tertiary fold of approximately 110 amino acids that perform signalling roles in diverse proteins from all kingdoms of life. The amino terminal PAS1 domain of NifL from Azotobacter vinelandii accommodates a redox-active FAD group; elevation of cytosolic oxygen concentrations result in FAD oxidation and a concomitant conformational re-arrangement that is relayed via a short downstream linker to a second PAS domain, PAS2. A...

  4. Cloning, characterization, and regulation of nifF from Rhodobacter capsulatus.

    OpenAIRE

    G. de Gennaro; Hübner, P.; Sandmeier, U; Yakunin, A. F.; Hallenbeck, P C

    1996-01-01

    The Rhodobacter capsulatus nifF gene and upstream sequence were cloned by using a probe based on the N-terminal sequence of NifF. nifF was found to not be contained in the previously described nif regions I, II, and III. Comparison of the deduced amino acid sequence showed that it is highly similar to NifF from Azotobacter vinelandii and NifF from Klebsiella pneumoniae. Analysis of translational fusions demonstrated that the regulation of transcription was the same as previously reported at t...

  5. Genetic and structural analysis of the Rhizobium meliloti fixA, fixB, fixC, and fixX genes.

    OpenAIRE

    Earl, C D; Ronson, C W; Ausubel, F M

    1987-01-01

    The fixA, fixB, fixC, and fixX genes of Rhizobium meliloti 1021 constitute an operon and are required for nitrogen fixation in alfalfa nodules. DNA homologous to the R. meliloti fixABC genes is present in all other Rhizobium and Bradyrhizobium species examined, but fixABC-homologous sequences were found in only one free-living diazotroph, Azotobacter vinelandii. To determine whether the fixABCX genes share sequence homology with any of the 17 Klebsiella pneumoniae nif genes, we determined the...

  6. NifS-directed assembly of a transient [2Fe-2S] cluster within the NifU protein

    OpenAIRE

    Yuvaniyama, Pramvadee; Agar, Jeffrey N.; Cash, Valerie L.; Johnson, Michael K.; Dean, Dennis R.

    2000-01-01

    The NifS and NifU proteins from Azotobacter vinelandii are required for the full activation of nitrogenase. NifS is a homodimeric cysteine desulfurase that supplies the inorganic sulfide necessary for formation of the Fe-S clusters contained within the nitrogenase component proteins. NifU has been suggested to complement NifS either by mobilizing the Fe necessary for nitrogenase Fe-S cluster formation or by providing an intermediate Fe-S cluster assembly site. As isolated, the homodimeric Nif...

  7. Biosynthesis of Iron-Sulfur Clusters

    OpenAIRE

    Yuvaniyama, Pramvadee

    1999-01-01

    It is not known whether biosynthesis of [Fe-S] clusters occurs through a spontaneous self-assembly process or an enzymatic process. However, in the Azotobacter vinelandii nitrogenase system, it has been proposed that NifS and NifU are involved in the mobilization of sulfur and iron necessary for nitrogenase-specific [Fe-S] cluster assembly. The NifS protein has been shown to have cysteine desulfurase activity and can be used to supply sulfur for the in vitro catalytic formation of [Fe-S] cl...

  8. Requirement of NifX and Other nif Proteins for In Vitro Biosynthesis of the Iron-Molybdenum Cofactor of Nitrogenase

    OpenAIRE

    Shah, Vinod K.; Rangaraj, Priya; Chatterjee, Ranjini; Allen, Ronda M.; Roll, Jon T.; Roberts, Gary P.; Ludden, Paul W.

    1999-01-01

    The iron-molybdenum cofactor (FeMo-co) of nitrogenase contains molybdenum, iron, sulfur, and homocitrate in a ratio of 1:7:9:1. In vitro synthesis of FeMo-co has been established, and the reaction requires an ATP-regenerating system, dithionite, molybdate, homocitrate, and at least NifB-co (the metabolic product of NifB), NifNE, and dinitrogenase reductase (NifH). The typical in vitro FeMo-co synthesis reaction involves mixing extracts from two different mutant strains of Azotobacter vineland...

  9. Products of the iron-molybdenum cofactor-specific biosynthetic genes, nifE and nifN, are structurally homologous to the products of the nitrogenase molybdenum-iron protein genes, nifD and nifK.

    OpenAIRE

    Brigle, K E; Weiss, M C; Newton, W E; Dean, D R

    1987-01-01

    The genes from Azotobacter vinelandii, which are homologous to the iron-molybdenum cofactor biosynthetic genes, nifE and nifN, from Klebsiella pneumoniae, have been cloned and sequenced. These genes comprise a single transcription unit and are located immediately downstream from the nitrogenase structural gene cluster (nifHDK). DNA sequence analysis has revealed that the products of the nifE and nifN genes contain considerable homology when compared with the nifD (MoFe protein alpha subunit) ...

  10. Eisen-Schwefel-Cluster-Biosynthese: Biochemische und kristallographische Untersuchung von NifS-ähnlichen Proteinen

    OpenAIRE

    Kaiser, Jens Thomas

    2007-01-01

    Eisen-Schwefel-Cluster (Fe/S-Cluster) sind ubiquitäre co-Faktoren in vielen Proteinen, deren Funktion vom Elektronentransport über enzymatische Aktivität bis zur Genregulation reicht. Trotz ihrer universellen Bedeutung und der einfachen Dar-stellung von Modellverbindungen aus Fe(II), S2-, S8 und Thiolen ist der Biosynthese-weg dieser anorganischen Einheiten bis heute nicht geklärt. In Azotobacter wurde das Protein NifS beschrieben, welches für die Bildung des Fe/S-Cluster in Nitrogenase essen...

  11. Quantification of Nitrogen Reductase and Nitrite Reductase Genes in Soil of Thinned and Clear-Cut Douglas-Fir Stands by Using Real-Time PCR ▿ †

    OpenAIRE

    Levy-Booth, David J.; Winder, Richard S.

    2010-01-01

    The abundance of nifH, nirS, and nirK gene fragments involved in nitrogen (N) fixation and denitrification in thinned second-growth Douglas-fir (Pseudotsuga menziesii subsp. menziesii [Mirb.] Franco) forest soil was investigated by using quantitative real-time PCR. Prokaryotic N cycling is an important aspect of N availability in forest soil. The abundance of universal nifH, Azotobacter sp.-specific nifH (nifH-g1), nirS, and nirK gene fragments in unthinned control and 30, 90, and 100% thinni...

  12. The Nifl PAS domain: Insight into its structure and function

    OpenAIRE

    Hefti, M.H.

    2003-01-01

    Azotobacter vinelandii is an aerobic soil-dwelling organism with a wide variety of metabolic capabilities which include the ability to fix atmospheric nitrogen by converting it to ammonia. The biosynthesis of ammonia is controlled by 15 to 20 different nif gene products. The activation of nif gene expression by the regulatory enhancer binding protein NifA is controlled by the sensor flavoprotein NifL in response to changes in oxygen or nitrogen levels. NifL contains a PAS domain, which is an ...

  13. Roles of nifF and nifJ gene products in electron transport to nitrogenase in Klebsiella pneumoniae.

    OpenAIRE

    Hill, S.; Kavanagh, E P

    1980-01-01

    Crude extracts of the wild-type Klebsiella pneumoniae reduced C2H2 with either pyruvate or formate as reductant (specific activity, 3 nmol min-1 mg of protein-1), whereas crude extracts of nifF mutant were almost inactive (specific activity, 0.05). However, activity in the latter extracts was stimulated by adding Azotobacter chroococcum flavodoxin (specific activity, 10). Thus, nifF mutants may lack an electron transport factor. Crude extracts of nifJ mutants had about 20% of the wild-type le...

  14. Identification and functional characterization of NifA variants that are independent of GlnB activation in the photosynthetic bacterium Rhodospirillum rubrum

    OpenAIRE

    Zou, Xiaoxiao; Zhu, Yu; Pohlmann, Edward L.; Li, Jilun; Zhang, Yaoping; Roberts, Gary P.

    2008-01-01

    The activity of NifA, the transcriptional activator of the nitrogen fixation (nif) gene, is tightly regulated in response to ammonium and oxygen. However, the mechanisms for the regulation of NifA activity are quite different among various nitrogen-fixing bacteria. Unlike the well-studied NifL–NifA regulatory systems in Klebsiella pneumoniae and Azotobacter vinelandii, in Rhodospirillum rubrum NifA is activated by a direct protein–protein interaction with the uridylylated form of GlnB, which ...

  15. Medio de cultivo utilizando residuos-sólidos para el crecimiento de una bacteria nativa con potencial biofertilizante

    OpenAIRE

    Cecilia Lara Mantilla; Liliana Pahola García Támara; Luis E. Oviedo Zumaqué

    2010-01-01

    En el presente trabajo se muestran los resultados obtenidos de la evaluación del crecimiento, desarrollo y viabilidad de una cepa bacteriana nativa Azotobacter A15M2G con potencial biofertilizante, sobre un medio de cultivo preparado con residuos sólidos vegetales procedentes del mercado: Brassica Oleracea (repollo), Lactusa sativa (lechuga) y Allium fistulosum (cebollín). El crecimiento de la bacteria en el medio de residuo vegetal a diferentes concentraciones: 25, 50 y 75% p/v fue evaluado,...

  16. Effect of microwave irradiation on alfalfa seeds germination and nitrogenase activity of endophytic diazotrophs in seeds

    International Nuclear Information System (INIS)

    Various microwave powers were used to irradiate alfalfa seeds with various time to study the effect of microwave irradiation on nitrogenase activity of endogenous azotobacter and germination of seeds. Germination rate, germination speed and nitrogenase activity of pure cultures that derived from seed-carried azotobacter were tested. The results indicate that : 800 W, 20 s and 500 W, 40 s are found with highest germination rate on the 1st day, which is 122% and 88.9% times higher than the control group (Pth day is 29.8% and 41.9% times longer than the control group, and more sensitive nitrogenase activity is found on condition of various time than various powers. Short time treatments on condition of the two irradiation powers can increase nitrogenase activity conspicuously, and the treatments that treated more than 32 s make nitrogenase activity lower than the control group, conspicuously. Nitrogenase activity is found 104.9% times higher than the control group on condition of 24 s. (authors)

  17. Characterization of diazotrophic bacteria non-symbiotic associated with eucalyptus (eucalyptus sp.) in Codazzi, Cesar (Colombia)

    International Nuclear Information System (INIS)

    The effect of climatic seasons (rainy and dry) and the stratum sample (rhizospheric soil, roots and leaves) the population of the genera Azotobacter, Beijerinckia, Derxia, Azospirillum, Herbaspirillum, Gluconacetobacter and Burkholderia in soil rhizosphere, roots and leaves of eucalyptus (eucalyptus sp.). It also assesses their ability to produce indoles compounds as plant growth promoters and their acetylene reduction activity as an indicator of biological fixation of nitrogen. The results showed no statistically significant differences in the Duncan test (p ≤ 0.05) in the population with respect to the climate epoch, suggesting that these bacteria are able to tolerate stress conditions by different physiological mechanisms. With respect to the stratum sample isolates attempts of Herbaspirillum sp. and Azospirillum sp. significant differences in rhizospheric soil and roots. we obtained 44 isolates of which were grouped by phenotypic characterization as 14 suspected of Beijerinckia sp., 12 Azotobacter sp., 8 Derxia sp., 4 Herbaspirillum sp., 5 Azospirillum sp., 1 Gluconacetobacter sp. and 1 Burkholderia sp. due to their high potential were selected isolates C27, C26 and C25. These four strains present the best values of efficiency in vitro, exceeding production values of the reference strains used (A. chroococcum (AC1) and a. brasilense (SP7)).

  18. Population of bacteria from soil in Tudu-Aog village, Passi district, Bolaang Mongondow, North Sulawesi

    Directory of Open Access Journals (Sweden)

    RIANI HARDININGSIH

    2004-01-01

    Full Text Available An experiment was conducted in order to know the population of bacteria from soil in Tudu-Aog village, Passi district, Bolaang Mongondow, North Sulawesi, the purpose of the research was to study the population of bacteria from soil. Fourthy six soil samples were taken from two location, namelyTudu-Aog village and Bugis mountain. Isolation was done by dilution methods on YEMA medium (for Rhizobium bacteria, Winogradsky’s (for Azotobacter bacteria, Pycosvkaya (for Phosphat Solubilizing Bacteria, and selective Difco Pseudomonas (for Pseudomonas bacteria. Incubation at room temperature (27-280C until 15 days, and the enumeration with plate count method. The highest enumeration of Rhizobium bacteria with plant rhizosphere of Alocasia esculenta (27x105 CFU/g soil, Theobroma cacao (29x105 CFU/g soil,and Euphorbia paniculata (26x105 CFU/g soil, Azotobacter bacteria with plant rhizosphere of Lycopersicum esculantum (38x105 CFU/g soil, Eugenia aromaticum (43x105 CFU/g soil, Andropogon sp. (34x105 CFU/g soil, Phosphat Solubilizing bacteria with plant rhizosphere of Sechium edule (27x105 CFU/g soil, Cinnamomum sp. (48x105 CFU/g soil, Cyathea sp. (72x105 CFU/g soil, and Pseudomonas bacteria with plant rhizosphere of Oryza sativa (18x105 CFU/g soil, Vanilla sp. (12x105 CFU/g soil, dan Saurauia sp.(19x105 CFU/g soil.

  19. Response of nitrogen, phosphorus and zinc efficiency of fenugreek (Trigonella foenum- graecum to combination of chemical and biological fertilizers in greenhouse culture

    Directory of Open Access Journals (Sweden)

    2015-06-01

    Full Text Available In order to investigate the effect of combination of chemical and biological fertilizers on dry matter, uptake and efficiency of nitrogen (N, phosphorus (P and zinc (Zn by fenugreek (Trigonella foenum- graecum, an experiment was conducted as randomized complete blocks design with three replications in the Research Greenhouse of Shahrekord University. Eight fertilizer treatments consisted of control (no fertilizer, urea fertilizer (UF, UF+ zinc sulfate (ZS, UF+ Azotobacter (Az, UF+ mycorrhiza (My, UF+ ZS+ Az, UF+ ZS+ My and UF+ ZS+ Az+ My. Results indicated that there was significant difference (P≤ 0.05 among different fertilizer treatments for agronomic efficiency of N, P and Zn. The highest agronomic efficiency of N, P and Zn (60, 96 and 198 g/g, respectively was achieved in UF+ZS+Az treatment. The highest P-uptake efficiency (18.7 % was observed in UF+My treatment and it had significant (P≤ 0.05 difference with other treatments, except UF+ZS treatment. The highest Zn physiologic efficiency was obtained in UF+ZS, which had no significant difference with UF+ ZS+ Az and UF+ ZS+ Az+ My. Maximum dry matter (292 g/m2 was produced in UF+ ZS+ Az treatment. In general, application of biofertilizers, especially Azotobacter, integrated with urea and zinc sulfate not only is effective in increasing dry matter, but also can increase productivity of fenugreek by increasing chemical fertilizers’ efficiency in greenhouse culture.

  20. 苹果树根际促生细菌种群分析%Analysis of plant growth promoting rhizobacteria population in apple rhizosphere soils

    Institute of Scientific and Technical Information of China (English)

    国辉; 毛志泉; 宋振; 张本峰; 仇念全; 刘训理

    2011-01-01

    Apple replant disease (ARD) is a complex syndrome of young apple trees in replanted orchards that causes death of fine feeder roots, stunted tree growth and low yield. Analyzing changes in the number and species of plant growth promoting rhizobacte-ria (PGPR) in perennial apple tree (PAT) and replanted young tree (RYT) fields could lay theoretical basis for understanding the interactions among ARD and rhizosphere microbes. In this study, rhizosphere soil samples were collected in PAT and RYT fields in Changli, Hebei Province. Rhizosphere bacteria of interest in the study included azotobacter, phosphate-dissolving bacteria, potas-sium-dissolving bacteria and antagonistic bacteria. While rhizosphere azotobacter, phosphobacteria, potassium-bacteria were cultivated by the selective media plate cultivation method, antagonistic bacteria (with antagonistic activity against Rhizoctonia solani or Fusarium camptoceras) were isolated using the in vitro screening technique. For soil samples from both fields, microbe species and population examined by colony-forming unit (CFU) count. Also BOX Polymerase Chain Reaction (BOX-PCR) was used to fingerprint the different PGPRs. Total rhizosphere bacteria, azotobacter, phosphate-dissolving bacteria, potassium-dissolving bacteria and antagonistic bacteria were more abundant in PAT than in RYT fields. In PAT fields, potassium-dissolving bacteria were the most abundant, followed by phosphate-dissolving bacteria and then azotobacter. Antagonistic bacteria were the least abundant. In RYT fields, phosphate-dissolving bacteria were the most abundant, followed by potassium-dissolving bacteria and then azotobacter. Antagonistic bacteria were also the least abundant. Based on BOX-PCR fingerprints cluster analysis of PGPR, there were over 1.2Sdissimilarities in both PAT and RYT fields. This somehow suggested close genetic evolutionary distance among the isolates. PGPR in PAT fields were divided into 79 clusters; including 18 azotobacter, 29

  1. Two distinct ferredoxins from Rhodobacter capsulatus: complete amino acid sequences and molecular evolution.

    Science.gov (United States)

    Saeki, K; Suetsugu, Y; Yao, Y; Horio, T; Marrs, B L; Matsubara, H

    1990-09-01

    Two distinct ferredoxins were purified from Rhodobacter capsulatus SB1003. Their complete amino acid sequences were determined by a combination of protease digestion, BrCN cleavage and Edman degradation. Ferredoxins I and II were composed of 64 and 111 amino acids, respectively, with molecular weights of 6,728 and 12,549 excluding iron and sulfur atoms. Both contained two Cys clusters in their amino acid sequences. The first cluster of ferredoxin I and the second cluster of ferredoxin II had a sequence, CxxCxxCxxxCP, in common with the ferredoxins found in Clostridia. The second cluster of ferredoxin I had a sequence, CxxCxxxxxxxxCxxxCM, with extra amino acids between the second and third Cys, which has been reported for other photosynthetic bacterial ferredoxins and putative ferredoxins (nif-gene products) from nitrogen-fixing bacteria, and with a unique occurrence of Met. The first cluster of ferredoxin II had a CxxCxxxxCxxxCP sequence, with two additional amino acids between the second and third Cys, a characteristics feature of Azotobacter-[3Fe-4S] [4Fe-4S]-ferredoxin. Ferredoxin II was also similar to Azotobacter-type ferredoxins with an extended carboxyl (C-) terminal sequence compared to the common Clostridium-type. The evolutionary relationship of the two together with a putative one recently found to be encoded in nifENXQ region in this bacterium [Moreno-Vivian et al. (1989) J. Bacteriol. 171, 2591-2598] is discussed. PMID:2277040

  2. The effect of use of nitrogen-fixators in forage pea production

    Directory of Open Access Journals (Sweden)

    Jokanović Svetlana

    2003-01-01

    Full Text Available Microorganisms are the most numerous group of living organisms in the pedosphere. They encompass bacteria, viruses, fungi, algae, protozoa and lichens. Their numbers amount to several million per one gram of absolutely dry soil while their biomass amounts to 5-20 tons per hectare. The aims of this investigation were to examine the effect of application of root nodule bacteria (single strain, mixture of strains, microbiological fertilizer "Nitragin" on the total number of microorganisms, the numbers of fungi actinomycetes, azotobacters, free nitrogen-fixing bacteria and ammonifiers and the activity of dehydrogenase, as well as how the application of bacteria affects some parameters of nitrogen fixation (dry mater mass, percentage and content of nitrogen. In the variant with "Nitragin", the total number of microorganisms and the numbers of fungi, azotobacters and free N-fixing bacteria increased. The largest number of actino-myceles was found in the variant with the mixture of strains. The largest number of ammonifiers was found in the variant with the single strain. The dehydrogenase activity, dry mater mass, percentage and content of nitrogen were increased in the variants with the single strain and the mixture of strains.

  3. Cyanobacterial inoculation elicits plant defense response and enhanced Zn mobilization in maize hybrids

    Directory of Open Access Journals (Sweden)

    Radha Prasanna

    2015-12-01

    Full Text Available The present investigation evaluated the effect of inoculating different cyanobacterial formulations on a set of hybrids of maize, in terms of plant defense enzyme activity, soil health parameters, Zn concentration, and yields. Microbial inoculation showed significant effects on accumulation of Zn in flag leaf, with A4 (Anabaena–Azotobacter biofilm recording the highest values. Analysis of variance (ANOVA indicated that both the hybrids and cyanobacterial treatments brought about significant variation in terms of glomalin-related soil proteins and polysaccharides in soil and the activity of defense enzymes in roots and shoots of the plants. Cyanobacterial inoculants—A4 (Anabaena–Azotobacter biofilm and A1 (Anabaena sp.–Providencia sp., CW1 + PW5 enhanced the activity of peroxidase, PAL and PPO in roots, which also showed a positive correlation with Zn concentration in the flag leaf. Grain yield ranged from 7.0 to 7.29 t/ha among the different inoculants. Comparative analyses of treatments showed that A3 (Anabaena–Trichoderma-biofilmed formulation and hybrid B8 (Bio-9681 were superior in terms of parameters investigated. This represents the first report on the genotypic responses of maize hybrids to cyanobacteria-based inoculants. Future research should focus on dissecting the role of root exudates and cyanobacteria-mediated Zn mobilization pathway in maize.

  4. Application of microbiological fertilizers in viticulture: Grape yield and quality of wine cv. Riesling

    Directory of Open Access Journals (Sweden)

    Sivčev Branislava

    2005-01-01

    Full Text Available The recommended cultivars for top quality wines Riesling in the vineyards of Grocka is in full crop. It was grafted on Kober 5 BB stock and planted on the soil type cambysoil. The content of total nitrogen is 0.1-0.15%. Supply of easily available potassium varies between 12.3-15 mg/100g a.d.s.2, i.e. phosphorus 0.4-3.6 mg/100g a.d.s. in layer up to 40 cm. Microbiological fertilizer was used in the study - biological preparation prepared with mixed natural populations Azotobacter chroococcum, Bacillus megaterium and Bacillus circulons. The space in row is idle land and the space between rows was sown each year (March-April with a mixture of field pea and barley and ploughed in the inflorescence phase of legumes. Grape yield varied between 8772-6804 kg/ha. Microbiological fertilizer with Azotobacter had the highest yield and the control treatment had the lowest yield, where only grass mixture was sown. Extremely dry climatic conditions in the trial period caused the grape yield in cv. Riesling to be extremely low. In combination of fertilizers Bacillus megaterium + Bacillus circulons wine with the most ethanol, extracts and polyphenols was obtained. The wine obtained from the control treatment had a typical taste.

  5. Increased root exudation of /sup 14/C-compounds by sorghum seedlings inoculated with nitrogen-fixing bacteria

    Energy Technology Data Exchange (ETDEWEB)

    Lee, K.J. (Institute of Forest Genetics, Suweon (Republic of Korea)); Gaskins, M.H. (Florida Univ., Gainesville (USA). Dept. of Agriculture)

    1982-01-01

    Organic components leaked from Sorghum bicolor seedlings ('root exudates') were examined by recovering /sup 14/C labelled compounds from root solutions of seedlings inoculated with Azospirillum brasilense, Azotobacter vinelandii or Klebsiella pneumoniae nif-. Up to 3.5% of the total /sup 14/C recovered from shoots, roots, and nutrient solutions was found in the root solutions. Inoculation with Azospirillum and Azotobacter increased the amounts of /sup 14/C and decreased the amounts of carbohydrates in the root solutions. When sucrose was added as a carbon source for the bacteria, the increase of /sup 14/C in the solutions did not occur. Quantities of /sup 14/C found in the root solutions were proportional to amounts of mineral nitrogen supplied to the plants. Bacterial growth also was proportional to nitrogen levels. When sorghum plants were grown in soil and labelled with /sup 14/CO/sub 2/, about 15% of the total /sup 14/C recovered within 48 hours exposure was found in soil leachates.

  6. INFLUENCIA DE DIFERENTES VARIANTES DE FERTILIZACIÓN EN EL CRECIMIENTO Y DESARROLLO DE POSTURAS DE Coffea canephora Pierre

    Directory of Open Access Journals (Sweden)

    A. Pérez

    2002-01-01

    Full Text Available En áreas experimentales de la Estación Central de Investigaciones de Café y Cacao (ECICC, se desarrolló un experimento dirigido a evaluar la respuesta de Coffea canephora Pierre a la fertilización con hongos micorrízicos arbusculares (HMA, Azotobacter chroococcum y urea. La cepa de Azotobacter utilizada se aisló de la rizosfera del cafeto cultivado en suelo Pardo ócrico sin carbonatos. El inóculo se obtuvo en el medio DIMARGON y se aplicó con título de 1010UFC.mL-1. El inóculo micorrízico (Glomus fasciculatum, Glomus clarum provino del cepario del Instituto Nacional de Ciencias Agrícolas; se utilizó además un concentrado de cepas nativas. Para la incoculación se utilizó una mezcla de propágulos de la micorrización del sorgo en suelo estéril que contenía hifas, raicillas y 40 esporas/g suelo. Se empleó un diseño de bloques al azar con 12 tratamientos y tres réplicas, realizándose a los seis meses de plantados los esquejes, las evaluaciones de altura (cm, diámetro del tallo (cm, área foliar (cm2, masa seca total (g, extracción de nutrientes (mg y se determinó además el porcentaje de colonización micorrízica. Se obtuvo una respuesta positiva de Coffea canephora a la inoculación con Azotobacter y HMA. El efecto positivo de las micorrizas dependió de las cepas utilizadas. Se reafirmó la utilización de la cepa certificada Glomus fasciculatum para la inoculación del cafeto en suelo Pardo. No se encontró respuesta positiva de la aplicación de urea foliar en el desarrollo de las posturas de Coffea canephora. La respuesta a la coinoculación dependió de ella y es factible cuando se utiliza el potencial de inóculo natural del suelo, lo que se expresa en el aumento de la absorción P. Con la cepa Glomus clarum la aplicación de Azotobacter deprimió o no causó efecto en la morfología de los esquejes, mientras que con Glomus fasciculatum aumentó la absorción de P. El concentrado de cepas nativas no debe aplicarse

  7. Bacterias fijadoras asimbióticas de nitrógeno de la zona agrícola de San Carlos. Córdoba, Colombia

    Directory of Open Access Journals (Sweden)

    Lara Mantilla Cecilia

    2007-12-01

    Full Text Available Se aislaron bacterias diazotróficas de los géneros Azotobacter sp y Azospirrillum sp a partir de la rizosfera de cultivos de plátano, pastos, maíz y de rastrojos (zonas sin cultivar en el municipio de San Carlos (Valle del Sinú medio en el departamento de Córdoba, Colombia. Las poblaciones microbianas se identificaron mediante pruebas bioquímicas y observación macroscópica y microscópica con tinción de Gram en diferentes medios de cultivo: a Burk´s, Asbhy y Jensen´s, (género Azotobacter sp, y b Burk´s, nfb y rojo congo (género Azospirillum sp. El objetivo del presente trabajo fue determinar la producción del ión amonio a partir de los géneros bacterianos aislados; la cuantificación del ión amonio fue llevada a cabo por el método colorimétrico de Berthelot (fenol-hipoclorito empleando un espectrofotómetro Perkin-Elmer Lamba 11 uv-Vis; la técnica fue modificada y estandarizada de acuerdo con las condiciones del equipo. Como resultado se obtuvieron 14 aislados que produjeron concentraciones de 0,9 hasta 5,2 mg/l, siendo los más destacados para el género Azotobacter sp, A16PG y A26M1P (5,1545 y 5,1743 mg/l de amonio, respectivamente, y para el género Azospirrillum spp, A5M1G (4,6741 mg/l de amonio. La fijación biológica del nitrógeno (fbn por bacterias diazotróficas ha contribuido a incrementar el rendimiento en las cosechas, reduciendo la necesidad de fertilizantes nitrogenados y la emisión de gases tóxicos como el N2O, obteniendo beneficios económicos y ambientales en las granjas.

  8. Effects of plant growth promoting bacteria and composed organic fertilizers on the reproduction of Meloidogyne incognita and tomato growth.

    Science.gov (United States)

    Siddiqui, Zaki A

    2004-11-01

    Glasshouse experiments were conducted to assess the influence of Pseudomonas fluorescens, Azotobacter chroococcum, Azospirillum brasilense and composted organic fertilizers (cow dung, horse dung, goat dung and poultry manure) alone and in combination on the multiplication of Meloidogyne incognita and growth of tomato. P. fluorescens was better at improving tomato growth and reducing galling and nematode multiplication than A. chroococcum or A. brasilense. Among composted organic fertilizers, poultry manure resulted in less galling and nematode multiplication than occurred with goat dung. However, composted goat dung was better in reducing nematode multiplication and improving plant growth than horse dung. Cow dung was the composted organic fertilizer least effective in reducing galling and nematode multiplication. Poultry manure with P. fluorescens was the best combination for the management of M. incognita on tomato but improved management of M. incognita can also be obtained if goat dung is used with P. fluorescens or poultry manure with A. chroococcum.

  9. [Physiological and biochemical activity of bacteria during germination of cucumber seeds and impact of ciliates Colpoda steinii on this process].

    Science.gov (United States)

    Chobotarova, V V; Bega, Z T; Kurdish, I K

    2015-01-01

    It is shown that the bacteria Bacillus subtilis B-7023 IMV produce indole-3-acetic acid and amino acids in the liquid medium Knoop. Processing cucumber seed suspension containing 10(7) cfu/ml as bacilli, and Azotobacter vinelandii IMV V-7076, resulted in a decrease in the length of the roots of plants. Reduction of bacterial load bacilli to 10(6) cfu/ml followed by reduction of indole-3-acetic acid in the medium, and to an increase in the length of roots, shoots and total plant mass. During the cultivation of Bacillus subtilis IMV V-7023 with ciliates Colpoda steinii reduced the amount of free forms of auxin in the medium to 5.5 times, and the related--to trace amounts. The content of histidine, phenylalanine, tyrosine, methionine and lysine significantly reduced. PMID:26036028

  10. Biofertilización de café orgánico en etapa de vivero en Chiapas, México Biofertilizer of organic coffee in stage of seedlings in Chiapas, Mexico

    Directory of Open Access Journals (Sweden)

    María de Lourdes Adriano Anaya

    2011-06-01

    Full Text Available En Chiapas, la producción de plántulas de café, se realiza convencionalmente con la aplicación de fertilizantes químicos. La producción de café orgánico, requiere la nutrición de plántulas con biofertilizantes y por ello el objetivo fue evaluar el efecto de algunos de éstos en el desarrollo de plántulas de café (Coffe arábica variedad Bourbon en vivero. El experimento se realizó durante 2007 y 2008 en Cacahohatan,Chiapas. Los inoculantes fueron una cepa Glomus intraradices Schenck y Smith, cepas PACHAZ08 de Azotobacter y 11B de Azospirillum. Se utilizó el diseño factorial 2³ con ocho tratamientos y 100 repeticiones por tratamiento. En las platulas inoculadas, se efectuaron 4 muestreos con intervalos de 28 días, midiendóse la altura, longitud de hojas, longitud de raíz, peso seco de hojas y raíces, contenido de clorofila y nitrógeno, y colonizacion de raíz por los inoculantes. Los datos se sometieron al análisis de varianza y comparacion de medias por Tukey p≤ 0.05. Las mejores características morfológicas y bioquímicas de las plántulas, se obtuvieron con Azospirillum sóla o coinoculada con Glomus y Azotobacter y estadísticamente fueron los mejores tratamientos. Azospirillum modificó la arquitectura de la raíz y estimuló la micorrización. Los diazotrofos en conjunto fueron antagónicos pero esta fue inhibida por Glomus. La interacción de los tres microorganismos indujo en las plántulas un mejor aprovechamiento de nutrimentos, agua, capacidad fotosintética y mayor acumulación de biomasa carbonada.In Chiapas, c offee seedlings product ion is conventionally done with chemical fertilizers. Organic coffee production requires see dlings nutrition with biofertilizers and therefore the objective was to evaluate the effect of some of these in coffee seedlings development (Coffee arabica Bourbon variety in a nursery. The experiment was conducted during 2007 and 2008 in Cacahohatan, Chiapas. Inoculants were a strain

  11. Efecto de la biofertilización y los biorreguladores en la germinación y el crecimiento de Carica papaya L.

    Directory of Open Access Journals (Sweden)

    Maricela Constantino

    2011-01-01

    Full Text Available Título en inglés: Effect of biofertilization and bioregulators on germination and growth of Carica papaya L. Resumen Con el objetivo de incrementar y acelerar el proceso de germinación de las semillas y obtener una alta producción y homogeneidad de plántulas de Carica papaya variedad Maradol en vivero, se evaluó el efecto de tres biofertilizantes aplicados solos o en combinación (Azotobacter chroococcum, Azospirillum brasilense y Glomus intraradices, y un biorregulador del crecimiento vegetal, el ácido giberélico (AG3, en la germinación y el crecimiento vegetal. Se realizó un experimento bajo un diseño completamente al azar con ocho tratamientos y tres repeticiones. A las semillas se les aplicó un pretratamiento germinativo con alternancia de temperatura para superar la dormancia. Los tratamientos simples con A. chroococcum y A. brasilense, incrementaron el porcentaje de germinación a 90,28 y 88,89% respectivamente. Además, con la aplicación de los biofertilizantes y el AG3, la velocidad de germinación se incrementó y el tiempo medio de germinación se redujo. La doble aplicación en semillas y foliar de los biofertilizantes y el AG3 en plántulas mejoró el crecimiento vegetal. La población de A. chroococcum fue mayor cuando se inoculó en combinación con G. intraradices. La prevalencia de colonización de las plántulas inoculadas con G. intraradices varió de 18,53 a 26,67%, con el mayor valor registrado para el tratamiento combinado con A. brasilense. Finalmente, aplicando esta metodología se logró acelerar la germinación, obteniéndose una mayor homogeneidad en la emergencia de las plántulas, disminuyendo así el tiempo de permanencia en el vivero. Palabras clave: Azospirillum brasilense; Azotobacter chroococcum; Glomus intraradices; ácido giberélico; dormancia. Abstract In order to increase and accelerate the process of seed germination and obtain a high yield and homogeneity of papaya seedlings cv. Maradol in

  12. Seasonal changes in microbial community structure and nutrients content in rhizospheric soil of Aegle marmelos tree

    Directory of Open Access Journals (Sweden)

    Shital M. Patel

    2010-12-01

    Full Text Available A preliminary investigation was carried out on dominance of different types of microbial communities at different monsoon seasons in rhizospheric soils of Aegle marmelos tree. Nutrients content of soil were also determined simultaneously to correlate with the microbial population. Results show that the rhizosphere of Aegle marmelos contains gram-negative bacteria, Rhizobium, Azotobacter,Actinomycetes and Yeast and major plant nutrients and their count as well as dominance changes with moisture content in rhizosphere.Except actinomycetes all the microorganisms were found highest duringmonsoon season whereas in post-monsoon season Actinomycetes were dominant. Amount of water in rhizosphere soil also affects soil chemical properties. Soil pH, organic carbon, C:N ratio, available nitrogen and available phosphorus were recorded maximum in monsoon, whereas electrical conductivity and total nitrogen content were found maximum in post-monsoon.

  13. Evaluating the biological activity of oil-polluted soils using a complex index

    Science.gov (United States)

    Kabirov, R. R.; Kireeva, N. A.; Kabirov, T. R.; Dubovik, I. Ye.; Yakupova, A. B.; Safiullina, L. M.

    2012-02-01

    A complex index characterizing the biological activity of soils (BAS) is suggested. It is based on an estimate of the level of activity of catalase; the number of heterotrophic and hydrocarbon oxidizing microorganisms, microscopic fungi, algae, and cyanobacteria; and the degree of development of higher plants and insects in the studied soil. The data on using the BAS coefficient for evaluating the efficiency of rehabilitation measures for oil-polluted soils are given. Such measures included introducing the following biological preparations: Lenoil based on a natural consortium of microorganisms Bacillus brevis and Arthrobacter sp.; the Azolen biofertilizer with complex action based on Azotobacter vinelandii; the Belvitamil biopreparation, which is the active silt of pulp and paper production; and a ready-mixed industrial association of aerobic and anaerobic microorganisms that contains hydrocarbon oxidizing microorganisms of the Arthrobacter, Bacillus, Candida, Desulfovibrio, and Pseudomonas genera.

  14. Expression, purification, crystallization and preliminary X-ray analysis of Pseudomonas aeruginosa AlgX

    Energy Technology Data Exchange (ETDEWEB)

    Weadge, J.T.; Robinson, H.; Yip, P. P.; Arnett, K.; Tipton, P. A.; Howell, P. L.

    2010-05-01

    AlgX is a periplasmic protein required for the production of the exopolysaccharide alginate in Pseudomonas sp. and Azotobacter vinelandii. AlgX has been overexpressed and purified and diffraction-quality crystals have been grown using iterative seeding and the hanging-drop vapor-diffusion method. The crystals grew as flat plates with unit-cell parameters a = 46.4, b = 120.6, c = 86.9 {angstrom}, {beta} = 95.7{sup o}. The crystals exhibited the symmetry of space group P2{sub 1} and diffracted to a minimum d-spacing of 2.1 {angstrom}. On the basis of the Matthews coefficient (V{sub M} = 2.25 {angstrom}{sup 3} Da{sup -1}), two molecules were estimated to be present in the asymmetric unit.

  15. Antibacterial Activity of Silver Nanoparticles Synthesized by Bark Extract of Syzygium cumini

    Directory of Open Access Journals (Sweden)

    Ram Prasad

    2013-01-01

    Full Text Available The unique property of the silver nanoparticles having the antimicrobial activity drags the major attention towards the present nanotechnology. The environmentally nontoxic, ecofriendly, and cost-effective method that has been developed for the synthesis of silver nanoparticles using plant extracts creates the major research interest in the field of nanobiotechnology. The synthesized silver nanoparticles have been characterized by the UV-visible spectroscopy, atomic force microscopy (AFM, and scanning electron microscopy (SEM. Further, the antibacterial activity of silver nanoparticles was evaluated by well diffusion method, and it was found that the biogenic silver nanoparticles have antibacterial activity against Escherichia coli (ATCC 25922, Staphylococcus aureus (ATCC 29213, Pseudomonas aeruginosa (ATCC 27853, Azotobacter chroococcum WR 9, and Bacillus licheniformis (MTCC 9555.

  16. Expression, Purification, Crystallization and Preliminary X-ray Analysis of Pseudomonas fluorescens AlgK

    International Nuclear Information System (INIS)

    AlgK is an outer-membrane lipoprotein involved in the biosynthesis of alginate in Pseudomonads and Azotobacter vinelandii. A recombinant form of Pseudomonas fluorescens AlgK with a C-terminal polyhistidine affinity tag has been expressed and purified from the periplasm of Escherichia coli cells and diffraction-quality crystals of AlgK have been grown using the hanging-drop vapour-diffusion method. The crystals grow as flat plates with unit-cell parameters a = 79.09, b = 107.85, c = 119.15 (angstrom), = 96.97o. The crystals exhibit the symmetry of space group P21 and diffract to a minimum d-spacing of 2.5 (angstrom) at Station X29 of the National Synchrotron Light Source, Brookhaven National Laboratory. On the basis of the Matthews coefficient (VM = 2.53 (angstrom)3 Da-1), four protein molecules are estimated to be present in the asymmetric unit

  17. Dicty_cDB: Contig-U10820-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available :none) Rhizobium sp. NGR234 plasmid pN... 58 3e-12 CP000614_1082( CP000614 |pid:none) Burkholderia vietnam...:none) Synechococcus sp. CC9605, comple... 74 3e-19 CP000447_2979( CP000447 |pid:none) Shewanella frigidimarina...otransferase... 71 1e-14 AL939130_44( AL939130 |pid:none) Streptomyces coelicolor A3(2) co...:none) Cyanothece sp. PCC 8801, comple... 61 7e-14 CP001157_2476( CP001157 |pid:none) Azotobacter vinelandii DJ, co...mplete... 62 2e-11 CP000447_3273( CP000447 |pid:none) Shewanella frigidimarina NCIMB ... 56 2e-11 CP

  18. Dicty_cDB: Contig-U10878-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available mple... 111 9e-23 CP000615_926( CP000615 |pid:none) Burkholderia vietnamiensis G4 ch... 111 9e-23 CP000387_91( CP000387 |pid...none) Renibacterium salmoninarum ATCC... 102 3e-20 AL939111_40( AL939111 |pid:none) Streptomyces coelicolor A3(2) co...7e-23 CP001157_62( CP001157 |pid:none) Azotobacter vinelandii DJ, comple... 111 7e-23 CP000083_4835( CP000083 |pid:none) Colwelli...re E Sequences producing significant alignments: (bits) Value N ( AY170439 ) Dictyostelium discoid...-21 CP000447_3906( CP000447 |pid:none) Shewanella frigidimarina NCIMB ... 107 1e-

  19. Dicty_cDB: Contig-U01787-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available :none) Podospora anserina genomic DNA c... 46 6e-06 CP000615_1850( CP000615 |pid:none) Burkholderia vietnam...... 58 8e-13 AL939104_218( AL939104 |pid:none) Streptomyces coelicolor A3(2) co... 68 8e-13 CP001027_958( CP001027 |pid...12 CT573213_4330( CT573213 |pid:none) Frankia alni str. ACN14A chromo... 62 2e-12 AL590463_43( AL590463 |pid:none) Streptomyces coeli...:none) Dictyostelium discoideum chromoso... 64 8e-21 FJ196388_4( FJ196388 |pid:none) Escherichia coli strain...:none) Azotobacter vinelandii DJ, comp... 70 1e-16 CP000284_588( CP000284 |pid:none) Methylobacillus flagel

  20. Dicty_cDB: Contig-U12088-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available :none) Nocardioides sp. JS614, complete... 289 4e-76 CP000616_180( CP000616 |pid:none) Burkholderia vietnam...omo sapiens cDNA FLJ61320 complet... 349 3e-94 CP000447_3168( CP000447 |pid:none) Shewanella frigidimarina N...mplet... 286 3e-75 AL939132_80( AL939132 |pid:none) Streptomyces coelicolor A3(2) com.....a 5-PRIME EST from clone LK0... 50 4e-06 2 >( BJ407081 ) Dictyostelium discoideum cDNA clone:dds37m08, 3' end, sin... pv. phaseo... 251 7e-65 CP001157_178( CP001157 |pid:none) Azotobacter vinelandii DJ, co

  1. Dicty_cDB: Contig-U16183-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available CP000615_1458( CP000615 |pid:none) Burkholderia vietnamiensis G4 c... 141 1e-48 CP000781_1346( CP000781 |pid...:none) Streptomyces coelicolor A3(2) com... 160 1e-56 AP007157_620( AP007157 |pid...... 34 0.026 23 ( U70317 ) Dictyostelium discoideum HydA (hydA) gene, partial ... 40 0.22 3 ( AJ314754 ) Ana...1-1... 34 4.3 2 ( EJ659522 ) 1092955018877 Global-Ocean-Sampling_GS-30-02-01-1... 34 4.3 2 ( AC116963 ) Dictyostelium discoid...:none) Burkholderia thailandensis E264 c... 137 3e-49 CP001157_1788( CP001157 |pid:none) Azotobacter vinelandii DJ, co

  2. Dicty_cDB: Contig-U12019-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available :none) Burkholderia vietnamiensis G4 chr... 259 2e-67 FN392319_906( FN392319 |pid:none) Pichi.... 129 4e-28 CP000615_1931( CP000615 |pid:none) Burkholderia vietnamiensis G4 c... 129 4e-28 CP000379_615( CP000379 |pid...:none) Azotobacter vinelandii DJ, comp... 305 3e-81 CP000359_959( CP000359 |pid:none) Deinococcus geothermali... 1... 230 1e-58 AL939125_230( AL939125 |pid:none) Streptomyces coelicolor A3(2) co... 230 2e-5...:none) Shewanella frigidimarina NCIMB ... 154 1e-35 AE017226_861( AE017226 |pid:none) Treponema dentico

  3. Dicty_cDB: Contig-U11308-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available m... 38 1.3 CP000615_180( CP000615 |pid:none) Burkholderia vietnam...:none) Ralstonia metallidurans CH34, co... 38 1.7 CP001157_4781( CP001157 |pid:none) Azotobacter vinelandii...27 AL939113_251( AL939113 |pid:none) Streptomyces coelicolor A3(2) co... 40 0.27 CP000088_946( CP000088 |pid:none) Thermobifid... 509 e-139 1 ( BJ359760 ) Dictyostelium discoideum cDNA clone:ddc2k09, 5' e... 76 8e-16 2 ( FE262209 ) CAZO2477.fwd CAZO Nae...-01-01-1... 46 5.6 1 >( BJ438220 ) Dictyostelium discoideum cDNA clone:ddv36a24, 3' end, single read. Length = 758 Sco

  4. Dicty_cDB: Contig-U15134-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available :none) Burkholderia vietnamiensis G4 c... 55 4e-06 CR940348_18( CR940348 |pid... ) EST1231844 ESTSYN-F Musa acuminata AAA Group cDNA... 46 3.3 1 >( C22923 ) Dictyostelium discoideum gamete...9 AL939131_20( AL939131 |pid:none) Streptomyces coelicolor A3(2) com... 65 4e-09 AM286415_1167( AM286415 |pid:none) Yersin...:none) Azotobacter vinelandii DJ, comp... 59 3e-07 CP001504_982( CP001504 |pid:none) Burkholderia glumae...x... 57 1e-06 AL939106_220( AL939106 |pid:none) Streptomyces coelicolor A3(2) co... 57 1e-06 AM167904_839( AM167904 |pid

  5. Dicty_cDB: Contig-U12852-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available :none) Bacillus cereus 03BB102, comple... 54 4e-06 CP000614_1327( CP000614 |pid:none) Burkholderia vietnam..... 105 8e-22 CP000614_962( CP000614 |pid:none) Burkholderia vietnamiensis G4 ch.....:none) Streptomyces coelicolor A3(2) co... 76 8e-13 DQ792504_55( DQ792504 |pid:none) Horsepox virus isolate MNR-76, co... 3 >( BJ339563 ) Dictyostelium discoideum cDNA clone:dda65e21, 5' end, single read. Length = 559 Score = 110...mp... 58 2e-07 CP001157_4674( CP001157 |pid:none) Azotobacter vinelandii DJ, comp... 57 3e-07

  6. Dicty_cDB: Contig-U11586-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available 05... 57 1e-06 CP000614_276( CP000614 |pid:none) Burkholderia vietnamiensis G4 ch...:none) Burkholderia vietnamiensis G4 ch... 74 7e-12 CP001172_2087( CP001172 |pid:none) Acinetobacter baumannii...:none) Streptomyces coelicolor A3(2) co... 66 2e-09 CP001074_2866( CP001074 |pid:none) Rhizobium etli...none) Chloroflexus aggregans DSM 9485... 53 2e-05 AL939121_243( AL939121 |pid:none) Streptomyces coelicolor A3(2) co...:none) Bacillus amyloliquefaciens FZB4... 52 3e-05 CP001157_4365( CP001157 |pid:none) Azotobacter vinelandii

  7. Dicty_cDB: Contig-U09571-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available :none) Burkholderia vietnamiensis G4 c... 102 2e-20 CP001114_790( CP001114 |pid:none) Deinococcus deserti VCD115, co...s wolfei subsp. wo... 99 3e-19 AL939110_99( AL939110 |pid:none) Streptomyces coelicolor A3(2) com...:none) Shewanella frigidimarina NCIMB ... 89 5e-16 CP000384_3111( CP000384 |pid:none) Mycobacterium sp. MCS, co...:none) Shewanella frigidimarina NCIMB ... 81 1e-13 AJ235271_100( AJ235271 |pid:none) Rickettsia prowazekii strain...:none) Azotobacter vinelandii DJ, compl... 63 3e-08 CP000749_2600( CP000749 |pid:none) Marinomonas sp. MWYL1, co

  8. Dicty_cDB: Contig-U15036-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available uence 14020 from Patent WO20090... 220 3e-55 CP000614_2701( CP000614 |pid:none) Burkholderia vietnamiensis G...-56 CP001157_119( CP001157 |pid:none) Azotobacter vinelandii DJ, compl... 221 1e-55 CP000438_5745( CP000438 |pid:none) Pseudomona...zole carboxylase ... 158 1e-36 AL939115_7( AL939115 |pid:none) Streptomyces coelicolor A3(2) comp... 158 1e-...0 3e-06 3 >( BJ437546 ) Dictyostelium discoideum cDNA clone:ddv34i15, 3' end, single read. Length = 756 Scor...FM180568_455( FM180568 |pid:none) Escherichia coli 0127:H6 E2348/6... 150 3e-34 CP001063_404( CP001063 |pid:none) Shigella boydii

  9. Dicty_cDB: Contig-U15061-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available e-14 CP000615_332( CP000615 |pid:none) Burkholderia vietnamiensis G4 ch... 80 1e-13 AY774282_1( AY774282 |pid:none) Synthetic co...-78 CP000614_1664( CP000614 |pid:none) Burkholderia vietnamiensis G4 c... 293 8e-78 CP000076_2520( CP000076 |pid:none) Pseudomona...ATCC 334... 56 2e-06 AL939109_65( AL939109 |pid:none) Streptomyces coelicolor A3(2) com... 56 2e-06 CP001131_3533( CP001131 |pid...re E Sequences producing significant alignments: (bits) Value N ( AU263172 ) Dictyostelium discoid... C g... 294 5e-78 CP001157_4528( CP001157 |pid:none) Azotobacter vinelandii DJ, comp... 294 5e

  10. Dicty_cDB: Contig-U12146-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available TCC 354... 86 1e-15 CP000614_2346( CP000614 |pid:none) Burkholderia vietnamiensis G4 c... 86 2e-15 CP000058_24( CP000058 |pid...) Methylobacterium extorquens AM1... 42 0.031 CP000615_1842( CP000615 |pid:none) Burkholderia vietnam...:none) Azotobacter vinelandii DJ, comple... 84 5e-15 FM209186_23( FM209186 |pid:none) Pseudomonas aerugin...hromobacterium violaceum ATCC ... 40 0.15 AL939117_280( AL939117 |pid:none) Streptomyces coelicolor A3(2) co...B284897 ) DF1717 Dermatophagoides farinae cDNA library Derm... 46 2.4 1 ( FF990576 ) CBWU108028.b1 Yutaka Satou unpublished cDNA li

  11. Dicty_cDB: Contig-U10369-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available :none) Burkholderia vietnamiensis G4 c... 116 2e-24 BA000026_814( BA000026 |pid:none) Myco...:none) Helicobacter pylori J99, comple... 122 3e-26 CP001157_1447( CP001157 |pid:none) Azotobacter vinelandii...27 1e-27 CP000447_2220( CP000447 |pid:none) Shewanella frigidimarina NCIMB ... 127 1e-27 FM204883_316( FM204883 |pid:none) Streptoco...8 5e-22 AL939115_98( AL939115 |pid:none) Streptomyces coelicolor A3(2) com... 108 5e-22 BT078001_1( BT078001 |pid...:none) Neisseria meningitidis serogroup... 119 2e-25 CP001104_1964( CP001104 |pid:none) Eubacterium eli

  12. Dicty_cDB: Contig-U12020-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available :none) Caulobacter crescentus NA1000, ... 151 5e-35 CP000614_1881( CP000614 |pid:none) Burkholderia vietnam...um discoideum histidine kinase DhkG (d... 46 3.7 1 ( AF088979 ) Dictyostelium discoideum beige protein...ccus opacus B4 DNA, comp... 160 1e-37 AL939110_99( AL939110 |pid:none) Streptomyces coelicolor A3(2) co...:none) Burkholderia sp. 383 chromosome ... 96 3e-18 AL939126_48( AL939126 |pid:none) Streptomyces coelico...:none) Psychromonas ingrahamii 37, com... 96 4e-18 CP001157_559( CP001157 |pid:none) Azotobacter vinelandii DJ, co

  13. [Change of the wheat lectin activity and degree of its interaction with different components of compositions of lectin nature].

    Science.gov (United States)

    Kyrychenko, O V

    2006-01-01

    The wheat lectin hemagglutination activity and degree of its interaction with the bacterium Azotobacter chroococcum T79 and aminosaccharide N-acetyl-D-glucosamin hapten of wheat lectin was studied in laboratory experiments with the purpose of creation of biologic activity compositions of lectin nature for plant growing. It was shown that plant-bacterial compositions encloses the "bacteria+lectin" complex, free lectin and bacterial cells. The addition of aminosaccharide N-acetyl-D-glucosamin to wheat lectin, to the bacterial culture and plant-bacterial composition decreases its hemagglutination activity. The possibility of creation of new complexes in this compositions effected by hapten "lectin+hapten", "lectin+hapten+bacteria", "bacteria+hapten" is under discussion.

  14. Assessment of free-living nitrogen fixing microorganisms for commercial nitrogen fixation

    Energy Technology Data Exchange (ETDEWEB)

    Stokes, B.O.; Wallace, C.J.

    1978-08-01

    Ammonia production by Klebsiella pneumoniae is not economical with present strains and improving nitrogen fixation to its theoretical limits in this organism is not sufficient to achieve economic viability. Because the value of both the hydrogen produced by this organism and the methane value of the carbon source required greatly exceed the value of the ammonia formed, ammonia (fixed nitrogen) should be considered the by-product. The production of hydrogen by Klebsiella or other anaerobic nitrogen fixers should receive additional study, because the activity of nitrogenase offers a significant improvement in hydrogen production. The production of fixed nitrogen in the form of cell mass by Azotobacter is also uneconomical and the methane value of the carbon substrate exceeds the value of the nitrogen fixed. Parametric studies indicate that as efficiencies approach the theoretical limits the economics may become competitive. The use of nif-derepressed microorganisms, particularly blue-green algae, may have significant potential for in situ fertilization in the environment.

  15. Assessment of free-living nitrogen fixing microorganisms for commercial nitrogen fixation. [economic analysis of ammonia production

    Science.gov (United States)

    Stokes, B. O.; Wallace, C. J.

    1978-01-01

    Ammonia production by Klebsiella pneumoniae is not economical with present strains and improving nitrogen fixation to its theoretical limits in this organism is not sufficient to achieve economic viability. Because the value of both the hydrogen produced by this organism and the methane value of the carbon source required greatly exceed the value of the ammonia formed, ammonia (fixed nitrogen) should be considered the by-product. The production of hydrogen by KLEBSIELLA or other anaerobic nitrogen fixers should receive additional study, because the activity of nitrogenase offers a significant improvement in hydrogen production. The production of fixed nitrogen in the form of cell mass by Azotobacter is also uneconomical and the methane value of the carbon substrate exceeds the value of the nitrogen fixed. Parametric studies indicate that as efficiencies approach the theoretical limits the economics may become competitive. The use of nif-derepressed microorganisms, particularly blue-green algae, may have significant potential for in situ fertilization in the environment.

  16. Cloning, characterization, and regulation of nifF from Rhodobacter capsulatus.

    Science.gov (United States)

    Gennaro, G; Hübner, P; Sandmeier, U; Yakunin, A F; Hallenbeck, P C

    1996-07-01

    The Rhodobacter capsulatus nifF gene and upstream sequence were cloned by using a probe based on the N-terminal sequence of NifF. nifF was found to not be contained in the previously described nif regions I, II, and III. Comparison of the deduced amino acid sequence showed that it is highly similar to NifF from Azotobacter vinelandii and NifF from Klebsiella pneumoniae. Analysis of translational fusions demonstrated that the regulation of transcription was the same as previously reported at the protein level. Insertional mutagen esis showed that NifF contributes significantly to nitrogenase activity under normal nitrogen-fixing conditions and that it is absolutely required for nitrogen fixation under iron limitation. PMID:8682802

  17. BIO-DIAGNOSTICS OF RESISTANCE OF GREY FOREST SOILS OF ADYGEA TO POLLUTION WITH Zn, Cd, Mo, Se

    Directory of Open Access Journals (Sweden)

    Tatlok D. R.

    2015-04-01

    Full Text Available The essential part of a soil cover of the Republic of Adygea is occupied by gray forest soils. Thus they still remain a little studied, including concerning their resistance to chemical pollution. Contamination of gray forest soils of Adygea with Zn, Cd, Mo, Se causes deterioration of their biological properties. In most cases, the degree of reduction of the values of biological indicators is directly dependent on the concentration of pollutant in the soil. According to the degree of toxicity to the biological properties of the investigated elements form the following sequence: Se > Zn > = Cd > Mo. Biological parameters investigated in research (activity of catalase and dehydrogenase, cellulolytic ability, abundance of bacteria of the genus Azotobacter, radish root length may be used for purposes of monitoring, diagnosis and regulation of chemical pollution of gray forest soils Zn, Cd, Mo, Se

  18. Purification and some properties of Fe protein of nitrogenase from. Anabaena cylindrica

    Science.gov (United States)

    Du, Daixian; Lin, Huimin; He, Zhenrong; Dai, Lingfen; Xin, Wusheng; Li, Shanghao

    1990-12-01

    The Fe protein of Anabaena cylindrica was first separated and purified by chromatography through DEAE-cellulose columns then by gel electrophoresis. The specific activity was up to 142.46 nmol C2H4/mg protein · min. It was homogeneous as shown by 1) a single band in the gel electrophorogram; 2) absence of Mo and tryptophan; 3) content of about 3.4 atoms of Fe per mole protein. The molecular weight of the Fe protein of A. cylindrica was about 61,000 daltons as estimated by SDS-gel electrophoresis and calculated from the amino acid composition. The residues of aspartate and glutamate were about 2.6 times that of arginine and lysine in the Fe protein. Crossing Fe protein of A. cylindrica with Mo-Fe protein of Azotobacter vinelandii gave positive result. The reciprocal crossing also showed activity.

  19. CARACTERIZACIÓN DE BACTERIAS DIAZOTRÓFICAS ASIMBIÓTICAS ASOCIADAS AL EUCALIPTO (Eucalyptussp. EN CODAZZI, CESAR (COLOMBIA Characterization of Diazotrophic Bacteria Non-Symbiotic Associated with Eucalyptus (Eucalyptussp. in Codazzi, Cesar (Colombia

    Directory of Open Access Journals (Sweden)

    DOLLY MELISSA OBANDO CASTELLANOS

    Full Text Available Se evaluó el efecto de las épocas climáticas (lluvia y sequía y del estrato de la muestra (suelo rizosférico, raíces y hojas sobre la población de los géneros Azotobacter, Beijerinckia, Derxia, Azospirillum, Herbaspirillum, Gluconacetobacter y Burkholderia en el Eucalipto (Eucalyptus sp.. Así mismo, se evalúo su capacidad en la producción de compuestos indólicos como promotores del crecimiento vegetal y su actividad de reducción de acetileno como indicador de la fijación biológica de nitrógeno. Los resultados no registraron diferencias estadísticas significativas en el test de Tukey (P ≤ 0.05 en la población con respecto a la época climática. Con respecto al estrato de muestra, los aislamientos tentativos de Herbaspirillum sp. y Azospirillum sp. presentaron diferencias significativas en suelo rizosférico y raíces. Se obtuvieron 44 aislamientos de los cuales se agruparon por caracterización fenotípica como: 14 presuntivos de Beijerinckia sp., 12 de Azotobacter sp., ocho de Derxia sp., cuatro de Herbarpirillum sp., cinco de Azospirillum sp., uno de Gluconacetobacter sp. y uno de Burkholderia sp. Por su alto potencial fueron seleccionados y criopreservados los aislamientos C27, C26 y C25, las cuales presentaron los mejores valores de eficiencia in vitro, superando valores de producción de las cepas de referencia utilizadas (A. chroococcum (AC1 y A. brasilense (SP7.The effect of climatic seasons (rainy and dry and the stratum sample (rhizospheric soil, roots and leaves the population of the genera Azotobacter, Beijerinckia, Derxia, Azospirillum, Herbaspirillum, Gluconacetobacter and Burkholderia in soil rhizosphere, roots and leaves of Eucalyptus (Eucalyptus sp.. It also assesses their ability to produce indoles compounds as plant growth promoters and their acetylene reduction activity as an indicator of biological fixation of nitrogen. The results showed no statistically significant differences in the Duncan test (P ≤ 0

  20. The level of glucose-6-phosphate dehydrogenase activity strongly influences xylose fermentation and inhibitor sensitivity in recombinant Saccharomyces cerevisiae strains

    DEFF Research Database (Denmark)

    Jeppsson, M.; Johansson, B.; Jensen, Peter Ruhdal;

    2003-01-01

    Disruption of the ZWF1 gene encoding glucose-6-phosphate dehydrogenase (G6PDH) has been shown to reduce the xylitol yield and the xylose consumption in the xylose-utilizing recombinant Saccharomyces cerevisiae strain TMB3255. In the present investigation we have studied the influence of different...... consumption, respectively, compared with the ZWF1-disrupted strain. Both strains exhibited decreased xylitol yields (0.13 and 0.19 g/g xylose) and enhanced ethanol yields (0.36 and 0.34 g/g xylose) compared with the control strain TMB3001 (0.29 g xylitol/g xylose, 0.31 g ethanol/g xylose). Cytoplasmic...... transhydrogenase (TH) from Azotobacter vinelandii has previously been shown to transfer NADPH and NAD(+) into NADP(+) and NADH, and TH-overproduction resulted in lower xylitol yield and enhanced glycerol yield during xylose utilization. Strains with low G6PDH-activity grew slower in a lignocellulose hydrolysate...

  1. Quantification and removal of some contaminating gases from acetylene used to study gas-utilizing enzymes and microorganisms.

    Science.gov (United States)

    Hyman, M R; Arp, D J

    1987-02-01

    Acetylene generated from various grades of calcium carbide and obtained from commercial- and purified-grade acetylene cylinders was shown to contain high concentrations of various contaminants. Dependent on the source of acetylene, these included, at maximal values, H(2) (0.023%), O(2) (0.779%), N(2) (3.78%), PH(3) (0.06%), CH(4) (0.073%), and acetone (1 to 10%). The concentration of the contaminants in cylinder acetylene was highly dependent on the extent of cylinder discharge. Several conventional methods used to partially purify cylinder acetylene were compared. A small-scale method for extensively purifying acetylene is described. An effect of acetylene quality on acetylene reduction assays conducted with purified nitrogenase from Azotobacter vinelandii was demonstrated.

  2. The influence of super-high-frequency radiation on the enzyme activity and number of microorganisms in soils of southern Russia

    Science.gov (United States)

    Denisova, T. V.; Kolesnikov, S. I.

    2009-04-01

    The effects of super-high-frequency radiation (SHF radiation) on the microflora and enzymatic activity of an ordinary chernozem, a chestnut soil, a brown forest soil, and gray sands were studied. The exposure time of the 800-W SHF radiation was 30 s, 1, 10, and 60 min. The activity of the soil enzymes (catalase and invertase) was found to be more resistant to the action of SHF radiation than the number of microorganisms (ammonifying bacteria (including sporogenous ones), bacteria of the genus Azotobacter, and micromycetes). According to the resistance of the enzymes, the soils studied form the following sequence: gray sands > ordinary chernozem ≥ chestnut soil > brown forest soil. Under the action of the SHF radiation, the number of microorganisms in the ordinary chernozem decreased to a lesser extent.

  3. Nuclear resonance vibrational spectroscopy (NRVS) of rubredoxin and MoFe protein crystals

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Yisong [University of California, Department of Applied Science (United States); Brecht, Eric [Montana State University, Department of Chemistry and Biochemistry (United States); Aznavour, Kristen [University of Southern California, Department of Chemistry (United States); Nix, Jay C. [Lawrence Berkeley National Laboratory, Physical Biosciences Division (United States); Xiao, Yuming; Wang, Hongxin [University of California, Department of Applied Science (United States); George, Simon J. [Lawrence Berkeley National Laboratory, Physical Biosciences Division (United States); Bau, Robert [University of Southern California, Department of Chemistry (United States); Keable, Stephen; Peters, John W. [Montana State University, Department of Chemistry and Biochemistry (United States); Adams, Michael W. W. [University of Georgia, Department of Biochemistry and Molecular Biology (United States); Jenney, Francis E. Jr. [Georgia Campus, Philadelphia College of Osteopathic Medicine (United States); Sturhahn, Wolfgang; Alp, Ercan E.; Zhao, Jiyong [Argonne National Laboratory, Advanced Photon Source (United States); Yoda, Yoshitaka [JASRI (Japan); Cramer, Stephen P., E-mail: spcramer@lbl.gov [University of California, Department of Applied Science (United States)

    2013-12-15

    We have applied {sup 57}Fe nuclear resonance vibrational spectroscopy (NRVS) for the first time to study the dynamics of Fe centers in Iron-sulfur protein crystals, including oxidized wild type rubredoxin crystals from Pyrococcus furiosus, and the MoFe protein of nitrogenase from Azotobacter vinelandii. Thanks to the NRVS selection rule, selectively probed vibrational modes have been observed in both oriented rubredoxin and MoFe protein crystals. The NRVS work was complemented by extended X-ray absorption fine structure spectroscopy (EXAFS) measurements on oxidized wild type rubredoxin crystals from Pyrococcus furiosus. The EXAFS spectra revealed the Fe-S bond length difference in oxidized Pf Rd protein, which is qualitatively consistent with the crystal structure.

  4. A STUDY ON NITROGEN FIXING AND PHOSPHATE SOLUBILIZING MICROORGANISMS ON GROWTH AND PHYSIOLOGY OF PLUMBAGO ZEYLANICA.L

    Directory of Open Access Journals (Sweden)

    D.Haribabu Rao

    2012-12-01

    Full Text Available Organisms that are commonly used as biofertilizers component are nitrogen fixers (N-fixer, potassium solubilizer (K-solubilizer and phosphorus solubilizer (P- solubilizer, or with the combination of molds or fungi. Most of the bacteria included in biofertilizer have close relationship with plant roots. In this work we have selected plumbago zeylanica.L plant to study the effect of Azotobacter on the growth of roots, stem, and leaves. Also biochemical characterization was done to identify the effect of Azotobacter in Plumbago. The maximum shoot length was recorded in T4 plants (43.51 on 90th days of plant growth after transplanting the plants. There was a significant increase at 5 % level in the root length from 30th days to 90th days in all the treatments. The maximum number of leaves were found in T4 treatment followed by T3 and T2. Minimum numbers of leaves were found in T1 (1083. On 60th day and 90th day also the total chlorophyll content was maximum in T4 treated plants followed by T3, T2 plants. The amount of reducing sugars (μg/g in shoots of T4, T3 and T2 plants on 30th, 60th and 90th days were significantly high when compared to T1 plants. The content of protein in roots of T2, T3 and T4 plants on 30th, 60th and 90th days were significantly high when compared to protein content of T1 plants.

  5. CARACTERIZACIÓN DE BACTERIAS DIAZOTRÓFICAS ASIMBIÓTICAS ASOCIADAS AL EUCALIPTO (Eucalyptus sp. EN CODAZZI, CESAR.

    Directory of Open Access Journals (Sweden)

    Divan Baldani Vera Lúcia

    2010-12-01

    Full Text Available Se evaluó el efecto de las épocas climáticas (lluvia y sequía y del estrato de la muestra (Suelo rizosférico, raíces y hojas sobre la población de los géneros Azotobacter, Beijerinckia, Derxia, Azospirillum, Herbaspirillum, Gluconacetobacter y Burkholderia en el Eucalipto (Eucalyptus sp.. Así mismo, se evalúo su capacidad en la producción de compuestos indólicos como promotores del crecimiento vegetal y su actividad de reducción de acetileno como indicador de la fijación biológica de nitrógeno. Los resultados no registraron diferencias estadísticas significativas en el test de Tukey (P ≤ 0.05 en la población con respecto a la época climática. Con respecto al estrato de muestra, los aislamientos tentativos a Herbaspirillum sp. y Azospirillum sp. presentaron diferencias significativas en suelo rizosférico y raíces. Se obtuvieron 44 aislamientos de los cuales se agruparon por caracterización fenotípica como: 14 presuntivos del género Beijerinckia sp., 12 de Azotobacter sp., 8 de Derxia sp., 4 de Herbarpirillum sp., 5 de Azospirillum sp., 1 de Gluconacetobacter sp. y 1 de Burkholderia sp. Por su alto potencial fueron seleccionados y criopreservados los aislamientos C27, C26, C25 y C45, las cuales presentaron los mejores valores de eficiencia in vitro, superando valores de producción de las cepas de referencia utilizadas (A. chroococcum (AC-01 y A. brasilense (SP7.

  6. The Influence of Mineral Fertilizer Combined With a Nitrification Inhibitor on Microbial Populations and Activities in Calcareous Uzbekistanian Soil Under Cotton Cultivation

    Directory of Open Access Journals (Sweden)

    Dilfuza Egamberdiyeva

    2001-01-01

    Full Text Available Application of fertilizers combined with nitrification inhibitors affects soil microbial biomass and activity. The objective of this research was to determine the effects of fertilizer application combined with the nitrification inhibitor potassium oxalate (PO on soil microbial population and activities in nitrogen-poor soil under cotton cultivation in Uzbekistan. Fertilizer treatments were N as urea, P as ammophos, and K as potassium chloride. The nitrification inhibitor PO was added to urea and ammophos at the rate of 2%. Three treatments—N200P140K60 (T1, N200 P140 POK60 (T2, and N200 P140 POK60 (T3 mg kg-1 soil—were applied for this study. The control (C was without fertilizer and PO. The populations of oligotrophic bacteria, ammonifying bacteria, nitrifying bacteria, denitrifying bacteria, mineral assimilating bacteria, oligonitrophilic bacteria, and bacteria group Azotobacter were determined by the most probable number method. The treatments T2 and T3 increased the number of oligonitrophilic bacteria and utilization mineral forms of nitrogen on the background of reducing number of ammonifying bacteria. T2 and T3 also decreased the number of nitrifying bacteria, denitrifying bacteria, and net nitrification. In conclusion, our experiments showed that PO combined with mineral fertilizer is one of the most promising compounds for inhibiting nitrification rate, which was reflected in the increased availability and efficiency of fertilizer nitrogen to the cotton plants. PO combined with mineral fertilizer has no negative effects on nitrogen-fixing bacteria Azotobacter and oligo-nitrophilic bacteria.

  7. Growth and Nutrient Uptake of Orchardgrass (Dactylis glomerata L. and Meadow Fescue (Festuca pratensis Huds. as Affected by Rhizobacteria

    Directory of Open Access Journals (Sweden)

    Olivera STAJKOVIĆ-SRBINOVIĆ

    2016-06-01

    Full Text Available A diverse group of soil bacteria found in the rhizosphere which can colonize plant roots and improve plant growth are designated as plant growth promoting rhizobacteria. The aim of this study was isolation and screening of different rhizobacterial strains for plant growth promoting characteristics and their ability to improve growth of two grass species, orchardgrass (Dactylis glomerata L. and meadow fescue (Festuca pratensis Huds.. The strains investigated, belonging to the genera Azotobacter, Bacillus, Pseudomonas and rhizobial bacteria, showed various plant growth promoting traits, such as phosphate solubilisation, siderophore production, and indole-3-acetic acid (IAA production. Co-inoculation of meadow fescue with Azotobacter chroococcum A2 and Sinorhizobium meliloti or Pseudomonas sp., and A. chroococcum A5 with S. meliloti, significantly increased shoot dry weight (SDW(25-33%, as well as total N (26-33%, P (24-31% and K (26-28% contents in plants (mg pot-1, compared to uninoculated control. In addition, inoculation of orchardgrass with A. chroococcum strain A1, as well as co-inoculation with B. megaterium and A. chroococcum A1 or A31, significantly increased SDW (51-59% and total N (54-59%, P (51-74% and K (49-55% contents, compared to uninoculated control. Nitrogen percentage in SDW was slightly higher than sufficiency ranges, while K percentage was optimal in all treatments in both species. Phosphorous percentage was lower than sufficiency ranges as a consequence of very low soil P content. The results emphasize the potential of particular rhizobacteria to improve the growth of forage grasses.

  8. Identification of a NifL-like protein in a diazotroph of the beta-subgroup of the Proteobacteria, Azoarcus sp. strain BH72.

    Science.gov (United States)

    Egener, Tanja; Sarkar, Abhijit; Martin, Dietmar E; Reinhold-Hurek, Barbara

    2002-10-01

    NifA, the transcriptional activator of nitrogenase (nif) genes, has up to now been described to be regulated in its activity via the sensor NifL only for members of the gamma-subgroup of the PROTEOBACTERIA: This paper reports a functionally similar NifL-like protein outside this group in Azoarcus sp. strain BH72, a diazotrophic grass endophyte belonging to the beta-subgroup of the PROTEOBACTERIA: Its structural genes for nitrogenase (nifHDK) are regulated in response to combined nitrogen and O(2) and expressed endophytically inside rice roots. In order to characterize nitrogen-regulatory genes, an Azoarcus sp. BH72 genomic library was used to select cosmids that complemented a nifA mutation in Azotobacter vinelandii. Sequence analysis of the 3.4 kb genomic region complementing nifA showed two ORFs with sequence identities of 44% to NifL and 61% to NifA of Azotobacter vinelandii. According to Northern blot and reverse transcriptase PCR analysis, the nifLA transcript was more abundant at low combined nitrogen and O(2) levels, results which were corroborated by GUS (beta-glucuronidase) assays using a transcriptional nifL::gusA fusion. N(2) fixation was abolished in a NifLA(-) and a NifA(-) mutant, wild-type fixation being restored by nifLA in trans. The NifLA(-) mutant also failed to activate nifH::gus expression, indicating that NifA is the obligate transcriptional activator for nifHDK. A nifL mutant was diazotrophic and did not show repression of nifH::gusA by ammonium or O(2), suggesting that NifL of Azoarcus sp. strain BH72 has a similar role in inactivating NifA in response to O(2) and combined nitrogen as NifL in bacteria of the gamma-PROTEOBACTERIA: PMID:12368454

  9. Bioinoculants: A sustainable approach to maximize the yield of Ethiopian mustard (Brassica carinata L.) under low input of chemical fertilizers.

    Science.gov (United States)

    Nosheen, Asia; Bano, Asghari; Ullah, Faizan

    2016-02-01

    This study aimed to find out the effect of plant growth-promoting rhizobacteria (PGPR; Azospirillum brasilense and Azotobacter vinelandii) either alone or in combination with different doses of nitrogen and phosphate fertilizers on growth, seed yield, and oil quality of Brassica carinata (L.) cv. Peela Raya. PGPR were applied as seed inoculation at 10(6) cells/mL(-1) so that the number of bacterial cells per seed was 2.6 × 10(5) cells/seed. The chemical fertilizers, namely, urea and diammonium phosphate (DAP) were applied in different doses (full dose (urea 160 kg ha(-1) + DAP 180 kg ha(-1)), half dose (urea 80 kg ha(-1) + DAP 90 kg ha(-1)), and quarter dose (urea 40 kg ha(-1) + DAP 45 kg ha(-1)). The chemical fertilizers at full and half dose significantly increased the chlorophyll, carotenoids, and protein content of leaves and the seed yield (in kilogram per hectare) but had no effect on the oil content of seed. The erucic acid (C22:1) content present in the seed was increased. Azospirillum performed better than Azotobacter and its effect was at par with full dose of chemical fertilizers (CFF) for pigments and protein content of leaves when inoculated in the presence of half dose of chemical fertilizers (SPH). The seed yield and seed size were greater. Supplementing Azospirillum with SPH assisted Azospirillum to augment the growth and yield, reduced the erucic acid (C22:1) and glucosinolates contents, and increased the unsaturation in seed oil. It is inferred that A. brasilense could be applied as an efficient bioinoculant for enhancing the growth, seed yield, and oil quality of Ethiopian mustard at low fertilizer costs and sustainable ways.

  10. Effect of Lanthanum on Major Microbial Populations in Red Soil

    Institute of Scientific and Technical Information of China (English)

    CHUHAIYAN; WANGJUNHUA; 等

    2001-01-01

    Pure culture and pot culture experiments were carried out to study the effect of lanthanum(La)on bacteria,actinomyces and fungus,and some microbial physiological groups,nitrifir,azotobacter and phos-phobacteria in a red soil taken form the Ecological Experimental Station of Red Soil,the Chinese Academy of Sciences,Jiangxi Province.LaCl3 was added into media at levels of 0,25,50,100,150,200,250 and 500 mg L-1 in the pure culture experiment ,and into soil samples in porcelain pots before rice growing at levles of 0,6,30,150,300,600 and 900 mg kg-1 dry soil in the pot culture experiment.The populations of the three soil microbes in the pure cultre experiment decreased with the addition level of La,indicating that La was toxic to the soil microbes in pure culture ,and the sensitivity of the 3 major mircrobial types to La was in a decreasing order of actinomyces>bacteria>fungus.In the pot experiment,La had slightly stimulaive effect on soil bacteria and actinomyces when applied at olw concentrations while had inhibitory effect on soil bacteria,actinomyces and fungus at high concentrations.When the concentration of La Was low,soil azotobacter was stimulated slightly while soil nitrifier was stimulated strongly and the maximum increase was up to 50%.When the concentration of La was highy,both soil aztobacter and nitrifier ware inhibited ,and the inhibition of La to the nitrifier increased with La conentration,La added at all the levels had stimulative effect on soil inorgaic and organic phosphobacteria.Among the 4 physiological groups,soil nitrifier was most sensitive to La,so,it migh be reasonble to assume that soil nitrifier was a sensitive indicator for evaluating the biological and environmental effects of rare earths.

  11. Effect of Lanthanum on Major Microbial Populationsin Red Soil

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Pure culture and pot culture experiments were carried out to study theeffect of lanthanum (La) on bacteria, actinomyces and fungus, and somemicrobial physiological groups, nitrifier, azotobacter andphosphobacteria, in a red soil taken form the Ecological ExperimentalStation of Red Soil, the Chinese Academy of Sciences, Jiangxi Province.LaCl{3 was added into media at levels of 0, 25, 50, 100, 150,200, 250 and 500 mg L-1 in the pure culture experiment, and intosoil samples in porcelain pots before rice growing at levels of 0, 6,30, 150, 300, 600 and 900 mg kg-1 dry soil in the pot cultureexperiment. Thepopulations of the three soil microbes in the pure culture experimentdecreased with the addition level of La, indicating that La was toxicto the soil microbes in pure culture, and the sensitivity of the 3major microbial types to La was in a decreasing order ofactinomyces > bacteria > fungus. In the pot experiment, Lahad slightly stimulative effect on soil bacteria and actinomyces whenapplied at low concentrations while had inhibitory effect on soilbacteria, actinomyces and fungus at high concentrations. When theconcentration of La was low, soil azotobacter was stimulated slightlywhile soil nitrifier was stimulated strongly and the maximum increasewas up to 50%. When the concentration of La was high, both soilazotobacter and nitrifier were inhibited, and the inhibition of La tothe nitrifier increased with La concentration. La added at all thelevels had stimulative effect on soil inorganic and organicphosphobacteria. Among the 4 physiological groups, soil nitrifier wasmost sensitive to La, so, it might be reasonable to assume that soilnitrifier was a sensitive indicator for evaluating the biological andenvironmental effects of rare earths.

  12. Efecto de la fertilización en la nutrición y rendimiento de ají (Capsicum spp. en el Valle del Cauca, Colombia

    Directory of Open Access Journals (Sweden)

    Edgar A Rodríguez Araujo

    2010-01-01

    Full Text Available En el estudio se evaluó el efecto de las fertilizaciones química y orgánica y biofertilización en la nutrición y rendimiento del ají (Capsicum spp. en el Valle del Cauca, Colombia, y en la producción de plántulas en vivero y en campo. Las variables evaluadas en vivero fueron: peso fresco de raíz y parte aérea, número de hojas, altura de la planta (cm, diámetro del tallo (mm, peso seco total, peso seco de raíz y parte aérea. Se evaluaron seis tratamientos, bajo un diseño estadístico de bloques completos al azar, de la forma siguiente: fertilización de síntesis química completa (testigo (FSQC, FSQC más fertilización orgánica (FSQC + O, FSQC + O más biofertilización 1 (solubilizador de fósforo con base en Penicillium janthinellum (1x10(7conidias/ml, FSQC + O más micorrizas (FSQC + O + M, FSQC + O más biofertilización 2 (fijador de nitrógeno con base en Azotobacter chroococcum (1x10(8 UFC/ml y Azospirillun sp. (1x10(8 UFC/ml, FSQC + O más biofertilización 3 (fijador de nitrógeno con base en Azotobacter chroococcum (1x10(8 UFC/ml. El experimento se instaló sobre un Typic Hapludolls. El análisis de resultados mostró que, en todos los tratamientos la fertilización de síntesis química + orgánica + micorrizas presentó los mejores resultados (P < 0.01, seguido de los tratamientos a los que se aplicó la fuente de biofertilización (microorganismos solubilizadores de fósforo y fijadores de nitrógeno. Para los suelos estudiados se concluyó que el mayor rendimiento de ají se consigue cuando se aplica al suelo una fuente química completa, más una fuente de materia orgánica, más micorrizas arbusculares. Además, que la biofertilización es un complemento de la fertilización química.

  13. Purification and Characterization of Cr-containing Nitrogenase Component Ⅰ%含铬固氮酶组分Ⅰ蛋白的纯化和特性

    Institute of Scientific and Technical Information of China (English)

    黄巨富; 董志刚; 张华峰; 吕玉兵; 赵颖; 汪志平

    2002-01-01

    在含Mo固氮培养基中不能生长而在无Mo条件下可固氮生长的固氮菌(Azotobacter vinelandii Lipmann)突变种UW3, 能在无Mo而含Cr的无氮培养基中生长.从菌体中分离得到的部分纯固氮酶组分Ⅰ蛋白含有Cr和Fe 原子(Fe/Mo/Cr为11.60∶0.41∶1.00),并能表达相当于棕色固氮菌野生型固氮菌MoFe蛋白对乙炔和质子还原的70%的活性.与从Mn中生长的UW3菌体中所提取纯化的MnFe蛋白不同,这种含铬蛋白与MoFe蛋白(α2β2)一样,是由两种亚基组成的四聚体.初步结果表明,这种含Cr蛋白可能是一种固氮酶组分Ⅰ蛋白.%A mutant UW3, which is unable to fix N2 in the presence of Mo (Nif-) but can undergo phenotypic reversal to Nif+ under Mo-deficient conditions, was able to grow in Cr-containing but Mo- and NH3-deficient medium. A partly purified nitrogenase component Ⅰ protein obtained from UW3 grown on the Cr-containing medium was shown to contain Fe and Cr (atom ratio of Fe to Cr and Mo to Cr: 11.60 and 0.41) and to have 70% of the C2H2- and H+-reduction activity of MoFe protein from the wild-type strain of Azotobacter vinelandii Lipmann. The Cr-containing protein was different in subunit composition from that of MnFe protein purified from the mutant strain grown in the presence of Mn, but similar to that of MoFe protein, that is, it was a tetramer composed of two different subunits (α2β2). The preliminary results indicated that the Cr-containing protein might be a nitrogenase component Ⅰ protein.

  14. Tubulinlike protein from Spirochaeta bajacaliforniensis

    Science.gov (United States)

    Bermudes, D.; Fracek, S. P. Jr; Laursen, R. A.; Margulis, L.; Obar, R.; Tzertzinis, G.

    1987-01-01

    Tubulin proteins are the fundamental subunits of all polymeric microtubule-based eukaryotic structures. Long, hollow structures each composed of 13 protofilaments as revealed by electron microscopy, microtubules (240 angstroms in diameter) are nearly ubiquitous in eukaryotes. These proteins have been the subject of intense biochemical and biophysical interest since the early 1970s and are of evolutionary interest as well. If tubulin-based structures (i.e., neurotubules, mitotic spindle tubules, centrioles, kinetosomes, axonemes, etc.) evolved from spirochetes by way of motility symbioses, tubulin homologies with spirochete proteins should be detectable. Tubulin proteins are widely thought to be limited to eukaryotes. Yet both azotobacters and spirochetes have shown immunological cross-reactivity with anitubulin antibodies. In neither of these studies was tubulin isolated nor any specific antigen identified as responsible for the immunoreactivity. Furthermore, although far less uniform in structure than eukaryotic microtubules, various cytoplasmic fibers and tubules (as seen by electron microscopy) have been reported in several types of prokaryotes (e.g., Spirochaeta; large termite spirochetes; treponemes; cyanobacteria; and Azotobacter. This work forms a part of our long-range study of the possible prokaryotic origin of tubulin and microtubules. Spirochetes are helically shaped gram-negative motile prokaryotes. They differ from all other bacteria in that the position of their flagella is periplasmic: their flagella lie between the inner and outer membranes of the gram-negative cell wall. Some of the largest spirochetes have longitudinally aligned 240 angstroms microtubules. Unfortunately, in spite of many attempts, all of the larger spirochetes (family Pillotaceae) with well-defined cytoplasmic tubules and antitubulin immunoreactivity are not cultivable. However, a newly described spirochete species (Spirochaeta bajacaliforniensis) possessing cytoplasmic fibers

  15. Identificación de algunos géneros microbianos asociados al cultivo del maíz (Zea mays L. en diferentes suelos de Cuba Identification of some microbial genera associated to the maize crop (Zea mays L in different Cuban soils

    Directory of Open Access Journals (Sweden)

    Heydrich Mayra

    2003-06-01

    Full Text Available Se ha demostrado que la aplicación de bioproductos a partir de microorganismos rizosféricos en la agricultura, provoca incrementos en la productividad de los cultivos. Si se trabaja con cepas nativas aumenta la factibilidad biológica de los mismos. Esta investigación se realizó con el objetivo de determinar algunos géneros microbianos asociados al cultivo del maíz variedad Francisco mejorado en suelos Nitisol Rhodic, Cambisol Eutric-Humic y Cambisol Eutric procedentes de diferentes localidades cubanas. Para ello se emplearon tres métodos de aislamiento: Método Convencional, Tubos Espermosféricos y Modelo Microcosmos. Los aislados fueron clasificados mediante la utilización de técnicas clásicas. Los resultados obtenidos demostraron que los géneros Pseudomona, Azospirillum, Azotobacter, Bacillus y Streptomyces forman parte de la comunidad microbiana de la rizosfera del cultivo del maíz en las condiciones estudiadas, constituyendo Pseudomonas el género dominante. Los métodos de aislamiento emplea­dos resultaron adecuados para la obtención de representantes típicos de las poblaciones microbianas en estudio, demostrándose la superioridad de los Tubos Espermosféricos y el Modelo Microcosmos para estos fines, ya que los mismos permiten aislar los microorganismos capaces de vivir a expensas de los exudados radicales del cultivo, en la interacción planta-bacteria. Palabras clave: rizosfera; maíz; modelo espermosférico; modelo microcosmos; Pseudomonas.It has been demonstrated that applying bio-products based on native rhizosphere micro-organisms in agriculture increases crop productivity. Working with native strains also improves their biological feasibility. Some microbial genera associated with the improved corn variety Francisco were isolated from Nitisol Rhodic, Cambisol Eutric-Humic and Cambisol Eutric soil from different Cuban regions using three isolation methods: the convencional method, the spermosphere model and the

  16. Efecto de la fertilización en la nutrición y rendimiento de ají (Capsicum spp. en el Valle del Cauca, Colombia

    Directory of Open Access Journals (Sweden)

    Rodríguez Araujo Edgar Alfonso

    2010-03-01

    Full Text Available En el estudio se evaluó el efecto de las fertilizaciones química y orgánica y biofertilización en la nutrición y rendimiento del ají (Capsicum spp. en el Valle del Cauca, Colombia, y en la producción de plántulas en vivero y en campo. Las variables evaluadas en vivero fueron: peso fresco de raíz y parte aérea, número de hojas, altura de la planta (cm, diámetro del tallo (mm, peso seco total, peso seco de raíz y parte aérea. Se evaluaron seis tratamientos, bajo un diseño estadístico de bloques completos al azar, de la forma siguiente: fertilización de síntesis química completa (testigo (FSQC, FSQC más fertilización orgánica (FSQC + O, FSQC + O más biofertilización 1 (solubilizador de fósforo con base en Penicillium janthinellum (1x107conidias/ml, FSQC + O más micorrizas (FSQC + O + M, FSQC + O más biofertilización 2 (fijador de nitrógeno con base en Azotobacter chroococcum (1x108 UFC/ml y Azospirillun sp. (1x108 UFC/ml, FSQC + O más biofertilización 3 (fijador de nitrógeno con base en Azotobacter chroococcum (1x108 UFC/ml. El experimento se instaló sobre un Typic Hapludolls. El análisis de resultados mostró que, en todos los tratamientos la fertilización de síntesis química + orgánica + micorrizas presentó los mejores resultados (P < 0.01, seguido de los tratamientos a los que se aplicó la fuente de biofertilización (microorganismos solubilizadores de fósforo y fijadores de nitrógeno. Para los suelos estudiados se concluyó que el mayor rendimiento de ají se consigue cuando se aplica al suelo una fuente química completa, más una fuente de materia orgánica, más micorrizas arbusculares. Además, que la biofertilización es un complemento de la fertilización química.

  17. Swimming Motility Reduces Deposition to Silica Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Nanxi [Univ. of Illinois, Urbana-Champaign, IL (United States); Massoudieh, Arash [The Catholic Univ. of America, Washington, DC (United States); Liang, Xiaomeng [The Catholic Univ. of America, Washington, DC (United States); Hu, Dehong [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Kamai, Tamir [Agricultural Research Organization, Bet Dagan (Israel); Ginn, Timothy R. [Univ. of California, Davis, CA (United States); Zilles, Julie L. [Univ. of Illinois, Urbana-Champaign, IL (United States); Nguyen, Thanh H. [Univ. of Illinois, Urbana-Champaign, IL (United States)

    2015-01-01

    The role of swimming motility on bacterial transport and fate in porous media was evaluated. We present microscopic evidence showing that strong swimming motility reduces attachment of Azotobacter vinelandii cells to silica surfaces. Applying global and cluster statistical analyses to microscopic videos taken under non-flow conditions, wild type, flagellated A. vinelandii strain DJ showed strong swimming ability with an average speed of 13.1 μm/s, DJ77 showed impaired swimming averaged at 8.7 μm/s, and both the non-flagellated JZ52 and chemically treated DJ cells were non-motile. Quantitative analyses of trajectories observed at different distances above the collector of a radial stagnation point flow cell (RSPF) revealed that both swimming and non-swimming cells moved with the flow when at a distance of at least 20 μm from the collector surface. Near the surface, DJ cells showed both horizontal and vertical movement diverging them from reaching surfaces, while chemically treated DJ cells moved with the flow to reach surfaces, suggesting that strong swimming reduced attachment. In agreement with the RSPF results, the deposition rates obtained for two-dimensional multiple-collector micromodels were also lowest for DJ, while DJ77 and JZ52 showed similar values. Strong swimming specifically reduced deposition on the upstream surfaces of the micromodel collectors.

  18. Growth promoting characteristics of rhizobacteria and AM Fungi for biomass amelioration of Zea mays

    Directory of Open Access Journals (Sweden)

    Kumar Manoj

    2015-01-01

    Full Text Available Plant growth promoting rhizobacteria (PGPR and mycorrhiza were evaluated on the growth (biomass and yield of Zea mays. In the present study, selective rhizospheric PGPR (Azotobacter chroococcum, Pseudomonas aeruginosa, Azospirillum brasilense and Streptomyces sp. and a combination of six strains of arbuscular mycorrhizal fungi (AMF (Acaulospora morrowae, Gigaspora margarita, Glomus constrictum, Glomus mossae, Glomus aggregatum and Scutellospora calospora were isolated and identified with standard methods and 16S rRNA sequence analysis. PGPR and AMF were checked for their growth-promoting behavior under specific treatment conditions. The 30-48-day-old treated plants in all combinations showed a significantly higher mass value. The average dry weight from the shoot was in a range from 41-52% as compared to the control. This increase also translated into a higher mass value of the roots. Overall, an 82% growth rate was observed in terms of height as the consequence of biomass production, specifically in the case of AMF + rhizobacteria combination. We report an efficient, sustainable and cost-effective biofertilizer for enhanced biomass of Z. mays, one of the staple food crops worldwide.

  19. Association with an ammonium-excreting bacterium allows diazotrophic culture of oil-rich eukaryotic microalgae.

    Science.gov (United States)

    Ortiz-Marquez, Juan Cesar Federico; Do Nascimento, Mauro; Dublan, Maria de Los Angeles; Curatti, Leonardo

    2012-04-01

    Concerns regarding the depletion of the world's reserves of oil and global climate change have promoted an intensification of research and development toward the production of biofuels and other alternative sources of energy during the last years. There is currently much interest in developing the technology for third-generation biofuels from microalgal biomass mainly because of its potential for high yields and reduced land use changes in comparison with biofuels derived from plant feedstocks. Regardless of the nature of the feedstock, the use of fertilizers, especially nitrogen, entails a potential economic and environmental drawback for the sustainability of biofuel production. In this work, we have studied the possibility of nitrogen biofertilization by diazotrophic bacteria applied to cultured microalgae as a promising feedstock for next-generation biofuels. We have obtained an Azotobacter vinelandii mutant strain that accumulates several times more ammonium in culture medium than wild-type cells. The ammonium excreted by the mutant cells is bioavailable to promote the growth of nondiazotrophic microalgae. Moreover, this synthetic symbiosis was able to produce an oil-rich microalgal biomass using both carbon and nitrogen from the air. This work provides a proof of concept that artificial symbiosis may be considered an alternative strategy for the low-N-intensive cultivation of microalgae for the sustainable production of next-generation biofuels and other bioproducts. PMID:22267660

  20. Fluorescence of Alexa fluor dye tracks protein folding.

    Directory of Open Access Journals (Sweden)

    Simon Lindhoud

    Full Text Available Fluorescence spectroscopy is an important tool for the characterization of protein folding. Often, a protein is labeled with appropriate fluorescent donor and acceptor probes and folding-induced changes in Förster Resonance Energy Transfer (FRET are monitored. However, conformational changes of the protein potentially affect fluorescence properties of both probes, thereby profoundly complicating interpretation of FRET data. In this study, we assess the effects protein folding has on fluorescence properties of Alexa Fluor 488 (A488, which is commonly used as FRET donor. Here, A488 is covalently attached to Cys69 of apoflavodoxin from Azotobacter vinelandii. Although coupling of A488 slightly destabilizes apoflavodoxin, the three-state folding of this protein, which involves a molten globule intermediate, is unaffected. Upon folding of apoflavodoxin, fluorescence emission intensity of A488 changes significantly. To illuminate the molecular sources of this alteration, we applied steady state and time-resolved fluorescence techniques. The results obtained show that tryptophans cause folding-induced changes in quenching of Alexa dye. Compared to unfolded protein, static quenching of A488 is increased in the molten globule. Upon populating the native state both static and dynamic quenching of A488 decrease considerably. We show that fluorescence quenching of Alexa Fluor dyes is a sensitive reporter of conformational changes during protein folding.

  1. Fluorescence of Alexa fluor dye tracks protein folding.

    Science.gov (United States)

    Lindhoud, Simon; Westphal, Adrie H; Visser, Antonie J W G; Borst, Jan Willem; van Mierlo, Carlo P M

    2012-01-01

    Fluorescence spectroscopy is an important tool for the characterization of protein folding. Often, a protein is labeled with appropriate fluorescent donor and acceptor probes and folding-induced changes in Förster Resonance Energy Transfer (FRET) are monitored. However, conformational changes of the protein potentially affect fluorescence properties of both probes, thereby profoundly complicating interpretation of FRET data. In this study, we assess the effects protein folding has on fluorescence properties of Alexa Fluor 488 (A488), which is commonly used as FRET donor. Here, A488 is covalently attached to Cys69 of apoflavodoxin from Azotobacter vinelandii. Although coupling of A488 slightly destabilizes apoflavodoxin, the three-state folding of this protein, which involves a molten globule intermediate, is unaffected. Upon folding of apoflavodoxin, fluorescence emission intensity of A488 changes significantly. To illuminate the molecular sources of this alteration, we applied steady state and time-resolved fluorescence techniques. The results obtained show that tryptophans cause folding-induced changes in quenching of Alexa dye. Compared to unfolded protein, static quenching of A488 is increased in the molten globule. Upon populating the native state both static and dynamic quenching of A488 decrease considerably. We show that fluorescence quenching of Alexa Fluor dyes is a sensitive reporter of conformational changes during protein folding.

  2. Kinetics of Nif gene expression in a nitrogen-fixing bacterium.

    Science.gov (United States)

    Poza-Carrión, César; Jiménez-Vicente, Emilio; Navarro-Rodríguez, Mónica; Echavarri-Erasun, Carlos; Rubio, Luis M

    2014-02-01

    Nitrogen fixation is a tightly regulated trait. Switching from N2 fixation-repressing conditions to the N2-fixing state is carefully controlled in diazotrophic bacteria mainly because of the high energy demand that it imposes. By using quantitative real-time PCR and quantitative immunoblotting, we show here how nitrogen fixation (nif) gene expression develops in Azotobacter vinelandii upon derepression. Transient expression of the transcriptional activator-encoding gene, nifA, was followed by subsequent, longer-duration waves of expression of the nitrogenase biosynthetic and structural genes. Importantly, expression timing, expression levels, and NifA dependence varied greatly among the nif operons. Moreover, the exact concentrations of Nif proteins and their changes over time were determined for the first time. Nif protein concentrations were exquisitely balanced, with FeMo cofactor biosynthetic proteins accumulating at levels 50- to 100-fold lower than those of the structural proteins. Mutants lacking nitrogenase structural genes or impaired in FeMo cofactor biosynthesis showed overenhanced responses to derepression that were proportional to the degree of nitrogenase activity impairment, consistent with the existence of at least two negative-feedback regulatory mechanisms. The first such mechanism responded to the levels of fixed nitrogen, whereas the second mechanism appeared to respond to the levels of the mature NifDK component. Altogether, these findings provide a framework to engineer N2 fixation in nondiazotrophs.

  3. THE CONSTRUCTION AND ANALYSIS OF A nifS DISRUPTION MUTANT%棕色固氮菌nifS敲除菌株的构建

    Institute of Scientific and Technical Information of China (English)

    汪道涌; 谢维; 毛晓华

    2003-01-01

    Azotobacter vinelandii中通过PCR扩增了5'和3'端分别缺失264bp和261bp的nifS'片段,克隆至载体pUC18,形成重组质粒pUCS,再通过同源重组的方法,将pUCS插入Azoto-bacter vinelandii的nifS中,形成nifS阻断突变体SU1,经Southern杂交和PCR扩增,证明所得确为nifS阻断突变株.SU1在外加氮源的BBGN培养基中能够快速生长,但在Burk's无氮培养基中,生长却极其缓慢,表明nifS基因的破坏,已造成SU1的固氮能力接近完全丧失.该突变体的成功构建,为进一步从中纯化固氮酶两组分,研究nifS对固氮酶结构及功能的影响及iscS与nifS之间的关系奠定了良好的基础.

  4. Chemotactic response of plant-growth-promoting bacteria towards roots of vesicular-arbuscular mycorrhizal tomato plants.

    Science.gov (United States)

    Gupta Sood, Sushma

    2003-08-01

    The chemotactic responses of the plant-growth-promoting rhizobacteria Azotobacter chroococcum and Pseudomonas fluorescens to roots of vesicular-arbuscular mycorrhizal (Glomus fasciculatum) tomato plants were determined. A significantly (P=0.05) greater number of bacterial cells of wild strains were attracted towards vesicular-arbuscular mycorrhizal tomato roots compared to non-vesicular-arbuscular mycorrhizal tomato roots. Substances exuded by roots served as chemoattractants for these bacteria. P. fluorescens was strongly attracted towards citric and malic acids, which were predominant constituents in root exudates of tomato plants. A. chroococcum showed a stronger response towards sugars than amino acids, but the response was weakest towards organic acids. The effects of temperature, pH, and soil water matric potential on bacterial chemotaxis towards roots were also investigated. In general, significantly (P=0.05) greater chemotactic responses of bacteria were observed at higher water matric potentials (0, -1, and -5 kPa), slightly acidic to neutral pH (6, 6.5 and 7), and at 20-30 degrees C (depending on the bacterium) than in other environmental conditions. It is suggested that chemotaxis of P. fluorescens and A. chroococcum towards roots and their exudates is one of the several steps in the interaction process between bacteria and vesicular-arbuscular mycorrhizal roots. PMID:19719591

  5. Efecto del uso del suelo sobre rizobacterias fosfatosolubizadoras y diazotroficas en el distrito de riego del río zulia,norte de santander (colombia

    Directory of Open Access Journals (Sweden)

    Ronal Fernando-Cañon

    2009-07-01

    Full Text Available It was quantified the population of diazotrophic and phosphate solubilizer bacteria with the aim of determine the effect of the use of soils during different periods of intervention with culture of rice in three agro-ecological zones of the District of Irrigation of the Zulia river. The results showed that the management of the culture of rice in the different studied zones significantly influenced the population of microorganisms in all the studied culture media, excepting the semi-solid culture media JMV. The populations of the genera Azospirillum spp., Azotobacter spp., Beijerinckia spp., were influenced by the fertility of the soils in the zones of Buena Esperanza and Restauración compared with Limoncito, where the quantities of organic matter and nutritional escential elements were lower. It were obtained 28 isolations of entophytic, associative, free-living diazotrophic and phosphate solubilizer rhizobacteria according with their macroscopic characteristics in the culture media Batata, JMV, Ashby and nutritive, from the analysis of the population in the zones of Buena Esperanza, Restauración and Limoncito. These isolations were purified and preserved in sterilized saline solution (0.85% NaCl at 4°C in the Laboratory of Microbiology of the Colombian Agricultural Institute, ICA, with the purpose to be used in subsequent studies about their potential as biofertilizers in rice cultured soils of the department.

  6. Effects of cultivation on N20 emission and seasonal quantitative variations of related microbes in a temperate grassland soil

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Laboratory and in situ experiments were done to investigate the influences of cultivation on temperate semi-arid grassland (for 17years spring wheat planted once every two years without fertilization) on soil N2O emission and quantitative variations of related soil microbes.In the laboratory (25℃ and soil moisture 18% ), cultivation increased soil transformations of fertilizer nitrogen ( 100 μg N/g as NaNO3, urea,or as urea with dicyandiamide I μg N/g). The N2O emissions from the cultivated and uncultivated soils with or without nitrogen additions were relatively Iow, and mainly originated from the nitrification. The soil N2O emission due to cultivation decreased somewhat upon no fertilization or NaNO3 addition, but significantly upon urea addition. The role of dicyandiamide as nitrification inhibitor was only considerable in the cultivated soil, and had small influence on decreasing N2O emission in the two soils. The influence of cultivation on soil N2O emission was also reflected by the number variations of microbes related with soil nitrogen transformation in the two soils. Compared to the uncultivated grassland, in situ ammonifiem and denitrifiers in the cultivated grassland quantitatively averagely increased, and aerobic no-symbiotic azotobacters were quantitatively similar, leading to the continued decrease of organic matter content and the decrease of N2O emission from the cultivated grassland soil.

  7. Phytoremediation of coal mine spoil dump through integrated biotechnological approach

    Energy Technology Data Exchange (ETDEWEB)

    Juwarkar, A.A.; Jambhulkar, H.P. [National Environmental Engineering Research Institute, Nagpur (India)

    2008-07-15

    Field experiment was conducted on mine spoil dump on an area of 10 ha, to restore the fertility and productivity of the coal mine spoil dump using integrated biotechnological approach. The approach involves use of effluent treatment plant sludge (ETP sludge), as an organic amendment, biofertilizers and mycorrihzal fungi along with suitable plant species. The results of the study indicated that amendment with effluent treatment plant sludge (ETP sludge), at 50 ton/ha improved the physico-chemical properties of coal mine spoil. Due to biofertilizer inoculation different microbial groups such as Rhizobium, Azotobacter and VAM spores, which were practically absent in mine spoil improved greatly. Inoculation of biofertilizer and application of ETP sludge helped in reducing the toxicity of heavy metals such as chromium, zinc, copper, iron, manganese lead, nickel and cadmium, which were significantly reduced to 41%, 43%, 37%, 37%, 34%, 39%, 37% and 40%, respectively, due to the increased organic matter content in the ETP sludge and its alkaline pH (8.10-8.28), at which the metals gets immobilized and translocation of metals is arrested. Thus, amendment and biofertilizer application provided better supportive material for anchorage and growth of the plant on coal mine spoil dump.

  8. Composting of a crop residue through treatment with microorganisms and subsequent vermicomposting

    Energy Technology Data Exchange (ETDEWEB)

    Singh, A.; Sharma, S. [Indian Institute of Technology, New Delhi (India). Centre for Rural Development and Technology

    2002-11-01

    Preliminary studies were conducted on wheat straw to test the technical viability of an integrated system of composting, with bioinoculants and subsequent vermicomposting, to overcome the problem of lignocellulosic waste degradation, especially during the winter season. Wheat straw was pre-decomposed for 40 days by inoculating it with Pleurotus sajor-caju, Trichoderma harzianum, Aspergillus niger and Azotobacter chroococcum in different combinations. This was followed by vermicomposting for 30 days. Chemical analysis of the samples showed a significant decrease in cellulose, hemicellulose and lignin contents during pre-decomposition and vermicomposting. The N, P, K content increased significantly during pre-decomposition with bioinoculants. The best quality compost, based on chemical analysis, was prepared where the substrate was treated with all the four bioinoculants together followed by vermicomposting. Results indicated that the combination of both the systems reduced the overall time required for composting and accelerated the composting of ligno-cellulosic waste during the winter season besides producing a nutrient-enriched compost product. (author)

  9. TEKNIK PENGATURAN AIR PADA INTENSIFIKASI PADI AEROB TERKENDALI-BERBASIS ORGANIK (IPAT-BO UNTUK MENINGKATKAN POPULASI RHIZOBACTERIA, EFISIENSI PENGGUNAAN AIR, PERAKARAN TANAMAN, DAN HASIL TANAMAN PADI

    Directory of Open Access Journals (Sweden)

    Hingdri -

    2013-03-01

    Full Text Available Teknik pengaturan air pada budidaya tanaman padi melalui Intensifikasi Padi Aerob Terkendali-Berbasis Organik (IPAT-BO perlu dilakukan untuk meningkatkan efisiensi penggunaan air. Penelitian ini bertujuan untuk mengtahui aktivitas rhizobacteria, tingkat efisiensi penggunaan air, perkaran tanaman, dan hasil tanaman pada berbagai teknik pengaturan air.Penelitian dilaksanakan di lahan percobaan Fakultas Pertanian Universitas Winaya Mukti, Tanjungsari pada inceptisol pada skala pot plastik. Rancangan percobaan yang digunakan adalah Rancangan Acak Kelompok (RAK faktor tunggal dengan 16 perlakuan dan diulang tiga kali, yaitu terdiri dari kombinasi antara perlakuan air dan empat varietas. Perlakuan air: tinggi muka air + 5cm, 0 cm, – 5 cm dan  – 10 cm. Empat varietas: Ciherang, Sintanur, Inpari 13 dan Fatmawati..Hasil penelitian menunjukkan terdapat pengaruhnyata terhadap populasi Rhizobacteria, perkembangan akar, dan hasil tanaman. Perlakuan tinggi muka air – 10 cm varietas Fatmawati memberikan hasil tertinggi pada volume akar 186,67 ml, populasi bakteri Azotobacter sp. (1,43 x 1010 CFU g-1, bakteri pelarut fosfat (6,07 x 108 CFU g-1, hasil tanaman tertinggi 95,9 g rumpun-1 setara dengan 9,14 ton ha-1 serta meningkatkan efisiensi penggunaan air 47,1 % dibandingkan dengan pengenangan 5 cm.Kata kunci:  Teknik pengaturan air, efisiensi penggunaan air, IPAT-BO, populasi rhizobakteria

  10. Topological switching between an alpha-beta parallel protein and a remarkably helical molten globule.

    Science.gov (United States)

    Nabuurs, Sanne M; Westphal, Adrie H; aan den Toorn, Marije; Lindhoud, Simon; van Mierlo, Carlo P M

    2009-06-17

    Partially folded protein species transiently exist during folding of most proteins. Often these species are molten globules, which may be on- or off-pathway to native protein. Molten globules have a substantial amount of secondary structure but lack virtually all the tertiary side-chain packing characteristic of natively folded proteins. These ensembles of interconverting conformers are prone to aggregation and potentially play a role in numerous devastating pathologies, and thus attract considerable attention. The molten globule that is observed during folding of apoflavodoxin from Azotobacter vinelandii is off-pathway, as it has to unfold before native protein can be formed. Here we report that this species can be trapped under nativelike conditions by substituting amino acid residue F44 by Y44, allowing spectroscopic characterization of its conformation. Whereas native apoflavodoxin contains a parallel beta-sheet surrounded by alpha-helices (i.e., the flavodoxin-like or alpha-beta parallel topology), it is shown that the molten globule has a totally different topology: it is helical and contains no beta-sheet. The presence of this remarkably nonnative species shows that single polypeptide sequences can code for distinct folds that swap upon changing conditions. Topological switching between unrelated protein structures is likely a general phenomenon in the protein structure universe.

  11. Development of Co-aggregated Cells as Bioinoculants Using Plant Seed Powders- A Novel Delivery System for Rice Grown under Lowland Condition

    Directory of Open Access Journals (Sweden)

    Palanivel Karpagavinayaga SIVAKUMAAR

    2008-12-01

    Full Text Available Co-aggregation was attempted in Azorhizobium caulinodans ORS-571 with other agriculturally important microorganisms such as Azospirillum brasilense MTCC-125, Azotobacter chroococcum MTCC-446, Bacillus megatherium MTCC-3353, and Pseudomonas fl uorescens MTCC-4828 to develop coaggregates with multiple benefi ts using seed powders of diff erent plants viz., Moringa oleifera, Strychnos potatorum and Sappindus emaignatus. Among the different treatments evaluated, the combination of Azorhizobium caulinodans ORS-571 and Azospirillum brasilense MTCC-125 with the plant seed powder of Moringa oleifera recorded the maximum co-aggregation of cells to the tune of 96.8%. The co-aggregates were also studied for their phyto-stimulatory effect such as seed vigour, plant height, plant dry weight, plant N content and endophytic colonization of A. caulinodans ORS-571 in rice var. ADT 43 grown under in vitro conditions. Th e co-aggregates of A. caulinodans and A. brasilense were found to be superior in positively augmenting the characters studied above.

  12. Bacterial biota of Nigeen Lake waters (Kashmir Valley).

    Science.gov (United States)

    Zaffar, Riasa M; Ganai, Bashir A

    2016-08-01

    One of the greatest apprehensions of water consumers all over the world with respect to the quality of drinking water is its contamination with pathogenic microorganisms. This research work determined the potential bacterial contaminants of the waters of Nigeen Lake, a subsidiary of Dal Lake and is regarded as a separate lake in Kashmir. The study was carried out from May 2014 to November 2014 excluding August and September at four different sites. During the study the bacterial flora showed variation in relation to the conditions prevailing at different sites. The highest viable count of bacteria was observed at Site:2 (surrounded by residential hamlets) followed by Site:1 (inlet) and Site:4 (centre) followed by Site:3 (outlet). Based on the examination of morphological features of bacterial colonies on nutrient agar plates after 48 h of incubation period, 40 different strains were isolated. The isolates were identified with the help of Gram's staining and DNA sequencing, 55% of the strains were Gram negative and 45% of the strains were Gram positive. With the help of 16S rRNA sequencing, out of the 40 isolates of bacteria, 7 strains were different at the genetic level. The bacteria which were identified with the help of DNA sequencing are Pseudomonas synxantha, Delftia acidovorans, Bacillus pumilus, Bacillus licheniformis, Macrococcus caseolyticus, Azotobacter vinelandii, and Stenotrophomonas maltophiria.

  13. CHARACTERIZATION, BIO-FORMULATION DEVELOPMENT AND SHELF-LIFE STUDIES OF LOCALLY ISOLATED BIO-FERTILIZER STRAINS

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    Vipin Kumar

    2014-03-01

    Full Text Available Nitrogen fixing, phosphate solubilizing and potash mobilizing bacterial strains were isolated from rhizosphere soil of agricultural land, the isolated bacterial strains were further characterized by a series of biochemical reactions and identified as genus Azotobacter, Bacillus and Pseudomonas respectively. A technology for their mass multiplication and their bio-formulation has been developed. Fly-ash was used as carrier materials for bio-formulation development of bio-fertilizer strains. Shelf-life studies of the bio-formulations were carried out during storage period. The selected isolates were found to be potent nitrogen fixer, phosphate solubilizers showing clear halo zone around their colonies and potash mobilizer showing mobilization of potassium on respective medium. A general decline in cfu count was noticed in fly-ash based bio-formulations. All the bio-formulations however, retained more than 108 cfu/g viable propagules up to 270 days. The present studies were shown encouraging results in respect to fly-ash as carrier materials for bio-fertilizer strains which are comparable to other commercially available carrier materials.

  14. EFFECT OF PGPR AND ORGANIC MANURES ON SOIL PROPERTIES OF ORGANICALLY CULTIVATED MUNGBEAN

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    IPSITA DAS

    2014-03-01

    Full Text Available A field experiment was undertaken in the organic farming plot of the Institute of Agricultural Sciences, BHU, Varanasi with a view to study the effects of manures and PGPR on soil properties. Mungbean (var. Malviya 12 was grown in the plot during kharif season of 2009. Organic manures such as Farm yard manure (FYM, Cereal compost, Legume compost and combination of all the manures with or without PGPR [PGPR: Plant Growth Promoting Rhizobacteria containing Rhizobium + Azotobacter + Pseudomonas + Trichoderma] was applied @ 5 t ha-1 in each plot. It was found that among all the manures tested for cultivation of mungbean, FYM was found to be superior having 320.91, 20.3, 286.72 kg ha-1 N, P2O5 and K2O respectively. The combined application of cereal compost and legume compost was effective over their sole application. Application of PGPR was beneficial showing higher nutrient content in soil. The most effective treatment was found to be FYM + PGPR among all the manures showing the highest amount of nutrients of 339.71, 22.33 and 298.66 kg ha-1 N, P2 O5 and K2O respectively.

  15. Evaluation Of The Impact Of Chemical And Biological Fertiliser Application On Agronomical Traits Of Safflower (Carthamus Tinctorius L. / Íîmiskâ Un Bioloìiskâ Mçslojuma Pielietojuma Ietekme Uz Saflora (Carthamus Tinctorius L. Agronomiskâm Pazîmçm

    Directory of Open Access Journals (Sweden)

    Janmohammadi Mohsen

    2015-12-01

    Full Text Available In order to investigate the influence of biological and chemical fertilisers on morphological traits, yield and yield components of safflower (Carthamus tinctorius L., a field experiment was conducted in Maragheh (37°23' N; 46°16' E, in north western Iran, for one year in the 2014 growing season. The effect of seven treatments was evaluated: T1 - control (no fertiliser application, T2 - seed inoculation with P biofertiliser (contains phosphate solubilising bacteria; Pantoea agglomerans strain P5 and Pseudomonas putida strain P13, T3 - seed inoculation with N biofertiliser (contains Azotobacter vinelandii strain O4, T4 - foliar application of iron chelate, T5 - soil application of complete NPK, T6: foliar application of manganese chelate, and T7 - foliar application of zinc sulphate. The result showed that although application of N biofertiliser did not have a significant effect on the evaluated traits, P biofertiliser slightly improved grain yield. However, the application of complete NPK fertiliser improved most of the traits, compared to the control and biofertiliser treatment. The best performance was obtained by foliar application of manganese chelate and zinc sulphate. The results showed that micronutrient-deficiencies have to be managed to unlock the potential yield of safflower in semiarid production systems.

  16. Effects of organic and biological fertilizers on fruit yield and essential oil of sweet fennel (Foeniculum vulgare var. dulce)

    Energy Technology Data Exchange (ETDEWEB)

    Moradi, R.; Rezvani Moghaddam, P.; Nasiri Mahallati, M.; Nezhadali, A.

    2011-07-01

    In order to evaluate the effects of different organic and biological fertilizers on quantity and quality of fennel essential oil, an experiment was conducted in a completely randomized block design with three replications. The experimental treatments included two organic (compost and vermicompost) and two biological (Pseudomonas putida and Azotobacter chroococcum) fertilizers, their all twin combinations (Ps. putida + A. chroococcum, Ps. putida + compost, Ps. putida + vermicompost, A. chroococcum + compost, A. chroococcum + vermicompost and compost + vermicompost) and control (non fertilized). There were significant differences between treatments in terms of seed essential oil percentage, essential oil yield; anethole, fenchone, limonene and straggle content in seed essential oil. Results showed that the highest and the lowest percentages of essential oil were obtained in control (2.9%) and A. chroococcum + vermicompost (2.2%) treatments, respectively. The highest essential oil yield (29.9 L ha{sup -}1) and anethole content of essential oil (69.7%) and the lowest contents of fenchone (6.14%), limonene (4.84%) and estragole (2.78%) in essential oil were obtained in compost + vermicompost treatment. It seems that compost + vermicompost treatment compared to other treatments supplied the highest equilibrium of nutrients and water in the root zone of sweet fennel which is led to increasing the anethole content, there upon, decreasing other compounds. Essential oil yield and percentage of anethole content in essential oil were significantly higher in all organic and biological treatments compared with control. (Author) 43 refs.

  17. Microbial Nitrogen-Cycle Gene Abundance in Soil of Cropland Abandoned for Different Periods.

    Directory of Open Access Journals (Sweden)

    Huhe

    Full Text Available In Inner Mongolia, steppe grasslands face desertification or degradation because of human overuse and abandonment after inappropriate agricultural management. The soils in these abandoned croplands exist in heterogeneous environments characterized by widely fluctuating microbial growth. Quantitative polymerase chain reaction analysis of microbial genes encoding proteins involved in the nitrogen cycle was used to study Azotobacter species, nitrifiers, and denitrifiers in the soils from steppe grasslands and croplands abandoned for 2, 6, and 26 years. Except for nitrifying archaea and nitrous oxide-reducing bacteria, the relative genotypic abundance of microbial communities involved in nitrogen metabolism differed by approximately 2- to 10-fold between abandoned cropland and steppe grassland soils. Although nitrogen-cycle gene abundances varied with abandonment time, the abundance patterns of nitrogen-cycle genes separated distinctly into abandoned cropland versus light-grazing steppe grassland, despite the lack of any cultivation for over a quarter-century. Plant biomass and plant diversity exerted a significant effect on the abundance of microbial communities that mediate the nitrogen cycle (P < 0.002 and P < 0.03, respectively. The present study elucidates the ecology of bacteria that mediate the nitrogen cycle in recently abandoned croplands.

  18. Bacterial biota of Nigeen Lake waters (Kashmir Valley).

    Science.gov (United States)

    Zaffar, Riasa M; Ganai, Bashir A

    2016-08-01

    One of the greatest apprehensions of water consumers all over the world with respect to the quality of drinking water is its contamination with pathogenic microorganisms. This research work determined the potential bacterial contaminants of the waters of Nigeen Lake, a subsidiary of Dal Lake and is regarded as a separate lake in Kashmir. The study was carried out from May 2014 to November 2014 excluding August and September at four different sites. During the study the bacterial flora showed variation in relation to the conditions prevailing at different sites. The highest viable count of bacteria was observed at Site:2 (surrounded by residential hamlets) followed by Site:1 (inlet) and Site:4 (centre) followed by Site:3 (outlet). Based on the examination of morphological features of bacterial colonies on nutrient agar plates after 48 h of incubation period, 40 different strains were isolated. The isolates were identified with the help of Gram's staining and DNA sequencing, 55% of the strains were Gram negative and 45% of the strains were Gram positive. With the help of 16S rRNA sequencing, out of the 40 isolates of bacteria, 7 strains were different at the genetic level. The bacteria which were identified with the help of DNA sequencing are Pseudomonas synxantha, Delftia acidovorans, Bacillus pumilus, Bacillus licheniformis, Macrococcus caseolyticus, Azotobacter vinelandii, and Stenotrophomonas maltophiria. PMID:27165539

  19. Alginate Production from Alternative Carbon Sources and Use of Polymer Based Adsorbent in Heavy Metal Removal

    Directory of Open Access Journals (Sweden)

    Çiğdem Kıvılcımdan Moral

    2016-01-01

    Full Text Available Alginate is a biopolymer composed of mannuronic and guluronic acids. It is harvested from marine brown algae; however, alginate can also be synthesized by some bacterial species, namely, Azotobacter and Pseudomonas. Use of pure carbohydrate sources for bacterial alginate production increases its cost and limits the chance of the polymer in the industrial market. In order to reduce the cost of bacterial alginate production, molasses, maltose, and starch were utilized as alternative low cost carbon sources in this study. Results were promising in the case of molasses with the maximum 4.67 g/L of alginate production. Alginates were rich in mannuronic acid during early fermentation independent of the carbon sources while the highest guluronic acid content was obtained as 68% in the case of maltose. The polymer was then combined with clinoptilolite, which is a natural zeolite, to remove copper from a synthetic wastewater. Alginate-clinoptilolite beads were efficiently adsorbed copper up to 131.6 mg Cu2+/g adsorbent at pH 4.5 according to the Langmuir isotherm model.

  20. Application of Bacteria Cellulose in Food Industry%细菌纤维素在食品工业中的应用

    Institute of Scientific and Technical Information of China (English)

    马霞; 王瑞明; 贾士儒; 关凤梅

    2002-01-01

    @@ 细菌纤维素(Bacterical cellulose,BC)是当今国内外生物材料研究的热点之一.一般认为合成纤维素是植物特有的功能,但是,有少数微生物也能合成纤维素.现已知道,在各种不同条件下能合成纤维素的微生物有醋酸菌属(Acetobacter)、土壤杆菌属(Agrobacterium)、假单胞杆菌属(Pseudomonas)、无色杆菌属(Achrombacter)、产碱杆菌属(Alcaligenes)、气杆菌属(Aerobacter)、固氮菌属(Azotobacter)、根瘤菌属(Rhizabium)和八叠球菌属(Sarcina)等的某些种,它们合成的纤维素统称为细菌纤维素.其中真正能够批量地工业化生产细菌纤维素且合成能力最强的是醋酸菌属(Acetobacter)中的木醋杆菌(Acetobacterxylnium).

  1. IN-VITRO EFFECTS OF HERBICIDES ON SOIL MICROBIAL COMMUNITIES

    Directory of Open Access Journals (Sweden)

    AABID HUSSAIN LONE

    2014-03-01

    Full Text Available Effect of six different herbicides representing four chemical families on soil microbial communities was studied using laboratory microcosm approach. The herbicides tested were isoproturon, metribuzin, clodinafop propargyl, atlantis (Mesosulfuron methyl 3% + Idosulfuron Methyl Sodium 0.6% WG and sulfosulfuron applied at normal agricultural rates, and UPH-110 (Clodinafop propargyl 12% + Metribuzin 42% WG tested at four different application rates. Microbial response to the applied herbicides was studied following cultivation dependent approach. The microbial community showed a mixed response towards applied herbicides. With a few exceptions, metribuzin displayed a negative, clodinafop a positive and sulphonylurea herbicides a neutral effect while as the effect of isoproturon was variable. Significant toxic impact of UPH-110 was mostly observed at higher concentrations (@ 600 and 1000 g ha-1. The magnitude of hazard and duration of toxicity increased as the dose of UPH-110 increased. The influence whether positive or negative, was only transitory in nature and recovered to the level of untreated microcosms by or before 30th day of application. Among the microbial groups studied, fungal population was least affected at field rate, bacteria, actinomycetes and Azotobacter showed mixed response while as the phosphorus solubilizers population showed a tendency to increase in response to the applied herbicides.The herbicidal impact on soil microbial population was found to depend on the nature and dose of herbicide used and also the type of microbial group

  2. Efecto de la fertilización en la nutrición y rendimiento de ají (Capsicum spp. en el Valle del Cauca, Colombia Effect of the fertilization on the nutrition and yield of the red pepper (Capsicum spp. in the Valley of the Cauca, Colombia.

    Directory of Open Access Journals (Sweden)

    Edgar A Rodríguez Araujo

    2010-01-01

    Full Text Available En el estudio se evaluó el efecto de las fertilizaciones química y orgánica y biofertilización en la nutrición y rendimiento del ají (Capsicum spp. en el Valle del Cauca, Colombia, y en la producción de plántulas en vivero y en campo. Las variables evaluadas en vivero fueron: peso fresco de raíz y parte aérea, número de hojas, altura de la planta (cm, diámetro del tallo (mm, peso seco total, peso seco de raíz y parte aérea. Se evaluaron seis tratamientos, bajo un diseño estadístico de bloques completos al azar, de la forma siguiente: fertilización de síntesis química completa (testigo (FSQC, FSQC más fertilización orgánica (FSQC + O, FSQC + O más biofertilización 1 (solubilizador de fósforo con base en Penicillium janthinellum (1x10(7conidias/ml, FSQC + O más micorrizas (FSQC + O + M, FSQC + O más biofertilización 2 (fijador de nitrógeno con base en Azotobacter chroococcum (1x10(8 UFC/ml y Azospirillun sp. (1x10(8 UFC/ml, FSQC + O más biofertilización 3 (fijador de nitrógeno con base en Azotobacter chroococcum (1x10(8 UFC/ml. El experimento se instaló sobre un Typic Hapludolls. El análisis de resultados mostró que, en todos los tratamientos la fertilización de síntesis química + orgánica + micorrizas presentó los mejores resultados (P This study was realised with the purpose of to evaluate the effect of the chemical, organic fertilization and biofertilization on the nutrition and yield of the red pepper (Capsicum spp. in the Valley of the Cauca in the initial production of plants in breeding ground and final production in field. Two experiments were realized, one in stage of fish-pond and other one in field stage. In fish-pond an experiment was realized where there was evaluated the effect of the different types of fertilization in chili and other one where there was evaluated the effect of the chemical, organic fertilization and biofertilización in chili. In field there was evaluated the effect of the

  3. The role of uridylyltransferase in the control of Klebsiella pneumoniae nif gene regulation.

    Science.gov (United States)

    Edwards, R; Merrick, M

    1995-04-20

    The glnD gene in enteric bacteria encodes a uridylyltransferase/uridylyl-removing enzyme which acts as the primary nitrogen sensor in the nitrogen regulation (Ntr) system. We have investigated the role of this enzyme in transcriptional regulation of nitrogen fixation genes in Klebsiella pneumoniae by cloning glnD from this organism and constructing a null mutant by insertional inactivation of the chromosomal gene using the omega interposon. K. pneumoniae glnD encodes a 102.3 kDa polypeptide which is highly homologous to the predicted products of both Escherichia coli glnD and Azotobacter vinelandii nfrX. The glnD-omega mutant was unable to uridylylate PII and was altered in adenylylation/deadenylylation of glutamine synthetase. Uridylyltransferase was required for derepression of ntr-regulated promoters such as glnAp2 and pnifL but was not involved in the nif-specific response to changes in nitrogen status mediated by the nifL product. We conclude that a separate, as yet uncharacterised, nitrogen control system may be responsible for nitrogen sensing by NifL. PMID:7753028

  4. Sequence and structural organization of a nif A-like gene and part of a nifB-like gene of Herbaspirillum seropedicae strain Z78.

    Science.gov (United States)

    Souza, E M; Funayama, S; Rigo, L U; Yates, M G; Pedrosa, F O

    1991-07-01

    The deduced amino acid sequence derived from the sequence of a fragment of DNA from the free-living diazotroph Herbaspirillum seropedicae was aligned to the homologous protein sequences encoded by the nifA genes from Azorhizobium caulinodans, Rhizobium leguminosarum, Rhizobium meliloti and Klebsiella pneumoniae. High similarity was found in the central domain and in the C-terminal region. The H. seropedicae putative NifA sequence was also found to contain an interdomain linker similar to that conserved among rhizobial NifA proteins, but not K. pneumoniae or Azotobacter vinelandii. Analysis of the regulatory sequences found 5' from nifA indicated that the expression of this gene in H. seropedicae is likely to be controlled by NifA, NtrC and RpoN, as judged by the presence of specific NifA- and NtrC-binding sites and characteristic -24/-12 promoters. Possible additional regulatory features included an 'anaerobox' and a site for integration host factor. The N-terminus of another open reading frame was found 3' from nifA and tentatively identified as nifB by amino acid sequence comparison. The putative nifB promoter sequence suggests that expression of H. seropedicae nifB may be activated by NifA and dependent on RpoN. PMID:1840608

  5. Sequencing and complementation analysis of the nifUSV genes from Azospirillum brasilense.

    Science.gov (United States)

    Frazzon, J; Schrank, I S

    1998-02-15

    The functionality of nitrogenase in diazotrophic bacteria is dependent upon nif genes other than the structural nifH, D, and K genes which encode the enzyme subunit proteins. Such genes are involved in the activation of nif gene expression, maturation of subunit proteins, cofactor biosynthesis, and electron transport. In this work, approximately 5500 base pairs located within the major nif gene cluster of Azospirillum brasilense Sp7 have been sequenced. The deduced open reading frames were compared to the nif gene products of Azotobacter vinelandii and other diazotrophs. This analysis indicates the presence of five ORFs encoding ORF2, nifU, nifS, nifV, and ORF4 in the same sequential organization as found in other organisms. Consensus sigma 54 and NifA binding sites are present in the putative promoter region upstream of ORF2 in the A. brasilense sequence. The nifV gene of A. brasilense but not nifU or nifS complemented corresponding mutants strains of A. vinelandii. PMID:9503607

  6. Identification, sequencing and structural analysis of a nifA-like gene of Acetobacter diazotrophicus.

    Science.gov (United States)

    Teixeira, K R; Morgan, T; Meletzus, D; Galler, R; Baldani, J I; Kennedy, C

    1999-01-01

    A recombinant plasmid, pAD101, containing a DNA fragment of Acetobacter diazotrophicus strain PAL5 was isolated by its ability to restore Nif+ phenotype to a nifA- ntrC- double mutant of Azotobacter vinelandii. Hybridization with the nifA genes of Azospirillum brasilense located the nifA gene more precisely to specific fragments of pAD101. DNA sequencing of appropriate subclones of pAD101 revealed that the nifA gene was adjacent to the nifB gene in A. diazotrophicus, and the 5' end of the nifB gene was located downstream of the nitrogenase MoFe subunit gene, nifK. The deduced aminoacid sequence of A. diazotrophicus nifA and nifB gene were most similar to the NifA and NifB proteins of Azorhizobium caulinodans and Rhodobacter capsulatus, respectively. In addition, nucleotide sequences upstream of the A. diazotrophicus nifA-encoding region indicate features similar to those in the A. caulinodans nifA promoter region involved in O2 and fixed N regulation of nifA expression. PMID:10530336

  7. Functional Bradyrhizobium japonicum NifA expression under a hybrid nptII-nifH promoter in E. coli and Acetobacter diazotrophicus SRT4.

    Science.gov (United States)

    Menéndez, C; Selman-Housein, G; Arrieta, J G; Coego, A; Hernández, L

    1998-01-01

    A hybrid promoter consisting of the in tandem fusion of the Tn5 nptII and the Klebsiella pneumoniae nifH promoters was constructed to study the functionality of the nif genes transcriptional activator NifA from Bradyrhizobium japonicum in two different host bacteria. beta-galactosidase experiments in E. coli revealed that the hybrid nptII-nifH promoter can behave as a constitutive or a NifA-inducible promoter depending on the aeration conditions. Expression of the B. japonicum NifA from the hybrid nptII-nifH promoter (plasmid pBPF204) induced "in trans" lacZ transcription from the Azotobacter chroococcum nifH promoter in E. coli and A. diazotrophicus cells grown at low pO2. Similarly, the plasmid pBPF204 increased nitrogenase activity in A. diazotrophicus cells grown under microaerobic conditions. Based on these results, we suggest that the B. japonicum NifA could function as an efficient O2-sensitive transcriptional activator of nif genes in genetically distant diazotrophic bacteria. PMID:10932742

  8. Nitrogen fixation: key genetic regulatory mechanisms.

    Science.gov (United States)

    Martinez-Argudo, I; Little, R; Shearer, N; Johnson, P; Dixon, R

    2005-02-01

    The necessity to respond to the level of fixed nitrogen and external oxygen concentrations and to provide sufficient energy for nitrogen fixation imposes common regulatory principles amongst diazotrophs. The NifL-NifA system in Azotobacter vinelandii integrates the signals of redox, fixed-nitrogen and carbon status to regulate nif transcription. Multidomain signalling interactions between NifL and NifA are modulated by redox changes, ligand binding and interaction with the signal-transduction protein GlnK. Under adverse redox conditions (excess oxygen) or when fixed nitrogen is in excess, NifL forms a complex with NifA in which transcriptional activation is prevented. Oxidized NifL forms a binary complex with NifA to inhibit NifA activity. When fixed nitrogen is in excess, the non-covalently modified form of GlnK interacts with NifL to promote the formation of a GlnK-NifL-NifA ternary complex. When the cell re-encounters favourable conditions for nitrogen fixation, it is necessary to deactivate the signals to ensure that the NifL-NifA complex is dissociated so that NifA is free to activate transcription. This is achieved through interactions with 2-oxoglutarate, a key metabolic signal of the carbon status, which binds to the N-terminal GAF (cGMP-specific and stimulated phosphodiesterases, Anabaena adenylate cyclases and Escherichia coli FhlA) domain of NifA. PMID:15667291

  9. Phylogeny of nitrogenase sequences in Frankia and other nitrogen-fixing microorganisms.

    Science.gov (United States)

    Normand, P; Bousquet, J

    1989-11-01

    The complete nucleotide sequence of a nitrogenase (nifH) gene was determined from a second strain (HRN18a) of Frankia, an aerobic soil bacterium. The open reading frame is 870 bp long and encodes a polypeptide of 290 amino acids. The amino acid and nucleotide sequences were compared with 21 other published sequences. The two Frankia strains were 96% similar at the amino acid level and 93% similar at the nucleotide level. A number of methods were used to infer phylogenies of these nitrogen fixers, based on nifH amino acid and nucleotide sequences. The results obtained do not agree completely with other phylogenies for these bacteria and thus make probable occurrences of lateral transfer of the nif genes. The time of divergence of the two Frankia strains could be estimated at about 100 million years. The vanadium-dependent (Type 2) nitrogenase present in Azotobacter spp. appears to be a recent derivation from the conventional molybdenum-dependent (Type 1) enzyme, whereas the iron-dependent (Type 3) alternative nitrogenase would have a much older origin. PMID:2515293

  10. The role of heterologous nifAc product in the regulation of nif expression in Agrobacterium tumefaciens.

    Science.gov (United States)

    Zhang, J; Zhang, J

    1997-01-01

    The plasmids pCK5, pCK3, pSZ36, and pSZ23-CA, which carried constitutive nifAc gene of Azotobacter chroococcum and Klebsiella pneumoniae were transferred into A. tumefaciens C58/pGV3850 with triparental mating. The growth rate of these transconjugants was similar to the wild type. Nitrogenase synthesis was demonstrated by Western blotting, in the presence of 10 mmol/L NH4+, and the nitrogenase activity was restored to 73%, 24%, 11%, and 62%, respectively. The results showed that the regulative gene of nitrogen fixation in A. chroococcum and K. pneumoniae played a regulative role for the expression of A. tumefaciens nitrogen fixation gene. Among them, the role of A. chroococcum nifAc gene was the strongest, the fusion plasmid pSZ23-CA which carried nifA-ntrC gene of K. pneumoniae was stronger, and the nifAc gene of K. pneumoniae was weak. PMID:9376504

  11. Functional participation of a nifH-arsA2 chimeric fusion gene in arsenic reduction by Escherichia coli

    International Nuclear Information System (INIS)

    The NifH (dimer) and ArsA proteins are structural homologs and share common motifs like nucleotide-binding domains, signal transduction domains and also possible similar metal center ligands. Given the similarity between two proteins, we investigated if the NifH protein from Azotobacter vinelandii could functionally substitute for the ArsA1 half of the ArsA protein of Escherichia coli. The chimeric NifH-ArsA2 protein was expressed and detected in the E. coli strain by Western blotting. Growth comparisons of E. coli strains containing plasmids encoding for complete ArsA, partial ArsA (ArsA2) or chimeric ArsA (NifH-ArsA2) in media with increasing sodium arsenite concentrations (0-5 mM) showed that the chimeric NifH-ArsA2 could substitute for the ArsA. This functional complementation demonstrated the strong conservation of essential domains that have been maintained in NifH and ArsA even after their divergence to perform varied functions

  12. Cloning, expression, purification, crystallization and preliminary crystallographic analysis of NifH1 from Methanocaldococcus jannaschii.

    Science.gov (United States)

    Wu, Hao; Yuan, Ye; Ma, Jinming; Gao, Yongxiang

    2011-05-01

    Nitrogen fixation is catalyzed by the nitrogenase complex in Azotobacter, which is composed of dinitrogenase and dinitrogenase reductase. Dinitrogenase is an α(2)β(2) heterotetramer of the proteins NifD and NifK. Dinitrogenase reductase is a homodimer of the protein NifH. The expression of NifD/K and NifH nitrogenase homologues (named NflD/K and NflH for Nif-like D and H, respectively) has been detected in the non-nitrogen-fixing hyperthermophilic methanogen Methanocaldococcus jannaschii. Solving the structure of MjNifH1 may help in better understanding its function and may supply some clues to understanding the evolution of nitrogenase. The full-length protein with an additional His(6) tag at the C-terminus was expressed, purified and crystallized by the hanging-drop vapour-diffusion method at 287 K. An X-ray diffraction data set was collected to a resolution of 3.3 Å. The crystal belonged to space group P4(1)32, with unit-cell parameters a = b = c = 139.45 Å, and was estimated to contain one protein molecule per asymmetric unit. PMID:21543862

  13. Kinetics of nif Gene Expression in a Nitrogen-Fixing Bacterium

    Science.gov (United States)

    Poza-Carrión, César; Jiménez-Vicente, Emilio; Navarro-Rodríguez, Mónica; Echavarri-Erasun, Carlos

    2014-01-01

    Nitrogen fixation is a tightly regulated trait. Switching from N2 fixation-repressing conditions to the N2-fixing state is carefully controlled in diazotrophic bacteria mainly because of the high energy demand that it imposes. By using quantitative real-time PCR and quantitative immunoblotting, we show here how nitrogen fixation (nif) gene expression develops in Azotobacter vinelandii upon derepression. Transient expression of the transcriptional activator-encoding gene, nifA, was followed by subsequent, longer-duration waves of expression of the nitrogenase biosynthetic and structural genes. Importantly, expression timing, expression levels, and NifA dependence varied greatly among the nif operons. Moreover, the exact concentrations of Nif proteins and their changes over time were determined for the first time. Nif protein concentrations were exquisitely balanced, with FeMo cofactor biosynthetic proteins accumulating at levels 50- to 100-fold lower than those of the structural proteins. Mutants lacking nitrogenase structural genes or impaired in FeMo cofactor biosynthesis showed overenhanced responses to derepression that were proportional to the degree of nitrogenase activity impairment, consistent with the existence of at least two negative-feedback regulatory mechanisms. The first such mechanism responded to the levels of fixed nitrogen, whereas the second mechanism appeared to respond to the levels of the mature NifDK component. Altogether, these findings provide a framework to engineer N2 fixation in nondiazotrophs. PMID:24244007

  14. Kinetics of Nif gene expression in a nitrogen-fixing bacterium.

    Science.gov (United States)

    Poza-Carrión, César; Jiménez-Vicente, Emilio; Navarro-Rodríguez, Mónica; Echavarri-Erasun, Carlos; Rubio, Luis M

    2014-02-01

    Nitrogen fixation is a tightly regulated trait. Switching from N2 fixation-repressing conditions to the N2-fixing state is carefully controlled in diazotrophic bacteria mainly because of the high energy demand that it imposes. By using quantitative real-time PCR and quantitative immunoblotting, we show here how nitrogen fixation (nif) gene expression develops in Azotobacter vinelandii upon derepression. Transient expression of the transcriptional activator-encoding gene, nifA, was followed by subsequent, longer-duration waves of expression of the nitrogenase biosynthetic and structural genes. Importantly, expression timing, expression levels, and NifA dependence varied greatly among the nif operons. Moreover, the exact concentrations of Nif proteins and their changes over time were determined for the first time. Nif protein concentrations were exquisitely balanced, with FeMo cofactor biosynthetic proteins accumulating at levels 50- to 100-fold lower than those of the structural proteins. Mutants lacking nitrogenase structural genes or impaired in FeMo cofactor biosynthesis showed overenhanced responses to derepression that were proportional to the degree of nitrogenase activity impairment, consistent with the existence of at least two negative-feedback regulatory mechanisms. The first such mechanism responded to the levels of fixed nitrogen, whereas the second mechanism appeared to respond to the levels of the mature NifDK component. Altogether, these findings provide a framework to engineer N2 fixation in nondiazotrophs. PMID:24244007

  15. Purification and in vitro activities of the native nitrogen fixation control proteins NifA and NifL.

    Science.gov (United States)

    Austin, S; Buck, M; Cannon, W; Eydmann, T; Dixon, R

    1994-06-01

    The prokaryotic enhancer-binding protein NifA stimulates transcription at a distance by binding to sequences upstream of nitrogen fixation (nif) promoters and catalyzing the formation of open promoter complexes by RNA polymerase containing the alternative sigma factor, sigma 54. The activity of NifA in vivo is modulated by the negative regulatory protein NifL in response to environmental oxygen and fixed nitrogen. To date, a detailed biochemical analysis of these proteins from the model diazotroph Klebsiella pneumoniae has been hindered by their insolubility. We have now purified NifA and NifL from Azotobacter vinelandii in their native form. NifA is competent in specific DNA binding, transcriptional activation, and response to negative regulation by NifL in vitro. In contrast to the conserved mechanism of phosphotransfer demonstrated by other two-component regulatory systems, our results support a model in which NifL regulates the activity of NifA via a protein-protein steric block interaction rather than a catalytic modification of NifA. PMID:8206822

  16. Nitrogen fixation genetics and regulation in a Pseudomonas stutzeri strain associated with rice.

    Science.gov (United States)

    Desnoues, Nicole; Lin, Min; Guo, Xianwu; Ma, Luyan; Carreño-Lopez, Ricardo; Elmerich, Claudine

    2003-08-01

    The Pseudomonas stutzeri strain A1501 (formerly known as Alcaligenes faecalis) fixes nitrogen under microaerobic conditions in the free-living state and colonizes rice endophytically. The authors characterized a region in strain A1501, corresponding to most of the nif genes and the rnf genes, involved in electron transport to nitrogenase in Rhodobacter capsulatus. The region contained three groups of genes arranged in the same order as in Azotobacter vinelandii: (1) nifB fdx ORF3 nifQ ORF5 ORF6; (2) nifLA-rnfABCDGEF-nifY2/nafY; (3) ORF13 ORF12-nifHDK-nifTY ORF1 ORF2-nifEN. Unlike in A. vinelandii, where these genes are not contiguous on the chromosome, but broken into two regions of the genome, the genes characterized here in P. stutzeri are contiguous and present on a 30 kb region in the genome of this organism. Insertion mutagenesis confirmed that most of the nif and the rnf genes in A1501 were essential for nitrogen fixation. Using lacZ fusions it was found that nif and rnf gene expression was under the control of ntrBC, nifLA and rpoN and that the rnf gene products were involved in the regulation of the nitrogen fixation process. PMID:12904565

  17. Role of conserved cysteine residues in Herbaspirillum seropedicae NifA activity.

    Science.gov (United States)

    Oliveira, Marco A S; Baura, Valter A; Aquino, Bruno; Huergo, Luciano F; Kadowaki, Marco A S; Chubatsu, Leda S; Souza, Emanuel M; Dixon, Ray; Pedrosa, Fábio O; Wassem, Roseli; Monteiro, Rose A

    2009-01-01

    Herbaspirillum seropedicae is an endophytic diazotrophic bacterium that associates with economically important crops. NifA protein, the transcriptional activator of nif genes in H. seropedicae, binds to nif promoters and, together with RNA polymerase-sigma(54) holoenzyme, catalyzes the formation of open complexes to allow transcription initiation. The activity of H. seropedicae NifA is controlled by ammonium and oxygen levels, but the mechanisms of such control are unknown. Oxygen sensitivity is attributed to a conserved motif of cysteine residues in NifA that spans the central AAA+ domain and the interdomain linker that connects the AAA+ domain to the C-terminal DNA binding domain. Here we mutagenized this conserved motif of cysteines and assayed the activity of mutant proteins in vivo. We also purified the mutant variants of NifA and tested their capacity to bind to the nifB promoter region. Chimeric proteins between H. seropedicae NifA, an oxygen-sensitive protein, and Azotobacter vinelandii NifA, an oxygen-tolerant protein, were constructed and showed that the oxygen response is conferred by the central AAA+ and C-terminal DNA binding domains of H. seropedicae NifA. We conclude that the conserved cysteine motif is essential for NifA activity, although single cysteine-to-serine mutants are still competent at binding DNA. PMID:19573596

  18. Identification and functional characterization of NifA variants that are independent of GlnB activation in the photosynthetic bacterium Rhodospirillum rubrum.

    Science.gov (United States)

    Zou, Xiaoxiao; Zhu, Yu; Pohlmann, Edward L; Li, Jilun; Zhang, Yaoping; Roberts, Gary P

    2008-09-01

    The activity of NifA, the transcriptional activator of the nitrogen fixation (nif) gene, is tightly regulated in response to ammonium and oxygen. However, the mechanisms for the regulation of NifA activity are quite different among various nitrogen-fixing bacteria. Unlike the well-studied NifL-NifA regulatory systems in Klebsiella pneumoniae and Azotobacter vinelandii, in Rhodospirillum rubrum NifA is activated by a direct protein-protein interaction with the uridylylated form of GlnB, which in turn causes a conformational change in NifA. We report the identification of several substitutions in the N-terminal GAF domain of R. rubrum NifA that allow NifA to be activated in the absence of GlnB. Presumably these substitutions cause conformational changes in NifA necessary for activation, without interaction with GlnB. We also found that wild-type NifA can be activated in a GlnB-independent manner under certain growth conditions, suggesting that some other effector(s) can also activate NifA. An attempt to use Tn5 mutagenesis to obtain mutants that altered the pool of these presumptive effector(s) failed, though much rarer spontaneous mutations in nifA were detected. This suggests that the necessary alteration of the pool of effector(s) for NifA activation cannot be obtained by knockout mutations. PMID:18757802

  19. Nucleotide sequence of the fixABC region of Azorhizobium caulinodans ORS571: similarity of the fixB product with eukaryotic flavoproteins, characterization of fixX, and identification of nifW.

    Science.gov (United States)

    Arigoni, F; Kaminski, P A; Hennecke, H; Elmerich, C

    1991-03-01

    The nucleotide sequence of a 4.1 kb DNA fragment containing the fixABC region of Azorhizobium caulinodans was established. The three gene products were very similar to the corresponding polypeptides of Rhizobium meliloti. The C-terminal domains of both fixB products displayed a high degree of similarity with the alpha-subunits of rat and human electron transfer flavoproteins, suggesting a role for the FixB protein in a redox reaction. Two open reading frames (ORF) were found downstream of fixC. The first ORF was identified as fixX on the basis of sequence homology with fixX from several Rhizobium and Bradyrhizobium strains. The second ORF potentially encoded a 69 amino acid product and was found to be homologous to a DNA region in the Rhodobacter capsulatus nif cluster I. Insertion mutagenesis of the A. caulinodans fixX gene conferred a Nif- phenotype to bacteria growth in the free-living state and a Fix- phenotype in symbiotic association with the host plant Sesbania rostrata. A crude extract from the fixX mutant had no nitrogenase activity. Furthermore, data presented in this paper also indicate that the previously identified nifO gene located upstream of fixA was probably a homologue of the nifW gene of Klebsiella pneumoniae and Azotobacter vinelandii. PMID:1850088

  20. Transcriptional activation of the nitrogenase promoter in vitro: adenosine nucleotides are required for inhibition of NIFA activity by NIFL.

    Science.gov (United States)

    Eydmann, T; Söderbäck, E; Jones, T; Hill, S; Austin, S; Dixon, R

    1995-03-01

    The enhancer-binding protein NIFA is required for transcriptional activation of nif promoters by the alternative holoenzyme form of RNA polymerase, which contains the sigma factor sigma 54 (sigma N). NIFA hydrolyzes nucleoside triphosphates to catalyze the isomerization of closed promoter complexes to transcriptionally competent open complexes. The activity of NIFA is antagonized by the regulatory protein NIFL in response to oxygen and fixed nitrogen in vivo. We have investigated the requirement for nucleotides in the formation and stability of open promoter complexes by NIFA and inhibition of its activity by NIFL at the Klebsiella pneumoniae nifH promoter. Open complexes formed by sigma 54-containing RNA polymerase are considerably more stable to heparin challenge in the presence of GTP than in the presence of ATP. This differential stability is most probably a consequence of GTP being the initiating nucleotide at this promoter. Adenosine nucleosides are specifically required for Azotobacter vinelandii NIFL to inhibit open complex formation by native NIFA, and the nucleoside triphosphatase activity of NIFA is strongly inhibited by NIFL under these conditions. We propose a model in which NIFL modulates the activity of NIFA via an adenosine nucleotide switch. PMID:7868590

  1. Open reading frame 5 (ORF5), encoding a ferredoxinlike protein, and nifQ are cotranscribed with nifE, nifN, nifX, and ORF4 in Rhodobacter capsulatus.

    Science.gov (United States)

    Moreno-Vivian, C; Hennecke, S; Pühler, A; Klipp, W

    1989-05-01

    DNA sequence analysis of a 1,600-base-pair fragment located downstream of nifENX in nif region A of Rhodobacter capsulatus revealed two additional open reading frames (ORFs): ORF5, encoding a ferredoxinlike protein, and nifQ. The ferredoxinlike gene product contained two cysteine motifs, typical of ferredoxins coordinating two 4Fe-4S clusters, but the distance between these two motifs was unusual for low-molecular-weight ferredoxins. The R. capsulatus nifQ gene product shared a high degree of homology with Klebsiella pneumoniae and Azotobacter vinelandii NifQ, including a typical cysteine motif located in the C-terminal part. nifQ insertion mutants and also an ORF5-nifQ double deletion mutant showed normal diazotrophic growth only in the presence of high concentrations of molybdate. This demonstrated that the gene encoding the ferredoxinlike protein is not essential for nitrogen fixation. No NifA-activated consensus promoter could be found in the intergenic region between nifENX-ORF4 and ORF5-nifQ. Analyses of a nifQ-lacZYA fusion revealed that transcription of nifQ was initiated at a promoter in front of nifE. In contrast to other nitrogen-fixing organisms, R. capsulatus nifE, nifN, nifX, ORF4, ORF5, and nifQ were organized in one transcriptional unit. PMID:2708314

  2. Isolation and properties of the complex between the enhancer binding protein NIFA and the sensor NIFL.

    Science.gov (United States)

    Money, T; Jones, T; Dixon, R; Austin, S

    1999-08-01

    In Azotobacter vinelandii, activation of nif gene expression by the transcriptional regulatory enhancer binding protein NIFA is controlled by the sensor protein NIFL in response to changes in levels of oxygen and fixed nitrogen in vivo. NIFL is a novel redox-sensing flavoprotein which is also responsive to adenosine nucleotides in vitro. Inhibition of NIFA activity by NIFL requires stoichiometric amounts of the two proteins, implying that the mechanism of inhibition is by direct protein-protein interaction rather than by catalytic modification of the NIFA protein. The formation of the inhibitory complex between NIFL and NIFA may be regulated by the intracellular ATP/ADP ratio. We show that adenosine nucleotides promote complex formation between purified NIFA and NIFL in vitro, allowing isolation of the NIFL-NIFA complex. The complex can also be isolated from cell extracts containing coexpressed NIFL and NIFA in the presence of MgADP. Removal of the nucleotide causes dissociation of the complex. Experiments with truncated proteins demonstrate that the amino-terminal domain of NIFA and the C-terminal region of NIFL potentiate the ADP-dependent stimulation of NIFL-NIFA complex formation. PMID:10419940

  3. Requirement of homocitrate for the transfer of a 49V-labeled precursor of the iron-vanadium cofactor from VnfX to nif-apodinitrogenase.

    Science.gov (United States)

    Ruttimann-Johnson, C; Rangaraj, P; Shah, V K; Ludden, P W

    2001-02-01

    A vanadium- and iron-containing cluster has been shown previously to accumulate on VnfX in the Azotobacter vinelandii mutant strain CA11.1 (DeltanifHDKvnfDGK::spc). In the present study, we show the homocitrate-dependent transfer of (49)V label from VnfX to nif-apodinitrogenase in vitro. This transfer of radiolabel correlates with acquisition of acetylene reduction activity. Acetylene is reduced both to ethylene and ethane by the hybrid holodinitrogenase so formed, a feature characteristic of alternative nitrogenases. Structural analogues of homocitrate prevent the acetylene reduction ability of the resulting dinitrogenase. Addition of NifB cofactor (-co) or a source of vanadium (Na(3)VO(4) or VCl(3)) does not increase nitrogenase activity. Our results suggest that there is in vitro incorporation of homocitrate into the V-Fe-S cluster associated with VnfX and that the completed cluster can be inserted into nif-apodinitrogenase. The homocitrate incorporation reaction and the insertion of the cluster into nif-apodinitrogenase (alpha(2)beta(2)gamma(2)) do not require MgATP. Attempts to achieve FeV-co synthesis using extracts of other FeV-co-negative mutants were unsuccessful, showing that earlier steps in FeV-co synthesis, such as the steps requiring VnfNE or VnfH, do not occur in vitro. PMID:11053414

  4. Expression, nucleotide sequence and mutational analysis of two open reading frames in the nif gene region of Anabaena sp. strain PCC7120.

    Science.gov (United States)

    Borthakur, D; Basche, M; Buikema, W J; Borthakur, P B; Haselkorn, R

    1990-04-01

    A 1.8 kb transcript corresponding to a region of the Anabaena 7120 chromosome 4 kb downstream of the nifHDK operon appears 12-18 h after heterocyst induction. The DNA corresponding to this transcript was sequenced and found to contain two open reading frames, designated ORF 1 and ORF 2. Two polypeptides, of 30 kDa and 13 kDa, encoded by these ORFs were expressed in Escherichia coli. An apparent start site for the transcript, detected by S1 nuclease protection, was located 42 bp upstream of the ATG start codon of ORF 1. ORF 2 shows strong sequence similarity to ORF 6 in the nif gene region of Azotobacter vinelandii. ORF 1 was interrupted using a 1.4 kb neomycin resistance cassette and the resulting mutant grew very slowly on medium lacking combined nitrogen. The mutant had 45% of wild-type acetylene reduction activity, which could be complemented by a 2.8 kb EcoRI fragment of wild-type Anabaena DNA containing only ORF 1 and ORF 2. Thus, one or both of these ORFs is required for efficient nitrogen fixation in Anabaena. PMID:2115111

  5. Enterococcus faecalis sufCDSUB complements Escherichia coli sufABCDSE.

    Science.gov (United States)

    Riboldi, Gustavo P; Larson, Timothy J; Frazzon, Jeverson

    2011-07-01

    Iron-sulfur [Fe-S] clusters are inorganic prosthetic groups that play essential roles in all living organisms. Iron and sulfur mobilization, formation of [Fe-S] clusters, and delivery to its final protein targets involves a complex set of specific protein machinery. Proteobacteria has three systems of [Fe-S] biogenesis, designated NIF, ISC, and SUF. In contrast, the Firmicutes system is not well characterized and has only one system, formed mostly by SUF homologs. The Firmicutes phylum corresponds to a group of pathological bacteria, of which Enterococcus faecalis is a clinically relevant representative. Recently, the E. faecalis sufCDSUB [Fe-S] cluster biosynthetic machinery has been identified, although there is no further information available about the similarities and/or variations of Proteobacteria and Firmicutes systems. The aim of the present work was to compare the ability of the different Proteobacteria and Firmicutes systems to complement the Azotobacter vinelandii and Escherichia coli ISC and SUF systems. Indeed, E. faecalis sufCDSUB is able to complement the E. coli SUF system, allowing viable mutants of both sufABCDSE and iscRSU-hscBA-fdx systems. The presence of all E. faecalis SUF factors enables proper functional interactions, which would not otherwise occur in proteins from different systems. PMID:21480963

  6. Cloning, expression, purification, crystallization and preliminary crystallographic analysis of NifH2 from Methanocaldococcus jannaschii

    International Nuclear Information System (INIS)

    NifH2, a homologue of nitrogenase reductase from Methanocaldococcus jannaschii was cloned, overexpressed, purified and crystallized. X-ray diffraction data were collected to 2.85 Å resolution and the crystals belonged to space group P2. Nitrogenases are protein complexes that are only found in Azotobacter and are required for biological nitrogen fixation. They are made up of a nitrogenase, which is a NifD2/NifK2 heterotetramer, and a nitrogenase reductase, which is a homodimer of NifH. Many homologues of nitrogenase have been found in various non-nitrogen-fixing prokaryotes; in particular, they are found in all known methanogens. This indicates that these homologues may play a role in methane production. Here, the cloning of NifH2, a homologue of the NifH nitrogenase component, from Methanocaldococcus jannaschii (MjNifH2) and its expression in Escherichia coli with a polyhistidine tag, purification and crystallization are described. MjNifH2 crystals were obtained by the hanging-drop vapour-diffusion method and diffracted to a resolution limit of 2.85 Å. The crystals belonged to space group P2, with unit-cell parameters a = 64.01, b = 94.38, c = 98.08 Å, α = γ = 90, β = 98.85°

  7. Efecto biofertilizante del preparado: residuos vegetales -bacteria nativa diazótrofa, sobre las variables biométricas en plántulas de Rhapanus sativus

    Directory of Open Access Journals (Sweden)

    Cecilia Lara Mantilla

    2011-04-01

    Full Text Available Biofertilizer effect of the prepared from vegetales wastes -diazotroph native bacterium on biometrics variables of Rhapanus sativus seedlings RESUMEN                                            El uso de bioinoculantes a base de microorganismos con potencial biofertilizante representa una alternativa económicamente viable y de producción limpia para el sector agrícola. El objetivo del presente trabajo fue evaluar el efecto biofertilizante de un preparado elaborado con residuos sólidos vegetales (RSV procedentes del mercado y la bacteria nativa diazótrofa Azotobacter A15M2G. Se elaboraron biopreparados utilizando diferentes concentraciones de bacteria (106, 107 y 108 UFC en un medio de cultivo obtenido a partir del 25% p/v de cada uno de los siguientes RSV: Brassica oleracea (repollo, Lactuca sativa (lechuga y Allium fistulosum (cebollín. Los biopreparados fueron evaluados en plantas de rábano (Rhapanus sativus en invernadero, utilizando un diseño estadístico completamente al azar de 5 tratamientos con 3 repeticiones: T1, control; T2, semillas pregerminadas tratadas con RSV al 25% p/v; T3, semillas pregerminadas con bioinoculante de 106 UFC; T4, semillas pregerminadas con bioinoculante de 107 UFC; T5, semillas pregerminadas con bioinoculante de 108 UFC. Se evaluó: número de hojas, área foliar, longitud de la planta, longitud de la raíz y peso seco de toda la planta (ensayos por triplicado. Se observó un incremento altamente significativo en peso seco para T5 (0,88 g y T4 (1,10 g; y diferencias significativas en el área foliar, para los mismos tratamientos, con un valor superior a 2000 cm2. El biopreparado con bacterias nativas y RSV mejoró el crecimiento y desarrollo de las plantas de rábano, pudiéndose dar un valor agregado a estos residuos y de esta manera obtener un biofertilizante potencialmente utilizable en otros cultivos. Palabras clave: Azotobacter A15M2G, Brassica oleracea

  8. CHANGE OF BIOLOGICAL ACTIVITY OF RENDZINA SOILS OF WESTERN CAUCASUS AT POLLUTION BY ZINC, CADMIUM, MOLYBDENUM AND SELENIUM

    Directory of Open Access Journals (Sweden)

    Tatlok D. R.

    2015-02-01

    Full Text Available Rendzina soils are very widespread in the Caucasus. Because of their ecological and genetic characteristics Rendzina has significant buffering capacity to chemical pollution. The object of investigation was calcareous leached soil. Location selection - Azishskaya ridge on the border of the Republic of Adygea and the Krasnodar region. As pollutants, we have selected Zn, Cd, Mo, Se, since soil contamination with these elements in the south of Russia is not uncommon. Contamination of zinc, cadmium, molybdenum and selenium causes deterioration in the biological properties of calcareous soils of the Western Caucasus. We have investigated the toxicity of the elements formed following series due to their influence on Rendzina soils: Zn> Se> Cd> = Mo. The study attempted to analyze the entire range of concentrations of the examined elements in the soil, currently occurring in nature. In most cases, all the investigated substances registered direct correlation between the concentration of the pollutant in the soil and the degree of reduction of biological indicators. The activity of catalase and dehydrogenase cellulolytic ability, plenty of bacteria of the genus Azotobacter, length of roots of radish can be used to monitor, diagnose and regulation of chemical pollution of soil Zn, Cd, Mo, Se

  9. Do prokaryotes contain microtubules?

    Science.gov (United States)

    Bermudes, D.; Hinkle, G.; Margulis, L.

    1994-01-01

    In eukaryotic cells, microtubules are 24-nm-diameter tubular structures composed of a class of conserved proteins called tubulin. They are involved in numerous cell functions including ciliary motility, nerve cell elongation, pigment migration, centrosome formation, and chromosome movement. Although cytoplasmic tubules and fibers have been observed in bacteria, some with diameters similar to those of eukaryotes, no homologies to eukaryotic microtubules have been established. Certain groups of bacteria including azotobacters, cyanobacteria, enteric bacteria, and spirochetes have been frequently observed to possess microtubule-like structures, and others, including archaebacteria, have been shown to be sensitive to drugs that inhibit the polymerization of microtubules. Although little biochemical or molecular biological information is available, the differences observed among these prokaryotic structures suggest that their composition generally differs among themselves as well as from that of eukaryotes. We review the distribution of cytoplasmic tubules in prokaryotes, even though, in all cases, their functions remain unknown. At least some tend to occur in cells that are large, elongate, and motile, suggesting that they may be involved in cytoskeletal functions, intracellular motility, or transport activities comparable to those performed by eukaryotic microtubules. In Escherichia coli, the FtsZ protein is associated with the formation of a ring in the division zone between the newly forming offspring cells. Like tubulin, FtsZ is a GTPase and shares with tubulin a 7-amino-acid motif, making it a promising candidate in which to seek the origin of tubulins.

  10. Effect of malachite green toxicity on non target soil organisms.

    Science.gov (United States)

    Gopinathan, R; Kanhere, J; Banerjee, J

    2015-02-01

    Although malachite green (MG), is banned in Europe and US for its carcinogenic and teratogenic effect, the dye being cheap, is persistently used in various countries for fish farming, silk, dye, leather and textile industries. Current research, however, fails to elucidate adequate knowledge concerning the effects of MG in our ecosystem. In the present investigation, for the first time, an attempt has been made to study the effects of MG on soil biota by testing Bacillus subtilis, Azotobacter chroococcum, Saccharomyces cerevisiae, Penicillium roqueforti, Eisenia fetida and seeds of three crop plants of different families. Various tests were conducted for determining cytotoxicity, genotoxicity, acute toxicity, morphological and germination effect. Our data confirmed MG toxicity on fungi and bacteria (gram positive and gram negative organisms) showing elevated level of ROS. Genotoxicity caused in the microorganisms was detected by DNA polymorphism and fragmentation. Also, scanning electron microscopy data suggests that the inhibitory effect of MG to these beneficial microbes in the ecosystem might be due to pore formation in the cell and its eventual disruption. Filter paper and artificial soil test conducted on earthworms demonstrated a LC 50 of 2.6 mg cm(-2) and 1.45 mg kg(-1) respectively with severe morphological damage. However, seed germination of Mung bean, Wheat and Mustard was found to be unaffected in presence of MG up to 100 mL(-1) concentration. Thus, understanding MG toxicity in non target soil organisms and emphasis on its toxicological effects would potentially explicate its role as an environmental contaminant. PMID:25462308

  11. Aromatic plants play an important role in promoting soil biological activity related to nitrogen cycling in an orchard ecosystem.

    Science.gov (United States)

    Chen, Xinxin; Song, Beizhou; Yao, Yuncong; Wu, Hongying; Hu, Jinghui; Zhao, Lingling

    2014-02-15

    Aromatic plants can substantially improve the diversity and structure of arthropod communities, as well as reduce the number of herbivore pests and regulate the abundance of predators and parasitoids. However, it is not clear whether aromatic plants are also effective in improving soil quality by enhancing nutrient cycling. Here, field experiments are described involving intercropping with aromatic plants to investigate their effect on soil nitrogen (N) cycling in an orchard ecosystem. The results indicate that the soil organic nitrogen and available nitrogen contents increased significantly in soils intercropped with aromatic plants. Similarly, the activities of soil protease and urease increased, together with total microbial biomass involved in N cycling, including nitrifying bacteria, denitrifying bacteria and azotobacters, as well as the total numbers of bacteria and fungi. This suggests that aromatic plants improve soil N cycling and nutrient levels by enriching the soil in organic matter through the regulation of both the abundance and community structure of microorganisms, together with associated soil enzyme activity, in orchard ecosystems.

  12. Community structure of soybean plant growth-promoting rhizobacteria in the black soil region of Northeast China%东北黑土区大豆根际促生菌群落组成研究

    Institute of Scientific and Technical Information of China (English)

    王志刚; 徐伟慧; 莫继先; 肖静; 孙剑秋; 王建丽

    2012-01-01

    As the black soil area of Northeast China is major soybean producing areas, it is important for the sustainable development of agriculture to study the soybean plant growth-promoting rhizobacteria (PGPR). For explaining the community structure of soybean PGPR in the black soil region of Northeast China, we chose four sample stations including Ewenki Autonomous Banner in Inner Mongolia Autonomous Region, Hailun City in Heilongjiang Province, Keshan County in Heilongjiang Province and Hongxinglong Farms in Heilongjiang Province, analyzed community composition of nitrogen-fixing bacteria, phosphate-dissolving bacteria, phosphate-solubilizing bacteria and silicate bacteria in soybean rhizosphere, and interpreted correspondence relationship between PGPR strains and areas. The results showed a large number of PGPR in soybean rhizosphere. The quantity of nitrogen-fixing bacteria reached to 104 cfu·g-1, these of phosphate-dissolving bacteria and phosphate-solubilizing bacteria reached to 105 cfu·g-1, and that of silicate bacteria reached to 103 cfu·g-1. Species groups of nitrogen-fixing bacteria, phosphate-dissolving bacteria, phosphate-solubilizing bacteria and silicate bacteria in soybean rhizosphere consisted of 5, 6, 7 and 4 species respectively. Shannon-Weiner biodiversity indices of nitrogen-fixing bacteria, phosphate-dissolving bacteria, phosphate-solubilizing bacteria and silicate bacteria were higher in soybean rhizosphere, which were in ranges of 0.94~1.60, 0.83~1.52, 1.07~1.67 and 0.52~0.96.Biodiversity indices of PGPR were more than 2 in sampling stations. Analysis on correspondence relationship between PGPR strains and areas indicated typical PGPR of different sampling stations. Nitrogen-fixing bacteria LLN8 (Azotobacter beijerinckia indica), phosphate-dissolving bacteria DHS13 (Micrococcus), phosphate-dissolving bacteria DHS19 (Pseudomonas), nitrogen-fixing bacteria LLN1 (A. Chrooco-ccum) and phosphate-dissolving bacteria DHS5 (Azotobacter) were

  13. Evaluation of antimicrobial activity of extracts of in vivo and in vitro grown Vinca rosea L. (Catharanthus roseus) against pathogens.

    Science.gov (United States)

    Naz, Shagufta; Haq, Rukhama; Aslam, Farah; Ilyas, Saiqa

    2015-05-01

    The antimicrobial activity of Vinca rosea was evaluated against pathogenic bacterial strains (Bacillus subtilis, B. licheniformis and Azotobacter sp.) and fungal strains (Asprgillus niger, Alternaria solani and Rhizopus oryzae) using agar well diffusion method. Methanolic extracts of in vivo leaf, in vitro leaf, in vitro calluses of leaf, nodal and fruit explants were used and exhibited antimicrobial activity as indicated by minimum inhibitory concentration (MIC). In vitro extracts showed better results as compared to the in vivo extracts for both the antibacterial as well as the antifungal activity. Among all the extracts, maximum zone of inhibition (30.3 mm ± 0.58(a)) was formed by in vitro leaf callus extract concentration of 2.0mg/ml against B. licheniformis. Similarly in case of antifungal activity, maximum zone of inhibition (34.6mm ± 0.57(a)) was formed by in vitro leaf callus extract and MIC value is 6.0mg/ml against A. niger. Hence these results clearly depicts that V. rosea possess a great strength to fight against the microbial activity and can be used against various infections. PMID:26004716

  14. Bacterial succession and metabolite changes during flax (Linum usitatissimum L.) retting with Bacillus cereus HDYM-02.

    Science.gov (United States)

    Zhao, Dan; Liu, Pengfei; Pan, Chao; Du, Renpeng; Ping, Wenxiang; Ge, Jingping

    2016-01-01

    High-throughput sequencing and GC-MS (gas chromatography-mass spectrometry) were jointly used to reveal the bacterial succession and metabolite changes during flax (Linum usitatissimum L.) retting. The inoculation of Bacillus cereus HDYM-02 decreased bacterial richness and diversity. This inoculum led to the replacement of Enterobacteriaceae by Bacillaceae. The level of aerobic Pseudomonadaceae (mainly Azotobacter) and anaerobic Clostridiaceae_1 gradually increased and decreased, respectively. Following the addition of B. cereus HDYM-02, the dominant groups were all degumming enzyme producers or have been proven to be involved in microbial retting throughout the entire retting period. These results could be verified by the metabolite changes, either degumming enzymes or their catalytic products galacturonic acid and reducing sugars. The GC-MS data showed a clear separation between flax retting with and without B. cereus HDYM-02, particularly within the first 72 h. These findings reveal the important bacterial groups that are involved in fiber retting and will facilitate improvements in the retting process. PMID:27585559

  15. Reprint of: Iron/sulfur proteins biogenesis in prokaryotes: formation, regulation and diversity.

    Science.gov (United States)

    Roche, Béatrice; Aussel, Laurent; Ezraty, Benjamin; Mandin, Pierre; Py, Béatrice; Barras, Frédéric

    2013-01-01

    Iron/sulfur centers are key cofactors of proteins intervening in multiple conserved cellular processes, such as gene expression, DNA repair, RNA modification, central metabolism and respiration. Mechanisms allowing Fe/S centers to be assembled, and inserted into polypeptides have attracted much attention in the last decade, both in eukaryotes and prokaryotes. Basic principles and recent advances in our understanding of the prokaryotic Fe/S biogenesis ISC and SUF systems are reviewed in the present communication. Most studies covered stem from investigations in Escherichia coli and Azotobacter vinelandii. Remarkable insights were brought about by complementary structural, spectroscopic, biochemical and genetic studies. Highlights of the recent years include scaffold mediated assembly of Fe/S cluster, A-type carriers mediated delivery of clusters and regulatory control of Fe/S homeostasis via a set of interconnected genetic regulatory circuits. Also, the importance of Fe/S biosynthesis systems in mediating soft metal toxicity was documented. A brief account of the Fe/S biosynthesis systems diversity as present in current databases is given here. Moreover, Fe/S biosynthesis factors have themselves been the object of molecular tailoring during evolution and some examples are discussed here. An effort was made to provide, based on the E. coli system, a general classification associating a given domain with a given function such as to help next search and annotation of genomes. This article is part of a Special Issue entitled: Metals in Bioenergetics and Biomimetics Systems.

  16. Iron/sulfur proteins biogenesis in prokaryotes: formation, regulation and diversity.

    Science.gov (United States)

    Roche, Béatrice; Aussel, Laurent; Ezraty, Benjamin; Mandin, Pierre; Py, Béatrice; Barras, Frédéric

    2013-03-01

    Iron/sulfur centers are key cofactors of proteins intervening in multiple conserved cellular processes, such as gene expression, DNA repair, RNA modification, central metabolism and respiration. Mechanisms allowing Fe/S centers to be assembled, and inserted into polypeptides have attracted much attention in the last decade, both in eukaryotes and prokaryotes. Basic principles and recent advances in our understanding of the prokaryotic Fe/S biogenesis ISC and SUF systems are reviewed in the present communication. Most studies covered stem from investigations in Escherichia coli and Azotobacter vinelandii. Remarkable insights were brought about by complementary structural, spectroscopic, biochemical and genetic studies. Highlights of the recent years include scaffold mediated assembly of Fe/S cluster, A-type carriers mediated delivery of clusters and regulatory control of Fe/S homeostasis via a set of interconnected genetic regulatory circuits. Also, the importance of Fe/S biosynthesis systems in mediating soft metal toxicity was documented. A brief account of the Fe/S biosynthesis systems diversity as present in current databases is given here. Moreover, Fe/S biosynthesis factors have themselves been the object of molecular tailoring during evolution and some examples are discussed here. An effort was made to provide, based on the E. coli system, a general classification associating a given domain with a given function such as to help next search and annotation of genomes. This article is part of a Special Issue entitled: Metals in Bioenergetics and Biomimetics Systems.

  17. Phasor approaches simplify the analysis of tryptophan fluorescence data in protein denaturation studies

    International Nuclear Information System (INIS)

    The intrinsic fluorescence of tryptophan is frequently used to investigate the structure of proteins. The analysis of tryptophan fluorescence data is challenging: fluorescence (anisotropy) decays typically have multiple lifetime (correlation time) components and fluorescence spectra are broad and exhibit only minor shifts. In this work, we show that phasor approaches can substantially simplify tryptophan fluorescence analysis. To demonstrate this, we re-analyse previously recorded datasets of the denaturant (guanidinium hydrochloride, GuHCl) induced unfolding of a single-tryptophan-containing variant of apoflavodoxin from Azotobacter vinelandii. For three methods—(1) time-resolved fluorescence, (2) time-resolved fluorescence anisotropy and (3) steady-state fluorescence spectroscopy—we show that the phasor analysis can readily identify the presence of a folding intermediate. Moreover, the fractional contributions of protein states at various stages of unfolding and the values of the free energy difference of the unfolding process (ΔGUN0) are obtained. The outcomes are compared to the global analysis results published previously. (paper)

  18. Biological seed priming mitigates the effects of water stress in sunflower seedlings.

    Science.gov (United States)

    Singh, Narsingh Bahadur; Singh, Deepmala; Singh, Amit

    2015-04-01

    The sunflower (Helianthus annuus L. cv. PAC 36) seedlings were inoculated with plant growth promoting rhizobacteria (PGPR), viz. Azotobacter chroococcum (A+), Bacillus polymyxa (B+), separately and in combination of the two (AB+). Relative water content and seedling growth were maximum in AB+ seedlings under control. Water stress significantly decreased the RWC, growth and dry mass of non-inoculated seedlings. However, inoculated seedlings maintained higher growth even under water stress. Pigments and protein contents decreased under water stress, but higher amount of the same was observed in stressed AB+ seedlings. Enhanced activity of nitrate reductase was recorded in AB+ seedlings with maximum in control. Water stress significantly decreased the nitrate reductase activity. A significant increase in the activity of superoxide dismutase (SOD) in leaves was recorded under water stress except in B+ with maximum increase in non-inoculated seedlings. Catalase (CAT) activity decreased in stressed non-inoculated seedlings while increased in the leaves of A+ and AB+ seedlings. Almost similar trends were recorded for both leaves and cotyledons. PGPR improved the water status in stressed seedlings and thereby physiological and biochemical parameters and thus ameliorated the severe effects of water stress. PMID:25964714

  19. Endophytes in commercial micropropagation - friend or foe?

    Directory of Open Access Journals (Sweden)

    Rödel, Philipp

    2016-07-01

    Full Text Available Medicinal and aromatic plants are superorganisms like all plant species- naturally colonized by bacteria, fungi and protists. Micropropagated plants are facing different challenges under in vitro and ex vitro conditions: Mixotrophic growth under low light conditions on artificial nutrient media, poor gas exchange in small vessels, abiotic stress, bad rooting, transplanting stress, low survival rate during acclimatization in greenhouse. The use of endophytes in micropropagation can improve plant growth, yield, and health and induce tolerance to abiotic and biotic stress. A tool for the use of competent endophytes in micropropagation under in vitro and ex vitro conditions is “biotization” of plantlets with useful bacterial and fungal inocula. Fungal inocula which are used commercially are e.g. arbuscular mycorrhizal fungi in form of spores and extraradical mycelium on different carrier materials like expanded clay, vermiculite, sand or peat. Furthermore representatives of the root fungal genus Trichoderma are applied as spores formulated in powder. Plantgrowth promoting rhizobacteria of the important genera Bacillus, Pseudomonas, Azospirillum and Azotobacter in form of lyophilised endospores/bacterial cells in powder or liquid formulation are also available on the market.

  20. Nitric oxide production in celomocytes of the earthworm Eisenia hortensis following bacterial challenge

    Directory of Open Access Journals (Sweden)

    SR Cook

    2015-02-01

    Full Text Available In this in vitro investigation, nitric oxide (NO production was induced within celomocytes of the earthworm Eisenia hortensis following microbial challenge. Celomocytes were pre-loaded with the fluorescent indicator 4-amino-5-methylamino-2’, 7’-difluorofluorescein diacetate (DAF-FM DA in order to detect the presence of intracellular nitric oxide subsequent to a 16 h incubation with chemically-fixed soil bacteria including Bacillus megaterium, Arthrobacter globiformis, Pseudomonas stutzeri, and Azotobacter chroococcum at a range of multiplicities of infection (MOIs. Flow cytometric analysis measuring increases in relative fluorescence intensity (RFI, which is directly proportional to the amount of intracellular NO produced, permitted determination of statistical significance (p < 0.05 of exposed celomocytes compared to baseline controls. Significant increases in NO were detected reproducibly in celomocytes treated with all bacterial species used. The most prominent results were observed after exposure to Gram positive B. megaterium and A. globiformis where 100 % of earthworms tested exhibited statistically significant increases of RFI at MOIs of 100:1 and 500:1, respectively. Furthermore, significant decreases in NO production in bacteria-stimulated earthworm celomocytes incubated with the NOS inhibitor aminoguanidine hydrochloride were observed. These results demonstrate microbial induction of NO synthesis in earthworms and provide evidence of an antimicrobial role of NO in the innate immune system.

  1. Sequence of the nifD gene coding for the α subunit of dinitrogenase from the cyanobacterium Anabaena

    Science.gov (United States)

    Lammers, Peter J.; Haselkorn, Robert

    1983-01-01

    The nucleotide sequence of nifD, the structural gene for the α subunit of dinitrogenase from Anabaena 7120, has been determined. The coding sequence contains 1,440 nucleotides, which predict an amino acid sequence of 480 residues and Mr of 54,283. The predicted sequence contains eight cysteines, of which five are conserved with respect to adjoining sequences and position relative to the α subunits of dinitrogenase from Azotobacter, Clostridium, and Klebsiella. Because there are also five conserved cysteines in the β subunit of Anabaena dinitrogenase [Mazur, B. J. & Chiu, C.-F. (1982) Proc. Natl. Acad. Sci. USA 79, 6782-6786], the number of cysteine residues participating as ligands to FeS clusters is likely to be 20 per α2β2 tetramer. This number is sufficient to accommodate the known four Fe4S4 clusters, leaving at least four cysteines to be shared among the two FeMo cofactors and the more poorly characterized two-iron center. Although the α- and β-subunit gene sequences are not recognizably homologous, their secondary structures, predicted from the sequences, indicate similar domains around three of the conserved cysteine residues. PMID:16593347

  2. RESISTANCE OF KARST CAVERNS NITROGEN-FIXING BACTERIA TO EXTREME FACTORS

    Directory of Open Access Journals (Sweden)

    Tashyrev O. B.

    2014-10-01

    Full Text Available To determine the studied bacteria resistance quantitative parameters of extreme factors such as toxic metals (Cu2+, organic xenobiotics (p-nitrochlorobenzene and UV-irradiation were the aim of the research. Six strains of nitrogen-fixing bacteria isolated from clays of two caverns Mushkarova Yama (Podolia, Ukraine and Kuybyshevskaya (Western Caucasus, Abkhazia and Azotobacter vinelandii УКМ В-6017 as a reference strain have been tested. For this purpose the maximum permissible concentration of Cu2+ and p-nitrochlorobenzene in the concentration gradient and lethal doses of UV by the survival caverns have been determined. Maximum permissible concentrations for strains were as 10 ppm Cu2+, 70–120 ppm of p-nitrochlorobenzene. The maximum doses of UV-irradiation varied in the range of 55–85 J/m2 (LD99.99. It is shown that three classes of extreme factors resistance parameters of karst caverns strains are similar to the strain of terrestrial soil ecosystems. The most active studied strains reduce the concentration of p-nitrochlorobenzene in the medium in 13 times. The ability of nitrogen-fixing bacteria to degrade p-nitrochlorobenzene could be used in creation new environmental biotechnology for industrial wastewater treatment from nitrochloroaromatic xenobiotics. Isolated strains could be used as destructors for soils bioremediation in agrobiotechnologies and to optimize plants nitrogen nutrition in terrestrial ecosystems.

  3. Survival of microorganisms in smectite clays: Implications for Martian exobiology

    Science.gov (United States)

    Moll, Deborah M.; Vestal, J. Robie

    1992-08-01

    Manned exploration of Mars may result in the contamination of that planet with terrestrial microbes, a situation requiring assessment of the survival potential of possible contaminating organisms. In this study, the survival of Bacillus subtilis, Azotobacter chroococcum, and the enteric bacteriophage MS2 was examined in clays representing terrestrial (Wyoming type montmorillonite) or Martian (Fe 3+-montmorillonite) soils exposed to terrestrial and Martian environmental conditions of temperature and atmospheric pressure and composition, but not to UV flux or oxidizing conditions. Survival of bacteria was determined by standard plate counts and biochemical and physiological measurements over 112 days. Extractable lipid phosphate was used to measure microbial biomass, and the rate of 14C-acetate incorporation into microbial lipids was used to determine physiological activity. MS2 survival was assayed by plaque counts. Both bacterial types survived terrestrial or Martian conditions in Wyoming montmorillonite better than Martian conditions in Fe 3+-montmorillonite. Decreased survival may have been caused by the lower pH of the Fe 3+-montmorillonite compared to Wyoming montmorillonite. MS2 survived simulated Mars conditions better than the terrestrial environment, likely due to stabilization of the virus caused by the cold and dry conditions of the simulated Martian environment. The survival of MS2 in the simulated Martian environment is the first published indication that viruses may be able to survive in Martian type soils. This work may have implications for planetary protection for future Mars missions.

  4. Influence of PAS domain flanking regions on oligomerisation and redox signalling by NifL.

    Directory of Open Access Journals (Sweden)

    Richard Little

    Full Text Available Per-ARNT-Sim (PAS domains constitute a typically dimeric, conserved α/β tertiary fold of approximately 110 amino acids that perform signalling roles in diverse proteins from all kingdoms of life. The amino terminal PAS1 domain of NifL from Azotobacter vinelandii accommodates a redox-active FAD group; elevation of cytosolic oxygen concentrations result in FAD oxidation and a concomitant conformational re-arrangement that is relayed via a short downstream linker to a second PAS domain, PAS2. At PAS2, the signal is amplified and passed on to effector domains generating the 'on' (inhibitory state of the protein. Although the crystal structure of oxidised PAS1 reveals regions that contribute to the dimerisation interface, 21 amino acids at the extreme N-terminus of NifL, are unresolved. Furthermore, the structure and function of the linker between the two PAS domains has not been determined. In this study we have investigated the importance to signalling of residues extending beyond the core PAS fold. Our results implicate the N-terminus of PAS1 and the helical linker connecting the two PAS domains in redox signal transduction and demonstrate a role for these flanking regions in controlling the oligomerisation state of PAS1 in solution.

  5. History on the biological nitrogen fixation research in graminaceous plants: special emphasis on the Brazilian experience

    Directory of Open Access Journals (Sweden)

    Baldani José I.

    2005-01-01

    Full Text Available This review covers the history on Biological Nitrogen Fixation (BNF in Graminaceous plants grown in Brazil, and describes research progress made over the last 40 years, most of whichwas coordinated by Johanna Döbereiner. One notable accomplishment during this period was the discovery of several nitrogen-fixing bacteria such as the rhizospheric (Beijerinckia fluminensis and Azotobacter paspali, associative (Azospirillum lipoferum, A. brasilense, A. amazonense and the endophytic (Herbaspirillum seropedicae, H. rubrisubalbicans, Gluconacetobacter diazotrophicus, Burkholderia brasilensis and B. tropica. The role of these diazotrophs in association with grasses, mainly with cereal plants, has been studied and a lot of progress has been achieved in the ecological, physiological, biochemical, and genetic aspects. The mechanisms of colonization and infection of the plant tissues are better understood, and the BNF contribution to the soil/plant system has been determined. Inoculation studies with diazotrophs showed that endophytic bacteria have a much higher BNF contribution potential than associative diazotrophs. In addition, it was found that the plant genotype influences the plant/bacteria association. Recent data suggest that more studies should be conducted on the endophytic association to strengthen the BNF potential. The ongoing genome sequencing programs: RIOGENE (Gluconacetobacter diazotrophicus and GENOPAR (Herbaspirillum seropedicae reflect the commitment to the BNF study in Brazil and should allow the country to continue in the forefront of research related to the BNF process in Graminaceous plants.

  6. Polyhydroxyalcanoates of strains of Azospirillum spp. isolated of roots of Lycopersicon esculentum Mill. “tomato” and Oryza sativa L. “rice” in Lambayeque

    Directory of Open Access Journals (Sweden)

    Katty Baca

    2010-12-01

    Full Text Available In this work was determined the concentration of polyhydroxyalkanoates (PHAs of Azospirillum strains isolated from roots of Lycopersicon esculentum Mill "tomato" and Oryza sativa L. "rice" as an alternative to accumulation of petroleum-based plastics. Previously disinfected root were plated in Nfb semisolid medium where nitrogen-fixing bacteria were recognized by a whitish film on the surface and turn from green to blue. The genus Azospirillum was identified in Congo red agar medium, obtained 96 isolates of A. lipoferum and A. brasilense on tomato and rice. Batch fermentation was performed with broth Azotobacter modified feeding a saturated solution of malic acid every 12 hours and were stained with Sudan Black B. Strains were selected with the greatest number of PHAs granules (in tomato, 18 of A. lipoferum and 2 of A. brasilense; in rice, 10 of A. lipoferum and 10 of A. brasilense and quantified the biomass and PHAs. PHAs concentration reached 0.661 gL-1 in A. lipoferum KM(T-73 and 0.738 gL-1 in A. brasilense KM(T-19, both isolated from tomato. Strains of A. lipoferum and A. brasilense isolated from tomato reached a higher concentration of biomass and PHAs against the strains of rice.

  7. FACTIBILIDAD ECONÓMICA DE LA APLICACIÓN DE INOCULANTES MICROBIANOS EN EL CULTIVO DEL TABACO NEGRO

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    Yarilis León González

    2016-01-01

    Full Text Available La investigación se realizó durante las campañas tabacaleras 2010/2011 y 2011/2012 en la Estación Experimental del Tabaco de San Juan y Martínez, Pinar del Río, Cuba. El objetivo fue determinar la factibilidad económica de dos métodos de aplicación de inoculantes microbianos en el cultivo del tabaco negro al sol. Se utilizó un diseño experimental de bloques al azar con 19 tratamientos y cuatro repeticiones. Se estudiaron diferentes dosis de fertilizante mineral en combinación con dos inoculantes microbianos (Azotobacter chroococcum y Bacillus megatherium var. phosphaticum. Se utilizaron dos variantes: una inoculación en el momento de la siembra del semillero y otra variante que incluye la inoculación inicial y una reinoculación en el trasplante. Con la reinoculación y disminución del fertilizante mineral se lograron mejores resultados que con el método de inoculación. Se demostró la factibilidad económica de la reinoculación de A. chroococcum + B. megatherium var. phosphaticum y el 75 % de la dosis total de nitrógeno y fósforo en el cultivo del tabaco negro al sol.

  8. [Effect of fibrous root extract of Coptis chinensis on soil microbes and enzyme activities].

    Science.gov (United States)

    Li, Yang-Bo; He, Lin-Wei; Zhang, Wei; Wu, Ye-Kuan; Yuan, Ling; Huang, Jian-Guo

    2014-11-01

    Coptis chinensis is widely used as Chinese medicine herbs and serious soil problems occur after continual cultivation of this medicinal plant. In the preset experiment, fibrous root extract of C. chinensis (REC) was added into soil to study the effect of REC on microbes and enzyme activity in soil. The results showed that both bacteria and actinomycetes decreased by about 2 times in contrast to fungi, which increased by about 3 folds. Phosphorus bacteria, potassium bacteria, azotobacter, ammonia bacteria, and nitrifying bacteria were also reduced significantly by REC, suggesting the inhibition of nitrogen biofixation and supply, mobilization of phosphorus and potassium, ad plant growth promotion as REC added into soil. There were multiple influences of REC on soil enzyme activities. Invertase activity was stimulated, while urease was inhibited and dehydrogenase unchanged by REC, indicating the interference of biochemical reactions in soil. In addition, type and total content of phosphorus lipid fatty acids (PLFAs) , the signature of microbes, decreased while the ratio of bacterium to fungus PLFAs increased as REC increased in soil, which suggested that fungi increased relatively with bacteria decreased thereby leading to easy occurrence of crop fungus diseases following cultivation of C. chinensis. The decrease in diversity and evenness indexes of microbial community in soil by REC indicated soil ecosystem deterioration and reduction of microbial groups and densities in soil. Therefore, allelopathic chemicals released from the roots of C. chinensis could change microbial community structure and resulted in serious soil problems by continual cropping of this medicinal plant. PMID:25775794

  9. Microbial Nitrogen-Cycle Gene Abundance in Soil of Cropland Abandoned for Different Periods.

    Science.gov (United States)

    Huhe; Borjigin, Shinchilelt; Buhebaoyin; Wu, Yanpei; Li, Minquan; Cheng, Yunxiang

    2016-01-01

    In Inner Mongolia, steppe grasslands face desertification or degradation because of human overuse and abandonment after inappropriate agricultural management. The soils in these abandoned croplands exist in heterogeneous environments characterized by widely fluctuating microbial growth. Quantitative polymerase chain reaction analysis of microbial genes encoding proteins involved in the nitrogen cycle was used to study Azotobacter species, nitrifiers, and denitrifiers in the soils from steppe grasslands and croplands abandoned for 2, 6, and 26 years. Except for nitrifying archaea and nitrous oxide-reducing bacteria, the relative genotypic abundance of microbial communities involved in nitrogen metabolism differed by approximately 2- to 10-fold between abandoned cropland and steppe grassland soils. Although nitrogen-cycle gene abundances varied with abandonment time, the abundance patterns of nitrogen-cycle genes separated distinctly into abandoned cropland versus light-grazing steppe grassland, despite the lack of any cultivation for over a quarter-century. Plant biomass and plant diversity exerted a significant effect on the abundance of microbial communities that mediate the nitrogen cycle (P bacteria that mediate the nitrogen cycle in recently abandoned croplands. PMID:27140199

  10. Microorganismos benéficos como biofertilizantes eficientes para el cultivo del tomate (Lycopersicon esculentum, Mill Beneficial microorganisms as efficient biofertilisers for tomato crops (Lycopersicon esculentum, Mill

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    Hernández Annia

    2005-12-01

    Full Text Available En el uso y manejo de biofertilizantes en la agricultura, uno de los principales problemas es el desconocimiento de las especies presentes en los agroecosistemas y en la rizosfera de los cultivos, para su posible utilización eficiente. Desde el punto de vista ecológico, es importante conocer los integrantes de la comunidad bacteriana que favorecen su aplicación como inoculantes y propician un efecto agrobiológico positivo en los cultivos agrícolas. Esta investigación se desarrolló con el objetivo de evaluar la efectividad agrobiológica de Azospirillum sp, en el crecimiento, desarrollo y rendimiento en el cultivo del tomate. Para ello, se partió de seleccionar el género microbiano predominante en la rizosfera del cultivo y posteriormente se evaluó el efecto de su inoculación a partir de la respuesta del cultivo. Los resultados demostraron que los géneros Pseudomonas, Azospirillum, Azotobacter, Bacillus y Streptomyces, forman parte de la comunidad microbiana de la rizosfera del tomate, en las condiciones estudiadas, y que Azospirillum es el género dominante. La inoculación artificial de esta rizobacteria causó un efecto positivo sobre el crecimiento de las plántulas, así como en el estado nutricional de las plantas, con un rendimiento agrícola superior a un 11 % con respecto a las plantas testigo. Se obtuvo un alto nivel poblacional en la rizosfera de las plantas inoculadas. Palabras clave: rizosfera, inoculante, crecimiento, rendimiento.One of the main problems regarding the efficient use and management of biofertilizers in agriculture lies in the unknown species present in agro-ecosystems and crop rhizospheres. From the ecological point of view, it is important to know the members of the bacterial population allowing them to be applied as inoculants and enable a positive agro-biological effect on agricultural crops. This investigation was aimed at evaluating the agro-biological effectiveness of Azospirillum sp. on tomato

  11. Inoculación de Cilantro (Coriandrum sativum L. con Rizobacterias en Villa del Rosario, Norte de Santander / Inoculation of Cilantro (Coriandrum sativum L. with Rhizobacterias in Villa del Rosario, Norte de Santander

    Directory of Open Access Journals (Sweden)

    Katherine Carrillo Becerra

    2014-12-01

    Full Text Available Resumen. Las rizobacterias promotoras de crecimiento vegetalrepresentan una alternativa de biofertilización. En este estudiose evaluó el efecto de su inoculación en plantas de cilantro y lautilización de la práctica de quema de cascarilla de arroz en lapreparación del suelo para el establecimiento del cultivo. Seempleó un diseño experimental en parcelas divididas donde, lasparcelas principales correspondieron a la preparación del suelo conquema de cascarilla de arroz y sin quema con la inoculación previade Trichoderma sp. Las subparcelas eran los tratamientos con lainoculación simple y en co-inoculación de Azospirillum RzH132y Azotobacter RzH120 y los testigos absoluto y químico. Unavez se comprobaron los supuestos en los residuales del modelo,normalidad, homogeneidad de varianzas y aleatoriedad, se realizóel análisis de varianza y pruebas de comparación múltiple porel test de Tukey y un análisis de componentes principales comotécnica de reducción de dimensiones. Los resultados mostraronun efecto positivo en el crecimiento de las plantas inoculadas conlas rizobacterias en las dos parcelas con quema y sin quema decascarilla de arroz; sin embargo, en la variable rendimiento nose obtuvieron diferencias significativas (P≤0,05. Así mismo, seencontró que la población de bacterias rizosféricas en los mediosde cultivo NFb semisólido, Ashby y King B, se vio favorecida por lano quema de cascarilla de arroz en el suelo. Es importante resaltarque los resultados se obtuvieron con la disminución al 30% de lafertilización química, con lo cual se puede reducir el uso de estosproductos químicos. /  Abstract. Plant growth promoting rhizobacteria (PGPR representan alternative biofertilization form. In this study, was evaluatedPGPR inoculation in cilantro plants. Likewise, was evaluatedthe practice of burning rice husk in soil preparation for cropestablishment. An experimental design was used in a split plotwhere the main plots were

  12. 润滑油高效降解菌的筛选及降解性能%Screening of lube oil biodegradation strain and degrading characteristics

    Institute of Scientific and Technical Information of China (English)

    郭晓燕; 张志红; 沈齐英; 李翠清

    2013-01-01

    实验以被石油污染的土壤为出发菌源,以润滑油为唯一碳源,经过筛选分离得到4株对润滑油具有降解能力的菌株.经过形态观察、生理生化实验初步鉴定发现,4株菌株分别为黄单胞菌属(Xanthomonas)、动胶菌属(Azotobacter)、假单胞菌属(Pseudomonas)和黄杆菌属(Flavobacterium),其中菌株G4为黄杆菌属,其润滑油降解效率最高.研究菌株G4降解性能的影响因素发现,实验中的各因素对润滑油降解率的影响大小依次为:温度>葡萄糖浓度>硫酸铵浓度> pH值.在温度20 ~ 40℃下,菌株G4对润滑油均具有一定的降解能力.在适宜的温度范围中,pH值5.0 ~9.0范围内,菌株G4的润滑油降解率随pH值的变化很小,且均在80%以上.菌株G4在以润滑油为唯一碳源时的最佳培养条件为:温度30℃,pH值为9.0,硫酸铵浓度为1.0 g/L.在此条件下培养36 h,100 mL的G4培养液对200 μL润滑油的降解率可达84.6%.%With oil contaminated soil as starting bacterial source and lube oil as sole carbon source, 4 lube oil biodegradation strains were screened. 4 strains were identified as Xanthomonas, Azotobacter, Pseudomonas and Flavobacterium separately, according to their morphological, physiological, and biochemical features. G4 in 4 screened strains had the highest biodegradation rate. Degrading characteristics of strain G4 were studied and a-mong the experimental factors, the culture temperature had the greatest effect on biodegradation rate, followed by the concentration of glucose, the concentration of ammonium sulphate, and pH. Strain G4 could degrade lube oil in the temperature range of 20 ~40℃. The degradation rate was over 80% in the pH range of 5.0 ~9.0 at appropriate temperature. When 200 μL lube oil, the sole carbon source, was degraded by 100 mL strain culture medium for 36 h, the biodegradation rate rose to 84. 6% under the optimum conditions as follows; ammonium sulphate concentration of 1. 0 g

  13. Azospirillum, a free-living nitrogen-fixing bacterium closely associated with grasses: genetic, biochemical and ecological aspects.

    Science.gov (United States)

    Steenhoudt, O; Vanderleyden, J

    2000-10-01

    Azospirillum represents the best characterized genus of plant growth-promoting rhizobacteria. Other free-living diazotrophs repeatedly detected in association with plant roots, include Acetobacter diazotrophicus, Herbaspirillum seropedicae, Azoarcus spp. and Azotobacter. Four aspects of the Azospirillum-plant root interaction are highlighted: natural habitat, plant root interaction, nitrogen fixation and biosynthesis of plant growth hormones. Each of these aspects is dealt with in a comparative way. Azospirilla are predominantly surface-colonizing bacteria, whereas A. diazotrophicus, H. seropedicae and Azoarcus sp. are endophytic diazotrophs. The attachment of Azospirillum cells to plant roots occurs in two steps. The polar flagellum, of which the flagellin was shown to be a glycoprotein, mediates the adsorption step. An as yet unidentified surface polysaccharide is believed to be essential in the subsequent anchoring phase. In Azoarcus sp. the attachment process is mediated by type IV pili. Nitrogen fixation structural genes (nif) are highly conserved among all nitrogen-fixing bacteria, and in all diazotrophic species of the class of proteobacteria examined, the transcriptional activator NifA is required for expression of other nif genes in response to two major environmental signals (oxygen and fixed N). However, the mechanisms involved in this control can vary in different organisms. In Azospirillum brasilense and H. seropedicae (alpha- and beta-subgroup, respectively), NifA is inactive in conditions of excess nitrogen. Activation of NifA upon removal of fixed N seems to involve, either directly or indirectly, the signal transduction protein P(II). The presence of four conserved cysteine residues in the NifA protein might be an indication that NifA is directly sensitive to oxygen. In Azotobacter vinelandii (gamma-subgroup) nifA is cotranscribed with a second gene nifL. The nifL gene product inactivates NifA in response to high oxygen tension and cellular

  14. Effects of Earthworms and Plant Growth Promoting Rhizobacteria on Availability of N and K in Soil%蚯蚓及植物促生根际细菌对土壤中氮和钾有效性的影响

    Institute of Scientific and Technical Information of China (English)

    吴福勇; 毕银丽; 毛艳丽

    2012-01-01

    A pot trial was conducted to investigate the single, dual or triple inoculation of earthworms or plant growth — promoting rhizobacteria (PGPR), including nitrogen-fixing bacteria (NFB) (Azotobacter chroococcum PDSN-5) and potassium-solubilizing bacteria (KSB) (Bacillus mucilaginous PDSK-1), on the growth of NFB and KSB and N and K availability in soils. All of the seven inoculation treatments apparently increased the growth of NFB and KSB. The activity of earthworm had limited influence on the growth of NFB, but significantly increased the growth of KSB. Three inoculation treatments including single inoculation of earthworm, single inoculation of NFB and dual inoculation of earthworm and NFB increased the activity of urease in soils obviously. There was a significant correlation between urease activity and total numbers of NFB and between concentration of NH4OAc-extractable K (r=0.47, P<0.05) and total number of KSB (r=0.44, P<0.05) in soil. The present study suggested that the mixture inoculation may be a promising approach for reducing the need for chemical fertilizers in agriculture.%采用室内试验的方法研究不同接种方式接种威廉环毛蚓(Pheretima guillelmi)、植物促生根际细菌(钾活化细菌(Bacillus mucilaginous PDSK-1)和固氮细菌(Azotobacter chroococcum PDSN-5))对土壤中固氮细菌和钾活化细菌的生长、土壤脲酶的活性以及土壤钾有效性的影响.7种接种方式均明显增加了土壤中固氮细菌和钾活化细菌的生长.蚯蚓活动对土壤中固氮细菌生长的影响有限,但明显增加了钾活化细菌的生长.接种蚯蚓、接种固氮细菌、接种蚯蚓和固氮细菌均明显增加了土壤中脲酶的活性.土壤中脲酶活性和速效钾的浓度分别与土壤中固氮细菌与钾活化细菌的数量成显著正相关关系(P<0.05).试验结果表明,混合接种方式是一种有潜力的生物技术,可以用来减少农业生产中化肥的施用量.

  15. Azospirillum, a free-living nitrogen-fixing bacterium closely associated with grasses: genetic, biochemical and ecological aspects.

    Science.gov (United States)

    Steenhoudt, O; Vanderleyden, J

    2000-10-01

    Azospirillum represents the best characterized genus of plant growth-promoting rhizobacteria. Other free-living diazotrophs repeatedly detected in association with plant roots, include Acetobacter diazotrophicus, Herbaspirillum seropedicae, Azoarcus spp. and Azotobacter. Four aspects of the Azospirillum-plant root interaction are highlighted: natural habitat, plant root interaction, nitrogen fixation and biosynthesis of plant growth hormones. Each of these aspects is dealt with in a comparative way. Azospirilla are predominantly surface-colonizing bacteria, whereas A. diazotrophicus, H. seropedicae and Azoarcus sp. are endophytic diazotrophs. The attachment of Azospirillum cells to plant roots occurs in two steps. The polar flagellum, of which the flagellin was shown to be a glycoprotein, mediates the adsorption step. An as yet unidentified surface polysaccharide is believed to be essential in the subsequent anchoring phase. In Azoarcus sp. the attachment process is mediated by type IV pili. Nitrogen fixation structural genes (nif) are highly conserved among all nitrogen-fixing bacteria, and in all diazotrophic species of the class of proteobacteria examined, the transcriptional activator NifA is required for expression of other nif genes in response to two major environmental signals (oxygen and fixed N). However, the mechanisms involved in this control can vary in different organisms. In Azospirillum brasilense and H. seropedicae (alpha- and beta-subgroup, respectively), NifA is inactive in conditions of excess nitrogen. Activation of NifA upon removal of fixed N seems to involve, either directly or indirectly, the signal transduction protein P(II). The presence of four conserved cysteine residues in the NifA protein might be an indication that NifA is directly sensitive to oxygen. In Azotobacter vinelandii (gamma-subgroup) nifA is cotranscribed with a second gene nifL. The nifL gene product inactivates NifA in response to high oxygen tension and cellular

  16. Shorter Life Span of Microorganisms and Plants as a Consequence of Shielded Magnetic Environment

    Science.gov (United States)

    Dobrota, C.; Piso, I. M.; Bathory, D.

    The geomagnetic field is an essential environmental factor for life and health on this planet. In order to survey how magnetic fields affect the life span and the nitrogenase (an iron-sulphur enzyme) activity of Azotobacter chroococcum as well as the life span, the main organic synthesis and the water balance of plants (22 species), the biological tests were incubated under shielded magnetic field and also in normal geo-magnetic environment. The shielding level was about 10-6 of the terrestrial magnetic field.Life cycles of all organisms require the co-ordinated control of a complex set of interlocked physiological processes and metabolic pathways. Such processes are likely to be regulated by a large number of genes. Our researches suggest that the main point in biological structures, which seems to be affected by the low magnetic environment, is the water molecule. Magnetic field induces a molecular alignment. Under shielded conditions, unstructured water molecules with fewer hydrogen bonds, which are producing a more reactive environment, are occurring. As compared to control, the life span of both microorganisms and plants was shorter in shielded environment. A higher nitrogenase affinity for the substrate was recorded in normal geo-magnetic field compared to low magnetic field. The synthesis of carbohydrates, lipids, proteins and enzymes was modified under experimental conditions. The stomatal conductance was higher between 158 and 300% in shielded environment indicating an important water loss from the plant cells.Our results support the idea that the shielded magnetic environment induces different reactions depending on the time of exposure and on the main metabolic pathways of the cells.

  17. Physico-chemical and microbiological characteristics of water for fish production using small ponds

    Science.gov (United States)

    Ntengwe, Felix W.; Edema, Mojisola O.

    The physical-chemical and biological characteristics of water in fish ponds were investigated with a view to optimise the conditions for fish productivity using small ponds. Five fish ponds were used in the study. The water samples were collected in each pond at a depth of 10-15 cm from the surface over a period of six months and analysed for pH, temperature, DO, alkalinity. The fish activity and growth rates were also assessed. The results showed that the ponds were slightly acidic to neutral (pH 6.69-7.66). The mean lowest and highest values of DO were 9.05 and 9.93 mg/L while the values for alkalinity were 67.86 and 90.57 mg/L respectively. The bacterial counts were in the order of 10 6 and the populations comprised Pseudomonas, Enterobacter, Salmonella, Staphylococcus, Bacillus, Azotobacter, Arthrobacter species and Escherichia coli. It was also observed that the fish activity increased as the temperature of the water varied from April to September as given by the activity ranges of 55-95, 40-80, 55-80, 70-95 and 55-95/m 2 for ponds P1, P2, P3, P4 and P5, respectively. The lowest values were in the months of April, May and June and highest values were in the months of July, August and September. The optimum conditions for increased fish productivity were found to be the warm temperatures (20 4 mg/L) and appropriate pH (6 characteristics were significant at 0.01 and 0.05 levels (2 tailed). Therefore, the fish productivity can be enhanced if the conditions in the ponds were maintained at optimum levels.

  18. LAS MICORRIZAS ARBUSCULARES Y LAS BACTERIAS RIZOSFÉRICAS COMO ALTERNATIVA A LA NUTRICIÓN MINERAL DEL TOMATE

    Directory of Open Access Journals (Sweden)

    María I. Hernández

    2004-01-01

    Full Text Available El presente estudio se desarrolló en el Instituto de Investigaciones Hortícolas "Liliana Dimitrova" durante los años 1996-2000 con la variedad de tomate HC 38-80 sembrada en período tardío. En la fase de semillero se realizó un screening, con el objetivo de seleccionar las cepas de micorrizas arbusculares y rizobacterias más eficientes para el cultivo del tomate, así como las mejores combinaciones. Para ello se determinaron la altura de la planta, el diámetro del tallo, la longitud radical y la masa seca total. Posteriormente, se evaluó el efecto de los biofertilizantes seleccionados y la fertilización mineral en el rendimiento del cultivo, sus componentes y el estado nutricional de la planta. El mejor comportamiento en la fase de semillero se obtuvo con la inoculación de las cepas Glomus mosseae, Glomus fasciculatum, Azospirillum brasilense, Azotobacter chroococcum, Glomus mosseae + Pseudomonas fluorescens y Glomus mosseae + Azospirillum brasilense. En la fase de campo se observó que el rendimiento y sus componentes se beneficiaron con la aplicación de niveles óptimos de fertilizantes, mientras que para los tratamientos inoculados los mayores valores correspondieron a Glomus mosseae, Glomus mosseae + Pseudomonas flourescens y Glomus mosseae + Azospirillum brasilense combinadas con el 50 % de la fertilización nitrogenada. Los HFMA y su coinoculación con bacterias rizosféricas influyeron de manera positiva en la absorción de nitrógeno y fósforo.

  19. Microbial consortium role in processing liquid waste of vegetables in Keputran Market Surabaya as organic liquid fertilizer ferti-plus

    Science.gov (United States)

    Rizqi, Fauziah; Supriyanto, Agus; Lestari, Intan; Lita Indri D., L.; Elmi Irmayanti, A.; Rahmaniyah, Fadilatur

    2016-03-01

    Many activities in this market is directly proportional to increase production of vegetables waste, especially surabaya. Therefore, in this study aims to utilize liquid waste of vegetables into liquid organic fertilizer by mixing microbial consorsium. The microbial consorsium consist of Azotobacter chrococcum, Azospirillum brasilense, Rhizobium leguminosarum, Bacillus subtilis, Bacillus megaterium, Pseudomonas putida, and Pseudomonas fluorescens. Ttreatment of microbial concentrations (5%, 10%, 15%) and the length of the incubation period (7 days, 14 days, 21 days) used in this research. The parameters used are: C/N ratio, levels of CNP, and BOD value. This study uses a standard organic fertilizer value according SNI19-7030-2004, The results show the value of C/N ratio comply with the ISO standards. C levels showed an increase during the incubation period but not compare with standards. N levels that compare with standards are microbial treatment in all group concentration except control group with an incubation period of 21 days is > 7. P levels compare with the existing standards in the group of microbe concentration of 10% and 15% during the incubation period. The value of the initial BOD liquid waste of vegetable is 790.25 mg / L, this value indicates that the waste should not go into the water body. Accordingly, the results of this study can not be used as a liquid organic fertilizer, but potentially if it is used as a natural career or build natural soil. The Building natural soil is defined as the natural ingredients that can be used to improve soil properties.

  20. Chestnut green waste composting for sustainable forest management: Microbiota dynamics and impact on plant disease control.

    Science.gov (United States)

    Ventorino, Valeria; Parillo, Rita; Testa, Antonino; Viscardi, Sharon; Espresso, Francesco; Pepe, Olimpia

    2016-01-15

    Making compost from chestnut lignocellulosic waste is a possible sustainable management strategy for forests that employs a high-quality renewable organic resource. Characterization of the microbiota involved in composting is essential to better understand the entire process as well as the properties of the final product. Therefore, this study investigated the microbial communities involved in the composting of chestnut residues obtained from tree cleaning and pruning. The culture-independent approach taken highlighted the fact that the microbiota varied only slightly during the process, with the exception of those of the starting substrate and mature compost. The statistical analysis indicated that most of the bacterial and fungal species in the chestnut compost persisted during composting. The dominant microbial population detected during the process belonged to genera known to degrade recalcitrant lignocellulosic materials. Specifically, we identified fungal genera, such as Penicillium, Fusarium, Cladosporium, Aspergillus and Mucor, and prokaryotic species affiliated with Bacilli, Actinobacteria, Flavobacteria and γ-Proteobacteria. The suppressive properties of compost supplements for the biocontrol of Sclerotinia minor and Rhizoctonia solani were also investigated. Compared to pure substrate, the addition of compost to the peat-based growth substrates resulted in a significant reduction of disease in tomato plants of up to 70 % or 51 % in the presence of Sclerotinia minor or Rhizoctonia solani, respectively. The obtained results were related to the presence of putative bio-control agents and plant growth-promoting rhizobacteria belonging to the genera Azotobacter, Pseudomonas, Stenotrophomonas, Bacillus, Flavobacterium, Streptomyces and Actinomyces in the chestnut compost. The composting of chestnut waste may represent a sustainable agricultural practice for disposing of lignocellulosic waste by transforming it into green waste compost that can be used to

  1. The effect of carfentrazone-ethyl on soil microorganisms and soil enzymes activity / Wpływ karfentrazonu etylu na mikroorganizmy i aktywność enzymów glebowych

    Directory of Open Access Journals (Sweden)

    Tomkiel Monika

    2015-09-01

    Full Text Available W pracy określono wpływ karfentrazonu etylu zaaplikowanego w dawkach 0,265, 5,280, 10,560, 21,180, 42,2 40 μg kg-1s.m. gleby na grzyby, promieniowce, bakterie organotrofi czne, oligotrofi czne ogółem i oligotrofi czne przetrwalnikujące oraz aktywność dehydrogenaz, katalazy, ureazy, fosfatazy alkalicznej, fosfatazy kwaśnej, arylosulfatazy i β-glukozydazy. W wyniku badań stwierdzono stymulujące działanie karfentrazonu etylu na bakterie oligotrofi czne ogółem i bakterie organotrofi czne, natomiast inhibicyjne na Azotobacter, grzyby, bakterie oligotrofi czne przetrwalnikujące oraz promieniowce. Preparat ten zmieniał strukturę zespołu drobnoustrojów. Największe zmiany wywoływał u grzybów. Najwyższe wartości wskaźników rozwoju kolonii (CD i ekofi zjologicznej różnorodności (EP odnotowano u bakterii organotrofi cznych. Karfentrazon etylu w dawce optymalnej zwiększał aktywność dehydrogenaz katalazy, ureazy, fosfatazy alkalicznej, fosfatazy kwaśnej i β-glukozydazy, a nie oddziaływał na arylosulfatazę, natomiast najwyższe dawki zmniejszały aktywność dehydrogenaz (obniżenie z 11,835 do 11,381 μmol TPF, ureazy (obniżenie z 0,545 do 0,500 mmol N-NH4 i arylosulfatazy (obniżenie z 0,210 do 0,168 mmol PNP. Najbardziej opornymi enzymami na działanie KE okazały się dehydrogenazy, a najmniej fosfataza kwaśna i arylosulfataza.

  2. Controlled expression of nif and isc iron-sulfur protein maturation components reveals target specificity and limited functional replacement between the two systems.

    Science.gov (United States)

    Dos Santos, Patricia C; Johnson, Deborah C; Ragle, Brook E; Unciuleac, Mihaela-Carmen; Dean, Dennis R

    2007-04-01

    The nitrogen-fixing organism Azotobacter vinelandii contains at least two systems that catalyze formation of [Fe-S] clusters. One of these systems is encoded by nif genes, whose products supply [Fe-S] clusters required for maturation of nitrogenase. The other system is encoded by isc genes, whose products are required for maturation of [Fe-S] proteins that participate in general metabolic processes. The two systems are similar in that they include an enzyme for the mobilization of sulfur (NifS or IscS) and an assembly scaffold (NifU or IscU) upon which [Fe-S] clusters are formed. Normal cellular levels of the Nif system, which supplies [Fe-S] clusters for the maturation of nitrogenase, cannot also supply [Fe-S] clusters for the maturation of other cellular [Fe-S] proteins. Conversely, when produced at the normal physiological levels, the Isc system cannot supply [Fe-S] clusters for the maturation of nitrogenase. In the present work we found that such target specificity for IscU can be overcome by elevated production of NifU. We also found that NifU, when expressed at normal levels, is able to partially replace the function of IscU if cells are cultured under low-oxygen-availability conditions. In contrast to the situation with IscU, we could not establish conditions in which the function of IscS could be replaced by NifS. We also found that elevated expression of the Isc components, as a result of deletion of the regulatory iscR gene, improved the capacity for nitrogen-fixing growth of strains deficient in either NifU or NifS.

  3. Increasing potassium (K release from K-containing minerals in the presence of insoluble phosphate by bacteria

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Sarikhani

    2016-03-01

    Full Text Available Introduction: Phosphorus and potassium are major essential macronutrients for biological growth and development. Application of soil microorganisms is one approach to enhance crop growth. Some bacteria are efficient in releasing K and solubilizing P from mineral sources but their behavior was not studied more in presence together. Materials and methods: In this study the ability of seven bacterial strains, including Pseudomonas putida P13, P. putida Tabriz, P. fluorescens Tabriz, P. fluorescens Chao, Pantoea agglomerans P5, Azotobacter sp. and Bacillus megaterium JK3 to release mineral K from muscovite and biotite with application of insoluble (Ca3(PO42 or soluble (Na2HPO4 P-sources was investigated. Nutrient Broth was used to prepare an overnight culture of bacteria to inoculate in Aleksandrov medium, which was used to study the dissolution of silicate minerals. It should be mentioned that Aleksandrov medium was used to determine the amount of released P from tricalcium phosphate (TCP while muscovite was added to the medium as a sole source of potassium. Concentration of P was determined spectrophotometrically by ammonium-vanadate-molybdate method and K was determined by flame photometry. Results: The insoluble P-source led to a significantly increased released K into assay medium (66%, and the net release of K from the biotite was significantly enhanced. Among bacterial strains, the highest mean of released K was observed with P. putida P13 which released more K (27% than the control. The amounts of released K from micas in the presence of insoluble and soluble phosphate by P. putida P13 were 8.25 and 4.87 mg/g, respectively. Discussion and conclusion: Application of insoluble phosphate could increase K release from mica minerals. The enhanced releasing of mineral K might be attributed to the release of organic acids from the bacteria, a mechanism which plays a pivotal role in solubilizing phosphate from inorganic source of phosphate.

  4. Selenocysteine Lyase.

    Science.gov (United States)

    Stadtman, Thressa C

    2004-12-01

    Selenocysteine is a naturally occurring analog of cysteine in which the sulfur atom of the latter is replaced with selenium. This seleno-amino acid occurs as a specific component of various selenoproteins and selenium-dependent enzymes. Incorporation of selenocysteine into these proteins occurs cotranslationally as directed by the UGA codon. For this process, a special tRNA having an anticodon complimentary to UGA, tRNASec, is utilized. In Escherichia coli and related bacteria, this tRNA first is amino acylated with serine, and the seryl-tRNASec is converted to selenocysteyl-tRNASec. The specific incorporation of selenocysteine into proteins directed by the UGA codon depends on the synthesis of selenocysteyl-tRNASec. Included in the selenium delivery protein category are rhodaneses that mobilize selenium from inorganic sources and NIFS-like proteins that liberate elemental selenium from selenocysteine. The NIFS protein from Azotobacter vinelandii was found to serve as an efficient catalyst in vitro for delivery of selenium from free selenocysteine to Escherichia coli selenophosphate synthetase for selenophosphate formation. The widespread distribution of selenocysteine lyase in numerous bacterial species was reported and the bacterial enzymes, like the pig liver enzyme, required pyridoxal phosphate as cofactor. Three NIFS-like genes were isolated from E. coli by Esaki and coworkers and the expressed gene products were isolated and characterized. One of these NIFS-like proteins also exhibited a high preference for selenocysteine over cysteine. M. vannielii, an anaerobic methane-producing organism, that grows in a mineral medium containing formate as sole organic carbon source, synthesizes several specific selenoenzymes required for growth and energy production under these conditions. PMID:26443359

  5. Actinorhizal Alder Phytostabilization Alters Microbial Community Dynamics in Gold Mine Waste Rock from Northern Quebec: A Greenhouse Study.

    Directory of Open Access Journals (Sweden)

    Katrina L Callender

    Full Text Available Phytotechnologies are rapidly replacing conventional ex-situ remediation techniques as they have the added benefit of restoring aesthetic value, important in the reclamation of mine sites. Alders are pioneer species that can tolerate and proliferate in nutrient-poor, contaminated environments, largely due to symbiotic root associations with the N2-fixing bacteria, Frankia and ectomycorrhizal (ECM fungi. In this study, we investigated the growth of two Frankia-inoculated (actinorhizal alder species, A. crispa and A. glutinosa, in gold mine waste rock from northern Quebec. Alder species had similar survival rates and positively impacted soil quality and physico-chemical properties in similar ways, restoring soil pH to neutrality and reducing extractable metals up to two-fold, while not hyperaccumulating them into above-ground plant biomass. A. glutinosa outperformed A. crispa in terms of growth, as estimated by the seedling volume index (SVI, and root length. Pyrosequencing of the bacterial 16S rRNA gene for bacteria and the ribosomal internal transcribed spacer (ITS region for fungi provided a comprehensive, direct characterization of microbial communities in gold mine waste rock and fine tailings. Plant- and treatment-specific shifts in soil microbial community compositions were observed in planted mine residues. Shannon diversity and the abundance of microbes involved in key ecosystem processes such as contaminant degradation (Sphingomonas, Sphingobium and Pseudomonas, metal sequestration (Brevundimonas and Caulobacter and N2-fixation (Azotobacter, Mesorhizobium, Rhizobium and Pseudomonas increased over time, i.e., as plants established in mine waste rock. Acetate mineralization and most probable number (MPN assays showed that revegetation positively stimulated both bulk and rhizosphere communities, increasing microbial density (biomass increase of 2 orders of magnitude and mineralization (five-fold. Genomic techniques proved useful in

  6. APLIKASI KOMBINASI KOMPOS JERAMI, KOMPOS AZOLLA DAN PUPUK HAYATI UNTUK MENINGKATKAN JUMLAH POPULASI BAKTERI PENAMBAT NITROGEN DAN PRODUKTIVITAS TANAMAN PADI BERRBASIS IPAT-BO

    Directory of Open Access Journals (Sweden)

    Ferina Rosiana

    2013-03-01

    Full Text Available Penelitian untuk mengetahui efek pemberian kombinasi kompos jerami dengan Azolla dan pupuk hayati majemuk terhadap peningkatan populasi bakteri penambat N dan produktivitas tanaman padi dengan teknologi IPAT-BO dilaksanakan dari bulan April hingga Juli 2012 di kebun percobaan Fakultas Pertanian, Universitas Padjadjaran, Jatinangor, dengan ketinggian + 740 m dpl. Penelitian ini menggunakan rancangan acak kelompok faktor tunggal dengan dua belas perlakuan dan tiga kali ulangan. Perlakuan terdiri dari (A tanpa kompos jerami, (B kompos jerami 2,5 ton ha-1, (C kompos jerami 5 ton ha-1, (D kompos Azolla 0,5 ton ha-1, (E kompos jerami 2,5 ton ha-1 + kompos Azolla 0,5 ton ha-1, (F kompos jerami 5 ton ha-1 + kompos Azolla 0,5 ton ha-1, (G pupuk hayati 400 g ha-1, (H kompos jerami 2,5 ton ha-1 + pupuk hayati 400 g ha-1, (I kompos jerami 5 ton ha-1 + pupuk hayati 400 g ha-1, (J kompos Azolla 0,5 ton ha-1 + pupuk hayati 400 g ha-1, (K kompos jerami 2,5 ton ha-1 + kompos Azolla 0,5 ton ha-1 + pupuk hayati 400 g ha-1, (L kompos jerami 5 ton ha-1 + kompos Azolla 0,5 ton ha-1 + pupuk hayati 400 g ha-1.Aplikasi perlakuan kompos jerami, kompos Azolla dan pupuk hayati majemuk memberikan pengaruh terhadap populasi penambat N (Azotobacter sp. dan Azospirilium sp. dan produktifitas tanaman padi. Aplikasi kompos jerami 2,5 ton ha-1 dengan pupuk hayati 400 g ha-1 memberikan hasil GKP yaitu 64,39 g tanaman-1 (6,13 ton ha-1. Kata kunci: IPAT-BO, kompos Azolla, kompos jerami, pupuk hayati.

  7. Assessment of compost as a bio-fertilizer for the growth of paddy.

    Science.gov (United States)

    Jelin, J; Dhanarajan, M S; Mariappan, V

    2013-11-01

    The vegetable wastes were converted into compost by a stepwise degradation and its characteristics were studied and analysed at each stage. The temperature increased from 290C to 60 degrees C on 60th day and reached 33 degrees C on 90th day. Shift of pH from 7.6 to 7.3 on 60th day caused a shift of microflora from 12.01 x 10(7) to 11.13 x 10(8) CFU ml(-1) on 30th day and 63.2 x 10(6) on 60th day and 36.75 x 10(6) on 90th day. Shift of microflora caused high decomposition of the waste into compost which were used for enriching the soil as manures. The other characteristics such as moisture, ash content and C:N ratio established the short period required for preparing a complete compost of good quality. The study showed the efficiency of these organisms as plant growth promoting rhizobacteria. Combinations of microorganisms with compost act as a good biofertilizer which improves the fertility of soil and increases plant growth. Better results were produced by organisms in combinations like Azospirillum, Rhizobium and Azotobacter. The least growth in shoot length (64 cm) total fresh weight (151g) and total dry weight (3.994 g) were observed in paddy grown in soil and Bacillus combination, but microbial mixture of compost and soil gave high paddy growth efficiency. The present study concludes that the rhizospheric organisms play well as plant growth promoting agents and gave a better yield and growth of plants in combination with the compost. PMID:24555324

  8. 啤酒糟发酵产高蛋白饲料菌种的的配伍%Compatibility of strains for producing higher protein feed by fermentation of brewer's residue

    Institute of Scientific and Technical Information of China (English)

    陶敏; 王维嘉; 蔡俊

    2011-01-01

    以啤酒糟为主要原料,采用多菌种混合固态发酵生产蛋白饲料,并通过菌种的配伍实验对发酵产蛋白饲料菌种的组合进行优化,试验结果表明:挑选的8株菌都能在以啤酒糟为唯一底物的平板上生长,并且菌种最佳组合为固氮菌、白地霉、绿色木霉、啤酒酵母、热带假丝酵母等5株菌,其发酵后的蛋白质含量为31.45%,粗蛋白为39.22%,无机氮转化率为56.42%.%With brewer's residue as main materials, through solid-state fermentation to produce protein feed by multiplex strains, and optimizing the strain compatibility experiment of producing protein feed by fermentation optimized combination.Experimental results showed that the selected eight strains were growing on the only substrate of brewer's residue, and the best combination of strains were Azotobacter,geotrichum candidum, trichoderma viride, beer yeast, candida tropicalis etc, after fermentation of brewer's residue, the protein content was 31.45%, crude protein was 39.22%, conversion of inorganic nitrogen was 56.42%.

  9. Characterization of nitrogen-fixing bacteria from a temperate saltmarsh lagoon, including isolates that produce ethane from acetylene.

    Science.gov (United States)

    Tibbles, B J; Rawlings, D E

    1994-01-01

    Nitrogen-fixing bacteria were isolated from sediments and water of a saltmarsh lagoon on the west coast of South Africa, and characterized according to factors that regulate nitrogen fixation in the marine environment. The majority of isolates were assigned to the Photobacterium or Vibrio genera on the basis of physiological and biochemical characteristics. One isolate was further assigned to the species Vibrio diazotrophicus. Carbohydrate utilization by each diazotrophic isolate was examined. Abilities of the isolates to utilize a range of mono-, di-, and polysaccharides largely reflected the predicted availability of organic carbon and energy in the lagoon, except that chitin was not utilized. Biochemical tests on the utilization of combined nitrogen showed that one isolate could utilize nitrate, and that this strain was susceptible to full repression of nitrogenase activity by 10mM nitrate. Urease activity was not detected in any of the isolates. In the absence of molybdenum two of the isolates, a Photobacterium spp. and V. diazotrophicus, reduced acetylene to ethylene and ethane, a property frequently associated with the activity of alternative nitrogenases. Addition of 25µM molybdenum inhibited ethane production by V. diazotrophicus, but stimulated ethylene and ethane production by the Photobacterium isolate. Addition of 28µM vanadium did not appear to regulate ethane production by either strain. Assays of nitrogenase activity in sediments from which some isolates were obtained indicated that molybdenum was not limiting nitrogenase activity at naturally-occurring concentrations. Southern hybridizations of the chromosomes of these strains with the anfH and vnfH genes of Azotobacter vinelandii and the nifH gene of Klebsiella pneumoniae indicated the presence of only one nitrogenase in these isolates.

  10. Study of quantitative and qualitative yield, chlorophyll content and some growth indices of wheat (Triticum aestivum L. in response to seed inoculation with PGPR at different levels of soil salinity

    Directory of Open Access Journals (Sweden)

    M. Hagh Bahari

    2014-07-01

    Full Text Available In order to study of quantitative and qualitative yield, chlorophyll content and some growth indices of wheart (Triticum aestivum L. in response to seed inoculation with plant growth promoting rhizobacteria (PGPR at different levels of soil salinity, a factorial experiment based on randomized complete block design with three replications was conducted at Research Greenhouse of Faculty of Agriculture, University of Mohaghegh Ardabili, Ardabil, in 2011. Experimental factors were soil salinity at four levels (0, 15, 30 and 60 Mm as Nacl and seed inoculation with PGPR in four levels (no inoculation as control, seed inoculation with Azotobacter chrocoocum strain 5, Azospirillum lipoferum strain OF, Pseudomonas putida strain 186. Comparison of means showed that in soil salinity conditions, grain yield per plant, number of grain per spike, grain 100 weight, spike length and root weight increased due to seed inoculation with PGPR compared to without seed inoculation. Investigation of total dry matter accumulation indicated that in all treatment combinations, it increased rapidly until 85 days after sowing. From 85 days after sowing till harvest time, it decreased due to increasing of competition, shedding and aging of leaves. In all treatment combinations, the highest grain yield and total dry matter accumulation per unit area was obtained in treatment combination of seed inoculation with Azosperilium × no soil salinity and the lowest amount was in the highest level of soil salinity × no seed inoculation. Similar trend was obtained in crop growth rate and relative growth rate. Hence, the results of this study showed that in order to increase the quantitative and qualitative yield, chlorophyll content and some other growth indices such as total biomass, crop growth rate and relative growth rate of wheat in soil salinity conditions, it could be suggested that wheat seed inoculation with Azospirillum be applied

  11. EFFICACY OF RHIZOBACTERIA AND HUMIC ACID FOR CONTROLLING FUSARIUM WILT DISEASE AND IMPROVEMENT OF PLANT GROWTH, QUANTITATIVE AND QUALITATIVE PARAMETERS IN TOMATO

    Directory of Open Access Journals (Sweden)

    Magd El-Morsy A. El-Morsy

    2012-12-01

    Full Text Available The effect of tomato seedling treated with plant growth promoting rhizobacteria (PGPR strains viz. Azotobacter sp. (AZM1,Bacillus cereus (BCM8, B. megaterium (BMM5 individually or combined with humic acid were evaluated for controlling wilt disease caused by Fusarium oxysporum f. sp. lycopersici, plant growth, fruit quantitative and qualitative (cv. Super Strain-B during 2010-2011 and 2011-2012 growing seasons. Under greenhouse conditions, all treatments significantly reduced area under disease progress curve (AUDPC and increased plant height, fresh and dry weights of survival plants growing in pots infested with the causal pathogen compared with control. Combination treatments of humic acid with PGPR reduced significantly wilt incidence and increased plant height, fresh and dry weights of tomato plants comparing with the application of each of them alone. Under laboratory conditions, all PGPR strains and humic acid able to inhibited leaner growth of the causal pathogen with different degrees and PGPR strains were more active than humic acid in this respect.  Under field conditions, all PGPR stains individually or combined with humic acid significantly reduced AUDPC and improved plant growth (plant height, number of branches plant -1 quantitative (number of fruits plant  -1, fruit weight plant -1, fruit weight, fruit yield fed.  -1, Number of fruit Kg  -1 and qualitative (degree of   fruit’s color, fruit diameters, firmness, fruit height, total soluble solids parameters of tomato fruits compared with untreated plants (control in both growing seasons. Combination treatments of humic acid with PGPR strains increase the effectiveness of them in this respect  more than   used alone.

  12. Effect of integrated nutrient management on herbage yield of black henbane (Hyoscyamus niger L.

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    Atul Kumar Gupta

    2011-11-01

    Full Text Available A field experiment was carried out at Medicinal Plants Research and Development Centre (MRDC , G.B. Pant University of Agriculture and Technology, Pantnagar, during Rabi season of 2008-09 and 2009-10 to quantify the effect of integrated nutrient management (INM on herbage yield of black henbane (Hyoscyamus niger L. . Soil of experimental field was sandy loam with pH 6.81, rich in organic carbon (0.92% medium in available phosphorus (23.41 kg ha-1 and exchangeable potassium (209.42 kg ha-1, but low in available nitrogen (223.46 kg ha-1. The experiment was laid out in a randomized block design (RBD with 12 treatments using inorganic fertilizers, vermicompost and biofertilizers (Azotobacter and phosphate solubilizing bacteria in different combinations including one control treatment. The treatments were control, recommended NPK (100:50:50 kg ha-1, 75% recommended NPK+2.5 tons ha-1 vermicompost (VC, 50% recommended NPK + 5.0 tons ha-1 VC, 25% recommended NPK + 7.5 tons ha-1 VC, 10 tons ha-1 VC, recommended NPK + biofertilizers, 75% recommended NPK + 2.5 tons ha-1 VC + biofertilizers, 50% recommended NPK + 5.0 tons ha-1 biofertilizers, 25% recommended NPK + 7.5 VC tons ha-1 + biofertilizers, 10 tons ha-1 VC + biofertilizers and biofertilizers alone. Dry herbage yield of H. niger increased with integrated application of inorganic and organic nutrients. A significant increase in herbage yield was observed with 75% recommended NPK + 2.5 tons ha-1 VC + biofertilizers followed by 75% recommended NPK + 2.5 tons ha-1 VC. It is therefore recommended that, 75 % recommended NPK along with 2.5 t ha-1 VC with or without biofertilizers is best to obtain maximum herbage yield of black henbane.

  13. Interrelated effects of mycorrhiza and free-living nitrogen fixers cascade up to aboveground herbivores.

    Science.gov (United States)

    Khaitov, Botir; Patiño-Ruiz, José David; Pina, Tatiana; Schausberger, Peter

    2015-09-01

    Aboveground plant performance is strongly influenced by belowground microorganisms, some of which are pathogenic and have negative effects, while others, such as nitrogen-fixing bacteria and arbuscular mycorrhizal fungi, usually have positive effects. Recent research revealed that belowground interactions between plants and functionally distinct groups of microorganisms cascade up to aboveground plant associates such as herbivores and their natural enemies. However, while functionally distinct belowground microorganisms commonly co-occur in the rhizosphere, their combined effects, and relative contributions, respectively, on performance of aboveground plant-associated organisms are virtually unexplored. Here, we scrutinized and disentangled the effects of free-living nitrogen-fixing (diazotrophic) bacteria Azotobacter chroococcum (DB) and arbuscular mycorrhizal fungi Glomus mosseae (AMF) on host plant choice and reproduction of the herbivorous two-spotted spider mite Tetranychus urticae on common bean plants Phaseolus vulgaris. Additionally, we assessed plant growth, and AMF and DB occurrence and density as affected by each other. Both AMF alone and DB alone increased spider mite reproduction to similar levels, as compared to the control, and exerted additive effects under co-occurrence. These effects were similarly apparent in host plant choice, that is, the mites preferred leaves from plants with both AMF and DB to plants with AMF or DB to plants grown without AMF and DB. DB, which also act as AMF helper bacteria, enhanced root colonization by AMF, whereas AMF did not affect DB abundance. AMF but not DB increased growth of reproductive plant tissue and seed production, respectively. Both AMF and DB increased the biomass of vegetative aboveground plant tissue. Our study breaks new ground in multitrophic belowground-aboveground research by providing first insights into the fitness implications of plant-mediated interactions between interrelated belowground fungi

  14. Kajian Penggunaan Pupuk Hayati untuk Mengendalikan Penyakit Akar Gada (Plasmodiophora brassicae pada Tanaman Sawi Daging

    Directory of Open Access Journals (Sweden)

    Diding Rachmawati

    2016-03-01

    Full Text Available Pada budidaya tanaman sawi daging (pakcoi  dijumpai berbagai masalah  serius  yang menghambat upaya peningkatan produksi dan kualitas hasil. Salah satu kendala utama adalah penyakit tular tanah yang disebabkan oleh cendawan Plasmopara brassicae Wor . Serangan patogen tular tanah dapat menekan produksi tanaman hortikultura secara significan. Berbagai upaya telah dilakukan untuk mengendalikan patogen tular tanah antara lain dengan menggunakan bekterisida sistemik . Salah satu alternatif pengendalian yang paling prospektif adalah dengan menggunakan pupuk hayati yang telah diperkaya dengan mikroorganisme. antara lain bakteri selulotik, Azotobacter sp., Azospirillium sp., Rhizobium sp., Pseudomonas sp., Lactobacillus sp., dan  bakteri pelarut fosfat yang bertujuan untuk memperbaiki struktur tanah dan mengendalikan penyakit tular tanah. Penelitian dilakukan di kebun percobaan Karangploso BPTP Jatim,  pada bulan Januari sampai dengan April 2014, menggunakan rancangan acak kelompok, 4 perlakuan dan 6 ulangan. Perlakuan  terdiri dari  : A = Pupuk hayati dosis 15 kg/ha,   B = Pupuk hayati dosis 30 kg/ha,  C = Pupuk hayati dosis 45 kg/ha, D = Cara petani. Tujuan penelitian adalah untuk mengetahui efektifitas pupuk hayati dalam mengendalikan penyakit akar gada  P.brassicae  pada tanaman sawi daging. Hasil penelitian menunjukkan bahwa pemberian pupuk hayati dosis 45 kg/ha dapat memberikan pertumbuhan yang baik terhadap tinggi tanaman ( 26,50 cm, jumlah daun (21 helai, lebar tajuk (33,25 cm, panjang akar (14,38 cm dan bobot/tanaman (380 g/tanaman. Persentase serangan penyakit akar gada terendah juga ditunjukkan oleh pemberian pupuk hayati dosis 45 kg/ha, yaitu sebesar 1,75 % dan penekanan penyakit sebesar 70,83 %.Kata Kunci : Brassica juncea, pupuk hayati, penyakit bengkak akar

  15. Integrated bioethanol and biomanure production from potato waste.

    Science.gov (United States)

    Chintagunta, Anjani Devi; Jacob, Samuel; Banerjee, Rintu

    2016-03-01

    Disposal of potato processing waste and the problem of pollution associated with it is a vital issue that is being faced by the potato processing plants. The conventional peeling methods presently followed in the processing plants for removing the potato peel, also result in the loss of some portion of the mash which is rich in starch. Indiscriminate discharge of the waste causes detrimental effects in the environment, so this problem can be resolved by successful utilization of the waste for the generation of value added products. Hence, the present work focuses on integrated production of bioethanol and biomanure to utilize the waste completely leading to zero waste generation. The first part of the work describes a comparative study of ethanol production from potato peel and mash wastes by employing co-culture of Aspergillus niger and Saccharomyces cerevisiae at various incubation time (24-120 h) instead of application of enzymes. The solid state fermentation of potato peel and mash inoculated with co-culture, resulted in bioethanol production of 6.18% (v/v) and 9.30% (v/v) respectively. In the second part of the work, the residue obtained after ethanol production was inoculated with seven different microorganisms (Nostoc muscorum, Fischerella muscicola, Anabaena variabilis, Aulosira fertilissima, Cylindrospermum muscicola, Azospirillium lipoferum, Azotobacter chroococcum) and mixture of all the organisms in equal ratio for nitrogen (N), phosphorous (P) and potassium (K) enrichment. Among them, A. variabilis was found to enrich N, P and K content of the residue by nearly 7.66, 21.66 and 15 fold than that of the initial content, ultimately leading to improved N:P:K ratio of approximately 2:1:1. The application of simultaneous saccharification and fermentation (SSF) for the conversion of potato waste to ethanol and enrichment of residue obtained after ethanol production with microorganisms to be used as manure envisages environmental sustainability. PMID:26316099

  16. Potential Endophytic Bacteria for Increasing Paddy Var Rojolele Productivity

    Directory of Open Access Journals (Sweden)

    Desriani Desriani

    2013-09-01

    Full Text Available Paddy var Rojoleleis asuperior paddy come from Klaten that released by Department of Agriculture in 2003. Its superior properties are resistant to pests leaf hoppers, fluffier, and fragrant. To increase the productivity of paddy that are of ten used by farmers is to use chemical-based fertilizers. The use of these chemicals will effect to adisruption of ecosystem balancing, reduction the amount of soil microflora which essential forplants. Endophytic bacteria are symbiotic microorganisms living within plant tissues, and does not cause negative effects on the host plant. Endophytic bacteria have a capability increasing crop productivity by producing growth hormone, contributes to plant health, and as bio-control agents. Some endophytic bacteria which contribute to plant growth are: Pseudomonas sp., Enterobacter sp., Staphylococcus sp., Azotobacter sp., And Azospirilum sp., Whereas endophytic bacteria that contribute to the health and plant protection several of them are: Pseudomonas sp., Serratia sp. ,Clavibacter sp., and Bacillus sp. This study was conducted to investigate potential of endophytic bacteria to increase Paddy var Rojolele productivity based on its ability to produce extracellular enzymes and resistance to multiple types of antibiotics. The method were endophytic bacteria isolation from three Paddy varRojolele plants, extracellular enzymes detection and antibiotic resistance testing to chloramfinekol, ampicillin and kanamycin. As the result, 43isolateswere isolated from Paddy var Rojolele. Four isolatesamong them havethe ability to produce extra cellular enzym esandresistant toampicillin, kanamycin, and chloramfinekol. Extra cellular enzyme production capability and resistance to antibiotics makes endophytic bacteria are potentialto improveplant health and also asbio-control agentwhich then willaffect to the productivity of rice. To further ensure its potential to plant, more research is needed.

  17. Actinorhizal Alder Phytostabilization Alters Microbial Community Dynamics in Gold Mine Waste Rock from Northern Quebec: A Greenhouse Study.

    Science.gov (United States)

    Callender, Katrina L; Roy, Sébastien; Khasa, Damase P; Whyte, Lyle G; Greer, Charles W

    2016-01-01

    Phytotechnologies are rapidly replacing conventional ex-situ remediation techniques as they have the added benefit of restoring aesthetic value, important in the reclamation of mine sites. Alders are pioneer species that can tolerate and proliferate in nutrient-poor, contaminated environments, largely due to symbiotic root associations with the N2-fixing bacteria, Frankia and ectomycorrhizal (ECM) fungi. In this study, we investigated the growth of two Frankia-inoculated (actinorhizal) alder species, A. crispa and A. glutinosa, in gold mine waste rock from northern Quebec. Alder species had similar survival rates and positively impacted soil quality and physico-chemical properties in similar ways, restoring soil pH to neutrality and reducing extractable metals up to two-fold, while not hyperaccumulating them into above-ground plant biomass. A. glutinosa outperformed A. crispa in terms of growth, as estimated by the seedling volume index (SVI), and root length. Pyrosequencing of the bacterial 16S rRNA gene for bacteria and the ribosomal internal transcribed spacer (ITS) region for fungi provided a comprehensive, direct characterization of microbial communities in gold mine waste rock and fine tailings. Plant- and treatment-specific shifts in soil microbial community compositions were observed in planted mine residues. Shannon diversity and the abundance of microbes involved in key ecosystem processes such as contaminant degradation (Sphingomonas, Sphingobium and Pseudomonas), metal sequestration (Brevundimonas and Caulobacter) and N2-fixation (Azotobacter, Mesorhizobium, Rhizobium and Pseudomonas) increased over time, i.e., as plants established in mine waste rock. Acetate mineralization and most probable number (MPN) assays showed that revegetation positively stimulated both bulk and rhizosphere communities, increasing microbial density (biomass increase of 2 orders of magnitude) and mineralization (five-fold). Genomic techniques proved useful in investigating

  18. 16S rDNA PCR-RFLP analysis and phylogeny of bacteria isolated from swamp and meadow aeolian soils in the Zoige Plateau, Sichuan, China%若尔盖高原沼泽土和草甸风沙土细菌16S rDNA PCR-RFLP和系统发育分析

    Institute of Scientific and Technical Information of China (English)

    张可; 陈强; 赵珂; 王文跃; 朱雪梅

    2010-01-01

    采用稀释平板法从若尔盖高原沼泽土和草甸风沙土分离获得66株细菌,在16S rDNA PCR-RFLP分析的基础上,测定了22株代表菌株的16S rDNA序列,构建了供试细菌的系统发育关系.16S rDNA PCR-RFLP分析中,在78%相似性水平处,除REG14,REG20,REG22和REG55单独成群外,其余菌株分为8个遗传群,其中,群Ⅰ和群Ⅳ最大,均有15个菌株,其次是群Ⅷ,由11个菌株组成,其余21个菌株分布于5个群内.对22个代表菌株16S rDNA全序列系统发育表明,这些菌株分布于不同的系统发育分支.其中,以芽孢杆菌属(Bacillus)、假单胞菌属(Pseudomonas)和分枝杆菌属(Mycobacterium)为主,其余菌株分布于Lysinibacillus属、中华根瘤菌属(Sinorhizobium)、不动杆菌(Acinetobacter)、固氮菌属(Azotobacter)、红球菌属(Rhodococcus)、微球菌属(Micrococcus)和醋酸杆菌属(Acetobacter)等7个属.

  19. Fate of nitrogen-fixing bacteria in crude oil contaminated wetland ultisol.

    Science.gov (United States)

    John, R C; Itah, A Y; Essien, J P; Ikpe, D I

    2011-09-01

    The effect of crude oil on the growth of legumes (Calopogonium muconoides and Centrosema pubescens) and fate of nitrogen-fixing bacteria in wetland ultisol was investigated using standard cultural techniques. The results revealed observable effects of oil on soil physico-chemistry, plant growth and nodulation as well as on densities of heterotrophic, hydrocarbonoclastic and nitrogen fixing bacteria. The effects however varied with different levels (0.5%, 1%, 5%, 10%, 15% and 20%) of pollution. Ammonium and nitrate levels were high in the unpolluted soil but decreased with increase in pollution levels. Nitrite was not detected in contaminated soil probably due to the reduction in numbers of nitrogen fixers, from 5.26 ± 0.23 × l0(6)cfu/g in unpolluted soil to 9.0 ± 0.12 × 10(5) and 2.2 ± 0.08 × l0(5) cfu/g in soils with 5% and 20% levels of pollution respectively. The contaminated soil also exhibited gross reduction in the nodulation of legumes. A range of 13-57 nodules was observed in legumes from polluted soil against 476 nodules recorded for plants cultured on unpolluted soil. The heterogeneity of the microbial loads between oil-polluted and unpolluted soil were statistically significant (p oil seriously affects rhizosphere microbial growth in legumes. Among the bacterial species isolated, Clostridium pasteurianum, Bacillus polymyxa and Pseudomonas aeruginosa exhibited greater ability to degrade hydrocarbons than Azotobacter sp, Klebsiella pneumoniae and Derxia gummusa while Nitrosomonas and Nitrobacter had the least degradability. A continuous monitoring of the environment is advocated to prevent extinction of nitrogen-fixing bacteria and total loss of soil fertility attributable to petroleum hydrocarbon contamination in the Niger Delta ultisol. PMID:21755289

  20. Microbial and enzymatic activity of soil contaminated with a mixture of diflufenican + mesosulfuron-methyl + iodosulfuron-methyl-sodium.

    Science.gov (United States)

    Baćmaga, Małgorzata; Borowik, Agata; Kucharski, Jan; Tomkiel, Monika; Wyszkowska, Jadwiga

    2015-01-01

    The aim of this study was to determine the effect of three active substances, diflufenican, mesosulfuron-methyl and iodosulfuron-methyl-sodium, applied in combination, on soil microbial counts, the structure of soil microbial communities, activity of soil enzymes and their resistance to the tested product, the biochemical indicator of soil fertility, and spring wheat yield. Soil samples with the granulometric composition of sandy loam with pHKCl 7.0 were used in a pot experiment. The herbicide was applied to soil at seven doses: 0.057 (dose recommended by the manufacturer), 1.140, 2.280, 4.560, 9.120, 18.240 and 36.480 mg kg(-1) soil DM. Uncontaminated soil served as the control treatment. It was found that a mixture of the tested active substances increased the counts of total oligotrophic bacteria and spore-forming oligotrophic bacteria, organotrophic bacteria and actinomycetes, decreased the counts of Azotobacter and fungi, and modified the structure of soil microbial communities. The highest values of the colony development (CD) index and the ecophysiological (EP) index were observed in fungi and organotrophic bacteria, respectively. The herbicide applied in the recommended dose stimulated the activity of catalase, urease and acid phosphatase, but it had no effect on the activity of dehydrogenases, alkaline phosphatase, arylsulfatase and β-glucosidase. The highest dose of the analyzed substances (36.480 mg kg(-1)) significantly inhibited the activity of dehydrogenases, acid phosphatase, alkaline phosphatase and arylsulfatase. The values of the biochemical soil fertility indicator (BA21) decreased in response to high doses of the herbicide. Urease was most resistant and dehydrogenases were least resistant to soil contamination with a mixture of diflufenican + mesosulfuron-methyl + iodosulfuron-methyl-sodium. The analyzed herbicide had an adverse influence on spring wheat yield, and doses of 18.240 and 36.480 mg kg(-1) led to eventual death of plants.

  1. NifX and NifEN exchange NifB cofactor and the VK-cluster, a newly isolated intermediate of the iron-molybdenum cofactor biosynthetic pathway.

    Science.gov (United States)

    Hernandez, Jose A; Igarashi, Robert Y; Soboh, Basem; Curatti, Leonardo; Dean, Dennis R; Ludden, Paul W; Rubio, Luis M

    2007-01-01

    The iron-molybdenum cofactor of nitrogenase (FeMo-co) is synthesized in a multistep process catalysed by several Nif proteins and is finally inserted into a pre-synthesized apo-dinitrogenase to generate mature dinitrogenase protein. The NifEN complex serves as scaffold for some steps of this synthesis, while NifX belongs to a family of small proteins that bind either FeMo-co precursors or FeMo-co during cofactor synthesis. In this work, the binding of FeMo-co precursors and their transfer between purified Azotobacter vinelandii NifX and NifEN proteins was studied to shed light on the role of NifX on FeMo-co synthesis. Purified NifX binds NifB cofactor (NifB-co), a precursor to FeMo-co, with high affinity and is able to transfer it to the NifEN complex. In addition, NifEN and NifX exchange another [Fe-S] cluster that serves as a FeMo-co precursor, and we have designated it as the VK-cluster. In contrast to NifB-co, the VK-cluster is electronic paramagnetic resonance (EPR)-active in the reduced and the oxidized states. The NifX/VK-cluster complex is unable to support in vitro FeMo-co synthesis in the absence of NifEN because further processing of the VK-cluster into FeMo-co requires the simultaneous activities of NifEN and NifH. Our in vitro studies suggest that the role of NifX in vivo is to serve as transient reservoir of FeMo-co precursors and thus help control their flux during FeMo-co synthesis. PMID:17163967

  2. Functional analysis of the cysteine motifs in the ferredoxin-like protein FdxN of Rhizobium meliloti involved in symbiotic nitrogen fixation.

    Science.gov (United States)

    Masepohl, B; Kutsche, M; Riedel, K U; Schmehl, M; Klipp, W; Pühler, A

    1992-05-01

    The Rhizobium meliloti fdxN gene, which is part of the nifA-nifB-fdxN operon, is absolutely required for symbiotic nitrogen fixation. The deduced sequence of the FdxN protein is characterized by two cysteine motifs typical of bacterial-type ferredoxins. The Fix-phenotype of an R. meliloti fdxN::[Tc] mutant could be rescued by the R. leguminosarum fdxN gene, whereas no complementation was observed with nif-associated genes encoding ferredoxins from Bradyrhizobium japonicum, Azotobacter vinelandii, A. chroococcum and Rhodobacter capsulatus. In addition to these heterologous genes, several R. meliloti fdxN mutant genes constructed by site-directed mutagenesis were analyzed. Not only a cysteine residue within the second cysteine motif (position 42), which is known to coordinate the Fe-S cluster in homologous proteins, but also a cysteine located down-stream of this motif (position 61), was found to be essential for the activity of the R. meliloti FdxN protein. Changing the amino acid residue proline in position 56 into methionine resulted in a FdxN mutant protein with decreased activity, whereas changes in positions 35 (Asp35Glu) and 45 (Gly45Glu) had no significant effect on the function of the FdxN mutant proteins. In contrast to bacterial-type ferredoxins, which contain two identical cysteine motifs of the form C-X2-C-X2-C-X3-C, nif-associated ferredoxins, including R. meliloti FdxN, are characterized by two different cysteine motifs. Six "additional" amino acids separate the second (Cys42) and the third cysteine (Cys51) in the C-terminal motif (C-X2-C-X8-C-X3-C).(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1603075

  3. Regulation of nif gene expression in Enterobacter agglomerans: nucleotide sequence of the nifLA operon and influence of temperature and ammonium on its transcription.

    Science.gov (United States)

    Siddavattam, D; Steibl, H D; Kreutzer, R; Klingmüller, W

    1995-12-20

    The nucleotide sequence of a plasmid-borne 3.9 kb XhoI-SmaI fragment comprising the 3'-region of the nifM gene, the nifL and nifA genes and the 5'-region of nifB gene of Enterobacter agglomerans was determined. The genes were identified by their homology to the corresponding nif genes of Klebsiella pneumoniae. A typical sigma 54-dependent promoter and a consensus NtrC-binding motif were identified upstream of nifL. The predicted amino acid sequence of NifL showed close similarities to NifL of K. pneumoniae and Azotobacter vinelandii. However, no histidine residue was found to correspond to histidine-304 of A. vinelandii NifL, which had been proposed to be required for the repressor activity of NifL. The NifA sequence with a putative DNA binding motif (Q(x3) A(x3) G(x5)I) and an ATP binding site in the C-terminal and central domains, respectively, resembles that of other known NifA proteins. The function of the nifL and nifA genes was demonstrated in vivo using a binary plasmid system by their ability to activate a nifH promoter-lacZ fusion at different temperatures and concentrations of NH4+. Maximal promoter activity occurred at 25 degrees C, and it appears that the sensitivity of NifA to elevated temperatures is independent of NifL. The expression of nifL inhibited promoter activity in the presence of NifA when the initial NH4+ concentration in the medium exceeded 4 mM. PMID:8544828

  4. N2和H+在固氮酶活性中心金属原子簇中还原位点的分析

    Institute of Scientific and Technical Information of China (English)

    关锋; 赵德华; 潘淼; 姜伟; 李季伦

    2007-01-01

    目前研究表明,固氮酶的生理底物氮气(N2)和质子(H+)在钼铁蛋白中的铁钼辅因子(FeMo-co、)上被还原,但其确切的还原位点尚未确定.对比分析了棕色固氮菌(Azotobacter vinelandii,Av)野生型(WT)与 5 种突变株(包括FeMo-co附近 2 个保守氨基酸α-191Gln 和α-195His 单突变菌株(Qα191K 和 Hα195Q)、FeMo-co 上钼原子相连的高柠檬酸突变株(nifv-)以及α-191Gln 和α-195Hns 与高柠檬酸的双突变菌株(Qα191K/nif-和 Hα195Q/nifv-))固氮酶催化还原 N2 和 H+活性的变化,结果表明,N2 在靠近 FeMo-co中心硫原子(S2B)的 Fe2 和 Fe6 上络合和还原,FeMo-co 上的钼原子是 H+还原的位点.结合生物信息学分析结果显示,[8Fe7S] 和 FeMo-co 之间可能存在两条平行的电子传递通路.

  5. Relative susceptibility and transcriptional response of nitrogen cycling bacteria to quantum dots.

    Science.gov (United States)

    Yang, Yu; Wang, Jing; Zhu, Huiguang; Colvin, Vicki L; Alvarez, Pedro J

    2012-03-20

    Little is known about the potential impacts of accidental or incidental releases of manufactured nanomaterials to microbial ecosystem services (e.g., nutrient cycling). Here, quantum dots (QDs) coated with cationic polyethylenimine (PEI) were more toxic to pure cultures of nitrogen-cycling bacteria than QDs coated with anionic polymaleic anhydride-alt-1-octadecene (PMAO). Nitrifying bacteria (i.e., Nitrosomonas europaea) were much more susceptible than nitrogen fixing (i.e., Azotobacter vinelandii, Rhizobium etli, and Azospirillum lipoferum) and denitrifying bacteria (i.e., Pseudomonas stutzeri). Antibacterial activity was mainly exerted by the QDs rather than by their organic coating or their released QD components (e.g., Cd and Zn), which under the near-neutral pH tested (to minimize QD weathering) were released into the bacterial growth media at lower levels than their minimum inhibitory concentrations. Sublethal exposure to QDs stimulated the expression of genes associated with nitrogen cycling. QD-PEI (10 nM) induced three types of nitrogenase genes (nif, anf, and vnf) in A. vinelandii, and one ammonia monooxygenase gene (amoA) in N. europaea was up-regulated upon exposure to 1 nM QD-PEI. We previously reported up-regulation of denitrification genes in P. stutzeri exposed to low concentrations of QD-PEI. (1) Whether this surprising stimulation of nitrogen cycling activities reflects the need to generate more energy to overcome toxicity (in the case of nitrification or denitrification) or to synthesize organic nitrogen to repair or replace damaged proteins (in the case of nitrogen fixation) remains to be determined. PMID:22360857

  6. Requirement of NifX and other nif proteins for in vitro biosynthesis of the iron-molybdenum cofactor of nitrogenase.

    Science.gov (United States)

    Shah, V K; Rangaraj, P; Chatterjee, R; Allen, R M; Roll, J T; Roberts, G P; Ludden, P W

    1999-05-01

    The iron-molybdenum cofactor (FeMo-co) of nitrogenase contains molybdenum, iron, sulfur, and homocitrate in a ratio of 1:7:9:1. In vitro synthesis of FeMo-co has been established, and the reaction requires an ATP-regenerating system, dithionite, molybdate, homocitrate, and at least NifB-co (the metabolic product of NifB), NifNE, and dinitrogenase reductase (NifH). The typical in vitro FeMo-co synthesis reaction involves mixing extracts from two different mutant strains of Azotobacter vinelandii defective in the biosynthesis of cofactor or an extract of a mutant strain complemented with the purified missing component. Surprisingly, the in vitro synthesis of FeMo-co with only purified components failed to generate significant FeMo-co, suggesting the requirement for one or more other components. Complementation of these assays with extracts of various mutant strains demonstrated that NifX has a role in synthesis of FeMo-co. In vitro synthesis of FeMo-co with purified components is stimulated approximately threefold by purified NifX. Complementation of these assays with extracts of A. vinelandii DJ42. 48 (DeltanifENX DeltavnfE) results in a 12- to 15-fold stimulation of in vitro FeMo-co synthesis activity. These data also demonstrate that apart from the NifX some other component(s) is required for the cofactor synthesis. The in vitro synthesis of FeMo-co with purified components has allowed the detection, purification, and identification of an additional component(s) required for the synthesis of cofactor. PMID:10217770

  7. The N-terminal and C-terminal portions of NifV are encoded by two different genes in Clostridium pasteurianum.

    Science.gov (United States)

    Wang, S Z; Dean, D R; Chen, J S; Johnson, J L

    1991-05-01

    The nifV gene products from Azotobacter vinelandii and Klebsiella pneumoniae share a high level of primary sequence identity and are proposed to catalyze the synthesis of homocitrate. While searching for potential nif (nitrogen fixation) genes within the genomic region located downstream from the nifN-B gene of Clostridium pasteurianum, we observed two open reading frames (ORFs) whose deduced amino acid sequences exhibit nonoverlapping sequence identity to different portions of the nifV gene products from A. vinelandii and K. pneumoniae. Conserved regions were located between the C-terminal 195 amino acid residues of the first ORF and the C-terminal portion of the nifV gene product and between the entire sequence of the second ORF (269 amino acid residues) and the N-terminal portion of the nifV gene product. We therefore designated the first ORF nifV omega and the second ORF nifV alpha. The deduced amino acid sequences of nifV omega and nifV alpha were also found to have sequence similarity when compared with the primary sequence of the leuA gene product from Salmonella typhimurium, which encodes alpha-isopropylmalate synthase. Marker rescue experiments were performed by recombining nifV omega and nifV alpha from C. pasteurianum, singly and in combination, into the genome of an A. vinelandii mutant strain which has an insertion and a deletion mutation located within its nifV gene. A NifV+ phenotype was obtained only when both the C. pasteurianum nifV omega and nifV alpha genes were introduced into the chromosome of this mutant strain. These results suggest that the nifV omega and nifV alpha genes encode separate domains, both of which are required for homocitrate synthesis in C. pasteurianum. PMID:2022611

  8. DNA sequence and genetic analysis of the Rhodobacter capsulatus nifENX gene region: homology between NifX and NifB suggests involvement of NifX in processing of the iron-molybdenum cofactor.

    Science.gov (United States)

    Moreno-Vivian, C; Schmehl, M; Masepohl, B; Arnold, W; Klipp, W

    1989-04-01

    Rhodobacter capsulatus genes homologous to Klebsiella pneumoniae nifE, nifN and nifX were identified by DNA sequence analysis of a 4282 bp fragment of nif region A. Four open reading frames coding for a 51,188 (NifE), a 49,459 (NifN), a 17,459 (NifX) and a 17,472 (ORF4) dalton protein were detected. A typical NifA activated consensus promoter and two imperfect putative NifA binding sites were located in the 377 bp sequence in front of the nifE coding region. Comparison of the deduced amino acid sequences of R. capsulatus NifE and NifN revealed homologies not only to analogous gene products of other organisms but also to the alpha and beta subunits of the nitrogenase iron-molybdenum protein. In addition, the R. capsulatus nifE and nifN proteins shared considerable homology with each other. The map position of nifX downstream of nifEN corresponded in R. capsulatus and K. pneumoniae and the deduced molecular weights of both proteins were nearly identical. Nevertheless, R. capsulatus NifX was more related to the C-terminal end of NifY from K. pneumoniae than to NifX. A small domain of approximately 33 amino acid residues showing the highest degree of homology between NifY and NifX was also present in all nifB proteins analyzed so far. This homology indicated an evolutionary relationship of nifX, nifY and nifB and also suggested that NifX and NifY might play a role in maturation and/or stability of the iron-molybdenum cofactor. The open reading frame (ORF4) downstream of nifX in R. capsulatus is also present in Azotobacter vinelandii but not in K. pneumoniae.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2747620

  9. Reconstruction and minimal gene requirements for the alternative iron-only nitrogenase in Escherichia coli

    Science.gov (United States)

    Yang, Jianguo; Xie, Xiaqing; Wang, Xia; Dixon, Ray; Wang, Yi-Ping

    2014-01-01

    All diazotrophic organisms sequenced to date encode a molybdenum-dependent nitrogenase, but some also have alternative nitrogenases that are dependent on either vanadium (VFe) or iron only (FeFe) for activity. In Azotobacter vinelandii, expression of the three different types of nitrogenase is regulated in response to metal availability. The majority of genes required for nitrogen fixation in this organism are encoded in the nitrogen fixation (nif) gene clusters, whereas genes specific for vanadium- or iron-dependent diazotophy are encoded by the vanadium nitrogen fixation (vnf) and alternative nitrogen fixation (anf) genes, respectively. Due to the complexities of metal-dependent regulation and gene redundancy in A. vinelandii, it has been difficult to determine the precise genetic requirements for alternative nitrogen fixation. In this study, we have used Escherichia coli as a chassis to build an artificial iron-only (Anf) nitrogenase system composed of defined anf and nif genes. Using this system, we demonstrate that the pathway for biosynthesis of the iron-only cofactor (FeFe-co) is likely to be simpler than the pathway for biosynthesis of the molybdenum-dependent cofactor (FeMo-co) equivalent. A number of genes considered to be essential for nitrogen fixation by FeFe nitrogenase, including nifM, vnfEN, and anfOR, are not required for the artificial Anf system in E. coli. This finding has enabled us to engineer a minimal FeFe nitrogenase system comprising the structural anfHDGK genes and the nifBUSV genes required for metallocluster biosynthesis, with nifF and nifJ providing electron transport to the alternative nitrogenase. This minimal Anf system has potential implications for engineering diazotrophy in eukaryotes, particularly in compartments (e.g., organelles) where molybdenum may be limiting. PMID:25139995

  10. Purification and characterization of a FeMo cofactor-deficient MoFe protein.

    Science.gov (United States)

    Gavini, N; Ma, L; Watt, G; Burgess, B K

    1994-10-01

    Previous studies have shown that the nifH gene product is required for FeMo cofactor biosynthesis and insertion and that a delta nifH strain of Azotobacter vinelandii designated DJ54 accumulates a FeMo cofactor-deficient MoFe protein that is distinct from the FeMo cofactor-deficient protein synthesis by Nif B-, N-, or E- strains [Tal, S., Chun, T., Gavini, N., & Burgess, B. K. (1991) J. Biol. Chem. 266, 10654-10657]. Here we report the purification and activation of the MoFe protein from DJ54. The purified protein is an alpha 2 beta 2 tetramer that is indistinguishable from the wild-type MoFe protein by the criteria of SDS-polyacrylamide gel electrophoresis, native gel electrophoresis, and two-dimensional gel electrophoresis. It binds normally to its redox partner, the Fe protein, by the criterion of chemical cross-linking. It does not contain FeMo cofactor and does not catalyze significant C2H2 reduction or reduction-independent MgATP hydrolysis. It can, however, be activated with FeMo cofactor following the addition of the Fe protein and MgATP when an additional required component(s) is supplied by cell-free extracts from a delta nifD strain of A. vinelandii. The purified DJ54 MoFe protein does contain P-clusters by the criteria of metal analysis, CD spectroscopy, cluster extrusion, and electrochemical reduction of the POX state. In the presence of dithionite it exhibits an axial S = 1/2 EPR signal that integrates to 0.1-0.3 spin per alpha 2 beta 2 tetramer.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7918402

  11. 100th American society for microbiology annual meeting.

    Science.gov (United States)

    Zawadzke, L; Thanassi, J; Pucci, M; Dougherty, T; Barrett, J F

    2000-08-01

    The 100th ASM Annual Meeting, attended by approximately 10,000 delegates, continued the trend of concentrating on bacteria and antibacterial therapy, mixed with genomics and a diverse number of additional topics. Of the various marketable drug classes, the quinolones received attention with respect to susceptibility studies and several drug comparison studies. New marketable drugs were also of interest, especially given the reservoirs of resistance presented by several speakers. Drugs in development include the antibacterial daptomycin and protegrins and the antifungal lipodepsinonapeptides and echinocandins, to name a few. It is still unclear whether or not antibiotic treatment regimens for Chlamydia pneumonia will he necessary, as association of this bacteria with several chronic diseases, such as atherosclerosis and asthma, was discussed. The development of novel antibiotics was highlighted and the potential role that microbial genomics technology could play was a recurring theme. In fact, a number of symposia treated the increasingly popular topic of genomics in a variety of themes, including phenotyping arrays, transcriptional profiling, proteomics, expression profiling, genome sequencing, target areas or essentiality of genes via gene knockout systems, the role of genomics in pharmaceutical development and fungal genomics. Similarly, genomics plays a role in developing a deeper appreciation for classical areas of interest in microbial physiology, such as gene regulation, cell division, fatty acid biosynthesis, DNA replication and cell signalling. Even in the bio-inorganic field of study in microbial metabolite activation, genomics plays a role. The sequencing of the large gene clusters of the auxiliary proteins necessary to synthesise or activate the metallo-proteins provided insights into the mechanisms of activation of these microbial enzymes, including the genes for the nif gene cluster in Azotobacter vinelandii, the urease from Kiebsiella aerogenes and

  12. Electron donation to the flavoprotein NifL, a redox-sensing transcriptional regulator.

    Science.gov (United States)

    Macheroux, P; Hill, S; Austin, S; Eydmann, T; Jones, T; Kim, S O; Poole, R; Dixon, R

    1998-06-01

    Transcriptional control of the nitrogen fixation (nif) genes in response to oxygen in Azotobacter vinelandii is mediated by nitrogen fixation regulatory protein L (NifL), a regulatory flavoprotein that modulates the activity of the transcriptional activator nitrogen fixation regulatory protein A (NifA). CD spectra of purified NifL indicate that FAD is bound to NifL in an asymmetric environment and the protein is predominantly alpha-helical. The redox potential of NifL is -226 mV at pH 8 as determined by the enzymic reduction of NifL by xanthine oxidase/xanthine in the presence of appropriate mediators. The reduction of NifL by xanthine oxidase prevented NifL from acting as an inhibitor of NifA. In the absence of electron mediators NifL could also be reduced by Escherichia coli flavohaemoprotein (Hmp) with NADH as reductant. Hmp contains a globin-like domain with haem B as prosthetic group and an FAD-containing oxidoreductase module. The carboxyferrohaem form of Hmp was competent to reduce NifL, suggesting that electron donation to NifL originates from the flavin in Hmp rather than by direct electron transfer from the haem. Spinach ferredoxin:NAD(P) oxidoreductase, which adopts a folding similar to the FAD- and NAD-binding domains of Hmp, also reduced NifL with NADH as reductant. Re-oxidation of NifL occurs rapidly in the presence of air, raising the possibility that NifL might sense intracellular oxygen. We propose a physiological redox cycle in which the oxidation of NifL by oxygen and hence the activation of its inhibitory properties occurs rapidly, in contrast with the switch from the active to the reduced form of NifL, which occurs more slowly. PMID:9601070

  13. Reconstruction and minimal gene requirements for the alternative iron-only nitrogenase in Escherichia coli.

    Science.gov (United States)

    Yang, Jianguo; Xie, Xiaqing; Wang, Xia; Dixon, Ray; Wang, Yi-Ping

    2014-09-01

    All diazotrophic organisms sequenced to date encode a molybdenum-dependent nitrogenase, but some also have alternative nitrogenases that are dependent on either vanadium (VFe) or iron only (FeFe) for activity. In Azotobacter vinelandii, expression of the three different types of nitrogenase is regulated in response to metal availability. The majority of genes required for nitrogen fixation in this organism are encoded in the nitrogen fixation (nif) gene clusters, whereas genes specific for vanadium- or iron-dependent diazotophy are encoded by the vanadium nitrogen fixation (vnf) and alternative nitrogen fixation (anf) genes, respectively. Due to the complexities of metal-dependent regulation and gene redundancy in A. vinelandii, it has been difficult to determine the precise genetic requirements for alternative nitrogen fixation. In this study, we have used Escherichia coli as a chassis to build an artificial iron-only (Anf) nitrogenase system composed of defined anf and nif genes. Using this system, we demonstrate that the pathway for biosynthesis of the iron-only cofactor (FeFe-co) is likely to be simpler than the pathway for biosynthesis of the molybdenum-dependent cofactor (FeMo-co) equivalent. A number of genes considered to be essential for nitrogen fixation by FeFe nitrogenase, including nifM, vnfEN, and anfOR, are not required for the artificial Anf system in E. coli. This finding has enabled us to engineer a minimal FeFe nitrogenase system comprising the structural anfHDGK genes and the nifBUSV genes required for metallocluster biosynthesis, with nifF and nifJ providing electron transport to the alternative nitrogenase. This minimal Anf system has potential implications for engineering diazotrophy in eukaryotes, particularly in compartments (e.g., organelles) where molybdenum may be limiting. PMID:25139995

  14. FeMo cofactor synthesis by a nifH mutant with altered MgATP reactivity.

    Science.gov (United States)

    Gavini, N; Burgess, B K

    1992-10-15

    We have characterized a Nif- mutant of Azotobacter vinelandii, designated UW91 (Shah, V. K., Davis, L. C., Gordon, J. K., Orme-Johnson, W. H., and Brill, W. J. (1973) Biochim. Biophys. Acta 292, 246-255). The specific Fe protein mutation giving rise to the Nif- phenotype was shown by DNA sequencing and site-directed mutagenesis to be the substitution of a conserved alanine at position 157 by a serine. The UW91 Fe protein was purified and shown to have a normal [4Fe-4S] cluster and normal MgATP binding activity. The substitution of alanine 157 by serine, however, prevents the MgATP-induced conformational change that occurs for the wild-type Fe protein, prevents MgATP hydrolysis, and prevents productive electron transfer to the MoFe protein. The UW91 Fe protein does bind to the MoFe protein to give a normal cross-linking pattern; however, it does not compete very successfully with wild-type Fe protein in an activity assay. The UW91 MoFe protein was also purified and characterized and shown to be indistinguishable from the wild-type protein. Thus, the substitution of Fe protein residue alanine 157 by serine does not change the Fe protein's ability to function in FeMo cofactor biosynthesis or insertion. This demonstrates that these events do not require the MgATP-induced conformational change, MgATP hydrolysis, or productive electron transfer to the MoFe protein. PMID:1400428

  15. GlnD is essential for NifA activation, NtrB/NtrC-regulated gene expression, and posttranslational regulation of nitrogenase activity in the photosynthetic, nitrogen-fixing bacterium Rhodospirillum rubrum.

    Science.gov (United States)

    Zhang, Yaoping; Pohlmann, Edward L; Roberts, Gary P

    2005-02-01

    GlnD is a bifunctional uridylyltransferase/uridylyl-removing enzyme and is thought to be the primary sensor of nitrogen status in the cell. It plays an important role in nitrogen assimilation and metabolism by reversibly regulating the modification of P(II) proteins, which in turn regulate a variety of other proteins. We report here the characterization of glnD mutants from the photosynthetic, nitrogen-fixing bacterium Rhodospirillum rubrum and the analysis of the roles of GlnD in the regulation of nitrogen fixation. Unlike glnD mutations in Azotobacter vinelandii and some other bacteria, glnD deletion mutations are not lethal in R. rubrum. Such mutants grew well in minimal medium with glutamate as the sole nitrogen source, although they grew slowly with ammonium as the sole nitrogen source (MN medium) and were unable to fix N(2). The slow growth in MN medium is apparently due to low glutamine synthetase activity, because a DeltaglnD strain with an altered glutamine synthetase that cannot be adenylylated can grow well in MN medium. Various mutation and complementation studies were used to show that the critical uridylyltransferase activity of GlnD is localized to the N-terminal region. Mutants with intermediate levels of uridylyltransferase activity are differentially defective in nif gene expression, the posttranslational regulation of nitrogenase, and NtrB/NtrC function, indicating the complexity of the physiological role of GlnD. These results have implications for the interpretation of results obtained with GlnD in many other organisms. PMID:15687189

  16. Controlled expression of nif and isc iron-sulfur protein maturation components reveals target specificity and limited functional replacement between the two systems.

    Science.gov (United States)

    Dos Santos, Patricia C; Johnson, Deborah C; Ragle, Brook E; Unciuleac, Mihaela-Carmen; Dean, Dennis R

    2007-04-01

    The nitrogen-fixing organism Azotobacter vinelandii contains at least two systems that catalyze formation of [Fe-S] clusters. One of these systems is encoded by nif genes, whose products supply [Fe-S] clusters required for maturation of nitrogenase. The other system is encoded by isc genes, whose products are required for maturation of [Fe-S] proteins that participate in general metabolic processes. The two systems are similar in that they include an enzyme for the mobilization of sulfur (NifS or IscS) and an assembly scaffold (NifU or IscU) upon which [Fe-S] clusters are formed. Normal cellular levels of the Nif system, which supplies [Fe-S] clusters for the maturation of nitrogenase, cannot also supply [Fe-S] clusters for the maturation of other cellular [Fe-S] proteins. Conversely, when produced at the normal physiological levels, the Isc system cannot supply [Fe-S] clusters for the maturation of nitrogenase. In the present work we found that such target specificity for IscU can be overcome by elevated production of NifU. We also found that NifU, when expressed at normal levels, is able to partially replace the function of IscU if cells are cultured under low-oxygen-availability conditions. In contrast to the situation with IscU, we could not establish conditions in which the function of IscS could be replaced by NifS. We also found that elevated expression of the Isc components, as a result of deletion of the regulatory iscR gene, improved the capacity for nitrogen-fixing growth of strains deficient in either NifU or NifS. PMID:17237162

  17. Cloning, expression, purification, crystallization and preliminary crystallographic analysis of NifH1 from Methanocaldococcus jannaschii

    International Nuclear Information System (INIS)

    Solving the structure of MjNifH1 may help in better understanding its function and may supply some clues to understanding the evolution of nitrogenase. The full-length protein with an additional His6 tag at the C-terminus was expressed, purified and crystallized by the hanging-drop vapour-diffusion method at 287 K. Nitrogen fixation is catalyzed by the nitrogenase complex in Azotobacter, which is composed of dinitrogenase and dinitrogenase reductase. Dinitrogenase is an α2β2 heterotetramer of the proteins NifD and NifK. Dinitrogenase reductase is a homodimer of the protein NifH. The expression of NifD/K and NifH nitrogenase homologues (named NflD/K and NflH for Nif-like D and H, respectively) has been detected in the non-nitrogen-fixing hyperthermophilic methanogen Methanocaldococcus jannaschii. Solving the structure of MjNifH1 may help in better understanding its function and may supply some clues to understanding the evolution of nitrogenase. The full-length protein with an additional His6 tag at the C-terminus was expressed, purified and crystallized by the hanging-drop vapour-diffusion method at 287 K. An X-ray diffraction data set was collected to a resolution of 3.3 Å. The crystal belonged to space group P4132, with unit-cell parameters a = b = c = 139.45 Å, and was estimated to contain one protein molecule per asymmetric unit

  18. Pseudomonas fluorescens F113 Can Produce a Second Flagellar Apparatus, Which Is Important for Plant Root Colonization

    Science.gov (United States)

    Barahona, Emma; Navazo, Ana; Garrido-Sanz, Daniel; Muriel, Candela; Martínez-Granero, Francisco; Redondo-Nieto, Miguel; Martín, Marta; Rivilla, Rafael

    2016-01-01

    The genomic sequence of Pseudomonas fluorescens F113 has shown the presence of a 41 kb cluster of genes that encode the production of a second flagellar apparatus. Among 2,535 pseudomonads strains with sequenced genomes, these genes are only present in the genomes of F113 and other six strains, all but one belonging to the P. fluorescens cluster of species, in the form of a genetic island. The genes are homologous to the flagellar genes of the soil bacterium Azotobacter vinelandii. Regulation of these genes is mediated by the flhDC master operon, instead of the typical regulation in pseudomonads, which is through fleQ. Under laboratory conditions, F113 does not produce this flagellum and the flhDC operon is not expressed. However, ectopic expression of the flhDC operon is enough for its production, resulting in a hypermotile strain. This flagellum is also produced under laboratory conditions by the kinB and algU mutants. Genetic analysis has shown that kinB strongly represses the expression of the flhDC operon. This operon is activated by the Vfr protein probably in a c-AMP dependent way. The strains producing this second flagellum are all hypermotile and present a tuft of polar flagella instead of the single polar flagellum produced by the wild-type strain. Phenotypic variants isolated from the rhizosphere produce this flagellum and mutation of the genes encoding it, results in a defect in competitive colonization, showing its importance for root colonization. PMID:27713729

  19. Characterization of algG encoding C5-epimerase in the alginate biosynthetic gene cluster of Pseudomonas fluorescens.

    Science.gov (United States)

    Morea, A; Mathee, K; Franklin, M J; Giacomini, A; O'Regan, M; Ohman, D E

    2001-10-31

    The organization of the alginate gene cluster in Pseudomonas fluorescens was characterized. A bank of genomic DNA from P. fluorescens was mobilized to a strain of Pseudomonas aeruginosa with a transposon insertion (algJ::Tn501) in the alginate biosynthetic operon that rendered it non-mucoid. Phenotypic complementation in this heterologous host was observed, and a complementing clone containing 32 kb of P. fluorescens DNA was obtained. Southern hybridization studies showed that genes involved in alginate biosynthesis (e.g. algD, algG, and algA) were approximately in the same order and position as in P. aeruginosa. When the clone was mobilized to a P. aeruginosa algG mutant that produced alginate as polymannuronate due to its C5-epimerase defect, complementation was observed and the alginate from the recombinant strain contained L-guluronate as determined by proton nuclear magnetic resonance spectroscopy. A sequence analysis of the P. fluorescens DNA containing algG revealed sequences similar to P. aeruginosa algG that were also flanked by algE- and algX-like sequences. The predicted AlgG amino acid sequence of P. fluorescens was 67% identical (80% similar) to P. aeruginosa AlgG and 60% identical (76% similar) to Azotobacter vinelandii AlgG. As in P. aeruginosa, AlgG from P. fluorescens appeared to have a signal sequence that would localize it to the periplasm where AlgG presumably acts as a C5-epimerase at the polymer level. Non-polar algG knockout mutants of P. fluorescens were defective in alginate production, suggesting a potential role for this protein in polymer formation.

  20. 转DREB基因大豆东农50对土壤氮素转化菌数量及生化强度的影响%Effect of Transgenic Soybean "Dongnong 50" with DREB Gene on Number of Soil Nitrogen Transforming Bacteria and Biochemical Intensity

    Institute of Scientific and Technical Information of China (English)

    董蕾; 任广明; 陈宝; 金羽; 曲娟娟

    2011-01-01

    In this study,the transgenic soybean "Dongnong 50" and soybean "Dongnong 50" were planted under normal soil water condition and drought stress condition to study transgenic soybean' s effect on the amount of nitrogen transforming bacteria and their corresponding biochemical intensity. The results showed that the number of aerobic azotobacter and the intensity of nitrogen fixation increased in the rhizosphere of transgenic soybean under drought stress treatment at the flowering stage. The number of the ammonification bacteria and the intensity of am-monification decreased while the number of denitrifying bacteria and the intensity of denitrification decreased. The number of the nitrifying bacteria and the intensity of nitrification were not affected during the whole growth period.%通过盆栽试验对转DREB基因大豆东农50与非转基因大豆东农50进行正常水分处理和干旱胁迫处理,研究转基因大豆在干旱条件下对土壤氮素转化相关细菌数量及生化强度的影响.结果表明,干旱条件下转DREB基因大豆在开花期对根际好氧性自生固氮茵的生长及土壤固氮强度有促进作用,在开花期和结荚鼓粒期对氨化细菌繁殖及氨化强度有抑制作用,在此时期对反硝化细菌的生长繁殖及其强度有抑制作用,在整个生长周期内转基因大豆对硝化细菌数量及其强度没有影响.

  1. Review: Biological fertilization and its effect on medicinal and aromatic plants

    Directory of Open Access Journals (Sweden)

    KHALID ALI KHALID

    2012-11-01

    Full Text Available Khalid KA. 2012. Review: Biological fertilization and its effect on medicinal and aromatic plants. Nusantara Bioscience 4: 124-133. The need of increase food production in the most of developing countries becomes an ultimate goal to meet the dramatic expansion of their population. However, this is also associated many cases with a reduction of the areas of arable land which leaves no opinion for farmers but to increase the yield per unit area through the use of improved the crop varieties, irrigation and fertilization. The major problem facing the farmer is that he cannot afford the cost of these goods, particularly that of chemical fertilizers. Moreover, in countries where fertilizer production relies on imported raw materials, the costs are even higher for farmer and for the country. Besides this, chemical fertilizers production and utilization are considered as air, soil and water polluting operations. The utilization of bio-fertilizers is considered today by many scientists as a promising alternative, particularly for developing countries. Bio-fertilization is generally based on altering the rhizosphere flora, by seed or soil inoculation with certain organisms, capable of inducing beneficial effects on a compatible host. Bio-fertilizers mainly comprise nitrogen fixes (Rhizobium, Azotobacter, Azospirellum, Azolla or blue green algae, phosphate dissolvers or vesicular-arbuscular mycorrhizas and silicate bacteria. These organisms may affect their host plant by one or more mechanisms such as nitrogen fixation, production of growth promoting substances or organic acids, enhancing nutrient uptake or protection against plant pathogens. Growth characters, yield, essential oil and its constituents, fixed oil, carbohydrates, soluble sugars and nutrients contents of medicinal and aromatic plants were significantly affected by adding the biological fertilizers compared with recommended chemical fertilizers.

  2. Comportamiento de la concentración microbiana aérea en la Fototeca del Archivo Nacional de Cuba

    Directory of Open Access Journals (Sweden)

    Sofía Borrego-Alonso

    2011-01-01

    Full Text Available Los objetivos del estudio fueron evaluar el predominio microbiano en el aire interior de la Fototeca del Archivo Nacional de la República de Cuba, realizar la caracterización fisiológica de los hongos aislados para determinar su potencial biodeteriorante y analizar a partir de la información especializada, las características patogénicas de los microorganismos que se aislaron con mayor frecuencia. En el muestreo microbiológico se utilizó un método de sedimentación y para ello, se emplearon placas Petri con medios de cultivo apropiados colocados a 1,5 m de altura del suelo. Se determinó cualitativamente la actividad celulolítica de las cepas fúngicas aisladas, así como la producción de pigmentos y ácidos. La concentración fúngica ambiental no varió con respecto al 2004, en tanto la bacteriana disminuyó significativamente. El género fúngico predominante fue Cladosporium (87,1 %, mientras que dentro de las bacterias, las Gram positivas fueron las que predominaron. Se evidenció que la mayoría de las cepas fúngicas aisladas mostraron actividad celulolítica, excretaron pigmentos y produjeron ácidos, lo que constituye un elevado riesgo de biodeterioro para el patrimonio documental. Entre las bacterias Gram positivas, se identificaron cepas de Staphylococcus, Streptococcus, Streptomyces y Bacillus. Dentro de las Gram negativas se identificaron cepas de Serratia marcenscens, Serratia sp., Enterobacter agglomerans, Beijerinckia sp., Azotobacter sp., Acinetobacter sp. y Pseudomonas sp. La mayoría de los géneros fúngicos y bacterianos aislados son agentes con potencialidades patogénicas.

  3. Impact of integrated nutrient management on tomato yield under farmers field conditions.

    Science.gov (United States)

    Pandey, S K; Chandra, K K

    2013-11-01

    Field trials were conducted in farmer's field of district Chandauli, Uttar Pradesh, India to assess the impact of integrated nutrient management (INM) on the performance of tomato crop during rabi (2008) and kharif (2009) season. Before conducting trials technological gap between actual and potential productivity were analyzed by interviewing growers to find out the major causes for low yield. Overall gap in use of fertilizers was recorded 64.90 % whereas overall mean gap in technology was 43.83%. On-farm experiments on INM were conducted by applying FYM (10t ha(-1)) + (NPK (150:80:60 kg ha(-1)) followed by dipping seedling roots in 1% Azotobacter solution for 15 min and foliar spray with 20 ppm ferrous ammonium sulphate after 30, 45 and 75 days of transplantation. The plant height, root length, number of primary branches, average fruit weight increased in INM plots as compared to farm practice. The increment in yield was found to be 28.84 and 33.86% during rabi and kharif season respectively. The maximum marketable yield obtained in INM plot during kharif and rabi seasons was 1025 q ha(-1) and 955 q ha(-1) respectively, whereas as farm practice yielded 740 q ha(-1) and 713 q ha(-1) during the same seasons. The percent loss from total production was recorded 8.5 % and 8.8 % in control plot and only 4.9 % and 5.7 % in INM plot during rabi and kharif seasons respectively. The higher fruit weight and lower incidence of disease and pest were observed in INM field in comparison to farm practice. The benefit cost ratio with INM treatment was recorded 4.25 and 4.23 in rabi and kharif season respectively against the benefit cost ratio of 2.98 and 2.82 in control plot during the same respective seasons. PMID:24555335

  4. Effect of diazotrophic bacteria as phosphate solubilizing and indolic compound producers on maize plants

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    Mónica Del Pilar López Ortega

    2013-12-01

    Full Text Available Phosphorus is limiting for growth of maize plants, and because of that use of fertilizers like Rock Phosphate has been proposed. However, direct use of Rock Phosphate is not recommended because of its low availability, so it is necessary to improve it. In this study, a group of diazotrophic bacteria were evaluated as phosphate-solubilizing bacteria, for their production of indolic compounds and for their effects on growth of maize plants. Strains of the genera Azosporillum, Azotobacter, Rhizobium and Klebsiella, were quantitatively evaluated for solubilization of Ca3(PO42 and rock phosphate as a single source of phosphorous in SRS culture media. Additionally, the phosphatase enzyme activity was quantified at pH 5.0, 7.0 and 8.0 using p-nitrophenyl phosphate, and production of indolic compound was determined by colorimetric quantification. The effect of inoculation of bacteria on maize was determined in a completely randomized greenhouse experiment where root and shoot dry weights and phosphorus content were assessed. Results showed that strain C50 produced 107.2 mg .L-1 of available-P after 12 days of fermentation, and AC10 strain had the highest phosphatase activity at pH 8 with 12.7 mg of p-nitrophenol mL .h-1. All strains synthetized indolic compounds, and strain AV5 strain produced the most at 63.03 µg .mL-1. These diazotrophic bacteria increased plant biomass up to 39 % and accumulation of phosphorus by 10%. Hence, use of diazotrphic phosphate-solubilizing bacteria may represent an alternative technology for fertilization systems in maize plants.

  5. The role of vanadium in biology.

    Science.gov (United States)

    Rehder, Dieter

    2015-05-01

    Vanadium is special in at least two respects: on the one hand, the tetrahedral anion vanadate(v) is similar to the phosphate anion; vanadate can thus interact with various physiological substrates that are otherwise functionalized by phosphate. On the other hand, the transition metal vanadium can easily expand its sphere beyond tetrahedral coordination, and switch between the oxidation states +v, +iv and +iii in a physiological environment. The similarity between vanadate and phosphate may account for the antidiabetic potential of vanadium compounds with carrier ligands such as maltolate and picolinate, and also for vanadium's mediation in cardiovascular and neuronal defects. Other potential medicinal applications of more complex vanadium coordination compounds, for example in the treatment of parasitic tropical diseases, may also be rooted in the specific properties of the ligand sphere. The ease of the change in the oxidation state of vanadium is employed by prokarya (bacteria and cyanobacteria) as well as by eukarya (algae and fungi) in respiratory and enzymatic functions. Macroalgae (seaweeds), fungi, lichens and Streptomyces bacteria have available haloperoxidases, and hence enzymes that enable the 2-electron oxidation of halide X(-) with peroxide, catalyzed by a Lewis-acidic V(V) center. The X(+) species thus formed can be employed to oxidatively halogenate organic substrates, a fact with implications also for the chemical processes in the atmosphere. Vanadium-dependent nitrogenases in bacteria (Azotobacter) and cyanobacteria (Anabaena) convert N2 + H(+) to NH4(+) + H2, but are also receptive for alternative substrates such as CO and C2H2. Among the enigmas to be solved with respect to the utilization of vanadium in nature is the accumulation of V(III) by some sea squirts and fan worms, as well as the purport of the nonoxido V(IV) compound amavadin in the fly agaric. PMID:25608665

  6. Comparative study of microflora in Rhizospheric soils of Argania spinosa and Acacia raddiana of the arid zone from Oued El Ma (Tindouf)

    Science.gov (United States)

    Tissouras, Fatiha; Habib, Semira; Missoum, Malika; Louacini, Braim Kamel

    2016-04-01

    Desert soils occupy a large area in Algeria (80Moreover, exploitation of the Saharan soil microorganisms has several interests and especially in maintaining the ecological equilibrium of ecosystems. Unfortunately, few of microbiological studies have been conducted so far about the Saharan soil Algerian, with the exception of some work done on the desert soils in the region of Beni Ounif. This work falls within the framework of Project CNEPRU F02320100009. The study focuses on an evaluation of the main germs rhizosphere soils from Argania spinosa and Acacia raddiana of the region of Oued El-ma (wilaya of Tindouf), located in southwest Algeria, followed by physicochemical analysis of some parameters (soil texture, pH, moisture content, organic matter). The results reveal that both rhizosphere soils have a sandy silt texture of alkali pH, with very low water content slightly different. Organic material of the rate varies from 0.2 to 1The type of vegetation influences positively the quantity and the dynamics of microbial population. Indeed, the two soils have an interesting microbial diversity, with densities of azotobacters, fungi, aerobic bacteria and actinomycetes are very high, followed germs ammonifiants, nitrifying and denitrifying. In the presence of Argania spinosa the microbial growth is most important (6.53 × 107 germs /g soil), compared with Acacia raddiana (3.13 × 107 germs /g). This shows the stimulating effect of the vegetation on the increase in the rate of these microorganisms in the soil. Well as the strong Fitness of adaptation the microbial biomass to drought. Keywords: Argania spinoza; Acacia raddiana; rhizospheric soil; microbiology evaluation.

  7. BIOFERTILIZATION USING RHIZOBACTERIA AND AMF IN THE PRODUCTION OF TOMATO (Lycopersicon esculentum Mill. AND ONION (Allium cepa L. SEEDLINGS. II. ROOT COLONIZATION AND NUTRITIONAL STATUS

    Directory of Open Access Journals (Sweden)

    L. E. Pulido

    2003-01-01

    Full Text Available Como complemento a estudios precedentes de la biofertilización en posturas de plantas hortícolas sobre suelos Ferralíticos Rojos compactados, eútricos y en áreas experimentales de la Universidad de Ciego de Ávila, se evaluaron los efectos de la inoculación simple y la coinoculación, mediante el recubrimiento de semillas y sin aplicar fertilizantes minerales, con rizobacterias promotoras del crecimiento vegetal -RPCV- (Azospirillum brasilense, Azotobacter chroococcum y Burkholderia cepacia y hongos micorrízicos arbusculares - HMA- (Glomus clarum y G. fasciculatum en algunos indicadores de la colonización radical por los microorganismos y el estado nutricional de plántulas de tomate y cebolla. A partir de los resultados, se evidenció que, para ambos cultivos, las poblaciones de A. chroococcum, B. cepacia y A. brasilense se incrementaron significativamente en aquellos tratamientos inoculados con estas rizobacterias, encontrando, en general, los mayores valores en los tratamientos que fueron coinoculados. Respecto a la micorrización, los mayores porcentajes de colonización micorrízica y masa del endófito en tomate se obtuvieron mediante la coinoculación de A. brasilense con ambas especies de HMA y, para la cebolla, la máxima colonización la realizó G. fasciculatum aplicada de forma independiente, mientras que la masa del endófito fue mayor en la coinoculación de G. clarum + A. chroococcum. En relación con el estado nutricional de las plantas, en tomate, los tratamientos con presencia conjunta de A. brasilense y ambas especies de HMA fueron los que hicieron mayores extracciones de N y estuvieron entre los que realizaron mayores extracciones de P y K. En cebolla, todos los tratamientos inoculados con ambos tipos de microorganismos fueron capaces de extraer mayores cantidades de N, P y K. Todos estos resultados permiten explicar las causas de la obtención de posturas de adecuada calidad mediante la biofertilización sin el uso

  8. Discovery of Evolutionary Divergence of Biological Nitrogen Fixation and Photosynthesis: Fine Tuning of Biogenesis of the NifH and the ChlL by a Peptidyl-Prolyl Cis/Trans Isomerase

    Directory of Open Access Journals (Sweden)

    Nara Gavini

    2011-01-01

    Full Text Available Problem statement: Despite the structural and functional similarities between the nitrogenase that performs biological nitrogen fixation reaction and the Dark Protochlorphyllide Oxidoreductase (DPOR that performs chlorophyll-biosynthesis, attempts to substitute nitrogenase-components with DPOR-components have hitherto failed. This investigation was undertaken to test if Chlamydomonas reinhardtii protochlorophyllide (Pchlide reductase (ChlL that shares some structural similarity with Nitrogenase Reductase (NifH could complement the functions of NifH in biological nitrogen fixation of Azotobacter vinelandii. Approach: Genetic complementation studies were performed to test if the chlL gene and its mutants cloned under transcriptional control of nifH promoter (nifHp in a broad-host range low copy plasmid pBG1380 could render a Nif+ phenotype to NifH-deficient A. vinelandii strains. Results: Expression of ChlL could render Nif+ phenotype to NifH-deficient A. vinelandii only in the absence of NifM, a nif-specific PPIase essential for biogenesis of NifH. The ChlL mutants Cys95Thr and Cys129Thr were unable to substitute for NifH. Thus, the conserved cysteine ligands of [4Fe-4S] cluster in ChlL are essential for successful substitution of NifH by ChlL. Since C-termini of NifH and ChlL demonstrated the least similarity and Pro258, a substrate for the PPIase activity of NifM, is located in the C-terminus of NifH, we posited that replacing the C-terminus of NifH with that of ChlL would render NifM-independence to NifH. The NifH-ChlL chimera could support the growth of NifH- and NifM-deficient A. vinelandii in nitrogen limiting conditions implying that it has acquired NifM-independence. Conclusion/Recommendations: Collectively, these observations suggest that NifM, an evolutionarily conserved nif-specific PPIase, could have contributed to the functional divergence of biological nitrogen fixation and photosynthesis during evolution by virtue of its ability to

  9. Global transcriptional analysis of nitrogen fixation and ammonium repression in root-associated Pseudomonas stutzeri A1501

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    Lu Wei

    2010-01-01

    Full Text Available Abstract Background Biological nitrogen fixation is highly controlled at the transcriptional level by regulatory networks that respond to the availability of fixed nitrogen. In many diazotrophs, addition of excess ammonium in the growth medium results in immediate repression of nif gene transcription. Although the regulatory cascades that control the transcription of the nif genes in proteobacteria have been well investigated, there are limited data on the kinetics of ammonium-dependent repression of nitrogen fixation. Results Here we report a global transcriptional profiling analysis of nitrogen fixation and ammonium repression in Pseudomonas stutzeri A1501, a root-associated and nitrogen-fixing bacterium. A total of 166 genes, including those coding for the global nitrogen regulation (Ntr and Nif-specific regulatory proteins, were upregulated under nitrogen fixation conditions but rapidly downregulated as early as 10 min after ammonium shock. Among these nitrogen fixation-inducible genes, 95 have orthologs in each of Azoarcus sp. BH72 and Azotobacter vinelandii AvoP. In particular, a 49-kb expression island containing nif and other associated genes was markedly downregulated by ammonium shock. Further functional characterization of pnfA, a new NifA-σ54-dependent gene chromosomally linked to nifHDK, is reported. This gene encodes a protein product with an amino acid sequence similar to that of five hypothetical proteins found only in diazotrophic strains. No noticeable differences in the transcription of nifHDK were detected between the wild type strain and pnfA mutant. However, the mutant strain exhibited a significant decrease in nitrogenase activity under microaerobic conditions and lost its ability to use nitrate as a terminal electron acceptor for the support of nitrogen fixation under anaerobic conditions. Conclusions Based on our results, we conclude that transcriptional regulation of nif gene expression in A1501 is mediated by the nif

  10. Redox balancing in recombinant strains of Saccharomyces cerevisiae

    Energy Technology Data Exchange (ETDEWEB)

    Anderlund, M.

    1998-09-01

    In metabolically engineered Saccharomyces cerevisiae expressing Pichia stipitis XYL1 and XYL2 genes, encoding xylose reductase (XR) and xylitol dehydrogenase (XDH), respectively, xylitol is excreted as the major product during anaerobic xylose fermentation and only low yields of ethanol are produced. This has been interpreted as a result of the dual cofactor dependence of XR and the exclusive use of NAD{sup +} by XDH. The excretion of xylitol was completely stopped and the formation of glycerol and acetic acid were reduced in xylose utilising S. cerevisiae strains cultivated in oxygen-limited conditions by expressing lower levels of XR than of XDH. The expression level of XYL1 and XYL2 were controlled by changing the promoters and transcription directions of the genes. A new functional metabolic pathway was established when Thermus thermophilus xylA gene was expressed in S. cerevisiae. The recombinant strain was able to ferment xylose to ethanol when cultivated on a minimal medium containing xylose as only carbon source. In order to create a channeled metabolic transfer in the two first steps of the xylose metabolism, XYL1 and XYL2 were fused in-frame and expressed in S. cerevisiae. When the fusion protein, containing a linker of three amino acids, was co expressed together with native XR and XDH monomers, enzyme complexes consisting of chimeric and native subunits were formed. The total activity of these complexes exhibited 10 and 9 times higher XR and XDH activity, respectively, than the original conjugates, consisting of only chimeric subunits. This strain produced less xylitol and the xylitol yield was lower than with strains only expressing native XR and XDH monomers. In addition, more ethanol and less acetic acid were formed. A new gene encoding the cytoplasmic transhydrogenase from Azotobacter vinelandii was cloned. The enzyme showed high similarity to the family of pyridine nucleotide-disulphide oxidoreductase. To analyse the physiological effect of

  11. Exploitation of inexpensive substrates for production of a novel SCL-LCL-PHA co-polymer by Pseudomonas aeruginosa MTCC 7925.

    Science.gov (United States)

    Singh, Akhilesh Kumar; Mallick, Nirupama

    2009-03-01

    Studies conducted with various inexpensive carbon sources such as whey, vegetable oils (palm, mustard, soybean and coconut), a low-cost source of glucose-D, rice and wheat bran, and mustard and palm oil cakes demonstrated palm oil as the best substrate for accumulation of a novel short-chain-length-long-chain-length polyhydroxyalkanoate (SCL-LCL-PHA) co-polymer containing SCL 3HAs [3-hydroxybutyric acid (3HB) and 3-hydroxyvaleric acid (3HV)] and LCL 3HAs of 3-hydroxyhexadecanoic acid (3HHD) and 3-hydroxyoctadecanoic acid (3HOD) units as constituents by a sludge-isolated Pseudomonas aeruginosa MTCC 7925. The co-polymer content reached up to 60% of dry cell weight (dcw) at 48 h of incubation in 0.5% (v/v) palm oil and the extract of 0.5% (v/v) palm oil cake supplemented vessels. The PHAs pool was further enhanced up to 69 and 75% (dcw), when the above culture was subjected to P- and N-limitation, respectively. The mol fraction of 3HB:3HV:3HHD:3HOD units were, respectively, 83.1:7.7:3.8:5.4 and 87.3:5.1:3.6:4.0 in P- and N-limited cultures. Consequently, a co-polymer yield of 5 g l(-1) (approx.) was achieved, which was about 80-fold higher as compared to 69 mg l(-1) of the control culture. On substrate basis, the accumulation reached up to 0.62 g PHAs per g substrate, which was significantly higher as compared to the yield obtained from starch by Haloferax mediterranei and Azotobacter chroococum, from molasses by A. vinelandii UWD, and from lactose and xylose by Pseudomonas cepacia. This novel P(3HB-co-3HV-co-3HHD-co-3HOD) co-polymer exhibited better thermal and mechanical properties as revealed from the differential scanning calorimetry and mechanical property studies, thus opens up new possibilities for various industrial applications.

  12. Spatial and temporal characteristics of soil microbial groups in Gaoligongshan%高黎贡山土壤微生物类群动态特征

    Institute of Scientific and Technical Information of China (English)

    张俊忠; 张成霞; 刘丽; 张东华

    2013-01-01

    The soil samples were collected in different vegetation types and different altitude gradients at depths of 0-20 cm and 20-40 cm in Gaoligongshan.The amount distribution of soil microbial groups with different vegetation types and different altitude were studied by using the microbial incubation methods.The results showed that with the increase of altitude gradients,most of soil microbial groups showed a single peak trend in their quantities,ie,low-high-low.The quantity of soil microbial groups was in the order,ammonifying bacteria > bacillus > denitrifying bacterial > aerobe azotobacte > nitrifiers >azotobacter>phosphorus solubilizing bacteria>aerobe cellulose decomposing bacteria>oligotrophic cellulose decomposing bacteria.Total numbers of soil microbial groups in different vegetation types was in the order,broadleaf forest>mixed wood>shrub forest>coffee land>snowfield.%采集高黎贡山国家自然保护区不同海拔及植被类型下0~20和20~40 cm土层的土壤样品,采用微生物常规分析法测定土壤中氨化细菌、芽孢杆菌、硝化细菌、反硝化细菌、好气性固氮菌、嫌气性固氮菌、好气性纤维素降解菌、嫌气性纤维素降解菌和溶磷菌的数量,分析了不同海拔及植被类型下土壤微生物类群数量的分布特征.结果表明,随海拔的升高,土壤微生物类群的总数量呈单峰变化趋势;各土壤微生物类群数量总体表现为氨化细菌>芽孢杆菌>反硝化细菌>好气性固氮菌>硝化细菌>嫌气性固氮菌>溶磷菌>好气性纤维素降解菌>嫌气纤维素降解菌的分布特点;不同植被类型土壤中,微生物类群总数不同,表现为阔叶林>针阔混交林>稀疏灌丛>咖啡地>雪地.

  13. LA PRODUCCIÓN CIENTÍFICA SOBRE BIOFERTILIZANTES EN CUBA EN EL PERÍODO 2008-2012: UN ANÁLISIS BIBLIOMETRICO DE LAS REVISTAS CUBANAS

    Directory of Open Access Journals (Sweden)

    Maida D. Peña Borrego

    2015-01-01

    Full Text Available El estudio tiene como objetivo caracterizar el comportamiento de la investigación científica sobre biofertilizantes en revistas científicas de Cuba durante el período 2008-2012, mediante el análisis de indicadores bibliométricos para determinar las regularidades de la producción científica por autores e instituciones, así como la colaboración entre provincias, instituciones y otras naciones, además de los microorganismos y cultivos agrícolas más trabajados en la temática. Se tomó como fuente de información los artículos publicados en 14 revistas científicas certificadas por el CITMA como publicaciones científicas y tecnológicas. Para el análisis de los datos, se empleó el Excel, ToolInf y Ucinet 6.0. Resultó que el año 2008 fue el más productivo, aunque se manifestó un decrecimiento de los artículos sobre biofertilizantes en el período. Las provincias Mayabeque, La Habana y Villa Clara, constituyen el nicho productivo de estas investigaciones. Las instituciones de mayor actividad científica fueron INCA, INIFAT y la Facultad de Biología de la Universidad de la Habana, estableciéndose fuertes lazos de colaboración en el país hacia la región occidental. Respecto a la colaboración internacional, fueron los países de Brasil y México, los que más contribuyeron a resultados de investigación con entidades cubanas a través de publicaciones nacionales. El sorgo ( Sorghum bicolor y Sorghum vulgare , arroz ( Oryza sativa , col ( Brassica oleracea , tomate ( Solanum lycopersicum , caña ( Saccharum officinarum , maíz ( Zea mays , papaya ( Carica papaya y canavalia ( Canavalia ensiformis fueron los principales cultivos agrícolas en los cuales se evaluaron un mayor número de microorganismos biofertilizantes, que entre los géneros de mayor nivel de estudio se encuentran Glomus , Rhizobium , Bradyrhizobium , Azotobacter , Gluconoacetobacter y Pseudomonas.

  14. Role of a ferredoxin gene cotranscribed with the nifHDK operon in N(2) fixation and nitrogenase "switch-off" of Azoarcus sp. strain BH72.

    Science.gov (United States)

    Egener, T; Martin, D E; Sarkar, A; Reinhold-Hurek, B

    2001-06-01

    The endophytic diazotroph Azoarcus sp. strain BH72 is capable of infecting rice roots and of expressing the nitrogenase (nif) genes there. In order to study the genetic background for nitrogen fixation in strain BH72, the structural genes of nitrogenase (nifHDK) were cloned and sequenced. The sequence analysis revealed an unusual gene organization: downstream of nifHDK, a ferredoxin gene (fdxN; 59% amino acid sequence identity to R. capsulatus FdxN) and open reading frames showing 52 and 36% amino acid sequence identity to nifY of Pseudomonas stutzeri A15 and ORF1 of Azotobacter vinelandii were located. Northern blot analysis, reverse transcriptase PCR and primer extension analysis revealed that these six genes are located on one transcript transcribed from a sigma(54)-type promoter. Shorter transcripts sequentially missing genes of the 3' part of the full-length mRNA were more abundantly detected. Mutational analyses suggested that FdxN is an important but not the essential electron donor for dinitrogenase reductase. An in-frame deletion of fdxN resulted in reduced growth rates (59% +/- 9%) and nitrogenase activities (81%) in nitrogen-fixing pure cultures in comparison to the wild type. Nitrogenase activity was fully complemented in an fdxN mutant which carried a nifH promoter-driven fdxN gene in trans. Also, in coculture with the ascomycete Acremonium alternatum, where strain BH72 develops intracytoplasmic membrane stacks, the nitrogenase activity in the fdxN deletion mutant was decreased to 56% of the wild-type level. Surprisingly, the fdxN deletion also had an effect on the rapid "switch-off" of nitrogenase activity in response to ammonium. Wild-type strain BH72 and the deletion mutant complemented with fdxN in trans showed a rapid reversible inactivation of acetylene reduction, while the deletion mutant did not cease to reduce acetylene. In concordance with the hypothesis that changes in the redox state of NifH or electron flux towards nitrogenase may be

  15. Cloning, functional organization, transcript studies, and phylogenetic analysis of the complete nitrogenase structural genes (nifHDK2) and associated genes in the archaeon Methanosarcina barkeri 227.

    Science.gov (United States)

    Chien, Y T; Zinder, S H

    1996-01-01

    Determination of the nucleotide sequence of the nitrogenase structural genes (nifHDK2) from Methanosarcina barkeri 227 was completed in this study by cloning and sequencing a 2.7-kb BamHI fragment containing the 3' end of nifK2 and 1,390 bp of the nifE2-homologous genes. Open reading frame nifK2 is 1,371 bp long including the stop codon TAA and encodes a polypeptide of 456 amino acids. Phylogenetic analysis of the deduced amino acid sequences of the nifK2 and nifE2 gene products from M. barkeri showed that both genes cluster most closely with the corresponding nif-1 gene products from Clostridium pasteurianum, consistent with our previous analyses of nifH2 and nifD2. The nifE gene product is known to be homologous to that of nifD, and our analysis shows that the branching pattern for the nifE proteins resembles that for the nifD product (with the exception of vnfE from Azotobacter vinelandii), suggesting that a gene duplication occurred before the divergence of nitrogenases. Primer extension showed that nifH2 had a single transcription start site located 34 nucleotides upstream of the ATG translation start site for nifH2, and a sequence resembling the archaeal consensus promoter sequence [TTTA(A/T)ATA] was found 32 nucleotides upstream from that transcription start site. A tract of four T's, previously identified as a transcription termination site in archaea, was found immediately downstream of the nifK2 gene, and a potential promoter was located upstream of the nifE2 gene. Hybridization with nifH2 and nifDK2 probes with M. barkeri RNA revealed a 4.6-kb transcript from N2-grown cells, large enough to harbor nifHDK genes and their internal open reading frames, while no transcript was detected from NH4(+)-grown cells. These results support a model in which the nitrogenase structural genes in M. barkeri are cotranscribed in a single NH4(+)-repressed operon. PMID:8550408

  16. Nucleotide sequence and genetic analysis of the Rhodobacter capsulatus ORF6-nifUI SVW gene region: possible role of NifW in homocitrate processing.

    Science.gov (United States)

    Masepohl, B; Angermüller, S; Hennecke, S; Hübner, P; Moreno-Vivian, C; Klipp, W

    1993-04-01

    DNA sequence analysis of a 3494-bp HindIII-BclI fragment of the Rhodobacter capsulatus nif region A revealed genes that are homologous to ORF6, nifU, nifS, nifV and nifW from Azotobacter vinelandii and Klebsiella pneumoniae. R. capsulatus nifU, which is present in two copies, encodes a novel type of NifU protein. The deduced amino acid sequences of NifUI and NifUII share homology only with the C-terminal domain of NifU from A. vinelandii and K. pneumoniae. In contrast to nifA and nifB, which are almost perfectly duplicated, the predicted amino acid sequences of the two NifU proteins showed only 39% sequence identity. Expression of the ORF6-nifUISVW operon, which is preceded by a putative sigma 54-dependent promoter, required the function of NifA and the nif-specific rpoN gene product encoded by nifR4. Analysis of defined insertion and deletion mutants demonstrated that only nifS was absolutely essential for nitrogen fixation in R. capsulatus. Strains carrying mutations in nifV were capable of very slow diazotrophic growth, whereas ORF6, nifUI and nifW mutants as well as a nifUI/nifUII double mutant exhibited a Nif+ phenotype. Interestingly, R. capsulatus nifV mutants were able to reduce acetylene not only to ethylene but also to ethane under conditions preventing the expression of the alternative nitrogenase system. Homocitrate added to the growth medium repressed ethane formation and cured the NifV phenotype in R. capsulatus. Higher concentrations of homocitrate were necessary to complement the NifV phenotype of a polar nifV mutant (NifV-NifW-), indicating a possible role of NifW either in homocitrate transport or in the incorporation of this compound into the iron-molybdenum cofactor of nitrogenase. PMID:8492805

  17. Clostridium pasteurianum W5 synthesizes two NifH-related polypeptides under nitrogen-fixing conditions.

    Science.gov (United States)

    Kasap, Murat; Chen, Jiann-Shin

    2005-07-01

    Previous studies identified five nifH-like genes (nifH2 through nifH6) in Clostridium pasteurianum (strain W5), where the nifH1 gene encodes the nitrogenase iron protein. Transcripts of these nifH genes, with the exception of nifH3, were detected in molybdenum-sufficient nitrogen-fixing cells. However, the size of the transcripts, the level of transcription and the presence of polypeptides encoded by the nifH-like genes were not reported. The nifH2 and nifH6 genes were extremely similar, as they seemed to differ by only two bases in a span of 2481 bp, one in the coding region and another in the upstream region. Re-examination of the DNA sequences revealed that the coding region of nifH2 and nifH6 was identical, whereas the difference in the upstream region was confirmed. Results from the authors' ongoing study of the nif genes of single-colony isolates of C. pasteurianum suggest that the nifH6 designation should be eliminated. Here the size of mRNA from nifH2 and the detection of the NifH2 polypeptide in nitrogen-fixing cells of C. pasteurianum are reported. Northern blot analysis of periodically collected nitrogen-fixing cells showed that the nifH1 and nifH2 mRNAs were present throughout growth. Addition of ammonium acetate repressed the transcription of both these genes similarly. Using an antiserum raised against NifH of Azotobacter vinelandii, two NifH-related bands were detected by Western blot analysis after electrophoretic separation of proteins in extracts of nitrogen-fixing C. pasteurianum cells. After separation of proteins by preparative SDS-PAGE, the NifH polypeptides were characterized by MALDI-TOF-MS (matrix-assisted laser desorption/ionization time-of-flight mass spectrometry) and by ES-MS/MS (electrospray tandem mass spectrometry) analyses. The results confirmed the presence of NifH2, in addition to NifH1, in nitrogen-fixing C. pasteurianum cells. PMID:16000725

  18. Iron is required to relieve inhibitory effects on NifL on transcriptional activation by NifA in Klebsiella pneumoniae.

    Science.gov (United States)

    Schmitz, R A; He, L; Kustu, S

    1996-08-01

    In Klebsiella pneumoniae, products of the nitrogen fixation nifLA operon regulate transcription of the other nif operons. NifA activates transcription by sigma54-holoenzyme. In vivo, NifL antagonizes the action of NifA under aerobic conditions or in the presence of combined nitrogen. In contrast to a previous report, we show that depletion of iron (Fe) from the growth medium with the chelating agent o-phenanthroline (20 microM) mimics aerobiosis or combined nitrogen in giving rise to inhibition of NifA activity even under anaerobic, nitrogen-limiting conditions. Adding back Fe in only twofold molar excess over phenanthroline restores NifA activity, whereas adding other metals fails to do so. By using strains that lack NifL, we showed that NifA activity itself does not require Fe and is not directly affected by phenanthroline. Hence, Fe is required to relieve the inhibition of NifA activity by NifL in vivo. Despite the Fe requirement in vivo, we have found no evidence that NifL contains Fe or an iron-sulfur (Fe-S) cluster. Determination of the molecular mass of an inhibitory form of NifL overproduced under aerobic conditions indicated that it was not posttranslationally modified. When NifL was synthesized in vitro, it inhibited transcriptional activation by NifA even when it was synthesized under anaerobic conditions in the presence of a high Fe concentration or of superoxide dismutase, which is known to protect some Fe-S clusters. Moreover, overproduction of superoxide dismutase in vivo did not relieve NifL, inhibition under aerobic conditions, and attempts to relieve NifL inhibition in vitro by reconstituting Fe-S clusters with the NifS enzyme (Azotobacter vinelandii) were unsuccessful. Since we obtained no evidence that Fe acts directly on NifL or NifA, we postulate that an additional Fe-containing protein, not yet identified, may be required to relieve NifL inhibition under anaerobic, nitrogen-limiting conditions. PMID:8755900

  19. IscA, an alternate scaffold for Fe-S cluster biosynthesis.

    Science.gov (United States)

    Krebs, C; Agar, J N; Smith, A D; Frazzon, J; Dean, D R; Huynh, B H; Johnson, M K

    2001-11-20

    An IscA homologue within the nif regulon of Azotobacter vinelandii, designated (Nif)IscA, was expressed in Escherichia coli and purified to homogeneity. Purified (Nif)IscA was found to be a homodimer of 11-kDa subunits that contained no metal centers or other prosthetic groups in its as-isolated form. Possible roles for (Nif)IscA in Fe-S cluster biosynthesis were assessed by investigating the ability to bind iron and to assemble Fe-S clusters in a NifS-directed process, as monitored by the combination of UV-vis absorption, Mössbauer, resonance Raman, variable-temperature magnetic circular dichroism, and EPR spectroscopies. Although (Nif)IscA was found to bind ferrous ion in a tetrahedral, predominantly cysteinyl-ligated coordination environment, the low-binding affinity argues against a specific role as a metallochaperone for the delivery of ferrous ion to other Fe-S cluster assembly proteins. Rather, a role for (Nif)IscA as an alternate scaffold protein for Fe-S cluster biosynthesis is proposed, based on the NifS-directed assembly of approximately one labile [4Fe-4S](2+) cluster per (Nif)IscA homodimer, via a transient [2Fe-2S](2+) cluster intermediate. The cluster assembly process was monitored temporally using UV-vis absorption and Mössbauer spectroscopy, and the intermediate [2Fe-2S](2+)-containing species was additionally characterized by resonance Raman spectroscopy. The Mössbauer and resonance Raman properties of the [2Fe-2S](2+) center are consistent with complete cysteinyl ligation. The presence of three conserved cysteine residues in all IscA proteins and the observed cluster stoichiometry of approximately one [2Fe-2S](2+) or one [4Fe-4S](2+) per homodimer suggest that both cluster types are subunit bridging. In addition, (Nif)IscA was shown to couple delivery of iron and sulfur by using ferrous ion to reduce sulfane sulfur. The ability of Fe-S scaffold proteins to couple the delivery of these two toxic and reactive Fe-S cluster precursors is likely to

  20. 接种蚯蚓及植物促生根际细菌对甘蓝生长·营养元素吸收的影响%Effects of Inoculation of Earthworms and Plant Growth Promoting Rhizobacteria (PGPR) on Growth of Brassica juncea

    Institute of Scientific and Technical Information of China (English)

    吴福勇; 毕银丽; 毛艳丽

    2012-01-01

    [目的]为阐明混合接种蚯蚓及植物促生根际细菌技术在蔬菜生产中的作用.[方法]采用室内盆栽试验的方法,研究接种蚯蚓、植物促生根际细菌(固氮细菌和钾活化细菌)对甘蓝生长的影响以及甘蓝对氮和钾的吸收.[结果]7种接种方式均明显促进了甘蓝根上部分的生长,其中混合接种蚯蚓、固氮细菌和钾活化细菌处理下甘蓝根上部分生物量最大.5种接种方式(接种蚯蚓、双接蚯蚓和固氮细菌、双接蚯蚓和钾活化细菌、双接钾活化细菌和固氮细菌以及混合接种)下甘蓝地上部分氮的吸收量在0.05水平显著高于对照.[结论 混合接种方式是一种有潜力的生物技术,可以用来减少蔬菜生产中化肥的施用量.%[ Objective ] The research aimed to clarify the roles of mixed inoculation of earthworm and plant growth-promoting rhizobacteria ( PGPR) on the growth of vegetables. [ Method ] A serials of pot trials were conducted to investigate the single, dual or triple inoculation of earthworms or PGPR, including nitrogen-fixing bacteria ( NFB) ( Azotobacter chroococcum PDSN-5) and potassium-solubilizing bacteria (KSB) (Bacillus mucilaginous PDSK-1) , on the growth of Chinese kale (Brassica juncea) and on uptake of N and K in the plant. [ Result] All of the seven inoculation treatments apparently increased the shoot growth of B. Juncea. The highest shoot biomass was recorded in the triple inoculation of earthworm, NFB and KSB. All of the seven inoculation treatments significantly increased N uptake in shoot of B. Juncea. [ Conclusion ] The triple inoculation may be a promising approach for reducing the need for chemical fertilizers in growing vegetables.

  1. [Diverse morphological types of dormant cells and conditions for their formation in Azospirillum brasilense].

    Science.gov (United States)

    Muliukin, A L; Suzina, N E; Pogorelova, A Iu; Antoniuk, L P; Duda, V I; El'-Registan, G I

    2009-01-01

    Differences in generation of dormant forms (DF) were revealed between two strains of non-sporeforming gram-negative bacteria Azospirillum brasilense, Sp7 (non-endophytic) and Sp245 (endophytic strain). In post-stationary ageing bacterial cultures grown in a synthetic medium with a fivefold decreased initial nitrogen content, strain Sp7 formed two types of cyst-like resting cells (CRC). Strain Sp245 did not form such types of DF under the same conditions. CRC of the first type were formed in strain Sp245 only under phosphorus deficiency (C > P). The endophytic strain was also shown to form structurally differentiated cells under complete starvation, i.e. at a transfer of early stationary cultures, grown in the media with C > N unbalance, to saline solution (pH 7.2). These DF had a complex structure similar to that of azotobacter cysts. The CRC, which are generated by both azospirilla strains and belong to distinct morphological types, possessed the following major features: absence of division; specific ultrastructural organization; long-term maintenance of viability (for 4 months and more); higher heat resistance (50-60 degrees C, 10 min) as compared with vegetative cells, i.e. the important criteria for dormant prokaryotic forms. However, CRC of non-endophytic strain Sp7 had higher heat resistance (50, 55, 60 degrees C). The viability maintenance and the portion of heat-resistant cells depended on the conditions of maturation and storage of CRC populations. Long-term storage (for 4 months and more) of azospirilla DF populations at -20 degrees C was optimal for maintenance of their colony-forming ability (57% of the CFU number in stationary cultures), whereas the largest percentage of heat-resistant cells was in CRC suspensions incubated in a spent culture medium (but not in saline solution) at room temperature. The data on the intraspecies diversity of azospirilla DF demonstrate the relation between certain type DF formation to the type of interaction (non

  2. Bionota: Bacterias promotoras de crecimiento de microalgas: una nueva aproximación en el tratamiento de aguas residuales Microalgae growth-promoting bacteria: A novel approach in wastewater treatment

    Directory of Open Access Journals (Sweden)

    Bashan Yoav

    2003-12-01

    Full Text Available Las bacterias promotoras de crecimiento en plantas (PGPB del género Azospirillum son conocidas porque mejo­ran el crecimiento de numerosas cosechas agrícolas; sin embargo, el presente trabajo pretende extender el uso de estas bacterias a "bacterias promotoras de crecimiento de microalgas" (MPGB para aumentar la capacidad de las microalgas de eliminar nutrientes de aguas residuales. La inoculación deliberada de las microalgas Chlorella spp. con PGPB de origen terrestre no ha sido reportada con anterioridad, tal vez debido al origen diferente de estos dos microorganismos. Al inmovilizar de manera conjunta Chlorella vulgaris y Azospirillum brasilense Cd en esferas de alginato, se obtuvo como resultado un aumento significativo en varios parámetros de crecimiento de la microalga, como el peso fresco y seco, el número total de células, el tamaño de las colonias de microalgas dentro de la esfera, el número de organismos por colonia y la concentración de pigmentos. Además, aumenta­ron los lípidos y la variedad de ácidos grasos. La microalga combinada con la MGPB tiene una mayor capacidad de eliminar amonio y fósforo tanto en agua residual sintética como en agua residual doméstica. Actualmente se ha estado experimentando con otras PGPB (Flavobacterium sp. Azospirillum sp. y Azotobacter sp. para propósitos acuícolas; por ejemplo aumentar el crecimiento de fitoplancton utilizado en el cultivo de carpas y estabilizar cultivos masivos de microalgas marinas utilizadas como alimento para organismos marinos, todo esto con resul­tados promisorios. Si bien el efecto de las PGPB en microorganismos acuáticos aún no ha sido suficientemente explorado, proponemos que la co-inmovilización de microalgas y bacterias promotoras de crecimiento es un medio efectivo para aumentar la población microalgal y también su capacidad de limpiar aguas residuales. Palabras clave: PGPB; microalgas; biotratamiento de aguas residuales; co

  3. Effects of Wheat Straw Mulching Amount on the Quantity of Microorganisms in Different Tobacco Planting Soil%小麦秸秆覆盖量对不同植烟土壤微生物数量的影响

    Institute of Scientific and Technical Information of China (English)

    林云红; 查永丽; 毛昆明; 刘彦中

    2012-01-01

    Field experiment was conducted to study the effects of different mulching amount of wheat (the mulching a-mount being 0,250,500,750 kilogram per 667 squarer meter as 4 treatments) on the quantity of microorganisms in different tobacco planting soil. Result showed that the quantity of bacteria, actinomycetes and cellulose - decomposing bacteria in rhizosphere soil of the upland and paddy increased with the amount of mulching. And the quantities of them reached biggest in treatment with mulching amount of 750 kilogram per 667 squarer meter after harvest, and were respectively 53. 03% , 47. 08% , 75. 72% and 63. 79% , 30. 27% , 69. 08% higher than contrast. The quantity of bacteria in rhizosphere soil of the upland in treatments with different mulching amount were 1.81 ~ 2. 13 times higher than that without mulching, actinomycetes and cellulose - decomposing bacteria were respectivelyl. 08 ~ 1. 89 and 1. 49 ~4. 1 times higher. The quantity of azotobacter were most in treatments with mulching amount of 500 kilogram per 667 squarer meter , and were significantly higher than contrast. There were no effects on the quantity of fungi with straw mulching. The quantity of bacteria in rhizosphere soil of the paddy in treatments with different mulching amount werel. 87 ~2. 76 times higher than that without mulching, actinomycetes and cellulose -decomposing bacteria were respectively 1. 12 ~ 1. 43 and 1.3 ~3. 39 times higher . The quantity of fungi and azotobacter were most in treatments with mulching amount of 500 kilogram per 667 squarer meter,, and were 2. 24 and 1. 60 times higher than contrast.%采用田间小区试验,研究了小麦秸秆覆盖量(覆盖量为0、250、500、750 kg/(667 m2)等4个处理)对不同植烟土壤微生物数量的影响.结果表明:覆盖量越大,地烟和田烟根际土壤细菌、放线菌和纤维分解菌的数量越大,覆盖量为750 kg/(667m2)时,采收后,地烟和田烟土壤中细菌、放线菌和纤维分解菌的数

  4. Effects of Effective Microbial Inoculants on Alfalfa Growth Character%苜蓿根际有益菌接种剂对苜蓿生长特性影响的研究

    Institute of Scientific and Technical Information of China (English)

    韩华雯; 孙丽娜; 姚拓; 张英; 王国基

    2013-01-01

    为探讨微生物肥源替代或部分替代化肥的应用潜力,利用前期从苜蓿(Medicago sativa L.)和小麦(Triticum aestivum L.)根际分离的3株溶磷菌(Bacillus sp.,Pseudomonas sp.和Azotobacter sp.)和1株根瘤菌(Sinorhizobium meliloti)研制苜蓿根际新型专用接种剂,并进行田间随机区组试验,测定其对苜蓿生长特性的影响.结果表明:单一菌种接种剂+半量磷肥对苜蓿的促生效果不及复合菌种接种剂+半量磷肥,与对照(全量磷肥)相比,复合菌种接种剂+半量磷肥处理对苜蓿的各项生长指标均有明显的促生效应,其中以复合接种剂+半量磷肥处理的效果最佳:苜蓿株高、叶绿素含量、叶茎比、干鲜比及产量分别较对照增加9.00%,51.98%,13.79%,19.57%,11.98%(第1茬)和8.26%,48.08%,16.87%,20.07%,20.95%(第2茬);单一菌种接种剂+半量磷肥处理的效果不及全量磷肥处理,但处理根瘤接种剂+半量磷肥效果较好.因此,推荐根瘤接种剂和Jm170+Jm92+ Lx191溶磷菌+根瘤菌复合接种剂为适用于苜蓿的最佳单一及复合菌株接种剂,研制的各接种剂质量达到农业部微生物肥料行业标准(NY227-94)的要求.%Maintenance of soil fertility is one of the more important requirements for sustainable agriculture in China because increasing chemical fertilizer use and highly productive systems has created environmental problems and resource overexploitation. In recent years, bio-fertilizers have emerged as an important component of the integrated nutrient supply system and show great promise to improve crop yields. The objective of this paper is to survey the possibility of applying bio-fertilizers to replace chemical fertilizers. Three phosphate-solubilizing bacteria strains (Bacillus sp. , Pseudomonas sp. and Azotobacter sp. ) and one rhi-zobium (Sinorhizobium meliloti) , isolated from alfalfa and wheat rhizosphere, were used to produce single and compound inoculants. A field

  5. Biochemical Properties of Cysteine Desulfurase and Its Mechanism for the Desulfuration of L-Cysteine%半胱氨酸脱硫酶的生化特性及其脱硫作用机制

    Institute of Scientific and Technical Information of China (English)

    彭加平; 韦平和; 周锡樑

    2011-01-01

    半胱氨酸脱硫酶是一类依赖磷酸吡哆醛的酶,为同质二聚体,能催化L-半胱氨酸脱硫生成L-丙氨酸和硫.NifS首先在棕色固氮菌中发现,并被认为在固氮酶铁硫簇的形成中起重要作用.NifS同系物也存在于许多非固氮的原核及真核生物中,它们在分子质量、分光光度特性、底物选择性、氨基酸序列和生物学功能等方面非常相似.根据氨基酸序列的相似性,将NifS同系物分成二组,Ⅰ组包括NifS和IscS等,Ⅱ组包括CSD和CsdB等.半胱氨酸脱硫酶均具有保守的赖氨酸和半胱氨酸残基,前者与PLP形成Schiff碱,后者参与半胱氨酸过硫化物中间物形成.半胱氨酸脱硫酶的作用机理涉及半胱氨酸残基亲核攻击底物L-半胱氨酸上的巯基,形成与酶结合的半胱氨酸过硫化物中间物,该过硫化物中间物作为供硫体,参与生物素、硫胺素、钼碟呤以及铁硫簇、硫代核苷等含硫分子的生物合成.%Cysteine desulfurases are pyridoxal phosphate dependent homodimeric enzymes that catalyze the desulfuration of L-cyste-ine to yield L-alanine and free sulfur. The enzyme NifS was first identified in Azotobacter vinelandii, indicating that it might serve a general role in the formation of Fe-S clusters in nitrogenase. NifS homologs also occur in many nondiazotrophic prokaryotes and eukaryotes, and they are very similar in molecular weight, spectrophotometric property, substrate specificity, amino acid sequence, and function to the A. Vinelandii NifS. On the basis of sequence similarity relationships, the NifS homologs are divided into groups I and II. NifS and IscS are group I enzymes, whereas CSD and CsdB are members of group II. All cysteine desulfurases contain a conserved lysine that forms a Schiff base with the PLP cofactor in the resting state and a conserved catalytic cysteine involved in transient persulfide formation. The mechanism for desulfuration of L-cysteine catalyzed by cysteine

  6. Structure of a putative BenF-like porin from Pseudomonas fluorescens Pf-5 at 2.6 A resolution

    Energy Technology Data Exchange (ETDEWEB)

    Sampathkumar, P.; Swaminathan, S.; Lu, F.; Zhao, X.; Li, Z.; Gilmore, J.; Bain, K.; Rutter, M. E.; Gheyi, T.; Schwinn, D.; Bonanno, J. B.; Pieper, U.; Fajardo, J. E.; Fiser, A.; Almo, S. C.; Chance, M. R.; Baker, D.; Atwell, S.; Thompson, D. A.; Emtage, J. S.; Wasserman, S. R.; Sali, A.; Sauder, J. M.; Burley, S. K.

    2010-11-01

    Gram-negative bacteria typically overcome poor permeability of outer membranes through general porins like OmpF and OmpC, which form water-filled transmembrane pores permitting diffusion of hydrophilic molecules with no particular selectivity. Many bacteria lacking such general porins use substrate-specific porins to overcome growth-limiting conditions and facilitate selective transport of metabolites. Exclusive reliance on substrate-specific porins yields lower membrane permeability to small molecules (<600 Da) versus that seen for Escherichia coli. In Pseudomonads, transit of most small molecules across the cell membrane is thought to be mediated by substrate-specific channels of the OprD superfamily. This property explains, at least in part, the high incidence of Pseudomonas aeruginosa antibiotic resistance. High-throughput DNA sequencing of the P. aeruginosa chromosome revealed the presence of 19 genes encoding structurally related, substrate-specific porins (with 30-45% pairwise amino acid sequence identity) that mediate transmembrane passage of small, water-soluble compounds. The OprD superfamily encompasses the eponymous OprD subfamily, which includes 9 P. aeruginosa proteins that convey basic amino acids and carbapenem antibiotics, and the OpdK subfamily, which includes 11 P. aeruginosa proteins that convey aromatic acids and other small aromatic compounds. Genome sequencing of other gram-negative bacteria has revealed additional members of the OprD and OpdK subfamilies in various organisms, including other pseudomonads. Among the many bacteria in which OprD superfamily members have been identified are P. putida, P. fluorescens Pf-5, P. syringae, and Azotobacter vinelandii, all of which share closely related genes that encode the so-called BenF-like porins. In P. putida, benF is part of an operon involved in benzoate catabolism regulated by benR. Within this operon, benK, benE, and benF genes have been suggested to contribute toward either influx or efflux

  7. 黄绿木霉T1010对樱桃番茄横向土壤环境性状改良效果研究%Modified Effects of Trichoderma aureoviride 1010 on Some Soil Properties from Axial Root of Cherry-tomato

    Institute of Scientific and Technical Information of China (English)

    陈建爱; 杜方岭

    2011-01-01

    为了研究黄绿木霉(Trichoderma aureoviride)T1010对土壤微生物群落、物理性状、化学性状的作用,评价T1010调整土壤环境性状生态效应的潜力,采用土壤稀释法测定土壤中微生物群落数,土壤称重法测定物理性状,无机化学反应法测定土壤中主要化学指标含量,结果表明:T1010促进土壤中细菌、放线菌、固氮菌的生长,与土壤处理前相比,固氮菌数量最大提高6.04倍,比对照提高58.02%;T1010抑制其他真菌的生长,比初始值下降52.99%,比对照下降79.47%;T1010改良物理性状,比重、容重比对照下降,总孔隙度趋近50%;水解氮、有机质比对照提高,与T1010的增殖正相关,有效磷比对照降低,与T1010的增殖负相关;T1010处理组侧根数比常规化肥处理组增加144%,立枯病感病指数降低36.36%。T1010具有改良土壤物理性状、提高微生物群体量、促进化学物质的可溶性等多种功能,是一种潜在、有效的土壤改良菌株。%Modified potential of soil environment of Trichoderma aureoviride T1010 was assessed in soil by its adjustment on microflora population and physical and chemical properties.The population of microflora was isolated from soil by the dilution method of counting.The physical property was assessed by soil weighting in laboratory.The chemical property was assessed by chemical reaction.With cherry-tomato growing,the T1010 promoted the growth of some beneficial microflora.The azotobacter population was 6.04 times higher than that in the beginning,and 58.02% higher than the control.The T1010 controlled the growth of the other fungus.The population of the other fungus was 52.99% lower than that at the beginning,and 79.47% lower than the control.The T1010 adjusted the physical property,the soil specific gravity and bulk density became lower than the control,and the porosity was close to 50%.The N and organic matter were higher than those of the control.The available P was lower

  8. EFFECTS OF PGPR AND ALFALFA ON SOIL BUILDING OF NEWLY-RECLAIMED LAND%复合型PGPR和苜蓿对新垦地土壤培肥效果研究

    Institute of Scientific and Technical Information of China (English)

    韩光; 张磊; 邱勤; 石杰; 胡正峰

    2011-01-01

    研究了利用根际有益微生物和豆科植物相结合培肥新垦地土壤的效果.试验采用裂区设计法研究了重庆北碚新垦坡耕地中性土壤上种植紫花苜蓿并接种根瘤菌和其他根际有益微生物(PGPR)(如联合固氮菌、解磷菌和解钾菌等)对土壤养分的影响.结果显示:接种根瘤菌+其他PGPR的处理对土壤有机质、全氮、全磷、全钾、有效磷和速效钾的提高均达到显著水平,较只接种根瘤菌的处理分别提高33.5%、22.7%、3.8%、11.5%、11.4%和22.3%,较不接种根瘤菌和PGPR的处理分别高42.2%、58.8%、8%、12.6%、37.2%和40.2%,接种根瘤菌+其他PGPR的效果优于只接种根瘤菌和不接种的.同时,上述处理对豆科植物苜蓿植株瘤重、株高、根鲜重、地上部鲜重以及植株全氮含量的提高均达到显著水平,比只接种根瘤菌的处理分别高44.5%、33.2%、77.3%、76.7%和17.7%.将苜蓿和相应的PGPR两者联合使用有更好的土壤改良效果,加速了新垦地贫瘠土壤的培肥过程.%Effect of planting legume crops and inoculation of Plant Growth Promoting Rhizobacteria (PGPR)and legumes on soil building in newly-reclaimed land was studied with a field experiment laid out in a newly-reclaimed slopeland in Beibei, Chongqing, China. The experiment field was divided into several plots, which were all planted with affaffa, but inoculated separately with nil, rhizobia or rhizobia + other PGPR (including associative azotobacters, P-releasing bacteria, and K-releasing bacteria). Results show that the incubation of rhizobium and PGPR in combination significantly increased organic matter, total N, total P and total K, available P and available K in the soil, by 33.5%, 22. 7%, 3.8% , 11.5%, 11.4% and 22.3%, respectively, over the incubation of rhizobia alone and by42.2%, 58.8% , 8%, 12.6% , 37.2% and 40.2%, respectively, over the treatment of no incubation. Furthermore, the treatment of

  9. Genes required for formation of the apoMoFe protein of Klebsiella pneumoniae nitrogenase in Escherichia coli.

    Science.gov (United States)

    Harris, G S; White, T C; Flory, J E; Orme-Johnson, W H

    1990-09-15

    peptides as the substrate for the processing to form the apoMoFe protein. We also find that nifM, the gene which processes the nifH protein into Fe protein (Howard, K.S., McLean, P.A., Hansen, F. B., Lemley, P.V., Kobla, K.S. & Orme-Johnson, W.H. (1986) J. Biol. Chem. 261, 772-778) can, under certain circumstances, partially replace other processing genes (i.e. nifTYU and/or WZ) although it is not essential for apoMoFe protein formation. It also appears that nifS and nifU, reported to play a role in Fe protein production in Azotobacter vinelandii, play no such role in K. pneumoniae, although these genes are involved in apoMoFe formation.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:2203791

  10. Soybean rhizosphere soil parameters in response to enhanced UV-B radia-tion under field condition%大田条件下UV-B辐射增强对大豆根际土壤相关指标的影响

    Institute of Scientific and Technical Information of China (English)

    张令瑄; 谢婷婷; 王瑾; 张文会; 吕志伟

    2016-01-01

    Soybean variety Xihuang 27 was exposed to enhanced UV⁃B radiation, under field condition, and rhizo⁃sphere soil parameters including soil microorganisms, content of organic matter, total nitrogen, activities of soil urease and invertase were measured during soybean development. At branching period, flowering period and seed⁃filling period, en⁃hanced UV⁃B radiation significantly inhibited the activities of soil urease by 17�9%, 11�7% and 5�7%, respectively and invertase by 23�5%, 6�1% and 13�2%, respectively. The amount of bacteria was deereased by 40�1%, 38�2% and 26�1%, respectively and the amount of aerobic azotobacter dropped by 72�2%, 33�3% and 35�7%, respectively. The a⁃mount of actinomycete was decreased by 36�3% and 50�0% only at branching and flowering whereas the amount of fungi was significantly decreased by 59�0% only at branching. No significant inhibition was found on the content of organic matter and total nitrogen. In conclusion, enhanced UV⁃B radiation could reduce the amounts of rhizosphere soil microorganisms and soil enzyme activities.%为了研究UV⁃B辐射增强对田间大豆根际土壤相关指标的影响,在大田条件下,通过模拟UV⁃B辐射增强,对大豆根际土壤微生物数量、根际土壤有机质含量、总氮含量以及根际土壤脲酶和转化酶酶活性进行测定。结果表明,在分枝期、花期及鼓粒期,UV⁃B辐射增强使脲酶的活性分别下降17�9%、1�7%和5�7%;转化酶的活性分别下降23�5%、6�1%和13�2%;细菌的数量显著降低40�1%、38�2%和26�1%;好氧固氮菌的数量显著降低72�2%、33�3%和35�7%。放线菌的数量只在分枝期和花期显著降低36�3%和50�0%,真菌的数量只在分枝期显著降低;UV⁃B辐射增强对土壤有机质、总氮含量没有显著影响。说明UV⁃B辐射增强可对大豆根际微生物的数量及土壤酶的活

  11. Comparative effectiveness of ACC-deaminase and/or nitrogen-fixing rhizobacteria in promotion of maize (Zea mays L.) growth under lead pollution.

    Science.gov (United States)

    Hassan, Waseem; Bano, Rizwana; Bashir, Farhat; David, Julie

    2014-09-01

    Lead (Pb) pollution is appearing as an alarming threat nowadays. Excessive Pb concentrations in agricultural soils result in minimizing the soil fertility and health which affects the plant growth and leads to decrease in crop production. Plant growth promoting rhizobacteria (PGPR) are beneficial bacteria which can protect the plants against many abiotic stresses, and enhance the growth. The study aimed to identify important rhizobacterial strains by using the 1-aminocyclopropane-1-carboxylate (ACC) enrichment technique and examine their inoculation effects in the growth promotion of maize, under Pb pollution. A pot experiment was conducted and six rhizobacterial isolates were used. Pb was added to 2 kg soil in each pot (with 4 seeds/pot) using Pb(NO3)2 at the rate of 0, 100, 200, 300, and 400 mg kg(-1) Pb with three replications in completely randomized design. Rhizobacterial isolates performed significantly better under all Pb levels, i.e., 100 to 400 Pb mg kg(-1) soil, compared to control. Comparing the efficacy of the rhizobacterial isolates under different Pb levels, rhizobacterial isolates having both ACC-deaminase and nitrogen-fixing activities (AN8 and AN12) showed highest increase in terms of the physical, chemical and enzymatic growth parameters of maize, followed by the rhizobacterial isolates having ACC-deaminase activity only (ACC5 and ACC8), and then the nitrogen-fixing rhizobia (Azotobacter and RN5). However, the AN8 isolate showed maximum efficiency, and highest shoot and root length (14.2 and 6.1 cm), seedling fresh and dry weights (1.91 and 0.14 g), chlorophyll a, b, and carotenoids (24.1, 30.2 and 77.7 μg/l), protein (0.82 mg/g), proline (3.42 μmol/g), glutathione S-transferase, peroxidase and catalase (12.3, 4.2 and 7.2 units/mg protein), while the lowest Pb uptake in the shoot and root (0.83 and 0.48 mg/kg) were observed under this rhizobial isolate at the highest Pb level (i.e., 400 Pb mg kg(-1) soil). The results revealed that PGPR

  12. 使用PGPR菌剂及苜蓿培肥新垦地土壤研究%Improving Fertility of Newly Reclaimed Soil by PGPR Inoculums in Combination with Alfalfa Growing

    Institute of Scientific and Technical Information of China (English)

    邱勤; 张磊; 韩光; 石杰; 胡正峰

    2011-01-01

    The split plot design was adopted in a one-year field experiment to investigate the effects of alfalfa planting in combination with PGPR inoculation on soil microbiological characteristics, alfalfa growth and soil properties in a newly reclaimed soil in Beibei, Chongqing, China. The PGPR (plant growth promoting rhizobacteria) involved in the study included alfalfa rhizobium, associative nitrogen fixation bacterium, silicate bacterium and Bacillus magatherium. The experiment included four treatments; alfalfa planting (A), alfalfa planting and rhizobium inoculation (A+R), alfalfa planting and PGPR inoculation (with rhizobium as well) (A+PGPR) and no crop planting (CK). Determined at the end of the experiment, the effects of the treatments on agronomic qualities of alfalfa, the amount of soil microorganisms and soil microbial biomass N (SMBN) were in the order of A + PGPR>A+R>A>CK, while those on soil microbial biomass C (SMBC) was in the order of A>A+PGPR>A+R>CK. Compared with CK, A +PGPR significantly raised nodule weight, plant height, root dry weight, shoot dry weight and total nitrogen (Pa-zotobacter in the soil (P<0. 05), enhanced SMBC and SMBN by 60. 12% and 63. 28% and significantly improved various indicators of soil fertility. Correlation analysis showed that SMBN was in significant positive correlations with plant total N and soil nutrients. It is, therefore, concluded that A+PGPR can increase the amount of microorganisms and the fertility of newly reclaimed soil.%本研究以重庆北碚新垦坡耕地中性土壤为对象,采用裂区设计法研究种植紫花苜蓿并配施根际有盖微生物(PGPR)对紫花苜蓿生长度土壤微生物的影响.本研究涉及的PGPR菌包括根瘤菌、联合固氮菌、硅酸盐细菌和巨大芽孢杆菌.设置种植紫花苜蓿不接种(A)、种植紫花苜蓿接种根瘤菌(A+R)、种植紫花苜蓿接

  13. 人工纳米材料对植物-微生物影响的研究进展%Review of Researches on Inlfuences of Engineered Nanomaterials on Plant-microorganism

    Institute of Scientific and Technical Information of China (English)

    曹际玲; 冯有智; 林先贵

    2016-01-01

    ,they form a plant-microorganism ecosystem. In this review,influences of ENMs on plants and microorganisms in the ecosystem are summarized. First,mechanisms of the potential ecotoxicities of ENMs and their relationships with the special properties of ENMs were collated and then researches of influences of ENMs on plants,soil microorganisms and plant-microorganism ecosystems were expounded. The review reveals that ENMs may have some impacts,varying in degree,on plant and microbes,and degree of the impact is related to kind of ENMs and species of the object and could be divided into three categories, negative,positive and insignificant. Moreover,researches have found plants and microbes may have some potentials to affect bioavailability of ENMs,which may serve as feedback to the ecological effect of ENMs on the plant-microorganism ecosystem. Recent studies on actual plant-microbe ecosystems found that ENMs affected functioning of arbuscular mycorrhizal fungi and azotobacters and excretion of iron chelator from soil microbes in the plant rhizosphere,thus altering eco-effect of ENMs,which suggests that to deem plants and soil microbes as an entity in the research may help the researchers go further in depth in studies on eco-effects of ENMs. Finally,the review lists out problems existing in the current researches with their pathways and techniques and focal points as well in ongoing researches.

  14. 木霉制剂改良滨海盐渍土台田生态效应%Ecological effect of Trichoderma agent on platform field soil improvement in saline coastal area

    Institute of Scientific and Technical Information of China (English)

    陈建爱; 段友臣; 郭峰; 杨武汉; 陈为京; 万书波

    2016-01-01

    azotobacters amounts increased by 170.95%, 82.68%, 152.17% and 471.93%, respectively, compared with those under CK. Beneficial properties to plants growth (e.g., soil compaction, ≥0.25 mm water stable aggregate, organic matter, microbial amount) of moderately saline coastal platform soils with Trichoderma agent (T1010) increased, respectively, by 1.53, 2.11, 3.20 and 28.33 times over that of flood land in coastal saline area. On the contrary, harmful property to plants growth, water soluble salts, reduced by 96.60%. Properties (such as soil compaction, porosity, moisture, contents of phosphorus and organic matter, and microbial amounts) of Trichoderma-amending moderately saline coastal soils were not significantly different from that of slightly saline coastal alkali soils. Reduced bulk density or increased porosity of moderately coastal saline platform fields with Trichoderma were close to that of the non-saline solar-greenhouse soils. Application of microbiological agents effectively improved soil properties of moderately saline coastal platform fields and ameliorated the ecological environment by enhancing soil aggregate structure, increasing soil nutrient and beneficial microorganisms amount.%生物改良滨海盐渍土是一种投资少、需时短、见效快、长期受益的环保生态型技术。通过田间试验将木霉制剂[活性成分为木霉分生孢子,1×107(CFU)·g-1]施用到滨海中度盐渍土台田(含盐量2.99 g·kg-1,砂壤土),对土壤改良台田试验区不同处理(施用木霉制剂和常规对照处理)及辅助试验区日光温室(含盐量0.98 g·kg-1,壤土)、滨海轻度盐渍土开垦田(含盐量1.75 g·kg-1,轻壤土)、滨海重度盐渍土河滩地(含盐量26.19 g·kg-1,砂壤土)的耕层土壤取样室内测定,探究木霉在滨海中度盐渍土台田施用的生态效应。滨海中度盐渍土台田木霉处理与对照处理相比,土壤紧实度提高177.04%,土壤水稳性团聚体数量(≥0.25 mm)提高265.78%,