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1

Degradation of p-xylene by a denitrifying enrichment culture.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Microbial cultures enriched from a diesel fuel-contaminated aquifer were able to grow on p-xylene under denitrifying conditions. The oxidation of p-xylene to CO2 was coupled to the reduction of NO3-. The enrichment cultures also grew on toluene and m-xylene, but they did not degrade benzene, ethylbenzene, and o-xylene.

Ha?ner, A.; Ho?hener, P.; Zeyer, J.

1995-01-01

2

Anaerobic ferrous oxidation by heterotrophic denitrifying enriched culture.  

Science.gov (United States)

Heterotrophic denitrifying enriched culture (DEC) from a lab-scale high-rate denitrifying reactor was discovered to perform nitrate-dependent anaerobic ferrous oxidation (NAFO). The DEC was systematically investigated to reveal their denitrification activity, their NAFO activity, and the predominant microbial population. The DEC was capable of heterotrophic denitrification with methanol as the electron donor, and autotrophic denitrification with ferrous salt as the electron donor named NAFO. The conversion ratios of ferrous-Fe and nitrate-N were 87.41 and 98.74 %, and the consumption Fe/N ratio was 2.3:1 (mol/mol). The maximum reaction velocity and half saturation constant of Fe were 412.54 mg/(l h) and 8,276.44 mg/l, and the counterparts of N were 20.87 mg/(l h) and 322.58 mg/l, respectively. The predominant bacteria were Hyphomicrobium, Thauera, and Flavobacterium, and the predominant archaea were Methanomethylovorans, Methanohalophilus, and Methanolobus. The discovery of NAFO by heterotrophic DEC is significant for the development of wastewater treatment and the biogeochemical iron cycle and nitrogen cycle. PMID:24619339

Wang, Ru; Zheng, Ping; Xing, Ya-Juan; Zhang, Meng; Ghulam, Abbas; Zhao, Zhi-Qing; Li, Wei; Wang, Lan

2014-05-01

3

Degradation of toluene and m-xylene and transformation of o-xylene by denitrifying enrichment cultures.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Seven different sources of inocula that included sediments, contaminated soils, groundwater, process effluent, and sludge were used to establish enrichment cultures of denitrifying bacteria on benzene, toluene, and xylenes in the absence of molecular oxygen. All of the enrichment cultures demonstrated complete depletion of toluene and partial depletion of o-xylene within 3 months of incubation. The depletion of o-xylene was correlated to and dependent on the metabolism of toluene. No losses o...

Evans, P. J.; Mang, D. T.; Young, L. Y.

1991-01-01

4

Molecular characterization and in situ quantification of anoxic arsenite-oxidizing denitrifying enrichment cultures.  

Science.gov (United States)

To explore the bacteria involved in the oxidation of arsenite (As(III)) under denitrifying conditions, three enrichment cultures (ECs) and one mixed culture (MC) were characterized that originated from anaerobic environmental samples. The oxidation of As(III) (0.5 mM) was dependent on NO(3) (-) addition and N(2) formation was dependent on As(III) addition. The ratio of N(2)-N formed to As(III) fed approximated the expected stoichiometry of 2.5. A 16S rRNA gene clone library analysis revealed three predominant phylotypes. The first, related to the genus Azoarcus from the division Betaproteobacteria, was found in the three ECs. The other two predominant phylotypes were closely related to the genera Acidovorax and Diaphorobacter within the Comamonadaceae family of Betaproteobacteria, and one of these was present in all of the cultures examined. FISH confirmed that Azoarcus accounted for a large fraction of bacteria present in the ECs. The Azoarcus clones had 96% sequence homology with Azoarcus sp. strain DAO1, an isolate previously reported to oxidize As(III) with nitrate. FISH analysis also confirmed that Comamonadaceae were present in all cultures. Pure cultures of Azoarcus and Diaphorobacter were isolated and shown to be responsible for nitrate-dependent As(III) oxidation. These results, taken as a whole, suggest that bacteria within the genus Azoarcus and the family Comamonadaceae are involved in the observed anoxic oxidation of As(III). PMID:19187211

Sun, Wenjie; Sierra-Alvarez, Reyes; Fernandez, Nuria; Sanz, Jose Luis; Amils, Ricardo; Legatzki, Antje; Maier, Raina M; Field, Jim A

2009-04-01

5

Anoxic biotransformation of 2,4-dinitrotoluene by denitrifying enrichment cultures  

Energy Technology Data Exchange (ETDEWEB)

The cometabolic biotransformation of 2,4-dinitrotoluene (DNT) under nitrogen reducing conditions by enrichment cultures using ethanol as the main source of carbon and energy was studied. Two microbial cultures were enriched from two different sources representing environments with and without previous exposure to DNT: the wastewater treatment system at the Radford Army Ammunition Plant in Radford, VA, and the municipal wastewater treatment plant in Urbana, IL. DNT was completely biotransformed. by both enrichment cultures. However, experiments with uniformly labeled [14C]-DNT demonstrated that no significant mineralization occurred. Losses by volatilization accounted for 9 and 7% of the original {sup 14}C-tracer in the unacclimated and acclimated cultures, respectively. The formation of insoluble materials was significant, with 41% of the tracer associated with this fraction in the unacclimated and 33% in the acclimated cultures. Most of the soluble metabolites were hydrophilic in the cultures from the unacclimated source. These metabolites were characterized according to their charge by HPLC and ion pairing chromatography. In the acclimated culture, 60% of the soluble metabolites were classified as hydrophobic materials. GC-MS analyses of this fraction revealed the presence of 2- and 4- mononitrotoluenes, 6-nitroindazole, acetylaminotoluene, and 4-acetylamino-2- nitrotoluene. These results indicate the inadequacy of setting a discharge limit only for DNT, since a number of the metabolites formed may also pose a significant toxicological hazard.

Noguera, D.R.; Freedman, D.L.

1996-12-31

6

Degradation of Phthalic Acids by Denitrifying, Mixed Cultures of Bacteria  

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Mixed cultures of bacteria, enriched from aquatic sediments, grew anaerobically on all three isomers of phthalic acid. Each culture grew anaerobically on only one isomer and also grew aerobically on the same isomer. Pure cultures were isolated from the phthalic acid (o-phthalic acid) and isophthalic acid (m-phthalic acid) enrichments that grew aerobically on phthalic and isophthalic acids. Cell suspension experiments indicated that protocatechuate is an intermediate of aerobic catabolism. Pur...

Aftring, R. Paul; Chalker, Bruce E.; Taylor, Barrie F.

1981-01-01

7

Utilization of Alkylbenzenes during Anaerobic Growth of Pure Cultures of Denitrifying Bacteria on Crude Oil  

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Four pure cultures of denitrifying bacteria, which had previously been isolated on defined alkylbenzenes, were capable of anaerobic growth with crude oil as the only source of organic substrates. Chemical analyses after growth revealed that the known growth substrates toluene, ethylbenzene, and m-xylene were selectively consumed from the oil. o-Xylene and p-xylene, which as pure compounds did not support growth, were consumed to a lesser extent.

Rabus, R.; Widdel, F.

1996-01-01

8

Anaerobic Toluene Activation by Benzylsuccinate Synthase in a Highly Enriched Methanogenic Culture  

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Permeabilized cells of a highly enriched, toluene-mineralizing, methanogenic culture catalyzed the addition of toluene to fumarate to form benzylsuccinate under anaerobic conditions. The specific in vitro rate of benzylsuccinate formation was >85% of the specific in vivo rate of toluene consumption. This is the first report of benzylsuccinate synthase activity in a methanogenic culture; the activity has previously been reported to occur in denitrifying, sulfate-reducing, and anoxygenic photot...

Beller, Harry R.; Edwards, Elizabeth A.

2000-01-01

9

Enrichment and molecular detection of denitrifying methanotrophic bacteria of the NC10 phylum.  

Science.gov (United States)

Anaerobic methane oxidation coupled to denitrification was recently assigned to bacteria belonging to the uncultured phylum NC10. In this study, we incubated sediment from a eutrophic ditch harboring a diverse community of NC10 bacteria in a bioreactor with a constant supply of methane and nitrite. After 6 months, fluorescence in situ hybridization showed that NC10 bacteria dominated the resulting population. The enrichment culture oxidized methane and reduced nitrite to dinitrogen gas. We assessed NC10 phylum diversity in the inoculum and the enrichment culture, compiled the sequences currently available for this bacterial phylum, and showed that of the initial diversity, only members of one subgroup had been enriched. The growth of this subgroup was monitored by quantitative PCR and correlated to nitrite-reducing activity and the total biomass of the culture. Together, the results indicate that the enriched subgroup of NC10 bacteria is responsible for anaerobic methane oxidation coupled to nitrite reduction. Due to methodological limitations (a strong bias against NC10 bacteria in 16S rRNA gene clone libraries and inhibition by commonly used stopper material) the environmental distribution and importance of these bacteria could be largely underestimated at present. PMID:19329658

Ettwig, Katharina F; van Alen, Theo; van de Pas-Schoonen, Katinka T; Jetten, Mike S M; Strous, Marc

2009-06-01

10

Enrichment and Molecular Detection of Denitrifying Methanotrophic Bacteria of the NC10 Phylum?  

Science.gov (United States)

Anaerobic methane oxidation coupled to denitrification was recently assigned to bacteria belonging to the uncultured phylum NC10. In this study, we incubated sediment from a eutrophic ditch harboring a diverse community of NC10 bacteria in a bioreactor with a constant supply of methane and nitrite. After 6 months, fluorescence in situ hybridization showed that NC10 bacteria dominated the resulting population. The enrichment culture oxidized methane and reduced nitrite to dinitrogen gas. We assessed NC10 phylum diversity in the inoculum and the enrichment culture, compiled the sequences currently available for this bacterial phylum, and showed that of the initial diversity, only members of one subgroup had been enriched. The growth of this subgroup was monitored by quantitative PCR and correlated to nitrite-reducing activity and the total biomass of the culture. Together, the results indicate that the enriched subgroup of NC10 bacteria is responsible for anaerobic methane oxidation coupled to nitrite reduction. Due to methodological limitations (a strong bias against NC10 bacteria in 16S rRNA gene clone libraries and inhibition by commonly used stopper material) the environmental distribution and importance of these bacteria could be largely underestimated at present.

Ettwig, Katharina F.; van Alen, Theo; van de Pas-Schoonen, Katinka T.; Jetten, Mike S. M.; Strous, Marc

2009-01-01

11

Enrichment and Molecular Detection of Denitrifying Methanotrophic Bacteria of the NC10 Phylum?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Anaerobic methane oxidation coupled to denitrification was recently assigned to bacteria belonging to the uncultured phylum NC10. In this study, we incubated sediment from a eutrophic ditch harboring a diverse community of NC10 bacteria in a bioreactor with a constant supply of methane and nitrite. After 6 months, fluorescence in situ hybridization showed that NC10 bacteria dominated the resulting population. The enrichment culture oxidized methane and reduced nitrite to dinitrogen gas. We as...

Ettwig, Katharina F.; Alen, Theo; Pas-schoonen, Katinka T.; Jetten, Mike S. M.; Strous, Marc

2009-01-01

12

IDENTIFICATION AND ECOPHYSIOLOGY OF ACTIVE DENITRIFIERS IN ACTIVATED SLUDGE  

DEFF Research Database (Denmark)

Denitrification is of crucial importance for nitrogen removal in wastewater treatment. However, due to the polyphyletic taxonomy of denitrifiers, little is known about their community composition and ecophysiology and the available knowledge derives mainly from culture-dependent studies or enriched reactor studies. To obtain better identification of active denitrifying communities in full-scale wastewater treatment plants (WWTPs) we applied DNA-SIP with 13C-labelled substrates, and RT-PCR of expressed denitrification genes (nirS, nirK and nosZ) upon various substrate-inductions. To come around the bias of horizontal gene transfer, the identities were verified by microautoradiography (MAR) combined with fluorescence in situ hybridization (FISH) with incorporation of radio-labelled substrates under denitrifying conditions. The in situ abundances of the identified denitrifiers in different WWTPs were determined with quantitative FISH, while their active metabolic pathways were investigated directly in activated sludge with a tag-based metatranscriptomic approach under acetate-utilizing and denitrifying conditions. The different methods revealed a majority of denitrifiers in all WWTPs belonging to Betaproteobacteria (Acidovorax, Azoarcus, Curvibacter and Thauera) and to a lesser extent Alphaproteobacteria (Paracoccus), while few denitrifying Gammaproteobacteria and Firmicutes were identified. A taxonomic discrepancy of the denitrifying communities was highly correlated to the configuration of the WWTPs and when external carbon sources were supplemented to the activated sludge the composition of the denitrifying communities was significantly affected. Transcriptome profiling provided detailed insight in the metabolic pathways in several of the active denitrifiers in activated sludge. In conclusion, this study has provided novel leads for the identity and distribution of denitrifiers in WWTPs as well as their physiological and metabolic capabilities in activated sludge.

Hansen, Aviaja Anna; Le-Quy, Vang

13

Enrichment of denitrifying methanotrophic bacteria from municipal wastewater sludge in a membrane bioreactor at 20°C.  

Science.gov (United States)

Simultaneous nitrogen and methane removal by the slow growing denitrifying methanotrophic bacterium 'Candidatus Methylomirabilis oxyfera' offers opportunities for a new approach to wastewater treatment. However, volumetric nitrite consumption rates should be increased by an order of magnitude before application in wastewater treatment becomes possible. A maximum volumetric nitrite consumption rate of 36mg NO2(-)-N/L d was achieved in a membrane bioreactor inoculated with wastewater sludge and operated at 20°C. This rate is similar to maximum rates reported in literature, though it was thought that by strict biomass retention using membranes, higher rates would be achieved. In experiments lasting several years, growth was not stable: every experiment showed a decrease in activity after 1-2 years. The cause remains unknown. Rates increased after addition of copper and operating a membrane bioreactor at shorter hydraulic retention times. Further research should focus on long-term effects of copper addition and operation at hydraulic retention times in the order of hours using membrane bioreactors. PMID:24809733

Kampman, Christel; Temmink, Hardy; Hendrickx, Tim L G; Zeeman, Grietje; Buisman, Cees J N

2014-06-15

14

[Rapid enrichment and cultivation of denitrifying phosphate-removal bacteria and its identification by fluorescence in situ hybridization technology].  

Science.gov (United States)

The present work focused on a rapid enrichment and cultivation of denitrifying phosphate-removal bacteria (DPB) in a membrane bio-reactor(MBR) by using A2/O anaerobic sludge from a wastewater treatment plant as seed, as well as providing an identification method. In the experiments, sodium acetate was used as the carbon source and a certain amount of nitrate was added to the MBR in the anoxic stage. Results showed that, with the efficient trap of the hollow-fiber membrane module, the proportion of DPB in all the phosphate-accumulating organisms (PAOs) increased from 24% to 93% within 35 days after two-stage's cultivation including anaerobic/aerobic and anaerobic/anoxic, during which the removal efficiency of nitrogen and phosphorus reached more than 90%. The activated sludge was identified by combining a regular method and the fluorescence in situ hybridization (FISH) technique, which demonstrated that Pseudomonas sp. and Rhodocyclus sp. were the dominant bacteria in the used bioreactor. PMID:24028025

Liu, Li; Tang, Bing; Huang, Shao-Song; Fu, Feng-Lian; Zhang, Qi-Qin; Li, Jian-Bin; Luo, Jian-Zhong

2013-07-01

15

[Research advances in aerobic denitrifiers].  

Science.gov (United States)

This paper reviewed the varieties and characteristics of aerobic denitrifiers, their action mechanisms, and the factors affecting aerobic denitrification. Aerobic denitrifiers mainly include Pseudomonas, Alcaligenes, Paracoccus and Bacillus, which are either aerobic or facultative aerobic, and heterotrophic. They can denitrify under aerobic conditions, with the main product being N2O. They can also convert NH4+ -N to gas product. The nitrate reductase which catalyzes the denitrification is periplasmic nitrate reductase rather than membrane-bound nitrate reductase. Dissolved oxygen concentration and C/N ratio are the main factors affecting aerobic denitrification. The main methods for screening aerobic denitrifiers, such as intermittent aeration and selected culture, were also introduced. The research advances in the application of aerobic denitrifiers in aquaculture, waste water processing, and bio-degradation of organic pollutants, as well as the contributions of aerobic denitrifiers to soil nitrogen emission were summarized. PMID:18260473

Wang, Wei; Cai, Zu-cong; Zhong, Wen-hui; Wang, Guo-xiang

2007-11-01

16

Microbial Manganese Reduction by Enrichment Cultures from Coastal Marine Sediments  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Manganese reduction was catalyzed by enrichment cultures of anaerobic bacteria obtained from coastal marine sediments. In the absence of oxygen, these enrichment cultures reduced manganates when grown on either lactate, succinate, or acetate in both sulfate-free and sulfate-containing artificial seawaters. Sodium azide as well as oxygen completely inhibited microbial manganese reduction by these enrichment cultures, whereas molybdate had no effect on them. The addition of nitrate to the mediu...

Burdige, David J.; Nealson, Kenneth H.

1985-01-01

17

Microbial characterization of toluene-degrading denitrifying consortia obtained from terrestrial and marine ecosystems.  

Science.gov (United States)

The degradation characteristics of toluene coupled to nitrate reduction were investigated in enrichment culture and the microbial communities of toluene-degrading denitrifying consortia were characterized by denaturing gradient gel electrophoresis (DGGE) technique. Anaerobic nitrate-reducing bacteria were enriched from oil-contaminated soil samples collected from terrestrial (rice field) and marine (tidal flat) ecosystems. Enriched consortia degraded toluene in the presence of nitrate as a terminal electron acceptor. The degradation rate of toluene was affected by the initial substrate concentration and co-existence of other hydrocarbons. The types of toluene-degrading denitrifying consortia depended on the type of ecosystem. The clone RS-7 obtained from the enriched consortium of the rice field was most closely related to a toluene-degrading and denitrifying bacterium, Azoarcus denitrificians (A. tolulyticus sp. nov.). The clone TS-11 detected in the tidal flat enriched consortium was affiliated to Thauera sp. strain S2 (T. aminoaromatica sp. nov.) that was able to degrade toluene under denitrifying conditions. This indicates that environmental factors greatly influence microbial communities obtained from terrestrial (rice field) and marine (tidal flat) ecosystems. PMID:15278317

An, Y-J; Joo, Y-H; Hong, I-Y; Ryu, H-W; Cho, K-S

2004-10-01

18

Enrichment of an Endosulfan-Degrading Mixed Bacterial Culture  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An endosulfan-degrading mixed bacterial culture was enriched from soil with a history of endosulfan exposure. Enrichment was obtained by using the insecticide as the sole source of sulfur. Chemical hydrolysis was minimized by using strongly buffered culture medium (pH 6.6), and the detergent Tween 80 was included to emulsify the insecticide, thereby increasing the amount of endosulfan in contact with the bacteria. No growth occurred in control cultures in the absence of endosulfan. Degradatio...

Sutherland, Tara D.; Horne, Irene; Lacey, Michael J.; Harcourt, Rebecca L.; Russell, Robyn J.; Oakeshott, John G.

2000-01-01

19

Metatranscriptome of an anaerobic benzene-degrading, nitrate-reducing enrichment culture reveals involvement of carboxylation in benzene ring activation.  

Science.gov (United States)

The enzymes involved in the initial steps of anaerobic benzene catabolism are not known. To try to elucidate this critical step, a metatranscriptomic analysis was conducted to compare the genes transcribed during the metabolism of benzene and benzoate by an anaerobic benzene-degrading, nitrate-reducing enrichment culture. RNA was extracted from the mixed culture and sequenced without prior mRNA enrichment, allowing simultaneous examination of the active community composition and the differential gene expression between the two treatments. Ribosomal and mRNA sequences attributed to a member of the family Peptococcaceae from the order Clostridiales were essentially only detected in the benzene-amended culture samples, implicating this group in the initial catabolism of benzene. Genes similar to each of two subunits of a proposed benzene-carboxylating enzyme were transcribed when the culture was amended with benzene. Anaerobic benzoate degradation genes from strict anaerobes were transcribed only when the culture was amended with benzene. Genes for other benzoate catabolic enzymes and for nitrate respiration were transcribed in both samples, with those attributed to an Azoarcus species being most abundant. These findings indicate that the mineralization of benzene starts with its activation by a strict anaerobe belonging to the Peptococcaceae, involving a carboxylation step to form benzoate. These data confirm the previously hypothesized syntrophic association between a benzene-degrading Peptococcaceae strain and a benzoate-degrading denitrifying Azoarcus strain for the complete catabolism of benzene with nitrate as the terminal electron acceptor. PMID:24795366

Luo, Fei; Gitiafroz, Roya; Devine, Cheryl E; Gong, Yunchen; Hug, Laura A; Raskin, Lutgarde; Edwards, Elizabeth A

2014-07-15

20

Enrichment and Short Term Culture of the Ovine Gonocyte  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The aim of this study was to investigate the effects of two types of ovine testis cells population as feeder cell on in vitro culture of the enriched ovine gonocytes. The feeder cell populations were prepared from 5-6 months old ovine testis. The 1-2 months old neonatal rams were used to isolate germ cells through a two step enzymatic digestion followed by differential plating for SSCs enrichment. Isolated and enriched cells were characterized by using PLZF and VASA antibody. During th...

Uyunbilig Borjigin; Xin Zhou; Xuejie Han; Rongfeng Li; Muren Herrid; Shorgan Bou

2011-01-01

 
 
 
 
21

Absence of microbial mineralization of lignin in anaerobic enrichment cultures.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The existence of anaerobic biodegradation of lignin was examined in mixed microflora. Egyptian soil samples, in which rapid mineralization of organic matter takes place in the presence of an important anaerobic microflora, were used to obtain the anaerobic enrichment cultures for this study. Specifically, 14CO2 or [14C]lignin wood was used to investigate the release of labeled gaseous or soluble degradation products of lignin in microbial cultures. No conversion of 14C-labeled lignin to 14CO2...

Odier, E.; Monties, B.

1983-01-01

22

Isolation and characterization of a new denitrifying spirillum capable of anaerobic degradation of phenol  

Energy Technology Data Exchange (ETDEWEB)

Two kinds of phenol-degrading denitrifying bacteria, Azoarcus sp. strain CC-11 and spiral bacterial strain CC-26, were isolated from the same enrichment culture after 1 and 3 years of incubation, respectively. Both strains required ferrous ions for growth, but strain CC-26 grew better than strain CC-11 grew under iron-limited conditions, which may have resulted in the observed change in the phenol-degrading bacteria during the enrichment process. Strain CC-26 grew on phenol, benzoate, and other aromatic compounds under denitrifying conditions. Phylogenetic analysis of 16S ribosomal DNA sequences revealed that this strain is most closely related to a Magnetospirillum sp., a member of the {alpha} subclass of the class Proteobacteria, and is the first strain of a denitrifying aromatic compound-degrading bacterium belonging to this group. Unlike previously described Magnetospirillum strains, however, this strain did not exhibit magnetotaxis. It grew on phenol only under denitrifying conditions. Other substrates, such as acetate, supported aerobic growth, and the strain exhibited microaerophilic features.

Shinoda, Yoshifumi; Sakai, Yasuyoshi; Ue, Makiko; Hiraishi, Akira; Kato, Nobuo

2000-04-01

23

Isolation and characterization of a new denitrifying spirillum capable of anaerobic degradation of phenol.  

Science.gov (United States)

Two kinds of phenol-degrading denitrifying bacteria, Azoarcus sp. strain CC-11 and spiral bacterial strain CC-26, were isolated from the same enrichment culture after 1 and 3 years of incubation, respectively. Both strains required ferrous ions for growth, but strain CC-26 grew better than strain CC-11 grew under iron-limited conditions, which may have resulted in the observed change in the phenol-degrading bacteria during the enrichment process. Strain CC-26 grew on phenol, benzoate, and other aromatic compounds under denitrifying conditions. Phylogenetic analysis of 16S ribosomal DNA sequences revealed that this strain is most closely related to a Magnetospirillum sp., a member of the alpha subclass of the class Proteobacteria, and is the first strain of a denitrifying aromatic compound-degrading bacterium belonging to this group. Unlike previously described Magnetospirillum strains, however, this strain did not exhibit magnetotaxis. It grew on phenol only under denitrifying conditions. Other substrates, such as acetate, supported aerobic growth, and the strain exhibited microaerophilic features. PMID:10742201

Shinoda, Y; Sakai, Y; Ué, M; Hiraishi, A; Kato, N

2000-04-01

24

Culture of Piscirickettsia salmonis on enriched blood agar.  

Science.gov (United States)

Piscirickettsia salmonis is the etiologic agent of piscirickettsiosis, an economically significant disease of fish. Isolation of P. salmonis by culturing on fish cell lines has been the standard technique since the initial isolation of the organism. The ability to grow P. salmonis on artificial media would relieve facilities of the cost of maintaining cell lines, permit isolation at fish culture sites with fewer contamination problems, and allow easier transport of isolates to diagnostic facilities for confirmation assays. This report describes the successful culture of P. salmonis on enriched blood agar. PMID:18319435

Mauel, Michael J; Ware, Cynthia; Smith, Pedro A

2008-03-01

25

Biodegradation of haloacetic acids by bacterial enrichment cultures.  

Science.gov (United States)

Haloacetic acids (HAAs) are toxic organic chemicals that are frequently detected in surface waters and in drinking water distribution systems. The aerobic biodegradation of HAAs was investigated in serum bottles containing a single HAA and inoculated with washed microorganisms obtained from enrichment cultures maintained on either monochloroacetic acid (MCAA) or trichloroacetic acid (TCAA) as the sole carbon and energy source. Biodegradation was observed for each of the HAAs tested at concentrations similar to those found in surface waters and in drinking water distribution systems. The MCAA culture was able to degrade both MCAA and monobromoacetic acid (MBAA) with pseudo-first order rate constants of 1.06 x 10(-2) and 1.13 x 10(-2) l(mg protein)(-1) d(-1), respectively, for concentrations ranging from 10(-5) to 2 mM. The pseudo-first order rate constant for TCAA degradation by the TCAA culture was 6.52 x 10(-3) l(mg protein)(-1) d(-1) for concentrations ranging from 5.33 x 10(-5) to 0.72 mM. The TCAA culture was also able to degrade MCAA with the rate accelerating as incubation time increased. Experiments with radiolabeled HAAs indicated that the 14C was primarily converted to 14CO2 with minor incorporation into cell biomass. The community structure of the enrichment cultures was analyzed by both cultivation-dependent and cultivation-independent approaches. Denaturing gradient gel electrophoresis (DGGE) of the PCR-amplified 16S rRNA gene fragments showed that each of the two enrichment cultures had multiple bacterial populations, none of which corresponded to HAA-degrading bacteria cultivated on HAA-supplemented agar plates. This research indicates that biodegradation is a potential loss mechanism for HAAs in surface waters and in drinking water distribution systems. PMID:15041296

McRae, Bethany M; LaPara, Timothy M; Hozalski, Raymond M

2004-05-01

26

Enrichment culture can bias the isolation of Campylobacter subtypes.  

Science.gov (United States)

Enrichment culture is often used to isolate Campylobacter. This study compared isolation of Campylobacter spp. from 119 broiler chicken environments from two farms, using Preston and modified Exeter (mExeter) and modified Bolton (mBolton) enrichments. mExeter was significantly more effective in isolating Campylobacter spp. from the environmental samples compared to Preston (P0.05). Enrichment broth type did not affect isolation from chicken faecal or soil and litter samples. C. jejuni was isolated from significantly more environmental samples using mExeter broth compared to Preston (Pdetection of C. coli (P>0.05). Only C. coli was isolated from the soil and litter samples and although both C. jejuni and C. coli were recovered from the faecal samples there was no effect of using different enrichment broths. The majority of samples where the same species had been isolated yielded the same or closely related genotypes as defined by pulsed-field gel electrophoresis. Isolates recovered using Preston and mBolton broths were less genetically diverse than those from mExeter broth. We conclude that the enrichment method used affects both the number and species of Campylobacter isolated from naturally contaminated samples. PMID:21923970

Williams, L K; Sait, L C; Cogan, T A; Jørgensen, F; Grogono-Thomas, R; Humphrey, T J

2012-07-01

27

Isolation and Characterization of a New Denitrifying Spirillum Capable of Anaerobic Degradation of Phenol  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Two kinds of phenol-degrading denitrifying bacteria, Azoarcus sp. strain CC-11 and spiral bacterial strain CC-26, were isolated from the same enrichment culture after 1 and 3 years of incubation, respectively. Both strains required ferrous ions for growth, but strain CC-26 grew better than strain CC-11 grew under iron-limited conditions, which may have resulted in the observed change in the phenol-degrading bacteria during the enrichment process. Strain CC-26 grew on phenol, benzoate, and oth...

Shinoda, Yoshifumi; Sakai, Yasuyoshi; Ue?, Makiko; Hiraishi, Akira; Kato, Nobuo

2000-01-01

28

Diaphorobacter oryzae sp. nov., isolated from a thiosulfate-oxidizing enrichment culture.  

Science.gov (United States)

A taxonomic study was performed on two isolates, strains RF3(T) and RF21, recovered from a thiosulfate-oxidizing enrichment culture. Comparative 16S rRNA gene sequence analysis showed that these isolates were clearly affiliated with the class Betaproteobacteria. Strains RF3(T) and RF21 were most closely related to Diaphorobacter nitroreducens NA10B(T) (97.9 and 98.2 % 16S rRNA gene sequence similarity, respectively). The level of 16S rRNA gene sequence similarity between strains RF3(T) and RF21 was 99.8 %. The two isolates were Gram-negative, aerobic and denitrifying. Growth was observed at 7-35 degrees C. Physiological and biochemical properties of strains RF3(T) and RF21 were different from those of D. nitroreducens NA10B(T) in that strains RF3(T) and RF21 were able to utilize l-histidine, 2-ketogluconate and caprate, but unable to utilize suberate. The G+C contents of the genomic DNA of strains RF3(T) and RF21 were 62.9 and 62.8 mol%, respectively, and the predominant quinone was ubiquinone-8. Strains RF3(T) and RF21 possessed C(16 : 0), C(17 : 0) cyclo, and C(16 : 1)omega7c and/or iso-C(15 : 0) 2-OH as major fatty acids. DNA-DNA relatedness data indicated that strains RF3(T) and RF21 represent a genomic species separate from D. nitroreducens. On the basis of the evidence presented from this polyphasic analysis, it is suggested that strains RF3(T) and RF21 represent a novel species of the genus Diaphorobacter, for which the name Diaphorobacter oryzae sp. nov. is proposed. The type strain is RF3(T) (=KCTC 22225(T)=LMG 24467(T)). PMID:19196757

Pham, Vinh Hoa; Park, Soo-Je; Roh, Yul; Roh, Dong-Hyun; Rhee, Sung-Keun

2009-02-01

29

Anaerobic degradation of long-chain alkylamines by a denitrifying Pseudomonas stutzeri.  

Science.gov (United States)

The anaerobic degradation of tetradecylamine and other long-chain alkylamines by a newly isolated denitrifying bacterium was studied. Strain ZN6 was isolated from a mixture of soil and active sludge and was identified as representing Pseudomonas stutzeri, based on partial 16S rRNA gene sequence analysis. Strain ZN6 was a mesophilic, motile, Gram-negative rod-shaped bacterium and was able to grow on a variety of compounds including even-numbered primary fatty amines with alkyl chains ranging from C(4) to C(18) coupled to nitrate reduction. Alkylamines were used as sole carbon, energy and nitrogen source and were completely mineralized. Nitrate was dissimilated by ZN6 to nitrite. When strain ZN6 was grown under nitrate limitation, nitrite was slowly dissimilated further. When cocultivated with the complete denitrifier Castellaniella defragens ZN3, anaerobic degradation under denitrifying of alkylamines by strain ZN6 was slightly faster. Strain ZN3 is a complete denitrifier, unable to convert tetradecylamine, and was copurified from the same enrichment culture as strain ZN6. The proposed pathway for the degradation of alkylamines in strain ZN6 starts with C-N cleavages to alkanals and further oxidation to the corresponding fatty acids. PMID:18721145

Nguyen, Phuong D; van Ginkel, Cornelis G; Plugge, Caroline M

2008-10-01

30

Chloroform degradation in methanogenic methanol enrichment cultures and by Methanosarcina barkeri 227.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The effects of methanol addition and consumption on chloroform degradation rate and product distribution in methanogenic methanol enrichment cultures and in cultures of Methanosarcina barkeri 227 were investigated. Degradation of chloroform with initial concentrations up to 27.3 microM in enrichment cultures and 4.8 microM in pure cultures was stimulated by the addition of methanol. However, methanol consumption was inhibited by as little as 2.5 microM chloroform in enrichment cultures and 0....

Bagley, D. M.; Gossett, J. M.

1995-01-01

31

Anaerobic oxidation of acetylene by estuarine sediments and enrichment cultures  

International Nuclear Information System (INIS)

Acetylene disappeared from the gas phase of anaerobically incubated estuarine sediment slurries, and loss was accompanied by increased levels of carbon dioxide. Acetylene loss was inhibited by chloroamphenicol, air, and autoclaving. Addition of 14C2H2 to slurries resulted in the formation of 14CO2 and the transient appearance of 14C-soluble intermediates, of which acetate was a major component. Acetylene oxidation stimulated sulfate reduction; however, sulfate reduction was not required for the loss of C2H2 to occur. Enrichment cultures were obtained which grew anaerobically at the expense of C2H2

1981-01-01

32

Methanogenic octadecene degradation by syntrophic enrichment culture from brackish sediments.  

Science.gov (United States)

A microbial enrichment culture from brackish sediments was able to grow on octadec-1-ene (an unsaturated aliphatic hydrocarbon) as sole source of carbon and energy, under methanogenic conditions. Octadecene degradation is stopped either when bromoethanesulfonic acid, a selective inhibitor of methanogenesis is introduced, or when hydrogen is introduced. In the presence of bromoethanesulfonic acid, the degradation is restored by the addition of a hydrogenotrophic sulfate-reducing microorganism with sulfate. Results of molecular biodiversity, which revealed the presence of bacteria as well as of acetoclastic and hydrogenotrophic methanogens, are consistent with a syntrophic degradation involving Bacteria and Archaea. This is the first demonstration of syntrophic alkene degradation by microbial communities, showing that syntrophy is more widespread than we could have thought so far. These results highlight the need for a better understanding of microbial interactions and their role in the organic-matter degradation in polluted environments. PMID:22842907

Hirschler-Réa, Agnès; Cravo-Laureau, Cristiana; Casalot, Laurence; Matheron, Robert

2012-11-01

33

Establishment of polychlorinated biphenyl-degrading enrichment culture with predominantly meta dechlorination.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Enrichment of polychlorinated biphenyl (PCB)-dechlorinating microorganisms from PCB-contaminated sediments from the Upper Hudson River, N.Y., was attempted. The enrichment strategy was to use pyruvate as the electron donor and dechlorination of Aroclor 1242 as the electron acceptor. The enrichment medium also contained non-PCB-contaminated Hudson River sediments, which were required for the PCB-dechlorinating activity. An enrichment culture (that had stable PCBT-dechlorinating activity over n...

Morris, P. J.; Mohn, W. W.; Quensen, J. F.; Tiedje, J. M.; Boyd, S. A.

1992-01-01

34

Microbial community and function of enrichment cultures with methane and toluene.  

Science.gov (United States)

The interaction effect of co-existence of toluene and CH4 on community and activity of methanotrophs and toluene-degrading bacteria was characterized in three consortia enriched with CH4 and toluene (MT), toluene (T), and CH4 (M), respectively, in this study. The CH4 oxidation activity in the enrichment culture of MT was significantly lower than that of M at the end of the experiment (P?=?0.001). The toluene degradation rate could be enhanced by continuous addition of CH4 and toluene in the initial days, but it was inhibited in the later days. Phylogenetic analysis of 16S rRNA genes showed that Proteobacteria and Bacteroidetes were dominant in the three enriched consortia, but the community of methanotrophs and toluene-degrading bacteria was significantly affected by the co-existence of CH4 and toluene. Both Methylosinus (91.8 %) and Methylocystis (8.2 %) were detected in the enrichment culture of MT, while only Methylocystis species were detected in M. The toluene-degrading bacteria including Burkholderia, Flavobacteria, Microbacterium, and Azoarcus were all detected in the enrichment culture of T. However, only Azoarcus was found in the enrichment culture of MT. Significantly higher contents of extracellular polymeric substances polysaccharose and protein in the enrichment culture of MT than that of T and M suggested that a higher environmental stress occurred in the enrichment culture of MT. PMID:24136469

Su, Yao; Xia, Fang-Fang; Tian, Bao-Hu; Li, Wei; He, Ruo

2014-04-01

35

Continuous enrichment cultures: insights into prokaryotic diversity and metabolic interactions in deep-sea vent chimneys.  

Science.gov (United States)

The prokaryotic diversity of culturable thermophilic communities of deep-sea hydrothermal chimneys was analysed using a continuous enrichment culture performed in a gas-lift bioreactor, and compared to classical batch enrichment cultures in vials. Cultures were conducted at 60 degrees C and pH 6.5 using a complex medium containing carbohydrates, peptides and sulphur, and inoculated with a sample of a hydrothermal black chimney collected at the Rainbow field, Mid-Atlantic Ridge, at 2,275 m depth. To assess the relevance of both culture methods, bacterial and archaeal diversity was studied using cloning and sequencing, DGGE, and whole-cell hybridisation of 16S rRNA genes. Sequences of heterotrophic microorganisms belonging to the genera Marinitoga, Thermosipho, Caminicella (Bacteria) and Thermococcus (Archaea) were obtained from both batch and continuous enrichment cultures while sequences of the autotrophic bacterial genera Deferribacter and Thermodesulfatator were only detected in the continuous bioreactor culture. It is presumed that over time constant metabolite exchanges will have occurred in the continuous enrichment culture enabling the development of a more diverse prokaryotic community. In particular, CO(2) and H(2) produced by the heterotrophic population would support the growth of autotrophic populations. Therefore, continuous enrichment culture is a useful technique to grow over time environmentally representative microbial communities and obtain insights into prokaryotic species interactions that play a crucial role in deep hydrothermal environments. PMID:17576518

Postec, Anne; Lesongeur, Françoise; Pignet, Patricia; Ollivier, Bernard; Querellou, Joël; Godfroy, Anne

2007-11-01

36

Heterotrophic nitrification among denitrifiers.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Twelve denitrifying bacteria representing six genera were tested for an ability to nitrify pyruvic oxime heterotrophically. Six of these bacteria exhibited appreciable nitrification activity, yielding as much as 5.8 mM nitrite and little or no nitrate when grown in a mineral salts medium containing 7 mM pyruvic oxime and 0.05% yeast extract. Of the six active bacteria, four (Pseudomonas denitrificans, Pseudomonas aeruginosa, and two strains of Pseudomonas fluorescens) could grow on yeast extr...

Castignetti, D.; Hollocher, T. C.

1984-01-01

37

Enrichment methodology to increase the positivity of cultures from body fluids  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Isolation and identification of etiological agents found in body fluids can be of critical importance for the recovery of patients suffering from potentially-severe infections, which are often followed by serious sequels. Eighty-two samples of different body fluids were analyzed using two different methods: (1) the conventional culture method (agar plating) and (2) the enrichment culture technique, using the Bact/Alert® blood culture bottle. The number of positive cultures increased on avera...

Alessandra Valle Daur; Francisco Klimak Jr.; Laura Lúcia Cogo; Gislene Diógenes Botão; Cristina Leise Bastos Monteiro; Libera Maria Dalla Costa

2006-01-01

38

Enrichment methodology to increase the positivity of cultures from body fluids  

Directory of Open Access Journals (Sweden)

Full Text Available Isolation and identification of etiological agents found in body fluids can be of critical importance for the recovery of patients suffering from potentially-severe infections, which are often followed by serious sequels. Eighty-two samples of different body fluids were analyzed using two different methods: (1 the conventional culture method (agar plating and (2 the enrichment culture technique, using the Bact/Alert® blood culture bottle. The number of positive cultures increased on average from 9.7% to 23.1% with the enrichment culture technique. Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus were the most frequently isolated bacteria. The enrichment method could provide a more accurate means the identifying etiological agents.

Alessandra Valle Daur

2006-12-01

39

Enhanced production and isotope enrichment of recombinant glycoproteins produced in cultured mammalian cells  

International Nuclear Information System (INIS)

NMR studies of post-translationally modified proteins are complicated by the lack of an efficient method to produce isotope enriched recombinant proteins in cultured mammalian cells. We show that reducing the glucose concentration and substituting glutamate for glutamine in serum-free medium increased cell viability while simultaneously increasing recombinant protein yield and the enrichment of non-essential amino acids compared to culture in unmodified, serum-free medium. Adding dichloroacetate, a pyruvate dehydrogenase kinase inhibitor, further improves cell viability, recombinant protein yield, and isotope enrichment. We demonstrate the method by producing partially enriched recombinant Thy1 glycoprotein from Lec1 Chinese hamster ovary (CHO) cells using U-13C-glucose and 15N-glutamate as labeled precursors. This study suggests that uniformly 15N,13C-labeled recombinant proteins may be produced in cultured mammalian cells starting from a mixture of labeled essential amino acids, glucose, and glutamate.

2010-10-01

40

Enhanced production and isotope enrichment of recombinant glycoproteins produced in cultured mammalian cells  

Energy Technology Data Exchange (ETDEWEB)

NMR studies of post-translationally modified proteins are complicated by the lack of an efficient method to produce isotope enriched recombinant proteins in cultured mammalian cells. We show that reducing the glucose concentration and substituting glutamate for glutamine in serum-free medium increased cell viability while simultaneously increasing recombinant protein yield and the enrichment of non-essential amino acids compared to culture in unmodified, serum-free medium. Adding dichloroacetate, a pyruvate dehydrogenase kinase inhibitor, further improves cell viability, recombinant protein yield, and isotope enrichment. We demonstrate the method by producing partially enriched recombinant Thy1 glycoprotein from Lec1 Chinese hamster ovary (CHO) cells using U-{sup 13}C-glucose and {sup 15}N-glutamate as labeled precursors. This study suggests that uniformly {sup 15}N,{sup 13}C-labeled recombinant proteins may be produced in cultured mammalian cells starting from a mixture of labeled essential amino acids, glucose, and glutamate.

Skelton, David; Goodyear, Abbey [Florida State University, Department of Chemistry and Biochemistry (United States); Ni, DaQun; Walton, Wendy J.; Rolle, Myron; Hare, Joan T. [Florida State University, Institute of Molecular Biophysics (United States); Logan, Timothy M., E-mail: tlogan@fsu.ed [Florida State University, Department of Chemistry and Biochemistry (United States)

2010-10-15

 
 
 
 
41

An Effectiveness Study of a Culturally Enriched School-Based CBT Anxiety Prevention Program  

Science.gov (United States)

Anxiety disorders are prevalent in the school-aged population and are present across cultural groups. Scant research exists on culturally relevant prevention and intervention programs for mental health problems in the Aboriginal populations. An established cognitive behavioral program, FRIENDS for Life, was enriched to include content that was…

Miller, Lynn D.; Laye-Gindhu, Aviva; Bennett, Joanna L.; Liu, Yan; Gold, Stephenie; March, John S.; Olson, Brent F.; Waechtler, Vanessa E.

2011-01-01

42

Isolation of Methylophaga spp. from Marine Dimethylsulfide-Degrading Enrichment Cultures and Identification of Polypeptides Induced during Growth on Dimethylsulfide?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Dimethylsulfide (DMS)-degrading enrichment cultures were established from samples of coastal seawater, nonaxenic Emiliania huxleyi cultures, and mixed marine methyl halide-degrading enrichment cultures. Bacterial populations from a broad phylogenetic range were identified in the mixed DMS-degrading enrichment cultures by denaturing gradient gel electrophoresis (DGGE). Sequences of dominant DGGE bands were similar to those of members of the genera Methylophaga and Alcanivorax. Several closely ...

Scha?fer, Hendrik

2007-01-01

43

Use of ?-hexachlorocyclohexane as a terminal electron acceptor by an anaerobic enrichment culture  

International Nuclear Information System (INIS)

Highlights: ? Use of ?-hexachlorocyclohexane as a terminal electron acceptor was demonstrated. ? H2 served as the electron donor for an enrichment culture that dechlorinated ?-HCH. ? H2 consumption for acetogenesis and methanogenesis stopped in HEPES media. ? Addition of vancomycin significantly slowed the rate of ?-HCH dechlorination. ? Previously identified chlororespiring microbes were not detected in the enrichment. - Abstract: The use of ?-hexachlorocyclohexane (HCH) as a terminal electron acceptor via organohalide respiration was demonstrated for the first time with an enrichment culture grown in a sulfate-free HEPES-buffered anaerobic mineral salts medium. The enrichment culture was initially developed with soil and groundwater from an industrial site contaminated with HCH isomers, chlorinated benzenes, and chlorinated ethenes. When hydrogen served as the electron donor, 79–90% of the electron equivalents from hydrogen were used by the enrichment culture for reductive dechlorination of the ?-HCH, which was provided at a saturation concentration of approximately 10 mg/L. Benzene and chlorobenzene were the only volatile transformation products detected, accounting for 25% and 75% of the ?-HCH consumed (on a molar basis), respectively. The enrichment culture remained active with only hydrogen as the electron donor and ?-HCH as the electron acceptor through several transfers to fresh mineral salts medium for more than one year. Addition of vancomycin to the culture significantly slowed the rate of ?-HCH dechlorination, suggesting that a Gram-positive organism is responsible for the reduction of ?-HCH. Analysis of the ?-HCH dechlorinating enrichment culture did not detect any known chlororespiring genera, including Dehalobacter. In bicarbonate-buffered medium, reductive dechlorination of ?-HCH was accompanied by significant levels of acetogenesis as well as methanogenesis.

2011-12-15

44

Use of {gamma}-hexachlorocyclohexane as a terminal electron acceptor by an anaerobic enrichment culture  

Energy Technology Data Exchange (ETDEWEB)

Highlights: Black-Right-Pointing-Pointer Use of {gamma}-hexachlorocyclohexane as a terminal electron acceptor was demonstrated. Black-Right-Pointing-Pointer H{sub 2} served as the electron donor for an enrichment culture that dechlorinated {gamma}-HCH. Black-Right-Pointing-Pointer H{sub 2} consumption for acetogenesis and methanogenesis stopped in HEPES media. Black-Right-Pointing-Pointer Addition of vancomycin significantly slowed the rate of {gamma}-HCH dechlorination. Black-Right-Pointing-Pointer Previously identified chlororespiring microbes were not detected in the enrichment. - Abstract: The use of {gamma}-hexachlorocyclohexane (HCH) as a terminal electron acceptor via organohalide respiration was demonstrated for the first time with an enrichment culture grown in a sulfate-free HEPES-buffered anaerobic mineral salts medium. The enrichment culture was initially developed with soil and groundwater from an industrial site contaminated with HCH isomers, chlorinated benzenes, and chlorinated ethenes. When hydrogen served as the electron donor, 79-90% of the electron equivalents from hydrogen were used by the enrichment culture for reductive dechlorination of the {gamma}-HCH, which was provided at a saturation concentration of approximately 10 mg/L. Benzene and chlorobenzene were the only volatile transformation products detected, accounting for 25% and 75% of the {gamma}-HCH consumed (on a molar basis), respectively. The enrichment culture remained active with only hydrogen as the electron donor and {gamma}-HCH as the electron acceptor through several transfers to fresh mineral salts medium for more than one year. Addition of vancomycin to the culture significantly slowed the rate of {gamma}-HCH dechlorination, suggesting that a Gram-positive organism is responsible for the reduction of {gamma}-HCH. Analysis of the {gamma}-HCH dechlorinating enrichment culture did not detect any known chlororespiring genera, including Dehalobacter. In bicarbonate-buffered medium, reductive dechlorination of {gamma}-HCH was accompanied by significant levels of acetogenesis as well as methanogenesis.

Elango, Vijai, E-mail: velango@g.clemson.edu [Hazardous Substance Research Center/South and Southwest, Louisiana State University, 3221 Patrick Taylor Hall, Baton Rouge, LA 70803 (United States); Kurtz, Harry D. [Department of Genetics and Biochemistry, Clemson University, 100 Jordan Hall, Clemson, SC 29634 (United States); Anderson, Christina; Freedman, David L. [Department of Environmental Engineering and Earth Sciences, Box 340919, Clemson University, Clemson, SC 29634-0919 (United States)

2011-12-15

45

Quantification of anaerobic ammonium-oxidizing bacteria in enrichment cultures by real-time PCR.  

Science.gov (United States)

The anaerobic ammonium-oxidizing (ANAMMOX) bacteria were enriched from a rotating disk reactor (RDR) biofilm in semi-batch cultures. Based on fluorescence in situ hybridization (FISH) analysis, this enrichment led to a relative population size of 36% ANAMMOX bacteria. Phylogenetic analysis revealed that all the detected clones were related to the previously reported ANAMMOX bacteria, Candidatus Brocadia anammoxidans (AF375994), with 92% sequence similarity. Furthermore, we successfully developed a real-time polymerase chain reaction (PCR) assay to quantify populations of ANAMMOX bacteria in the enrichment cultures. For this real-time PCR assay, PCR primer sets targeting 16S ribosomal RNA genes of ANAMMOX bacteria were designed and used. The quantification range of this assay was 6 orders of magnitude, from 8.9x10(1) to 8.9x10(6) copies per PCR, corresponding to the detection limit of 3.6x10(3) target copies mL(-1). A significant correlation was found between the increase in copy numbers of 16S rRNA gene of ANAMMOX bacteria and the increase in nitrogen removal rates in the enrichment cultures. Quantifying ANAMMOX bacterial populations in the enrichment culture made it possible to estimate the doubling time of the enriched ANAMMOX bacteria to be 3.6 to 5.4 days. The real-time PCR assay gave comparable population sizes in the enrichment cultures with the FISH results. These results suggest that the real-time PCR assay developed in this study is useful and reliable for quantifying the populations of ANAMMOX bacteria in environmental and engineering samples. PMID:17215016

Tsushima, Ikuo; Kindaichi, Tomonori; Okabe, Satoshi

2007-02-01

46

Enriching Chinese Cultural Heritage at the Queens Library  

Directory of Open Access Journals (Sweden)

Full Text Available

???13-18

The Queens Borough Public Library through its New Americans Program has been providing opportunities for the Chinese Community to experience quality library service for many years. By building collections, providing opportunities to learn English, providing job information, coping skills classes, cultural programs and electronic access to Chinese vernacular script, the Library provides a unique public library experience to its many immigrants. Through demographic analysis, the Library places its collections in the communities where immigrants live and provides programs of relevance to celebrate the cultures and traditions of the Chinese community.

Gary E. Strong

2001-10-01

47

Detection of Salmonella invA gene in shrimp enrichment culture by polymerase chain reaction.  

Science.gov (United States)

Contamination of seafood with salmonellae is a major public health concern. Detection of Salmonella by standard culture methods is time consuming. In this study, an enrichment culture step prior to polymerase chain reaction (PCR) was applied to detect 284 bp fragment of Salmonella invA in comparison with the conventional culture method in 100 shrimp samples collected from four different shrimp farms and fresh food markets around Bangkok. Samples were pre-enriched in non-selective lactose broth (LB) and selective tetrathionate broth (TTB). PCR detection limit was 10 pg and 10(4) cfu/ml of viable salmonellae with 100% specificity. PCR assay detected 19 different Salmonella serovars belonging to 8 serogroups (B, C1, C2-C3, D1, E1, E4 and K) commonly found in clinical and environmental samples in Thailand. The detection rate of PCR following TTB enrichment (24%) was higher than conventional culture method (19%). PCR following TTB, but not in LB enrichment allowed salmonella detection with 84% sensitivity, 90% specificity and 89% accuracy. Shrimp samples collected from fresh food markets had higher levels of contaminated salmonellae than those from shrimp farms. The results indicated that incorporation of an enrichment step prior to PCR has the potential to be applied for detection of naturally contaminated salmonellae in food, environment and clinical samples. PMID:20578527

Upadhyay, Bishnu Prasad; Utrarachkij, Fuangfa; Thongshoob, Jarinee; Mahakunkijcharoen, Yuvadee; Wongchinda, Niracha; Suthienkul, Orasa; Khusmith, Srisin

2010-03-01

48

Two-stage mineralization of phenanthrene by estuarine enrichment cultures  

International Nuclear Information System (INIS)

The polycyclic aromatic hydrocarbon phenanthrene was mineralized in two stages by soil, estuarine water, and sediment microbial populations. At high concentrations, phenanthrene was degraded, with the concomitant production of biomass and accumulation of Folin-Ciocalteau-reactive aromatic intermediates. Subsequent consumption of these intermediates resulted in a secondary increase in biomass. Analysis of intermediates by high-performance liquid chromatography, thin-layer chromatography, and UV absorption spectrometry showed 1-hydroxy-2-naphthoic acid (1H2NA) to be the predominant product. A less pronounced two-stage mineralization pattern was also observed by monitoring 14CO2 production from low concentrations (0.5 mg liter-1) of radiolabeled phenanthrene. Here, mineralization of 14C-labeled 1H2NA could explain the incremental 14CO2 produced during the later part of the incubations. Accumulation of 1H2NA by isolates obtained from enrichments was dependent on the initial phenanthrene concentration. The production of metabolites during polycyclic aromatic hydrocarbon biodegradation is discussed with regard to its possible adaptive significance and its methodological implications

1988-01-01

49

Anaerobic degradation of alkylbenzenes in crude oil. I. Isolation and characterization of alkylbenzene-degrading sulfate-reducing and denitrifying bacteria  

Energy Technology Data Exchange (ETDEWEB)

Marine, sulfate-reducing bacteria have been enriched from the water phase of a North Sea-oil tank. The enrichment culture grew on crude oil at the expense of alkylbenzenes with concomitant production of hydrogen sulfide. Whole cell hybridization with fluorescent oligonucleotide probes revealed that the enrichment culture consisted mainly of completely oxidizing sulfate-reducing bacteria. The findings demonstrate that alkylbenzenes in crude oil can be regarded as potential electron donors for sulfate-reduction in oil fields. The resulting formation of hydrogen sulfide may lead to souring of oil and corrosion of pipelines, In addition, we examined denitrifying bacteria. New types of dentrifying bacteria, which were isolated from fresh water sediments with various alkylbenzenes, grew on crude oil as the only source of organic substrates and nitrate as electron acceptor. In agreement with the nutritional capacities of the different bacterial strains, the pattern of alkylbenzene utilization from the crude oil was shown to be strain-specific.

Rabus, R.; Aeckerberg, F.; Zengler, K. [Max-Planck-Institute fuer Marine, Bremen (Germany)] [and others

1996-10-01

50

Reductive Dechlorination of Tetrachloroethene to cis-1,2-Dichloroethene by a Thermophilic Anaerobic Enrichment Culture  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Thermophilic anaerobic biodegradation of tetrachloroethene (PCE) was investigated with various inocula from geothermal and nongeothermal areas. Only polluted harbor sediment resulted in a stable enrichment culture that converted PCE via trichloroethene to cis-1,2-dichloroethene at the optimum temperature of 60 to 65°C. After several transfers, methanogens were eliminated from the culture. Dechlorination was supported by lactate, pyruvate, fructose, fumarate, and malate as electron donor but ...

Kengen, Serve? W. M.; Breidenbach, Caroline G.; Felske, Andreas; Stams, Alfons J. M.; Schraa, Gosse; Vos, Willem M.

1999-01-01

51

High-Affinity Methane Oxidation by a Soil Enrichment Culture Containing a Type II Methanotroph  

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Methanotrophic bacteria in an organic soil were enriched on gaseous mixing ratios of 1020 times the initial soil inoculum), a mixed culture was obtained which displayed an apparent half-saturation constant [Km(app)] for CH4 of 56 to 186 nM (40 to 132 ppmv). This value was the same as that measured in the soil itself and about 1 order of magnitude lower than reported values for pure cultur...

Dunfield, Peter F.; Liesack, Werner; Henckel, Thilo; Knowles, Roger; Conrad, Ralf

1999-01-01

52

Cooperative catabolic pathways within an atrazine-degrading enrichment culture isolated from soil.  

Science.gov (United States)

Atrazine degradation previously has been shown to be carried out by individual bacterial species or by relatively simple consortia that have been isolated using enrichment cultures. Here, the degradative pathway for atrazine was examined for a complex 8-membered enrichment culture. The species composition of the culture was determined by PCR-DGGE. The bacterial species included Agrobacterium tumefaciens, Caulobacter crescentus, Pseudomonas putida, Sphingomonas yaniokuyae, Nocardia sp., Rhizobium sp., Flavobacterium oryzihabitans, and Variovorax paradoxus. All of the isolates were screened for the presence of known genes that function for atrazine degradation including atzA,-B,-C,-D,-E,-F and trzD,-N. Dechlorination of atrazine, which was obligatory for complete mineralization, was carried out exclusively by Nocardia sp., which contained the trzN gene. Following dechlorination, the resulting product, hydroxyatrazine was further degraded via two separate pathways. In one pathway Nocardia converted hydroxyatrazine to N-ethylammelide via an unidentified gene product. In the second pathway, hydroxyatrazine generated by Nocardia sp. was hydrolyzed to N-isopropylammelide by Rhizobium sp., which contained the atzB gene. Each member of the enrichment culture contained atzC, which is responsible for ring cleavage, but none of the isolates carried the atzD,-E, or -F genes. Each member further contained either trzD or exhibited urease activity. The enrichment culture was destabilized by loss of Nocardia sp. when grown on ethylamine, ethylammelide, and cyanuric acid, after which the consortium was no longer able to degrade atrazine. The analysis of this enrichment culture highlights the broad level bacterial community interactions that may be involved in atrazine degradation in nature. PMID:16329946

Smith, Daniel; Alvey, Sam; Crowley, David E

2005-07-01

53

Enrichment of nitrous oxide reducing bacteria from coastal marsh sediments  

Directory of Open Access Journals (Sweden)

Full Text Available We attempted to recover organisms capable of respiratory nitrous oxide reduction with acetate as an electron donor from a variety of coastal marine sediments from Lavaca Bay area, Texas by use of liquid enrichment cultures. Putative positive cultures were analyzed by amplifying eubacterial and archaeal 16S rRNA gene fragments and analyzing their diversity by separating them by a denaturing gradient gel electrophoresis (DGGE. No Archaea was detected in our enrichments; however, positive enrichments from coastal salt marsh indicated the presence of putative nitrous oxide reducing bacteria. DGGE patterns of the amplified DNA were similar between enrichments, with ca. 7 obvious bands. The dominant bands were tentatively identified as members of the Gammaproteobacteria class, closely related to various denitrifying pseudomonads. Our results indicate that coastal marine environments may sustain a nitrous oxide reducing community, although nitrous oxide reduction is probably an opportunistic form of metabolism in that environment.

Khuong B. T. Nguyen

2013-07-01

54

Biodegradation of endocrine disruptors in solid-liquid two-phase partitioning systems by enrichment cultures.  

Science.gov (United States)

Naturally occurring and synthetic estrogens and other molecules from industrial sources strongly contribute to the endocrine disruption of urban wastewater. Because of the presence of these molecules in low but effective concentrations in wastewaters, these endocrine disruptors (EDs) are only partially removed after most wastewater treatments, reflecting the presence of these molecules in rivers in urban areas. The development of a two-phase partitioning bioreactor (TPPB) might be an effective strategy for the removal of EDs from wastewater plant effluents. Here, we describe the establishment of three ED-degrading microbial enrichment cultures adapted to a solid-liquid two-phase partitioning system using Hytrel as the immiscible water phase and loaded with estrone, estradiol, estriol, ethynylestradiol, nonylphenol, and bisphenol A. All molecules except ethynylestradiol were degraded in the enrichment cultures. The bacterial composition of the three enrichment cultures was determined using 16S rRNA gene sequencing and showed sequences affiliated with bacteria associated with the degradation of these compounds, such as Sphingomonadales. One Rhodococcus isolate capable of degrading estrone, estradiol, and estriol was isolated from one enrichment culture. These results highlight the great potential for the development of TPPB for the degradation of highly diluted EDs in water effluents. PMID:23728808

Villemur, Richard; Dos Santos, Silvia Cristina Cunha; Ouellette, Julianne; Juteau, Pierre; Lépine, François; Déziel, Eric

2013-08-01

55

Selenium reduction by a denitrifying consortium  

Energy Technology Data Exchange (ETDEWEB)

A denitrifying bacterial consortium obtained from the Pullman, Washington wastewater treatment facility was enriched under denitrifying conditions and its ability to reduce selenite and selenate was studied. Replicate experiments at two different experimental conditions were performed. All experiments were performed under electron-acceptor limiting conditions, with acetate as the carbon source and nitrate the electron acceptor, in the first set of experiments, selenite was present, whereas, in the second set, selenate was added. A significant lag period of approximately 150 h was necessary before selenite or selenate reduction was observed. During this lag period, nitrate and nitrite use was observed. Once selenite or selenate reduction had started, nitrate and nitrite reduction was concomitant with selenium species reduction. Trace amounts of selenite were detected during the selenate reduction study. Analysis of the data indicates that, once selenium species reduction was induced, the rate of reduction was proportional to the selenium species concentration and to the biomass concentration. Furthermore, at similar biomass and contaminant concentrations, selenite reduction is approximately four times faster than selenate reduction.

Rege, M.A.; Yonge, D.R.; Mendoza, D.P.; Petersen, J.N.; Bereded-Samuel, Y.; Johnstone, D.L. [Washington State Univ., Pullman, WA (United States). Center for Multiphase Environmental Research; Apel, W.A.; Barnes, J.M. [Idaho National Engineering and Environmental Lab., Idaho Falls, ID (United States). Biotechnologies Dept.

1999-02-20

56

Biodegradation of haloacetic acids by bacterial isolates and enrichment cultures from drinking water systems.  

Science.gov (United States)

Biodegradation is a potentially important loss process for haloacetic acids (HAAs), a class of chlorination byproducts, in water treatment and distribution systems, but little is known about the organisms involved (i.e., identity, substrate range, biodegradation kinetics). In this research, 10 biomass samples (i.e., tap water, distribution system biofilms, and prechlorinated granular activated carbon filters) from nine drinking water systems were used to inoculate a total of thirty enrichment cultures fed monochloroacetic acid (MCAA), dichloroacetic acid (DCAA), or trichloroacetic (TCAA) as sole carbon and energy source. HAA degraders were successfully enriched from the biofilm samples (GAC and distribution system) but rarely from tap water. Half of the MCAA and DCAA enrichment cultures were positive, whereas only one TCAA culture was positive (two were inconclusive). Eight unique HAA-degrading isolates were obtained including several Afipia spp. and a Methylobacterium sp.; all isolates were members of the phylum Proteobacteria. MCAA, monobromoacetic acid (MBAA), and monoiodoacetic acid (MIAA) were rapidly degraded by all isolates, and DCAA and tribromoacetic (TBAA) were also relatively labile. TCAA and dibromoacetic acid (DBAA)were degraded by only three isolates and degradation lagged behind the other HAAs. Detailed DCAA biodegradation kinetics were obtained for two selected isolates and two enrichment cultures. The maximum biomass-normalized degradation rates (Vm) were 0.27 and 0.97 microg DCAA/ microg protein/h for Methylobacterium fujisawaense strain PAWDI and Afipia felis strain EMD2, respectively, which were comparable to the values obtained for the enrichment cultures from which those organisms were isolated (0.39 and 1.37 microg DCAN/microg protein/h, respectively). The half-saturation constant (Km) values ranged from 4.38 to 77.91 microg DCAA/L and the cell yields ranged from 14.4 to 36.1 mg protein/g DCAA. PMID:19534130

Zhang, Ping; Lapara, Timothy M; Goslan, Emma H; Xie, Yuefeng; Parsons, Simon A; Hozalski, Raymond M

2009-05-01

57

Microbial diversity of western Canadian subsurface coal beds and methanogenic coal enrichment cultures  

Energy Technology Data Exchange (ETDEWEB)

Coalbed methane is an unconventional fuel source associated with certain coal seams. Biogenic methane can comprise a significant portion of the gas found in coal seams, yet the role of microbes in methanogenesis in situ is uncertain. The purpose of this study was to detect and identify major bacterial and archaeal species associated with coal sampled from sub-bituminous methane-producing coal beds in western Canada, and to examine the potential for methane biogenesis from coal. Enrichment cultures of coal samples were established to determine how nutrient amendment influenced the microbial community and methane production in the laboratory. 16S rRNA gene clone libraries were constructed using DNA extracted and amplified from uncultured coal samples and from methanogenic coal enrichment cultures. Libraries were screened using restriction fragment length polymorphism, and representative clones were sequenced. Most (> 50%) of the bacterial sequences amplified from uncultured coal samples were affiliated with Proteobacteria that exhibit nitrate reduction, nitrogen fixation and/or hydrogen utilization activities, including Pseudomonas, Thauera and Acidovorax spp., whereas enrichment cultures were dominated by Bacteroidetes, Clostridia and/or Lactobacillales. Archaeal 16S rRNA genes could not be amplified from uncultured coal, suggesting that methanogens are present in coal below the detection levels of our methods. However, enrichment cultures established with coal inocula produced significant volumes of methane and the archaeal clone libraries were dominated by sequences closely affiliated with Methanosarcina spp. Enrichment cultures incubated with coal plus organic nutrients produced more methane than either nutrient or coal supplements alone, implying that competent methanogenic consortia exist in coal beds but that nutrient limitations restrict their activity in situ. This report adds to the scant literature on coal bed microbiology and suggests how microbes may be involved in biogenic coal bed methane production in situ. (author)

Penner, Tara J.; Foght, Julia M. [Department of Biological Sciences, University of Alberta, Edmonton, Alberta (Canada); Budwill, Karen [Carbon and Energy Management, Alberta Innovates-Technology Futures, 250 Karl Clark Road, Edmonton, Alberta (Canada)

2010-05-01

58

Enrichment of a mixed bacterial culture with a high polyhydroxyalkanoate storage capacity.  

Science.gov (United States)

Polyhydroxyalkanoates (PHAs) are microbial storage polymers that attract interest as bioplastics. PHAs can be produced with open mixed cultures if a suitable enrichment step based on the ecological role of PHA is used. An acetate-fed sequencing batch reactor operated with 1 day biomass residence time and with feast-famine cycles of 12 h was used to enrich a mixed culture of PHA producers. In subsequent fed-batch experiments under growth limiting conditions, the enriched mixed culture produced PHA up to a cellular content of 89 wt % within 7.6 h (average rate of 1.2 g/g/h). The PHA produced from acetate was the homopolymer polyhydroxybutyrate. The culture was dominated by a Gammaproteobacterium that showed little similarity on 16S rRNA level with known bacteria (<90% sequence similarity). The mixed culture process for PHA production does not require aseptic conditions. Waste streams rather than pure substrates could be used as raw materials. PMID:19193058

Johnson, Katja; Jiang, Yang; Kleerebezem, Robbert; Muyzer, Gerard; van Loosdrecht, Mark C M

2009-04-13

59

Summary report on the aerobic degradation of diesel fuel and the degradation of toluene under aerobic, denitrifying and sulfate reducing conditions  

Energy Technology Data Exchange (ETDEWEB)

This report contains a number of studies that were performed to better understand the technology of the biodegradation of petroleum hydrocarbons. Topics of investigation include the following: diesel fuel degradation by Rhodococcus erythropolis; BTEX degradation by soil isolates; aerobic degradation of diesel fuel-respirometry; aerobic degradation of diesel fuel-shake culture; aerobic toluene degradation by A3; effect of HEPES, B1, and myo-inositol addition on the growth of A3; aerobic and anaerobic toluene degradation by contaminated soils; denitrifying bacteria MPNs; sulfate-reducing bacteria MPNs; and aerobic, DNB and SRB enrichments.

Coyne, P.; Smith, G. [New Mexico State Univ., Las Cruces, NM (United States)

1995-08-15

60

Summary report on the aerobic degradation of diesel fuel and the degradation of toluene under aerobic, denitrifying and sulfate reducing conditions  

International Nuclear Information System (INIS)

This report contains a number of studies that were performed to better understand the technology of the biodegradation of petroleum hydrocarbons. Topics of investigation include the following: diesel fuel degradation by Rhodococcus erythropolis; BTEX degradation by soil isolates; aerobic degradation of diesel fuel-respirometry; aerobic degradation of diesel fuel-shake culture; aerobic toluene degradation by A3; effect of HEPES, B1, and myo-inositol addition on the growth of A3; aerobic and anaerobic toluene degradation by contaminated soils; denitrifying bacteria MPNs; sulfate-reducing bacteria MPNs; and aerobic, DNB and SRB enrichments

1995-01-01

 
 
 
 
61

Composition and Activity of an Autotrophic Fe(II)-Oxidizing, Nitrate-Reducing Enrichment Culture?  

Science.gov (United States)

16S rRNA gene libraries from the lithoautotrophic Fe(II)-oxidizing, nitrate-reducing enrichment culture described by Straub et al. (K. L. Straub, M. Benz, B. Schink, and F. Widdel, Appl. Environ. Microbiol. 62:1458-1460, 1996) were dominated by a phylotype related (95% 16S rRNA gene homology) to the autotrophic Fe(II) oxidizer Sideroxydans lithotrophicus. The libraries also contained phylotypes related to known heterotrophic nitrate reducers Comamonas badia, Parvibaculum lavamentivorans, and Rhodanobacter thiooxidans. The three heterotrophs were isolated and found to be capable of only partial (12 to 24%) Fe(II) oxidation, suggesting that the Sideroxydans species has primary responsibility for Fe(II) oxidation in the enrichment culture.

Blothe, Marco; Roden, Eric E.

2009-01-01

62

Composition and activity of an autotrophic Fe(II)-oxidizing, nitrate-reducing enrichment culture.  

Science.gov (United States)

16S rRNA gene libraries from the lithoautotrophic Fe(II)-oxidizing, nitrate-reducing enrichment culture described by Straub et al. (K. L. Straub, M. Benz, B. Schink, and F. Widdel, Appl. Environ. Microbiol. 62:1458-1460, 1996) were dominated by a phylotype related (95% 16S rRNA gene homology) to the autotrophic Fe(II) oxidizer Sideroxydans lithotrophicus. The libraries also contained phylotypes related to known heterotrophic nitrate reducers Comamonas badia, Parvibaculum lavamentivorans, and Rhodanobacter thiooxidans. The three heterotrophs were isolated and found to be capable of only partial (12 to 24%) Fe(II) oxidation, suggesting that the Sideroxydans species has primary responsibility for Fe(II) oxidation in the enrichment culture. PMID:19749073

Blöthe, Marco; Roden, Eric E

2009-11-01

63

Autologous non-cultured basal cell-enriched epidermal cell suspension transplantation in vitiligo: Indian experience  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Introduction : Autologous non-cultured basal cell-enriched epidermal cell suspension transplantation is a simple yet effective cell-based therapy for vitiligo. Materials and Methods : This report is a retrospective analysis of 58 patients who were operated between December 2003 and August 2006 and were under follow-up for at least 2 years. Nine patients did not come for follow-up, and were excluded. At the time of transplantation all patients were having stable disease for at le...

Paul Munish

2011-01-01

64

Degradation of unsaturated hydrocarbons by methanogenic enrichment cultures : (Aromatic compounds; alcohol degradation; hexadecene; squalene; hydratation; carboxylation)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The biodegradability of hydrocarbons under anaerobic conditions was studied in enrichment cultures using mineral media inoculated with sewage sludge or sediment samples of limnic and marine origin. No indication of methanogenic degradation was obtained with either n-hexane, n-hexadecane, n-heptadecane, 1-hexene, cis-2-hexene, trans-2-hexene, isoprene, 1-hexine, benzene, toluene, xylene, cyclohexene, cycloheptatriene, cyclopentadiene, styrene, naphthalene, azulene, or fl-carotene. Squalene was...

Schink, Bernhard

1985-01-01

65

Salmonella isolation with Rappaport-Vassiliadis enrichment medium seeded with different sized inocula of pre-enrichment cultures of meat products and sewage polluted water.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A total of 574 samples, of seven different types, were examined for the presence of salmonellas. All the specimens were pre-enriched in buffered peptone water and enriched in Rappaport-Vassiliadis medium (RV medium). In one trial 0.1 ml of pre-enrichment culture of 497 samples (79 chicken carcasses, 228 specimens of minced meat, 100 pork sausages, 19 samples of dried powdered chicken meat, 11 specimens of faeces of healthy pigs and 60 samples of sewage polluted natural sea water) was seeded t...

1985-01-01

66

Establishment and Characterization of an Anaerobic Thermophilic (55 degrees C) Enrichment Culture Degrading Long-Chain Fatty Acids  

DEFF Research Database (Denmark)

A thermophilic, long-chain fatty acid-oxidizing culture was enriched. Stearate was used as the substrate, and methane and carbon dioxide were the sole end products. Cultivation was possible only when a fed-batch system was used or with addition of activated carbon or bentonite. The enrichment culture consisted of a short rod and two bacteria antigenically related to Methanobacterium thermoautotrophicum DELTA-H and Methanosarcina thermophila TM-1.

Angelidaki, Irini; Ahring, Birgitte Kiær

1995-01-01

67

Microbial dynamics in anaerobic enrichment cultures degrading di-n-butyl phthalic acid ester  

DEFF Research Database (Denmark)

Although anaerobic biodegradation of di-n-butyl phthalic acid ester (DBP) has been studied over the past decade, only little is known about the microorganisms involved in the biological anaerobic degradation pathways. The aim of this work is to characterize the microbial community dynamics in enrichment cultures degrading phthalic acid esters under methanogenic conditions. A selection pressure was applied by adding DBP at 10 and 200 mg L(-1) in semi-continuous anaerobic reactors. The microbial dynamics were monitored using single strand conformation polymorphism (SSCP). While only limited abiotic losses were observed in the sterile controls (20-22%), substantial DBP biodegradation was found in the enrichment cultures (90-99%). In addition, significant population changes were observed. The dominant bacterial species in the DBP-degrading cultures was affiliated to Soehngenia saccharolytica, a microorganism described previously as an anaerobic benzaldehyde degrader. Within the archaeal community, there was a shift between two different species of the genus Methanosaeta sp., indicating a highly specific impact of DBP or degradation products on archaeal species. RNA-directed probes were designed from SSCP sequences, and FISH observations confirmed the dominance of S. saccharolytica, and indicated floccular microstructures, likely providing favourable conditions for DBP degradation.

Trably, Eric; Batstone, Damien J.

2008-01-01

68

Phylogenetic and functional diversity of denitrifying bacteria isolated from various rice paddy and rice-soybean rotation fields.  

Science.gov (United States)

Denitrifiers can produce and consume nitrous oxide (N(2)O). While little N(2)O is emitted from rice paddy soil, the same soil produces N(2)O when the land is drained and used for upland crop cultivation. In this study, we collected soils from two types of fields each at three locations in Japan; one type of field had been used for continuous cultivation of rice and the other for rotational cultivation of rice and soybean. Active denitrifiers were isolated from these soils using a functional single-cell isolation method, and their taxonomy and denitrifying properties were examined. A total of 110 denitrifiers were obtained, including those previously detected by a culture-independent analysis. Strains belonging to the genus Pseudogulbenkiania were dominant at all locations, suggesting that Pseudogulbenkiania denitrifiers are ubiquitous in various rice paddy soils. Potential denitrifying activity was similar among the strains, regardless of the differences in taxonomic position and soil of origin. However, relative amounts of N(2) in denitrification end products varied among strains isolated from different locations. Our results also showed that crop rotation had minimal impact on the functional diversity of the denitrifying strains. These results indicate that soil and other environmental factors, excluding cropping systems, could select for N(2)-producing denitrifiers. PMID:21487200

Tago, Kanako; Ishii, Satoshi; Nishizawa, Tomoyasu; Otsuka, Shigeto; Senoo, Keishi

2011-01-01

69

Inhibition of anaerobic ammonium oxidizing (anammox) enrichment cultures by substrates, metabolites and common wastewater constituents.  

Science.gov (United States)

Anaerobic ammonium oxidation (anammox) is an emerging technology for nitrogen removal that provides a more environmentally sustainable and cost effective alternative compared to conventional biological treatment methods. The objective of this study was to investigate the inhibitory impact of anammox substrates, metabolites and common wastewater constituents on the microbial activity of two different anammox enrichment cultures (suspended and granular), both dominated by bacteria from the genus Brocadia. Inhibition was evaluated in batch assays by comparing the N(2) production rates in the absence or presence of each compound supplied in a range of concentrations. The optimal pH was 7.5 and 7.3 for the suspended and granular enrichment cultures, respectively. Among the substrates or products, ammonium and nitrate caused low to moderate inhibition, whereas nitrite caused almost complete inhibition at concentrations higher than 15 mM. The intermediate, hydrazine, either stimulated or caused low inhibition of anammox activity up to 3mM. Of the common constituents in wastewater, hydrogen sulfide was the most severe inhibitor, with 50% inhibitory concentrations (IC(50)) as low as 0.03 mM undissociated H(2)S. Dissolved O(2) showed moderate inhibition (IC(50)=2.3-3.8 mg L(-1)). In contrast, phosphate and salinity (NaCl) posed very low inhibition. The suspended- and granular anammox enrichment cultures had similar patterns of response to the various inhibitory stresses with the exception of phosphate. The findings of this study provide comprehensive insights on the tolerance of the anammox process to a wide variety of potential inhibiting compounds. PMID:23245574

Carvajal-Arroyo, José M; Sun, Wenjie; Sierra-Alvarez, Reyes; Field, Jim A

2013-03-01

70

Anaerobic Biotransformation of High Concentrations of Chloroform by an Enrichment Culture and Two Bacterial Isolates ? †  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A fermentative enrichment culture (designated DHM-1) was developed that is capable of cometabolically biotransforming high concentrations of chloroform (CF) to nontoxic end products. Two Pantoea spp. were isolated from DHM-1 that also possess this dechlorination capability. Following acclimation to increasing levels of CF, corn syrup-grown DHM-1 was able to transform over 500 mg/liter CF in the presence of vitamin B12 (approximately 3% of CF on a molar basis) at a rate as high as 22 mg/liter/...

Shan, Huifeng; Kurtz, Harry D.; Mykytczuk, Nadia; Trevors, Jack T.; Freedman, David L.

2010-01-01

71

Batch fermentative hydrogen production by enriched mixed culture: Combination strategy and their microbial composition.  

Science.gov (United States)

The effect of individual and combined mixed culture on dark fermentative hydrogen production performance was investigated. Mixed cultures from cow dung (C1), sewage sludge (C2), and pig slurry (C3) were enriched under strict anaerobic conditions at 37°C with glucose as the sole carbon source. Biochemical hydrogen production test in peptone-yeast-glucose (PYG) and basal medium was performed for individual mixed cultures (C1, C2 and C3) and their combinations (C1-C2, C2-C3, C1-C3 and C1-C2-C3) at a glucose concentration of 10 g/L, 37°C and initial pH 7. Maximum hydrogen yields (HY) of 2.0 and 1.86 [Formula: see text] by C2, and 1.98 and 1.95 mol(H2)/mol(glucose) by C2-C3 were obtained in PYG and basal medium, respectively. Butyrate and acetate were the major soluble metabolites produced by all the cultures, and the ratio of butyrate to acetate was ?2 fold higher in basal medium than PYG medium, indicating strong influence of media formulation on glucose catabolism. The major hydrogen-producing bacterial strains, observed in all mixed cultures, belonged to Clostridium butyricum, C. saccharobutylicum, C. tertium and C. perfringens. The hydrogen production performance of the combined mixed culture (C2-C3) was further evaluated on beverage wastewater (10 g/L) at pH 7 and 37°C. The results showed an HY of 1.92 mol(H2)/mol(glucose-equivalent). Experimental evidence suggests that hydrogen fermentation by mixed culture combination could be a novel strategy to improve the HY from industrial wastewater. PMID:24095211

Sivagurunathan, Periyasamy; Sen, Biswarup; Lin, Chiu-Yue

2014-02-01

72

Modeling PHA-producing microbial enrichment cultures-towards a generalized model with predictive power.  

Science.gov (United States)

Polyhydroxyalkanoate (PHA) production from waste streams using microbial enrichment cultures is a promising option for cost price reduction of this biopolymer. For proper understanding and successful optimization of the process, a consistent mechanistic model for PHA conversion by microbial enrichment cultures is needed. However, there is still a lack of mechanistic expressions describing the dynamics of the feast-famine process. The scope of this article is to provide an overview of the current models, investigate points of improvement, and contribute concepts for creation of a generalized model with more predictive value for the feast-famine process. Based on experimental data available in literature we have proposed model improvements for (i) modeling mixed substrates uptake, (ii) growth in the feast phase, (iii) switching between feast and famine phase, (iv) PHA degradation and (v) modeling the accumulation phase. Finally, we provide an example of a simple uniform model. Herewith we aim to give an impulse to the establishment of a generalized model. PMID:24333144

Tamis, Jelmer; Marang, Leonie; Jiang, Yang; van Loosdrecht, Mark C M; Kleerebezem, Robbert

2014-06-25

73

Accelerated biotransformation of carbon tetrachloride and chloroform by sulfate-reducing enrichment cultures  

Energy Technology Data Exchange (ETDEWEB)

The biotransformation of carbon tetrachloride (CT) and chloroform (CF) was examined with lactate- and acetate-grown sulfate-reducing enrichment cultures. Both cultures transformed CT, with approximately 50% reductively dechlorinated to CF and up to 10% to dichloromethane (DCM). Addition of cyanocobalamin increased the rate of CT transformation more than 100-fold. The principal product from [{sup 14}C]CT with cyanocobalamin added was carbon disulfide (CS{sub 2}); less than 3% was reduced to CF plus DCM. Autoclaved cultures that received cyanocobalamin were only one third as fast as their live counterparts, but produced similar amounts of CS{sub 2}. With CF, addition of cyanocobalamin to acetate- and lactate-grown cultures also increased the rate of transformation more than 100-fold. DCM was the principal transformation product until CF additions reached 270 mg/L, at which point almost no increase in DCM was observed. Thus, low levels of cyanocobalamin substantially accelerated the rate of CT and CF transformation and altered the distribution of products formed.

Freedman, D.L.; Hashsham, S. [Univ. of Illinois, Urbana, IL (United States). Dept. of Civil Engineering; Lasecki, M. [HDR Engineering Inc., Lake Oswego, OR (United States); Scholze, R. [Army Corps of Engineers, Champaign, IL (United States). Construction Engineering Research Labs.

1995-12-31

74

Halobacterium denitrificans sp. nov., an extremely halophilic denitrifying bacterium  

Science.gov (United States)

Halobacterium denitrificans was one of several carbohydrate-utilizing, denitrifying, extremely halophilic bacteria isolated by anaerobic enrichment in the presence of nitrate. Anaerobic growth took place only when nitrate (or nitrite) was present and was accompanied by the production of dinitrogen. In the presence of high concentrations of nitrate (i.e., 0.5 percent), nitrous oxide and nitrite were also detected. When grown aerobically in a mineral-salts medium containing 0.005 percent yeast extract, H. denitrificans utilized a variety of carbohydrates as sources of carbon and energy. In every case, carbohydrate utilization was accompanied by acid production.

Tomlinson, G. A.; Jahnke, L. L.; Hochstein, L. I.

1986-01-01

75

Halobacterium denitrificans sp. nov. - An extremely halophilic denitrifying bacterium  

Science.gov (United States)

Halobacterium denitrificans was one of several carbohydrate-utilizing, denitrifying, extremely halophilic bacteria isolated by anaerobic enrichment in the presence of nitrate. Anaerobic growth took place only when nitrate (or nitrite) was present and was accompanied by the production of dinitrogen. In the presence of high concentrations of nitrate (i.e., 0.5 percent), nitrous oxide and nitrite were also detected. When grown aerobically in a mineral-salts medium containing 0.005 percent yeast extract, H. denitrificans utilized a variety of carbohydrates as sources of carbon and energy. In every case, carbohydrate utilization was accompanied by acid production.

Tomlinson, G. A.; Jahnke, L. L.; Hochstein, L. I.

1986-01-01

76

Bacterial oxidation of dibromomethane and methyl bromide in natural waters and enrichment cultures  

Science.gov (United States)

Bacterial oxidation of 14CH2Br2 and 14CH3Br was measured in freshwater, estuarine, seawater, and hypersaline-alkaline samples. In general, bacteria from the various sites oxidized similar amounts of 14CH2Br2 and comparatively less 14CH3Br. Bacterial oxidation of 14CH3Br was rapid in freshwater samples compared to bacterial oxidation of 14CH3Br in more saline waters. Freshwater was also the only site in which methyl fluoride-sensitive bacteria (e.g., methanotrophs or nitrifiers) governed brominated methane oxidation. Half-life calculations indicated that bacterial oxidation of CH2Br2 was potentially significant in all of the waters tested. In contrast, only in freshwater was bacterial oxidation of CH3Br as fast as chemical removal. The values calculated for more saline sites suggested that bacterial oxidation of CH3Br was relatively slow compared to chemical and physical loss mechanisms. However, enrichment cultures demonstrated that bacteria in seawater can rapidly oxidize brominated methanes. Two distinct cultures of nonmethanotrophic methylotrophs were recovered; one of these cultures was able to utilize CH2Br2 as a sole carbon source, and the other was able to utilize CH3Br as a sole carbon source.

Goodwin, K. D.; Schaefer, J. K.; Oremland, R. S.

1998-01-01

77

Phylogenetic analysis of anaerobic psychrophilic enrichment cultures obtained from a greenland glacier ice core  

Science.gov (United States)

The examination of microorganisms in glacial ice cores allows the phylogenetic relationships of organisms frozen for thousands of years to be compared with those of current isolates. We developed a method for aseptically sampling a sediment-containing portion of a Greenland ice core that had remained at -9 degrees C for over 100,000 years. Epifluorescence microscopy and flow cytometry results showed that the ice sample contained over 6 x 10(7) cells/ml. Anaerobic enrichment cultures inoculated with melted ice were grown and maintained at -2 degrees C. Genomic DNA extracted from these enrichments was used for the PCR amplification of 16S rRNA genes with bacterial and archaeal primers and the preparation of clone libraries. Approximately 60 bacterial inserts were screened by restriction endonuclease analysis and grouped into 27 unique restriction fragment length polymorphism types, and 24 representative sequences were compared phylogenetically. Diverse sequences representing major phylogenetic groups including alpha, beta, and gamma Proteobacteria as well as relatives of the Thermus, Bacteroides, Eubacterium, and Clostridium groups were found. Sixteen clone sequences were closely related to those from known organisms, with four possibly representing new species. Seven sequences may reflect new genera and were most closely related to sequences obtained only by PCR amplification. One sequence was over 12% distant from its closest relative and may represent a novel order or family. These results show that phylogenetically diverse microorganisms have remained viable within the Greenland ice core for at least 100,000 years.

Sheridan, Peter P.; Miteva, Vanya I.; Brenchley, Jean E.

2003-01-01

78

Autologous non-cultured basal cell-enriched epidermal cell suspension transplantation in vitiligo: Indian experience  

Directory of Open Access Journals (Sweden)

Full Text Available Introduction : Autologous non-cultured basal cell-enriched epidermal cell suspension transplantation is a simple yet effective cell-based therapy for vitiligo. Materials and Methods : This report is a retrospective analysis of 58 patients who were operated between December 2003 and August 2006 and were under follow-up for at least 2 years. Nine patients did not come for follow-up, and were excluded. At the time of transplantation all patients were having stable disease for at least 1 year. Epidermal cell suspension transplantation was done using Mulekar?s method. Repigmentation was assessed and classified into excellent (>90% repigmentation, good (70-89%, fair (30-69% and poor (<30%. Results : Of the 49 patients who came for follow-up, 32 (65% had excellent (>90% repigmentation; 9 (18% had good (70-89%; 4 (8% had fair (30-69% and 4 (8% patients had poor (<30% repigmentation. During the follow-up, eight patients(16% showed relapse of the disease. Conclusion : Autologous noncultured basal cell-enriched epidermal cell suspension transplantation is an effective, simple and safe method.

Paul Munish

2011-01-01

79

Selective enrichment and production of highly urease active bacteria by non-sterile (open) chemostat culture.  

Science.gov (United States)

In general, bioprocesses can be subdivided into naturally occurring processes, not requiring sterility (e.g., beer brewing, wine making, lactic acid fermentation, or biogas digestion) and other processes (e.g., the production of enzymes and antibiotics) that typically require a high level of sterility to avoid contaminant microbes overgrowing the production strain. The current paper describes the sustainable, non-sterile production of an industrial enzyme using activated sludge as inoculum. By using selective conditions (high pH, high ammonia concentration, and presence of urea) for the target bacterium, highly active ureolytic bacteria, physiologically resembling Sporosarcina pasteurii were reproducibly enriched and then continuously produced via chemostat operation of the bioreactor. When using a pH of 10 and about 0.2 M urea in a yeast extract-based medium, ureolytic bacteria developed under aerobic chemostat operation at hydraulic retention times of about 10 h with urease levels of about 60 ?mol min?¹ ml?¹ culture. For cost minimization at an industrial scale the costly protein-rich yeast extract medium could be replaced by commercial milk powder or by lysed activated sludge. Glutamate, molasses, or glucose-based media did not result in the enrichment of ureolytic bacteria by the chemostat. The concentration of intracellular urease was sufficiently high such that the produced raw effluent from the reactor could be used directly for biocementation in the field. PMID:23892419

Cheng, Liang; Cord-Ruwisch, Ralf

2013-10-01

80

Reductive dechlorination of chlorinated ethene DNAPLs by a culture enriched from contaminated groundwater  

Energy Technology Data Exchange (ETDEWEB)

A microbial culture enriched from a trichloroethene-contaminated groundwater aquifer reductively dechlorinated trichloroethene (TCE) and tetrachloroethene (PCE) to ethene. Initial PCE dechlorination rate studies indicated a first-order dependence with respect to substrate at low PCE concentrations, and a zero-order dependence at high concentrations. Studies of TCE and vinyl chloride (VC) dechlorination indicated a first-order dependence at all substrate concentrations. VC had little or no effect on the initial rate of TCE dechlorination. With subsaturating concentrations of chlorinated ethenes, nearly stoichiometric amounts of the toxic intermediate vinyl chloride accumulated prior to its dechlorination to ethene. In contrast, under saturating conditions, in which a dense, nonaqueous-phase liquid existed in equilibrium with the aqueous phase, the chlorinated ethene was dechlorinated to ethene, at a rapid rate, with the accumulation of relatively small amounts of chlorinated intermediates.

Nielsen, R.B.; Keasling, J.D. [Univ. of California, Berkeley, CA (United States). Dept. of Chemical Engineering

1999-01-20

 
 
 
 
81

Rapid and specific detection of Salmonella spp. in animal feed samples by PCR after culture enrichment  

DEFF Research Database (Denmark)

A PCR procedure has been developed for routine analysis of viable Salmonella spp. in feed samples. The objective was to develop a simple PCR-compatible enrichment procedure to enable DNA amplification without any sample pretreatment such as DNA extraction or cell lysis. PCR inhibition by 14 different feed samples and natural background flora was circumvented by the use of the DNA polymerase Tth. This DNA polymerase was found to exhibit a high level of resistance to PCR inhibitors present in these feed samples compared to DyNAzyme II, FastStart Taq, Platinum Taq, Pwo, rTth, Taq, and Tfl. The specificity of the Tth assay was confirmed by testing 101 Salmonella and 43 non-Salmonella strains isolated from feed and food samples. A sample preparation method based on culture enrichment in buffered peptone water and DNA amplification with Tth DNA polymerase was developed. The probability of detecting small numbers of salmonellae in feed, in the presence of natural background flora, was accurately determined and foundto follow a logistic regression model. From this model, the probability of detecting I CFU per 25 g of feed in artificially contaminated soy samples was calculated and found to be 0.81. The PCR protocol was evaluated on 155 naturally contaminated feed samples and compared to an established culture-based method, NMKL-71. Eight percent of the samples were positive by PCR, compared with 3% with the conventional method. The reasons for the differences in sensitivity are discussed. Use of this method in the routine analysis of animal feed samples would improve safety in the food chain.

Löfström, Charlotta; Knutsson, R.

2004-01-01

82

High yield derivation of enriched glutamatergic neurons from suspension-cultured mouse ESCs for neurotoxicology research  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Recently, there has been a strong emphasis on identifying an in vitro model for neurotoxicity research that combines the biological relevance of primary neurons with the scalability, reproducibility and genetic tractability of continuous cell lines. Derived neurons should be homotypic, exhibit neuron-specific gene expression and morphology, form functioning synapses and consistently respond to neurotoxins in a fashion indistinguishable from primary neurons. However, efficient methods to produce neuronal populations that are suitable alternatives to primary neurons have not been available. Methods With the objective of developing a more facile, robust and efficient method to generate enriched glutamatergic neuronal cultures, we evaluated the neurogenic capacity of three mouse embryonic stem cell (ESC lines (R1, C57BL/6 and D3 adapted to feeder-independent suspension culture. Neurogenesis and neuronal maturation were characterized as a function of time in culture using immunological, genomic, morphological and functional metrics. The functional responses of ESNs to neurotropic toxins with distinctly different targets and mechanisms of toxicity, such as glutamate, ?-latrotoxin (LTX, and botulinum neurotoxin (BoNT, were also evaluated. Results Suspension-adapted ESCs expressed markers of pluripotency through at least 30 passages, and differentiation produced 97×106 neural progenitor cells (NPCs per 10-cm dish. Greater than 99% of embryonic stem cell-derived neurons (ESNs expressed neuron-specific markers by 96 h after plating and rapidly developed complex axodendritic arbors and appropriate compartmentalization of neurotypic proteins. Expression profiling demonstrated the presence of transcripts necessary for neuronal function and confirmed that ESN populations were predominantly glutamatergic. Furthermore, ESNs were functionally receptive to all toxins with sensitivities and responses consistent with primary neurons. Conclusions These findings demonstrate a cost-effective, scalable and flexible method to produce a highly enriched glutamatergic neuron population. The functional characterization of pathophysiological responses to neurotropic toxins and the compatibility with multi-well plating formats were used to demonstrate the suitability of ESNs as a discovery platform for molecular mechanisms of action, moderate-throughput analytical approaches and diagnostic screening. Furthermore, for the first time we demonstrate a cell-based model that is sensitive to all seven BoNT serotypes with EC50 values comparable to those reported in primary neuron populations. These data providing compelling evidence that ESNs offer a neuromimetic platform suitable for the evaluation of molecular mechanisms of neurotoxicity.

Hubbard Kyle S

2012-10-01

83

Cometabolic degradation of MTBE using methane-propane- and butane-utilizing enrichment cultures and rhodococcus sp. BU3  

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The fuel oxygenated methyl tert-butyl ether (MTBE) is used worldwide to replace leaded organic compounds. Although MTBE is persistent in the environment, chiefly due to its low biodegradability, some microbial cultures are able to mineralize it. This paper reports on the cometabolic degradation of MTBE by methane-, propane- and butane-utilizing enrichment cultures and the pure Rhodococcus sp. BU3 culture isolated from natural habitats. Three methane-, three propane- and four butane-utilizing cultures, which degrade MTBE cometabolically, were enriched. In experiments with resting cells at 20 C, enrichment cultures grown on methane degraded MTBE at a maximum rate of 1.0 mg MTBE/(g biomass . h). Propane- and butane-utilizing enrichment cultures degraded MTBE and the intermediate tert-butyl alcohol (TBA) cometabolically at temperatures of 20 C at maximum rates of 7.2 mg MTBE/(g biomass . h) and 5.2 mg MTBE/(g biomass . h), respectively. Propane-utilizing cultures were also able to degrade MTBE and TBA consecutively after growth on 1-propanol. However, the MTBE degradation rate after growth on 1-propanol was lower than on propane. The isolated pure culture BU3 specified as Rhodococcus sp. degraded MTBE at maximum rates of 5.4 mg MTBE/(g biomass . h) when grown on propane and 2.3 mg MTBE/(g biomass . h) when grown on 1-propanol, respectively. In column systems with recirculation, it is shown that Rhodococcus sp. BU3 degraded 95 mg/L MTBE over a time period of 6 days. The degradation activity of the immobilized bacteria could be regenerated by the addition of growth substrates (propanol or propane). The results of these experiments provide a promising basis for their implementation in an enhanced natural attenuation approach. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

Haase, K.; Wendlandt, K.D.; Graeber, A.; Stottmeister, U. [UFZ-Umweltforschungszentrum Leipzig-Halle GmbH, Leipzig (Germany)

2006-10-15

84

Continuous enrichment culture and molecular monitoring to investigate the microbial diversity of thermophiles inhabiting deep-sea hydrothermal ecosystems  

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The microflora developing during a continuous enrichment culture from a hydrothermal chimney sample was investigated by molecular methods. The culture was performed in a gas-lift bioreactor under anaerobic conditions, at 90 degrees C and pH 6.5, on a complex medium containing sulfur as the terminal electron acceptor. Archaeal and bacterial diversity was studied. Microorganisms affiliated with the genera Pyrococcus, Marinitoga, and Bacillus were detected through DGGE analysis of 16S rDNA. Addi...

Postec, Anne; Urios, Laurent; Lesongeur, Francoise; Ollivier, Bernard; Querellou, Joel; Godfroy, Anne

2005-01-01

85

Isolation and characterization of a nitrite reductase gene and its use as a probe for denitrifying bacteria. [Pseudomonas stutzeri  

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The dissimilatory nitrite reductase gene (nir) from denitrifying bacterium Pseudomonas stutzeri JM300 was isolated and sequenced. In agreement with recent sequence information from another strain P. Stutzeri (strain ZoBell), strain JM300 nir is the first gene in an operon and is followed immediately by a gene which codes for a tetraheme protein; 2.5 kb downstream from the nitrite reductase carboxyl terminus is the cytochrome c{sub 551} gene. P. stutzeri JM300 nir is 67% homologous to P. aeruginosa nir and 88% homologous to P. stutzeri ZoBell nir. Within the nitrite reductase promoter region is an fnr-like operator very similar to an operator upstream to a separate anaerobic pathway, that for arginine catabolism in P. aeruginosa. The denitrification genes in P. stutzeri thus may be under the same regulatory control as that found for other anaerobic pathways of pseudomonads. The authors have generated gene probes from restriction fragments within the nitrite reductase operon to evaluate their usefulness in ecology studies of denitrification. Probes generated from the carboxyl terminus region hybridized to denitrifying bacteria from five separate genera and did not cross-hybridize to any nondenitrifying bacteria among six genera tested. The denitrifier probes were successful in detecting denitrifying bacteria from samples such as a bioreactor consortium, aquifer microcosms, and denitrifying toluene-degrading enrichments. The probes also were used to reveal restriction fragment length polymorphism patterns indicating the diversity of denitrifiers present in these mixed communities.

Smith, G.B.; Tiedje, J.M. (Michigan State Univ., East Lansing (United States))

1992-01-01

86

Sustained growth of explants from Mediterranean sponge Crambe crambe cultured in vitro with enriched RPMI 1640.  

Science.gov (United States)

Marine sponges are potential sources of many unique metabolites, including cytotoxic and anticancer compounds. Natural sponge populations are insufficient or inaccessible for producing commercial quantities of metabolites of interest. It is commonly accepted that tissue (fragments, explants, and primmorphs) and in vitro cell cultivation show great potential. However, there is little knowledge of the nutritional requirements of marine sponges to carry out efficient and sustained in vitro culture and progress has been slow. In marine invertebrate fila many unsuccessful attempts have been made with in vitro cultures using typical commercial animal cell media based on sources of dissolved organic carbon (DOC) (e.g., DMEM, RPMI, M199, L-15, etc.). One of the reasons for this failure is the use of hardly identifiable growth promoters, based on terrestrial animal sera. An alternative is the use of extracts from marine animals, since they may contain nutrients necessary for growth. In this work we have cultivated in vitro explants of the encrusting marine sponge Crambe crambe. It is one of the most abundant sponges on the Mediterranean coastline and also possesses an array of potentially active metabolites (crambines and crambescidins). Initially a new approach was developed in order to show consumption of DOC by explants. Thus, different initial DOC concentrations (300, 400, 700 and 1200 mg DOC L(-1)) were assayed. Consumption was evident in all four assays and was more marked in the first 6 h. The DOC assimilation data were adjusted to an empirical model widely used for uptake kinetics of organic dissolved compounds in marine invertebrates. Second, a protocol was established to cultivate explants in vitro. Different medium formulations based on RPMI 1640 commercial medium enriched with amino acids and inorganic salts to emulate seawater salinity were assayed. The enrichment of this medium with an Octopus aqueous extract in the proportions of 10% and 20% (v/v) resulted in an evident sustained long-term growth of C. crambe explants. This growth enhancement produced high metabolic activity in the explants, as is confirmed by the high ammonium and lactate content in the medium a few days after its renewal and by the consumption of glucose. The lactate accumulation increased with the size and age of explants. Prior to these experiments, we successfully developed a robust new alternative method, based on digital image treatment, for accurate determination of the explant apparent volume as growth measure. PMID:16739962

Garcia Camacho, F; Chileh, T; Cerón García, M C; Sanchez Mirón, A; Belarbi, E H; Contreras Gómez, A; Molina Grima, E

2006-01-01

87

Sphere Culture of Murine Lung Cancer Cell Lines Are Enriched with Cancer Initiating Cells  

Science.gov (United States)

Cancer initiating cells (CICs) represent a unique cell population essential for the maintenance and growth of tumors. Most in vivo studies of CICs utilize human tumor xenografts in immunodeficient mice. These models provide limited information on the interaction of CICs with the host immune system and are of limited value in assessing therapies targeting CICs, especially immune-based therapies. To assess this, a syngeneic cancer model is needed. We examined the sphere-forming capacity of thirteen murine lung cancer cell lines and identified TC-1 and a metastatic subclone of Lewis lung carcinoma (HM-LLC) as cell lines that readily formed and maintained spheres over multiple passages. TC-1 tumorspheres were not enriched for expression of CD133 or CD44, putative CIC markers, nor did they demonstrate Hoechst 33342 side population staining or Aldefluor activity compared to adherent TC-1 cells. However, in tumorsphere culture, these cells exhibited self-renewal and long-term symmetric division capacity and expressed more Oct-4 compared to adherent cells. HM-LLC sphere-derived cells exhibited increased Oct-4, CD133, and CD44 expression, demonstrated a Hoechst 33342 side population and Aldefluor activity compared to adherent cells or a low metastatic subclone of LLC (LM-LLC). In syngeneic mice, HM-LLC sphere-derived cells required fewer cells to initiate tumorigenesis compared to adherent or LM-LLC cells. Similarly TC-1 sphere-derived cells were more tumorigenic than adherent cells in syngeneic mice. In contrast, in immunocompromised mice, less than 500 sphere or adherent TC-1 cells and less than 1,000 sphere or adherent LLC cells were required to initiate a tumor. We suggest that no single phenotypic marker can identify CICs in murine lung cancer cell lines. Tumorsphere culture may provide an alternative approach to identify and enrich for murine lung CICs. Furthermore, we propose that assessing tumorigenicity of murine lung CICs in syngeneic mice better models the interaction of CICs with the host immune system.

Morrison, Brian J.

2012-01-01

88

The culture of cancer cell lines as tumorspheres does not systematically result in cancer stem cell enrichment.  

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Cancer stem cells (CSC) have raised great excitement during the last decade and are promising targets for an efficient treatment of tumors without relapses and metastases. Among the various methods that enable to enrich cancer cell lines in CSC, tumorspheres culture has been predominantly used. In this report, we attempted to generate tumorspheres from several murine and human cancer cell lines: B16-F10, HT-29, MCF-7 and MDA-MB-231 cells. Tumorspheres were obtained with variable efficiencies from all cell lines except from MDA-MB-231 cells. Then, we studied several CSC characteristics in both tumorspheres and adherent cultures of the B16-F10, HT-29 and MCF-7 cells. Unexpectedly, tumorspheres-forming cells were less clonogenic and, in the case of B16-F10, less proliferative than attached cells. In addition, we did not observe any enrichment in the population expressing CSC surface markers in tumorspheres from B16-F10 (CD133, CD44 and CD24 markers) or MCF-7 (CD44 and CD24 markers) cells. On the contrary, tumorspheres culture of HT-29 cells appeared to enrich in cells expressing colon CSC markers, i.e. CD133 and CD44 proteins. For the B16-F10 cell line, when 1 000 cells were injected in syngenic C57BL/6 mice, tumorspheres-forming cells displayed a significantly lower tumorigenic potential than adherent cells. Finally, tumorspheres culture of B16-F10 cells induced a down-regulation of vimentin which could explain, at least partially, the lower tumorigenicity of tumorspheres-forming cells. All these results, along with the literature, indicate that tumorspheres culture of cancer cell lines can induce an enrichment in CSC but in a cell line-dependent manner. In conclusion, extensive characterization of CSC properties in tumorspheres derived from any cancer cell line or cancer tissue must be performed in order to ensure that the generated tumorspheres are actually enriched in CSC. PMID:24586931

Calvet, Christophe Y; André, Franck M; Mir, Lluis M

2014-01-01

89

Nitrite reductase genes in halobenzoate degrading denitrifying bacteria.  

Science.gov (United States)

Abstract Diversity of the functional genes encoding dissimilatory nitrite reductase was investigated for the first time in denitrifying halobenzoate degrading bacteria and in two 4-chlorobenzoate degrading denitrifying consortia. Nitrite reductase genes were PCR-amplified with degenerate primers (specific to the two different types of respiratory nitrite reductase, nirS and nirK), cloned and sequenced to determine which type of nitrite reductase was present in each isolate and consortium. Halobenzoate degrading isolates belonging to the genera Ochrobactrum, Ensifer and Mesorhizobium, as well as Pseudomonas mendocina CH91 were found to have nirK genes, which were closely related to the previously published nirK genes of Ochrobactrum anthropi, Achromobacter cycloclastes, Alcaligenes faecalis and Pseudomonas aureofaciens, respectively. The isolates assigned to the genera Acidovorax, Azoarcus and Thauera as well as all other species in the genera Thauera and Azoarcus contained nirS genes, which were closely related to the nirS genes from Pseudomonas stutzeri with some exceptions. In addition, only nirS genes were found in 4-chlorobenzoate degrading denitrifying consortia. Three different major terminal restriction fragments from the nirS genes were detected by terminal restriction fragment length polymorphism analysis of the consortia, and five different nirS genes were cloned from one consortium. Three nirS gene clones were closely related to nirS genes from Thauera chlorobenzoica, Azoarcus tolulyticus and Pseudomonas aeruginosa, respectively. The phylogeny of nir genes was not entirely congruent with the 16S rRNA phylogeny of the genera nor was it correlated with the ecological and geographical origins or isolation substrates used for isolation and enrichment of consortia. PMID:19719666

Song, Bongkeun; Ward, Bess B

2003-04-01

90

Functional gene pyrosequencing and network analysis: an approach to examine the response of denitrifying bacteria to increased nitrogen supply in salt marsh sediments  

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Full Text Available Functional gene pyrosequencing is emerging as a useful tool to examine the diversity and abundance of microbes that facilitate key biogeochemical processes. One such process, denitrification, is of particular importance because it converts fixed nitrate (NO3- to N2 gas, which returns to the atmosphere. In N limited salt marshes, removal of NO3- prior to entering adjacent waters helps prevent eutrophication. Understanding the dynamics of salt marsh microbial denitrification is thus imperative for the maintenance of healthy coastal ecosystems. We used pyrosequencing of the nirS gene to examine the denitrifying community response to fertilization in experimentally enriched marsh plots. A key challenge in the analysis of sequence data derived from pyrosequencing is understanding whether small differences in gene sequences are ecologically meaningful. We apply a novel approach from information theory that determined that the optimal similarity level for clustering DNA sequences into OTUs, while still capturing the ecological complexity of the system, was 88% similarity. With this clustering, phylogenetic analysis yielded 6 dominant clades of denitrifiers, the largest of which, accounting for more than half of all the sequences collected, had no close cultured representatives. Of the 638 OTUs identified, only 11 were present in all plots and no single OTU was dominant. We did, however, find a large number of specialist OTUs that were present only in a single plot. The high degree of endemic OTUs, while accounting for a large proportion of the nirS diversity in the plots, were found in lower abundance than the generalist taxa. The proportion of specialist taxa increased with increasing supply of nutrients, suggesting that addition of fertilizer may create conditions that expand the niche space for denitrifying organisms and may enhance the genetic capacity for denitrification.

JenniferL.Bowen

2013-11-01

91

Effects of base-pretreatment on continuous enriched culture for hydrogen production from food waste  

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This study aimed to achieve a reliable start-up method for continuous enriched culture for hydrogen production from food waste. When ground and diluted food waste (volatile solids (VS) 4.4 {+-} 0.2% containing 27 g carbohydrate-chemical oxygen demand/L) was fed, H{sub 2} production decreased below 7.1 mL H{sub 2}/g VS (0.10 mol H{sub 2}/mol hexose{sub added}) within 20 days, because the substrate was consumed via non-H{sub 2}-producing acidogenesis. To suppress the unintended microbial reactions, three methods were examined: lowering H{sub 2} content by continuous CO{sub 2} sparging, acid-pretreatment of food waste at pH 2.0 for 1 day, and base-pretreatment of food waste at pH 12.5 for 1 day. The base-pretreatment reduced indigenous anaerobic bacteria in food waste by 4.9 log and enabled a stable long-term operation over 90 days with the H{sub 2} yields of 62.6 mL H{sub 2}/g VS (0.87 mol H{sub 2}/mol hexose{sub added}). All bacterial species were affiliated with H{sub 2}-producing Clostridium spp. at the cases. Base dosage was increased by 11% compared to the un-pretreated condition. (author)

Kim, Sang-Hyoun [Department of Civil, Construction, and Environmental Engineering, Iowa State University, 394 Town Engineering Building, Ames, IA 50011 (United States); Shin, Hang-Sik [Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, 335 Gwahangno, Yuseong-gu, Daejeon 305-701 (Korea)

2008-10-15

92

Diversity of reductive dehalogenase genes from environmental samples and enrichment cultures identified with degenerate primer PCR screens.  

Science.gov (United States)

Reductive dehalogenases are the critical enzymes for anaerobic organohalide respiration, a microbial metabolic process that has been harnessed for bioremediation efforts to resolve chlorinated solvent contamination in groundwater and is implicated in the global halogen cycle. Reductive dehalogenase sequence diversity is informative for the dechlorination potential of the site or enrichment culture. A suite of degenerate PCR primers targeting a comprehensive curated set of reductive dehalogenase genes was designed and applied to 12 DNA samples extracted from contaminated and pristine sites, as well as six enrichment cultures capable of reducing chlorinated compounds to non-toxic end-products. The amplified gene products from four environmental sites and two enrichment cultures were sequenced using Illumina HiSeq, and the reductive dehalogenase complement of each sample determined. The results indicate that the diversity of the reductive dehalogenase gene family is much deeper than is currently accounted for: one-third of the translated proteins have less than 70% pairwise amino acid identity to database sequences. Approximately 60% of the sequenced reductive dehalogenase genes were broadly distributed, being identified in four or more samples, and often in previously sequenced genomes as well. In contrast, 17% of the sequenced reductive dehalogenases were unique, present in only a single sample and bearing less than 90% pairwise amino acid identity to any previously identified proteins. Many of the broadly distributed reductive dehalogenases are uncharacterized in terms of their substrate specificity, making these intriguing targets for further biochemical experimentation. Finally, comparison of samples from a contaminated site and an enrichment culture derived from the same site 8 years prior allowed examination of the effect of the enrichment process. PMID:24312087

Hug, Laura A; Edwards, Elizabeth A

2013-01-01

93

Passive markers as a low-cost method of enriching cultural visits on user’s demand  

Directory of Open Access Journals (Sweden)

Full Text Available The idea of enriching a cultural heritage visitor’s experience by employing mobile devices such as smartphones and tablets is an active research domain. This is mainly due to the worldwide user penetration of such devices along with their continuous hardware performance enhancement. This work presents the experience and feedback gained by one year of operation of an experimental information system that aims in enhancing the experience of a visitor on his/her demand. The evaluated system is based on the use case-scenario where the a mobile device is used to capture and decode passive markers (such as QR-codes that are located on facades of selected important buildings in the old town of Xanthi, Greece, in order to enrich the visitor’s experience through a broad context of historical and architectural information delivered over the Web.   Keywords: On-demand information, Passive marker, QR-code, Smartphone, Visit enrichment.

Anestis Koutsoudis

2014-01-01

94

Persistence of Denitrifying Enzyme Activity in Dried Soils †  

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The effects of air drying soil on denitrifying enzyme activity, denitrifier numbers, and rates of N gas loss from soil cores were measured. Only 29 and 16% of the initial denitrifying enzyme activity in fresh, near field capacity samples of Maury and Donerail soils, respectively, were lost after 7 days of air drying. The denitrifying activity of bacteria added to soil and activity recently formed in situ were not stable during drying. When dried and moist soil cores were irrigated, evolution ...

1985-01-01

95

Diversity of cold-active protease-producing bacteria from arctic terrestrial and marine environments revealed by enrichment culture.  

Science.gov (United States)

A new approach for enrichment culture was applied to obtain cold-active protease-producing bacteria for marine and terrestrial samples from Svalbard, Norway. The method was developed for the enrichment of bacteria by long-term incubation at low temperatures in semi-solid agar medium containing meat pieces as the main source of carbon and energy. ZoBell and 0.1x nutrient broth were added for marine and terrestrial microorganisms, respectively, to supply basal elements for growth. One to three types of colonies were observed from each enrichment culture, indicating that specific bacterial species were enriched during the experimental conditions. Among 89 bacterial isolates, protease activity was observed from 48 isolates in the screening media containing skim milk. Good growth was observed at 4 degrees C and 10 degrees C while none of the isolates could grow at 37 degrees C. At low temperatures, enzyme activity was equal to or higher than activity at higher temperatures. Bacterial isolates were included in the genera Pseudoalteromonas (33 isolates), Arthrobacter (24 isolates), Pseudomonas (16 isolates), Psychrobacter (6 isolates), Sphingobacterium (6 isolates), Flavobacterium (2 isolates), Sporosarcina (1 isolate), and Stenotrophomonas (1 isolate). Protease activity was observed from Pseudoalteromonas (33 isolates), Pseudomonas (10 isolates), Arthrobacter (4 isolates), and Flavobacterium (1 isolate). PMID:20799082

Kim, Eun Hye; Cho, Kyeung Hee; Lee, Yung Mi; Yim, Joung Han; Lee, Hong Kum; Cho, Jang-Cheon; Hong, Soon Gyu

2010-08-01

96

A Real-Time PCR Assay for the Detection of Campylobacter jejuni in Foods after Enrichment Culture  

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A real-time PCR assay was developed for the quantitative detection of Campylobacter jejuni in foods after enrichment culture. The specificity of the assay for C. jejuni was demonstrated with a diverse range of Campylobacter species, related organisms, and unrelated genera. The assay had a linear range of quantification over six orders of magnitude, and the limit of detection was approximately 12 genome equivalents. The assay was used to detect C. jejuni in both naturally and artificially cont...

2003-01-01

97

Biodegradation of azo dyes in cocultures of anaerobic granular sludge with aerobic aromatic amine degrading enrichment cultures.  

Science.gov (United States)

A prerequisite for the mineralization (complete biodegradation) of many azo dyes is a combination of reductive and oxidative steps. In this study, the biodegradation of two azo dyes, 4-phenylazophenol (4-PAP) and Mordant Yellow 10 (4-sulfophenylazo-salicylic acid; MY10), was evaluated in batch experiments where anaerobic and aerobic conditions were integrated by exposing anaerobic granular sludge to oxygen. Under these conditions, the azo dyes were reduced, resulting in a temporal accumulation of aromatic amines. 4-Aminophenol (4-AP) and aniline were detected from the reduction of 4-PAP. 5-Aminosalicylic acid (5-ASA) and sulfanilic acid (SA) were detected from the reduction of MY10. Subsequently, aniline was degraded further in the presence of oxygen by the facultative aerobic bacteria present in the anaerobic granular sludge. 5-ASA and SA were also degraded, if inocula from aerobic enrichment cultures were added to the batch experiments. Due to rapid autoxidation of 4-AP, no enrichment culture could be established for this compound. The results of this study indicate that aerobic enrichment cultures developed on aromatic amines combined with oxygen-tolerant anaerobic granular sludge can potentially be used to completely biodegrade azo dyes under integrated anaerobic/aerobic conditions. PMID:10422231

Tan, N C; Prenafeta-Boldú, F X; Opsteeg, J L; Lettinga, G; Field, J A

1999-06-01

98

Fermentative degradation of nonionic surfactants and polyethylene glycol by enrichment cultures and by pure cultures of homoacetogenic and propionate-forming bacteria  

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Linear alkyl ethoxylates (polyethylene glycol alkyl ethers) were fermented completely to methane and CO2 in enrichment cultures inoculated with anoxic sewage sludge. Long-chain fatty acids were released as intermediates. No degradation was found with polypropylene glycol and polypropylene glycol-containing surfactants. Two types of primary ethoxylate-degrading bacteria were isolated and characterized. Both degraded polyethylene glycols with molecular weights of 1,000 completely. Strain KoB35 ...

1988-01-01

99

Fermentative degradation of nonionic surfactants and polyethylene glycol by enrichment cultures and by pure cultures of homoacetogenic and propionate-forming bacteria.  

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Linear alkyl ethoxylates (polyethylene glycol alkyl ethers) were fermented completely to methane and CO2 in enrichment cultures inoculated with anoxic sewage sludge. Long-chain fatty acids were released as intermediates. No degradation was found with polypropylene glycol and polypropylene glycol-containing surfactants. Two types of primary ethoxylate-degrading bacteria were isolated and characterized. Both degraded polyethylene glycols with molecular weights of 1,000 completely. Strain KoB35 ...

1988-01-01

100

Building Learning Communities for Research Collaboration and Cross-Cultural Enrichment in Science Education  

Science.gov (United States)

The GLOBE program has provided opportunities for environmental science research and education collaborations among scientists, teachers and K-12 students, and for cross-cultural enrichment nationally and abroad. In Alaska, GLOBE has also provided funding leverage in some cases, and a base for several other science education programs that share a common goal of increasing student interest, understanding, process skills and achievement in science, through involvement in ongoing research investigations. These programs that use GLOBE methodologies (standardized scientific measurements and learning activities developed by scientists and educators) are: Global Change Education Using Western Science and Native Knowledge also known as "Observing Locally, Connecting Globally" (OLCG); Alaska Earth System Science Education Alliance: Improving Understanding of Climate Variability and Its Relevance to Rural Alaska; Schoolyard Long Term Ecological Research; Alaska Rural Research Partnership; Alaska Partnership for Teacher Enhancement; Alaska Lake Ice and Snow Observatory Network; Alaska Boreal Forest Council Education Outreach; Calypso Farm and Ecology Center; Environmental Education Outreach; and also GLOBE Arctic POPs (persistent organic pollutants) a program that involves countries in the circumpolar North. The University of Alaska GLOBE Partnership has collaborated with the BLM Campbell Creek Science Center Globe Partnership in facilitating GLOBE Training Workshops and providing teacher support. GLOBE's extensive website including data entry, archive, analysis and visualization capabilities; GLOBE Teacher Guide, videos and other materials provided; excellent GLOBE science research and education staff, training support office, GLOBE help desk, alignment of GLOBE curriculum with national science education standards and GLOBE certification of teachers trained on even just one GLOBE investigation, have made it easier to implement GLOBE in the classroom. Using GLOBE, whole classes of students have engaged in and contributed data to science investigations. In Alaska, classes and individual students have conducted their own inquiry studies and have successfully presented their investigations and competed at science fairs and statewide high school science symposium and international conferences. Two students presented their research investigations at the GLOBE Learning Expedition in Croatia and four students presented their study at the GLOBE Arctic POPs Conference in Sweden. These students increased not only their understanding and knowledge of science but also in appreciation of people in other countries and their cultures. Friendships have also bloomed. The learning community in Alaska has expanded to include family and community members including Native elders (using OLCG), teachers, scientists and students from other countries. The following challenges remain: 1) getting funds to be able to provide GLOBE equipment and continuous support to GLOBE teachers and students throughout the year, 2) reaching teachers and students in remote areas, 3) rapid teacher turn-over rate in rural areas, 4) using inquiry-based pedagogies during GLOBE professional development workshops including the opportunity for teacher participants to conduct their own inquiries during the workshop, 5) time, school curriculum and national education requirement constraints, 6) involving school administrators, and more local scientists and community members, and 7) providing culturally relevant and responsive science education programs and life-long learning communities.

Sparrow, E. B.

2003-12-01

 
 
 
 
101

Members of the Family Comamonadaceae as Primary Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate)-Degrading Denitrifiers in Activated Sludge as Revealed by a Polyphasic Approach  

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The distribution and phylogenetic affiliations of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)-degrading denitrifying bacteria in activated sludge were studied by a polyphasic approach including culture-independent biomarker and molecular analyses as well as cultivation methods. A total of 23 strains of PHBV-degrading denitrifiers were isolated from activated sludges from different sewage treatment plants. 16S ribosomal DNA (rDNA) sequence comparisons showed that 20 of the isolates wer...

2002-01-01

102

Relative binding and biochemical effects of heterodimeric and homodimeric isoforms of platelet-derived growth factor in osteoblast-enriched cultures from fetal rat bone  

International Nuclear Information System (INIS)

indicate that each PDGF isoform produces biochemical effects proportional to binding site occupancy and suggest that receptors that favor PDGF-B subunit binding preferentially mediate these results in osteoblast-enriched bone cell cultures

1991-01-01

103

Sedimentation field flow fractionation monitoring of in vitro enrichment in cancer stem cells by specific serum-free culture medium.  

Science.gov (United States)

The development of methods to enrich cell populations for cancer stem cells (CSC) is urgently needed to help understand tumor progression, therapeutic escape and to evaluate new drugs, in particular for colorectal cancer (CRC). In this work, we describe the in vitro use of OncoMiD for colon, a CRC-specific primary cell culture medium, to enrich CRC cell lines in CSC. Sedimentation field flow fractionation (SdFFF) was used to monitor the evolution of subpopulations composition. In these models, medium induced a loss of adherence properties associated with a balance between proliferation and apoptosis rates and, more important, an increased expression of relevant CSC markers, leading to specific SdFFF elution profile changes. PMID:24927420

Mélin, Carole; Perraud, Aurélie; Bounaix Morand du Puch, Christophe; Loum, Elodie; Giraud, Stéphanie; Cardot, Philippe; Jauberteau, Marie-Odile; Lautrette, Christophe; Battu, Serge; Mathonnet, Muriel

2014-07-15

104

Biodiversity within hot spring microbial mat communities: molecular monitoring of enrichment cultures  

Science.gov (United States)

We have begun to examine the basis for incongruence between hot spring microbial mat populations detected by cultivation or by 16S rRNA methods. We used denaturing gradient gel electrophoresis (DGGE) to monitor enrichments and isolates plated therefrom. At near extincting inoculum dilutions we observed Chloroflexus-like and cyanobacterial populations whose 16S rRNA sequences have been detected in the 'New Pit' Spring Chloroflexus mat and the Octopus Spring cyanobacterial mat. Cyanobacterial populations enriched from 44 to 54 degrees C and 56 to 63 degrees C samples at near habitat temperatures were similar to those previously detected in mat samples of comparable temperatures. However, a lower temperature enrichment from the higher temperature sample selected for the populations found in the lower temperature sample. Three Thermus populations detected by both DGGE and isolation exemplify even more how enrichment may bias our view of community structure. The most abundant population was adapted to the habitat temperature (50 degrees C), while populations adapted to 65 degrees C and 70 degrees C were 10(2)- and 10(4)-fold less abundant, respectively. However, enrichment at 70 degrees C favored the least abundant strain. Inoculum dilution and incubation at the habitat temperature favored the more numerically relevant populations. We enriched many other aerobic chemoorganotrophic populations at various inoculum dilutions and substrate concentrations, most of whose 16S rRNA sequences have not been detected in mats. A common feature of numerically relevant cyanobacterial, Chloroflexus-like and aerobic chemorganotrophic populations, is that they grow poorly and resist cultivation on solidified medium, suggesting plating bias, and that the medium composition and incubation conditions may not reflect the natural microenvironments these populations inhabit.

Ward, D. M.; Santegoeds, C. M.; Nold, S. C.; Ramsing, N. B.; Ferris, M. J.; Bateson, M. M.

1997-01-01

105

In situ detection of denitrifying bacteria by mRNA-targeted nucleic acid probes and catalyzed reporter deposition  

DEFF Research Database (Denmark)

In situ detection of denitrifying bacteria by mRNA-targeted nucleic acid probes and catalyzed reporter deposition   Michael V.W. Kofoed, Peter Stief, Morten Poulsen, and Andreas Schramm Department of Biological Sciences, Microbiology, University of Aarhus, Denmark Denitrification, the sequential reduction of nitrate to dinitrogen gas, is essential for the removal of fixed nitrogen from natural and engineered ecosystems. However, community structure and activity dynamics of denitrifying bacteria in most systems are poorly understood, partially due to difficulties in identifying and quantifying (active) denitrifiers. The goal of this study was therefore to develop a protocol for the in situ detection of denitrifying bacterial cells by targeting the mRNA of denitrification genes, hereby linking denitrification activity directly to the single-cell level. Target genes were narG (encoding nitrate reductase) and nosZ (encoding nitrous oxide reductase), to detect nitrate-reducing and completely denitrifying bacteria, respectively. Enzyme-labelled oligonucleotide probes and digoxygenin-labelled polynucleotide probes were evaluated for in situ hybridization in combination with immunochemical detection and catalyzed fluorescent reporter deposition (CARD-FISH). The general feasibility of the approach was first tested with pure cultures of Pseudomonas stutzeri and various denitrifying and nitrate-reducing isolates. Detailed studies of probe specificity and hybridization conditions using Clone-FISH of narG and nosZ libraries prepared from freshwater sediment revealed a sequence similarity threshold of about 80% for detectable hybridization with polynucleotide probes. Consequently, polynucleotide probes need to be designed based on habitat-specific sequence information. In contrast, oligonucleotide probes can be designed to target a broader range of denitrifying bacteria; however, they require two-pass CARD-FISH, which may result in (too) high background fluorescence. In a first application example, habitat-specific polynucleotide probes were used to quantify bacteria expressing narG and nosZ in freshwater sediments and the guts of benthic invertebrates.    

Kofoed, Michael Vedel; Stief, Peter

106

Passport to Cultural Enrichment: The Peace Corps World Wise Schools Experience  

Science.gov (United States)

In recent studies, youths in the United States have demonstrated a remarkable lack of cultural literacy. As the world is becoming increasingly interconnected, it is imperative that students enhance their understanding of other cultures. A classroom correspondence match with a Peace Corps volunteer through the Coverdell Peace Corps World Wise…

Carano, Kenneth T.

2009-01-01

107

Nitric oxide reductase (norB) gene sequence analysis reveals discrepancies with nitrite reductase (nir) gene phylogeny in cultivated denitrifiers.  

Science.gov (United States)

Gene sequence analysis of cnorB and qnorB, both encoding nitric oxide reductases, was performed on pure cultures of denitrifiers, for which previously nir genes were analysed. Only 30% of the 227 denitrifying strains rendered a norB amplicon. The cnorB gene was dominant in Alphaproteobacteria, and dominantly coexisted with the nirK gene, coding for the copper-containing nitrite reductase. Both norB genes were equally present in Betaproteobacteria but no linked distributional pattern of nir and norB genes could be observed. The overall cnorB phylogeny was not congruent with the widely accepted organism phylogeny based on 16S rRNA gene sequence analysis, with strains from different bacterial classes having identical cnorB sequences. Denitrifiers and non-denitrifiers could be distinguished through qnorB gene phylogeny, without further grouping at a higher taxonomic resolution. Comparison of nir and norB phylogeny revealed that genetic linkage of both genes is not widespread among denitrifiers. Thus, independent evolution of the genes for both nitrogen oxide reductases does also occur. PMID:17359277

Heylen, Kim; Vanparys, Bram; Gevers, Dirk; Wittebolle, Lieven; Boon, Nico; De Vos, Paul

2007-04-01

108

Signatures of Autotrophic and Heterotrophic Metabolic Activity in Enrichment Cultures from a Sulphur Oxidizing Acid Mine Site  

Science.gov (United States)

Delineating the role of microorganisms in geochemical processes of interest in natural environments requires the development of tools that provide the ability to distinguish amongst microbial activity associated with different metabolic guilds. The gap between phylogenetic characterization and phenotypic understanding remains, underscoring the need to consider alternative methods. Compound specific analysis of cellular components has the potential to differentiate between active metabolic processes supporting microbial communities and may be especially useful in extreme environments. The goal of this study was to determine whether the phospholipids fatty acid (PLFA) distribution and isotopic signatures associated with autotrophs and heterotrophs enriched from an acid mine drainage (AMD) system differed, and further whether natural consortial autotrophic isolates showed similar signatures to autotrophic pure strains of Acidithiobacillus ferrooxidans and A. thiooxidans. Two distinct initial enrichments with tetrathionate and CO2 yielded primarily autotrophic (95%) Acidithiobaccillus spp. sulphur oxidizing communities. The remaining microbial members of theses enrichments (<5%) were morphologically distinct and heterotrophic, as subculture of the consortial isolates in a medium amended with glucose but without tetrathionate selectively resulted in their visible growth. PLFA profiles and ?13C signatures from autotrophic (1) natural enrichments, pure cultures of (2) A. ferrooxidans and (3) A. thiooxidans were similar, but collectively differed from those of the natural heterotrophic enrichment cultures. The PLFA profiles for the heterotrophic communities were made up of primarily (88-99%) C16:0 and two isomers of C18:1. In contrast, the autotrophic communities had high proportions of C16:1 (up to 18%) as well as cyclo C17 and cyclo C19 PLFA that combined comprised 18 to 58% of the observed PLFA. The ?13C signatures of the PLFA also differed strongly between the two trophic levels. The ?13C of the autotrophic PLFA, - 24 to -30 ‰, were significantly more negative than that for the heterotrophic PLFA, which ranged from -7 to -14 ‰. This distinction in PLFA pattern and isotopic composition demonstrates the ability to distinguish the relative importance of these two metabolic processes in situ in AMD, and likely extends in utility to other types of extreme environments.

Slater, G. F.; Bernier, L.; Cowie, B. R.; Warren, L. A.

2006-12-01

109

Rapid and specific detection of Salmonella spp. in animal feed samples by PCR after culture enrichment  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A PCR procedure has been developed for routine analysis of viable Salmonella spp. in feed samples. The objective was to develop a simple PCR-compatible enrichment procedure to enable DNA amplification without any sample pretreatment such as DNA extraction or cell lysis. PCR inhibition by 14 different feed samples and natural background flora was circumvented by the use of the DNA polymerase Tth. This DNA polymerase was found to exhibit a high level of resistance to PCR inhibitors present in t...

Lo?fstro?m, Charlotta; Knutsson, Rickard; Axelsson, Ce; Ra?dstro?m, Peter

2004-01-01

110

Rapid and Specific Detection of Salmonella spp. in Animal Feed Samples by PCR after Culture Enrichment  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A PCR procedure has been developed for routine analysis of viable Salmonella spp. in feed samples. The objective was to develop a simple PCR-compatible enrichment procedure to enable DNA amplification without any sample pretreatment such as DNA extraction or cell lysis. PCR inhibition by 14 different feed samples and natural background flora was circumvented by the use of the DNA polymerase Tth. This DNA polymerase was found to exhibit a high level of resistance to PCR inhibitors present in t...

Lo?fstro?m, Charlotta; Knutsson, Rickard; Axelsson, Charlotta Engdahl; Ra?dstro?m, Peter

2004-01-01

111

Biological Enrichment of Mycoplasma Agents by Cocultivation with Permissive Cell Cultures?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this study, we describe our results on the evaluation of the ability of different permissive mammalian cell lines to support the biological enrichment of mycoplasma species known to be bacterial contaminants of cell substrates. The study showed that this approach is able to significantly improve the efficiency of mycoplasma detection based on nucleic acid testing or biochemical technologies (e.g., MycoAlert mycoplasma detection). Of 10 different cell lines (Vero, MDBK, HEK-293, Hep-G2, CV-...

Volokhov, Dmitriy V.; Kong, Hyesuk; George, Joseph; Anderson, Christine; Chizhikov, Vladimir E.

2008-01-01

112

Evaluation of liquid and solid culture media for the recovery and enrichment of Burkholderia cenocepacia from distilled water.  

Science.gov (United States)

Burkholderia cepacia complex (BCC) presence has been the cause of recalls of both sterile and non-sterile pharmaceutical products since these opportunistic pathogens have been implicated to cause infections to susceptible individuals. BCC are ubiquitous in nature, but in pharmaceutical settings the most common source is contaminated water systems. Some strains of BCC, previously described as Pseudomonas cepacia, were not readily detected by standard culture methods. We have explored different strategies to recover and enrich Burkholderia cenocepacia previously cultured in distilled water for 40 days. Enrichment media of varied nutrient concentrations and composition were used, including modified Tryptic Soy Agar or Broth (TSA or TSB), Reasoner's 2nd Agar or Broth (R2A or R2AB), Brain-Heart Infusion Broth (BHIB), Mueller-Hinton Broth (MHB), and Ashdown's (ASH) medium. Of the various broth media tested, cell growth was significantly greater in TSB and R2AB than in BHIB, MHB, or ASH broth. TSB and R2AB were also compared for their recovery efficiency. Generally, there was no significant difference between the numbers of B. cenocepacia grown on 15 differently modified TSA and five modified R2A solid media. Overall, however, diluted TSA and TSB media, and R2A and R2AB showed better recovery efficiency than TSA and TSB for inocula containing small numbers of cells. All strains persisted in distilled water for 40 days. Broth media were more effective than solid media for recovery of B. cenocepacia from distilled water. These results may assist in improving detection assays with recovery and enrichment strategies to maximize recovery of these fastidious organisms. PMID:24756630

Ahn, Youngbeom; Kim, Jeong Myeong; Ahn, Hyeri; Lee, Yong-Jin; LiPuma, John J; Hussong, David; Cerniglia, Carl E

2014-07-01

113

eXTRA: A Culturally Enriched Malay Text to Speech System  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper concerns the incorporation of naturalness into Malay Text-to-Speech (TTS) systems through the addition of a culturally-localized affective component. Previous studies on emotion theories were examined to draw up assumptions about emotions. These studies also include the findings from observations by anthropologists and researchers on culturalspecific emotions, particularly, the Malay culture. These findings were used to elicit the requirements for modeling affect in the TTS that co...

Lutfi, Syaheerah L.; Montero Marti?nez, Juan Manuel; Ainon, Raja Noor; Mohd Don, Zuraidah

2008-01-01

114

Natural attenuation of perchlorate in denitrified groundwater.  

Science.gov (United States)

Monitoring of a well-defined septic system groundwater plume and groundwater discharging to two urban streams located in southern Ontario, Canada, provided evidence of natural attenuation of background low level (ng/L) perchlorate (ClO4?) under denitrifying conditions in the field. The septic system site at Long Point contains ClO4? from a mix of waste water, atmospheric deposition, and periodic use of fireworks, while the nitrate plume indicates active denitrification. Plume nitrate (NO3? -N) concentrations of up to 103 mg/L declined with depth and downgradient of the tile bed due to denitrification and anammox activity, and the plume was almost completely denitrified beyond 35 m from the tile bed. The ClO4? natural attenuation occurs at the site only when NO3? -N concentrations are <0.3 mg/L, after which ClO4? concentrations decline abruptly from 187 ± 202 to 11 ± 15?ng/L. A similar pattern between NO3? -N and ClO4? was found in groundwater discharging to the two urban streams. These findings suggest that natural attenuation (i.e., biodegradation) of ClO4? may be commonplace in denitrified aquifers with appropriate electron donors present, and thus, should be considered as a remediation option for ClO4? contaminated groundwater. PMID:23448242

Robertson, William D; Roy, James W; Brown, Susan J; Van Stempvoort, Dale R; Bickerton, Greg

2014-01-01

115

Academic Enrichment Programs for Culturally and Linguistically Diverse Children: A Service-Learning Experience  

Science.gov (United States)

In this article, the author introduces a service-learning component that enabled her to create a meaningful university-school relationship. This reciprocal relationship allowed her students to contribute over 1,500 hours of academic tutoring for culturally and linguistically diverse children in central Florida, benefiting not only children, but…

Szente, Judit

2008-01-01

116

Cultivation of Mesophilic Soil Crenarchaeotes in Enrichment Cultures from Plant Roots  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Because archaea are generally associated with extreme environments, detection of nonthermophilic members belonging to the archaeal division Crenarchaeota over the last decade was unexpected; they are surprisingly ubiquitous and abundant in nonextreme marine and terrestrial habitats. Metabolic characterization of these nonthermophilic crenarchaeotes has been impeded by their intractability toward isolation and growth in culture. From studies employing a combination of cultivation and molecular...

Simon, Holly M.; Jahn, Courtney E.; Bergerud, Luke T.; Sliwinski, Marek K.; Weimer, Paul J.; Willis, David K.; Goodman, Robert M.

2005-01-01

117

Denitrification by intact soybean nodules in relation to natural 15N enrichment of nodules  

International Nuclear Information System (INIS)

The natural 15N abundance of nodules of soybeans (Glycine max (L.) Merrill) which are actively fixing N2 is considerably higher than other tissues. To investigate the question of whether isotopic fractionation associated with denitrification by bacteroids causes this 15N enrichment, we inoculated soybeans with two strains of Rhizobium japonicum. Free-living cultures of one of these (strain USDA 33) were unable to denitrify or respire NO3-, while free-living cultures of the second (strain USDA 138) were capable of denitrification. USDA 138 formed nodules which fixed N2 very efficiently. The N of these nodules was enriched in 15N and the nodules reduced a substantial amount of NO3- to NO2- and N2O. Nodules infected with USDA 33 fixed about half as much N2 as those infected with USDA 138. The former nodules were enriched in 15N (although less so than nodules infected with USDA 138), despite the fact that the nodules formed by USDA 33 did not reduce NO3-. Clearly denitrification could not have been the cause of 15N enrichment of nodules infected with strain USDA 33. Alternative causes of 15N enrichment of soybean nodules and their possible metabolic significance are discussed

1985-01-01

118

Simultaneous oxidation of ammonium and p-cresol linked to nitrite reduction by denitrifying sludge.  

Science.gov (United States)

The metabolic capability of denitrifying sludge to oxidize ammonium and p-cresol was evaluated in batch cultures. Ammonium oxidation was studied in presence of nitrite and/or p-cresol by 55 h. At 50 mg/L NH4+-N and 76 mg/L NO2--N, the substrates were consumed at 100% and 95%, respectively, being N2 the product. At 50 mg/L NH4+-N and 133 mg/L NO2--N, the consumption efficiencies decreased to 96% and 70%, respectively. The increase in nitrite concentration affected the ammonium oxidation rate. Nonetheless, the N2 production rate did not change. In organotrophic denitrification, the p-cresol oxidation rate was slower than ammonium oxidation. In litho-organotrophic cultures, the p-cresol and ammonium oxidation rates were affected at 133 mg/L NO2--N. Nonetheless, at 76 mg/L NO2--N the denitrifying sludge oxidized ammonium and p-cresol, but at different rate. Finally, this is the first work reporting the simultaneous oxidation of ammonium and p-cresol with the production of N2 from denitrifying sludge. PMID:22029961

González-Blanco, G; Beristain-Cardoso, R; Cuervo-López, F; Cervantes, F J; Gómez, J

2012-01-01

119

Degradation of Trimethylbenzene Isomers by an Enrichment Culture under N(inf2)O-Reducing Conditions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A microbial culture enriched from a diesel fuel-contaminated aquifer was able to grow on 1,3,5-trimethylbenzene (1,3,5-TMB) and 1,2,4-TMB under N(inf2)O-reducing conditions, but it did not degrade 1,2,3-TMB. The oxidation of 1,3,5-TMB to CO(inf2) was coupled to the production of biomass and the reduction of N(inf2)O. N(inf2)O was used to avoid toxic effects caused by NO(inf2)(sup-) accumulation during growth with NO(inf3)(sup-) as the electron acceptor. In addition to 1,3,5-TMB and 1,2,4-TMB,...

Haner, A.; Hohener, P.; Zeyer, J.

1997-01-01

120

Fermentative degradation of nonionic surfactants and polyethylene glycol by enrichment cultures and by pure cultures of homoacetogenic and propionate-forming bacteria.  

Science.gov (United States)

Linear alkyl ethoxylates (polyethylene glycol alkyl ethers) were fermented completely to methane and CO2 in enrichment cultures inoculated with anoxic sewage sludge. Long-chain fatty acids were released as intermediates. No degradation was found with polypropylene glycol and polypropylene glycol-containing surfactants. Two types of primary ethoxylate-degrading bacteria were isolated and characterized. Both degraded polyethylene glycols with molecular weights of 1,000 completely. Strain KoB35 fermented polyethylene glycol, ethoxyethanol, and lactate to acetate and propionate and was assigned to the described species Pelobacter propionicus. Strain KoB58 converted polyethylene glycol and many other substrates to acetate only and was assigned to the genus Acetobacterium. The pathways of anaerobic degradation of nonionic surfactants are discussed with respect to their limitations and the various groups of bacteria involved. PMID:3355141

Wagener, S; Schink, B

1988-02-01

 
 
 
 
121

Quantification of anaerobic ammonium-oxidizing bacteria in enrichment cultures by quantitative competitive PCR.  

Science.gov (United States)

The anaerobic ammonium-oxidizing (ANAMMOX) bacteria were enriched from a sequencing batch biofilm reactor (SBBR). A quantitative competitive polymerase chain reaction (QC-PCR) system was successfully developed to detect and quantify ANAMMOX bacteria in environmental samples. For QC-PCR system, PCR primer sets targeting 16S ribosomal RNA genes of ANAMMOX bacteria were designed and used. The quantification range of this system was 4 orders of magnitude, from 10(3) to 10(6) copies per PCR, corresponding to the detection limit of 300 target copies per mL. A 312-bp internal standard was constructed, which showed very similar amplification efficiency with the target amxC fragment (349 bp) over 4 orders of magnitude (10(3)-10(6)). The linear regressions were obtained with R2 of 0.9824 for 10(3) copies, 0.9882 for 10(4) copies, 0.9857 for 10(5) copies and 0.9899 for 10(6) copies, respectively. Using this method, ANAMMOX bacteria were quantified in a shortcut nitrification/denitrification-anammox system which was set for piggery wastewater treatment. PMID:20108690

Hao, Chun; Wang, Huan; Liu, Qinhua; Li, Xudong

2009-01-01

122

Enriching the Content Provided by Cultural Catalogues with Data from Institutional Repositories  

Science.gov (United States)

Institutional repositories play a key role in universities and research centers for the preservation and dissemination of the knowledge generated or collected by these agents. Part of the information contained is related with Cultural Heritage and, therefore, it could be taken into account by thematic catalogues such as Europeana. In this paper, the opportunities and limitations of this connection are considered and presented by means of an ongoing case at the University of the Basque Country's institutional repository. In particular, we will deal with the information gathered about San Prudencio's Monastery (Clavijo, Spain), which includes a wide range of data from original datasets (photographs, pointclouds, coordinates, sketches and so on) up to finals results (reports, plans, 3D models, papers and so on).

Rodríguez Miranda, Á.; Valle Melón, J. M.; Porcal-Gonzalo, M. C.

2013-07-01

123

Interactions of deoxynivalenol and lipopolysaccharides on cytotoxicity protein synthesis and metabolism of DON in porcine hepatocytes and Kupffer cell enriched hepatocyte cultures  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The cytotoxicity of deoxynivalenol (DON), effects on protein synthesis and albumin secretion was investigated in porcine hepatocytes and Kupffer cell-enriched hepatocyte cultures (co-cultures) in the presence and absence of lipopolysaccharides (LPS). Up to 16microM DON did not reduce the metabolic activity of hepatocytes. Lysosomal activity reacted more sensitively as neutral red uptake was decreased starting at 2 or 4microM DON irrespective of LPS exposure. The synthesis of secreted proteins...

Do?ll, S.; Schrickx, J. A.; Valenta, Hana; Da?nicke, Sven; Fink-gremmels, J.

2009-01-01

124

Effect of pH on N?O reduction and accumulation during denitrification by methanol utilizing denitrifiers.  

Science.gov (United States)

Acidic pH has previously been found to increase nitrous oxide (N?O) accumulation during heterotrophic denitrification in biological wastewater treatment. However, the mechanism of this phenomenon still needs to be clarified. By using an enriched methanol utilizing denitrifying culture as an example, this paper presents a comprehensive study on the effect of pH (6.0-9.0) on N?O reduction kinetics with N?O as the sole electron acceptor, as well as the effect of pH on N?O accumulation with N?O as an intermediate of nitrate reduction. The pH dependency of nitrate and nitrite reduction was also investigated. The maximum biomass-specificN?O reduction rate is higher than the corresponding maximum nitrate and nitrite reduction rates in the entire pH range studied. However, the maximum biomass-specific N?O reduction rate is much more sensitive to pH variation outside of the optimal range (pH 7.5 to pH 8.0) than the maximum biomass-specific nitrate and nitrite reduction rates. The half-saturation coefficient of the N?O reductase increased from 0.10 mg N?O-N/L to 0.92 mg N?O-N/L as pH increased from pH 6.0 to 9.0. At pH 6.0, approximately 20% and 40% of the denitrified nitrate accumulated as N?O in the presence and absence of methanol (as an exogenous carbon source), respectively. However, at pH 6.5, these fractions decreased to 0% and 30%, respectively. No N?O accumulation occurred at pH 7.0 to 9.0 independent of the availability of methanol. These results suggest that the competition for electrons among different nitrogen oxides reductases likely plays a role in N?O accumulation at low pH conditions. PMID:22749904

Pan, Yuting; Ye, Liu; Ni, Bing-Jie; Yuan, Zhiguo

2012-10-01

125

DNA-based and culture-based characterization of a hydrocarbon-degrading consortium enriched from Arctic soil.  

Science.gov (United States)

A hydrocarbon-degrading consortium was enriched from fuel-contaminated soil from the northeastern tip of Ellesmere Island (82 degrees 30'N, 62 degrees 19'W). The enrichment culture was grown on Jet A-1 fuel at 7 degrees C. Bacterial 16S RNA gene (rDNA) fragments were amplified by polymerase chain reaction (PCR) from members of the above consortium and cloned into a plasmid vector. Partial sequences (approximately 500 bp) were determined for 29 randomly selected rDNA clones. The majority of sequences were most similar to the corresponding rDNA sequences of Rhodococcus erythropolis (15 sequences), Sphingomonas spp. (six sequences), and Pseudomonas synxantha (four sequences). Amplified ribosomal DNA restriction analysis confirmed that a larger set of 50 clones had frequencies of the three phylotypes similar to those above. Phylotype-specific PCR assays were developed and validated for the above three phylotypes. The consortium was plated and grown on Jet A-1 fuel vapors, and randomly selected isolated colonies were screened with the above PCR assays. Of 17 colonies, six matched the Rhodococcus phylotype, and three matched the Pseudomonas phylotype. A representative strain of each phylotype was physiologically characterized. Both isolates grew on alkanes at low temperature and had general characteristics consistent with their respective phylotypes. During growth of the consortium, the three phylotype populations were monitored by a most probable number PCR assay. All three phylotypes were detected, but their relative abundance was not consistent with that of the phylotypes in the clone library. The relative abundance of all three phylotypes changed substantially during long-term incubation of the consortium. The DNA-based approach used identified phylotypes consistently present in the consortium, but it failed to predict the relative abundance of their populations. PMID:11822837

Thomassin-Lacroix, E J; Yu, Z; Eriksson, M; Reimer, K J; Mohn, W W

2001-12-01

126

Proteins differentially expressed in human beta-cells-enriched pancreatic islet cultures and human insulinomas  

DEFF Research Database (Denmark)

In view of the great demand for human beta-cells for physiological and medical studies, we generated cell lines derived from human insulinomas which secrete insulin, C-peptide and express neuroendocrine and islet markers. In this study, we set out to characterize their proteomes, comparing them to those of primary beta-cells using DIGE followed by MS. The results were validated by Western blotting. An average of 1800 spots was detected with less than 1% exhibiting differential abundance. Proteins more abundant in human islets, such as Caldesmon, are involved in the regulation of cell contractility, adhesion dependent signaling, and cytoskeletal organization. In contrast, almost all proteins more abundant in insulinoma cells, such as MAGE2, were first described here and could be related to cell survival and resistance to chemotherapy. Our proteomic data provides, for the first time, a molecular snapshot of the orchestrated changes in expression of proteins involved in key processes which could be correlated with the altered phenotype of human beta-cells. Collectively our observations prompt research towards the establishment of bioengineered human beta-cells providing a new and needed source of cultured human beta-cells for beta-cell research, along with the development of new therapeutic strategies for detection, characterization and treatment of insulinomas.

Terra, Letícia F; Teixeira, Priscila C

2013-01-01

127

Enrichment of hepatocytes in a HepaRG culture using spatially selective photodynamic treatment  

Science.gov (United States)

The human hepatoma HepaRG cell line is an in vitro cell model that is becoming an important tool in drug metabolism, hepatotoxicity, genotoxicity, and enzyme induction studies. The cells are highly proliferative during their undifferentiated state but once committed, they differentiate into two distinctly different cell types, namely, hepatocyte-like and biliary epithelial-like cells. The presence of the latter in the cell culture is considered to be a drawback of the cell model. Since the proliferating undifferentiated HepaRG cells have a bipotent character, the only way to improve the content ratio of hepatic versus biliary cells of differentiated HepaRG cells is to eradicate biliary cells in situ, in a way that free surface space does not become available and thus no transdifferentiation can occur. Spatially selective photodynamic therapy has proven to be effective for that purpose. First, all the cells were administered aminolevulinic acid (?-ALA) to stimulate the synthesis of protoporphyrin IX (PpIX), a naturally occurring photosensitizer. Then, the biliary cells were automatically identified and outlined by bright-field image processing. Last, UV light patterns were projected onto the epithelial cells alone by a spatial light modulation device connected to an optical microscope; therefore, only these cells were destroyed by photodynamic therapy.

Bednarkiewicz, Artur; Rodrigues, Robim M.; Whelan, Maurice P.

2010-03-01

128

The metabolism of neonicotinoid insecticide thiamethoxam by soil enrichment cultures, and the bacterial diversity and plant growth-promoting properties of the cultured isolates.  

Science.gov (United States)

A soil enrichment culture (SEC) rapidly degraded 96% of 200 mg L(-1) neonicotinoid insecticide thiamethoxam (TMX) in MSM broth within 30 d; therefore, its metabolic pathway of TMX, bacterial diversity and plant growth-promoting rhizobacteria (PGPR) activities of the cultured isolates were studied. The SEC transformed TMX via the nitro reduction pathway to form nitrso, urea metabolites and via cleavage of the oxadiazine cycle to form a new metabolite, hydroxyl CLO-tri. In addition, 16S rRNA gene-denaturing gradient gel electrophoresis analysis revealed that uncultured rhizobacteria are predominant in the SEC broth and that 77.8% of the identified bacteria belonged to uncultured bacteria. A total of 31 cultured bacterial strains including six genera (Achromobacter, Agromyces, Ensifer, Mesorhizobium, Microbacterium and Pseudoxanthomonas) were isolated from the SEC broth. The 12 strains of Ensifer adhaerens have the ability to degrade TMX. All six selected bacteria showed PGPR activities. E. adhaerens TMX-23 and Agromyces mediolanus TMX-25 produced indole-3-acetic acid, whereas E. adhaerens TMX-23 and Mesorhizobium alhagi TMX-36 are N2-fixing bacteria. The six-isolated microbes were tolerant to 200 mg L(-1) TMX, and the growth of E. adhaerens was significantly enhanced by TMX, whereas that of Achromobacter sp. TMX-5 and Microbacterium sp.TMX-6 were enhanced slightly. The present study will help to explain the fate of TMX in the environment and its microbial degradation mechanism, as well as to facilitate future investigations of the mechanism through which TMX enhances plant vigor. PMID:24762175

Zhou, Guang-Can; Wang, Ying; Ma, Yuan; Zhai, Shan; Zhou, Ling-Yan; Dai, Yi-Jun; Yuan, Sheng

2014-06-01

129

Macrofaunal Impact on the Denitrifying Bacterial Community in Freshwater Sediment  

DEFF Research Database (Denmark)

Sediment-dwelling macroinvertebrates alter their habitat by transporting oxic water into the sediment and enriching it for organic matter, thereby affecting microbial processes in the sediment. Here we report that burrowing macroinvertebrates can also have a pronounced effect on microbial diversity, with nitrate-reducing and denitrifying bacteria as examples. The diversity of these functional groups was compared in sediment microcosms with and without Chironomus plumosus larvae, using the genes encoding nitrate reductase (narG) and nitrous oxide reductase (nosZ) as functional markers. The estimated phylotype richness of narG increased from 68 in sediment without larvae to 170 in sediment with larvae. Part of this increase in narG diversity could be explained by metabolic activation of certain nitrate-reducing bacteria in the gut of C. plumosus, since 18.3 % of the additional phylotypes were found actively expressed in the gut contents of C. plumosus. The remaining increase may be due to the creationof a (on the microscale) more structured habitat by larval activities like burrow construction, bioturbation, and water pumping, possibly combined with a general activation of microbes by enriching the sediment with partly degraded organic material excreted by the larvae. In contrast to narG, nosZ phylotype richness was unaffected by the presence of chironomid larvae, and very few nosZ phylotypes were actively expressed in the larvae gut. Our results suggest that burrowing macroinvertebrates affect the microbial diversity in sediments, both indirectly by their behaviour and directly by activating certain functional groups of microorganisms passing through their gut.

Poulsen, Morten; Stief, Peter

130

Geochemical diversity in S processes mediated by culture-adapted and environmental-enrichments of Acidithiobacillus spp.  

Science.gov (United States)

Coupled S speciation and acid generation resulting from S processing associated with five different microbial treatments, all primarily Acidithiobacillus spp. (i.e. autotrophic S-oxidizers) were evaluated in batch laboratory experiments. Microbial treatments included two culture-adapted strains, Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans, their consortia and two environmental enrichments from a mine tailings lake that were determined to be >95% Acidithiobacillus spp., by whole-cell fluorescent hybridization. Using batch experiments simulating acidic mine waters with no carbon amendments, acid generation, and S speciation associated with the oxidation of three S substrates (thiosulfate, tetrathionate, and elemental S) were evaluated. Aseptic controls showed no observable pH decrease over the experimental time course (1 month) for all three S compounds examined. In contrast, pH decreased in all microbial treatments from starting pH values of 4 to 2 or less for all three S substrates. Results show a non-linear relationship between the pH dynamics of the batch cultures and their corresponding sulfate concentrations, and indicate how known microbial S processing pathways have opposite impacts, ultimately on pH dynamics. Associated geochemical modeling indicated negligible abiogenic processes contributing to the observed results, indicating strong microbial control of acid generation extending over pH ranges from 4 to less than 2. However, the observed acid generation rates and associated S speciation were both microbial treatment and substrate-specific. Results reveal a number of novel insights regarding microbial catalysis of S oxidation: (1) metabolic diversity in S processing, as evidenced by the observed geochemical signatures in S chemical speciation and rates of acid generation amongst phylogenetically similar organisms (to the genus level); (2) consortial impacts differ from those of individual strain members; (3) environmental enrichments of Acidithiobacillus spp. catalyze different S reaction arrays than pure strain Acidithiobacillus spp.; and (4) microbial catalysis of S reactions involves significant disproportionation tied to substantial H + consumption, with the formation of as yet, poorly characterized intermediate S species, most likely polythionates and polysulfane monosulfonic acids that are thought to be involved in microbial S storage mechanisms.

Bernier, Luc; Warren, Lesley A.

2007-12-01

131

Interactions of deoxynivalenol and lipopolysaccharides on cytokine excretion and mRNA expression in porcine hepatocytes and Kupffer cell enriched hepatocyte cultures  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The effects of deoxynivalenol (DON) on the mRNA expression of cytokines and inflammation-related genes, as well as the cytokine secretion of porcine hepatocytes and Kupffer cell enriched hepatocyte cultures (co-cultures), were investigated in the absence or presence of LPS. DON and LPS acted in a synergistic manner with regard to a significantly increased mRNA expression of TNF-alpha in hepatocytes exposed to 500 nM or 2000 nM DON, or non-significant increase in co-cultures after 3h of exposu...

Do?ll, S.; Schrickx, J. A.; Danicke, Sven; Fink-gremmels, J.

2009-01-01

132

Pseudomonas aeruginosa and Achromobacter sp.: nitrifying aerobic denitrifiers have a plasmid encoding for denitrifying functional genes.  

Science.gov (United States)

In the present work, novel heterotrophic nitrifying and aerobic denitrifying bacteria have been isolated from greenwater system of coastal aquaculture. Based on the 16S rRNA gene, FAME analysis and biochemical test, the isolates have been identified as Pseudomonas aeruginosa and Achromobacter sp. These have been named as P. aeruginosa strain DBT1BNH3 and Achromobacter sp. strain DBTN3. Denitrifying functional genes such as nitrite reductase (nirS), nitric oxide reductase (qnorB) and nitrous oxide reductase (nosZ) genes have been identified. These strains found to have a 27 kb plasmid coding for nirS and nosZ. The possibility of horizontal transfer of plasmid among Pseudomonadaceae and Alcaligenaceae families in coastal aquaculture has been explored. Further, we have studied combined nitrification and oxygen tolerant denitrification potential in the same isolates. PMID:24165750

Kathiravan, V; Krishnani, K K

2014-04-01

133

Analysis of the syntrophic anaerobic digestion of volatile fatty acids using enriched cultures in a fixed-bed reactor.  

Science.gov (United States)

Volatile fatty acids (VFAs) are key intermediates in anaerobic digestion. Enriched acetogenic and methanogenic cultures were used for the syntrophic anaerobic digestion of VFAs in a continuous fixed-bed reactor at mesophilic conditions. The interactive effects of propionic (HPr), butyric (HBu), and acetic (HAc) acids were analyzed. Furthermore, hydraulic retention time (HRT) and methanogen-to-acetogen ratios (M/As) were investigated as the key microbiological and operating variables of VFA anaerobic degradations. Experiments were carried out based on central composite design (CCD) and results were analyzed using response surface methodology (RSM). Effluent concentrations of HPr, HBu, HAc, and biogas production rate (BPR) were directly measured as responses. The optimum conditions were found to be HPr = 1122.9 mg/L, HBu = 1792.4 mg/L, HAc = 1735.4 mg/L, HRT = 21 hours, and M/A = 2.4 (corresponding to the maximum VFA removal and BPR). The results of verification experiments and predicted values from fitted correlations were in close agreement at a 95% confidence interval. PMID:22852432

Amani, T; Nosrati, M; Mousavi, S M; Kermanshahi, R K

2012-05-01

134

Using enriched cultures for elevation of anaerobic syntrophic interactions between acetogens and methanogens in a high-load continuous digester.  

Science.gov (United States)

Volatile fatty acids (VFAs) are key intermediates in anaerobic digestion. Enriched acetogenic and methanogenic cultures were used for syntrophic anaerobic digestion of VFAs in a high-load continuous reactor fed with acetic (HAc), propionic (HPr) and butyric (HBu) acids at maximum concentrations of 5, 3 and 4 g/L, respectively. Interactive effects of HPr, HBu and HAc were analyzed. Furthermore, hydraulic retention time (HRT) and methanogen to acetogen population ratio (M/A) were investigated as key microbiological and operating variables of VFA anaerobic degradations. Optimum conditions were found to be HPr=1125.0mg/L, HBu=1833.4 mg/L, HAc=1727.4 mg/L, HRT=21 h and M/A=2.5 (corresponding to maximum VFA removal and biogas production rate (BPR)). Results of verification experiments and predicted values from fitted correlations were in close agreement at 95% confidence interval. HRT and M/A had positive effects on VFA removal and BPR. M/A was the most important factor that affected BPR. All VFAs inhibited VFA removals. PMID:21186121

Amani, T; Nosrati, M; Mousavi, S M

2011-02-01

135

Molecular analysis of enrichment cultures of ammonia oxidizers from the Salar de Huasco, a high altitude saline wetland in northern Chile.  

Science.gov (United States)

We analyzed enrichment cultures of ammonia-oxidizing bacteria (AOB) collected from different areas of Salar de Huasco, a high altitude, saline, pH-neutral water body in the Chilean Altiplano. Samples were inoculated into mineral media with 10 mM NH4+ at five different salt concentrations (10, 200, 400, 800 and 1,400 mM NaCl). Low diversity (up to three phylotypes per enrichment) of beta-AOB was detected using 16S rDNA and amoA clone libraries. Growth of beta-AOB was only recorded in a few enrichment cultures and varied according to site or media salinity. In total, five 16S rDNA and amoA phylotypes were found which were related to Nitrosomonas europaea/Nitrosococcus mobilis, N. marina and N. communis clusters. Phylotype 1-16S was 97% similar with N. halophila, previously isolated from Mongolian soda lakes, and phylotypes from amoA sequences were similar with yet uncultured beta-AOB from different biofilms. Sequences related to N. halophila were frequently found at all salinities. Neither gamma-AOB nor ammonia-oxidizing Archaea were recorded in these enrichment cultures. PMID:18305895

Dorador, Cristina; Busekow, Annika; Vila, Irma; Imhoff, Johannes F; Witzel, Karl-Paul

2008-05-01

136

Molecular analysis of enrichment cultures of ammonia oxidizers from the Salar de Huasco, a high altitude saline wetland in northern Chile  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We analyzed enrichment cultures of ammonia-oxidizing bacteria (AOB) collected from different areas of Salar de Huasco, a high altitude, saline, pH-neutral water body in the Chilean Altiplano. Samples were inoculated into mineral media with 10 mM NH4+ at five different salt concentrations (10, 200, 400, 800 and 1,400 mM NaCl). Low diversity (up to three phylotypes per enrichment) of beta-AOB was detected using 16S rDNA and amoA clone libraries. Growth of beta-AOB was only recorded in a few e...

2008-01-01

137

Enhanced enrichment of prostate cancer stem-like cells with miniaturized 3D culture in liquid core-hydrogel shell microcapsules.  

Science.gov (United States)

Cancer stem-like cells (CSCs) are rare subpopulations of cancer cells that are reported to be responsible for cancer resistance and metastasis associated with conventional cancer therapies. Therefore, effective enrichment/culture of CSCs is of importance to both the understanding and treatment of cancer. However, it usually takes approximately 10 days for the widely used conventional approach to enrich CSCs through the formation of CSC-containing aggregates. Here we report the time can be shortened to 2 days while obtaining prostate CSC-containing aggregates with better quality based on the expression of surface receptor markers, dye exclusion, gene and protein expression, and in vivo tumorigenicity. This is achieved by encapsulating and culturing human prostate cancer cells in the miniaturized 3D liquid core of microcapsules with an alginate hydrogel shell. The miniaturized 3D culture in core-shell microcapsules is an effective strategy for enriching/culturing CSCs in vitro to facilitate cancer research and therapy development. PMID:24952981

Rao, Wei; Zhao, Shuting; Yu, Jianhua; Lu, Xiongbin; Zynger, Debra L; He, Xiaoming

2014-09-01

138

Drinking Water Denitrification using Autotrophic Denitrifying Bacteria in a Fluidized Bed Bioreactor   

Directory of Open Access Journals (Sweden)

Full Text Available Background and Objectives: Contamination of drinking water sources with nitrate may cause adverse effects on human health. Due to operational and maintenance problems of physicochemical nitrate removal processes, using biological denitrification processes have been performed. The aim of this study is to evaluate nitrate removal efficiency from drinking water using autotrophic denitrifying bacteria immobilized on sulfur impregnated activated carbon in a fluidized bed bioreactor. Materials and Methods: After impregnating activated carbon by sulfur as a microorganism carriers and enrichment and inoculation of denitrifying bacteria, a laboratory-scale fluidized bed bioreactor was operated. Nitrate removal efficiency, nitrite, turbidity, hardness and TOC in the effluent were examined during the whole experiment under various conditions including constant influent nitrate concentration as 90 mg NO3--N/l corresponding to different HRT ranging from 5.53 to 1.5 hr. Results: We found that  the denitrification rates was depended on the hydraulic retention time and the nitrate removal efficiency was up to 98%  and nitrite concentration was lower than 1mg/l at optimum HRT=2.4 hr respectively. Moreover, there was no difference in hardness between influent and effluent due to supplying sodium bicarbonate as carbon source for denitrifying bacteria.  However pH, TOC, hardness, and turbidity of the effluent met the W.H.O guidelines for drinking water.  Conclusion: This study demonstrated that an innovative carrier as sulfur impregnated activated carbon could be used as both the biofilm carrier and energy source for treating nitrate contaminated drinking water in the lab-scale fluidized bed bioreactor.

Abdolmotaleb Seid-mohammadi

2013-02-01

139

Preparation of glycerol-enriched yeast culture and its effect on blood metabolites and ruminal fermentation in goats.  

Science.gov (United States)

The aim of this study was to isolate a glycerol-producing yeast strain from nature to prepare glycerol-enriched yeast culture (GY), and preliminarily evaluate the effects of GY on blood metabolites and ruminal fermentation in goats. During the trial, six isolates were isolated from unprocessed honey, and only two isolates with higher glycerol yield were identified by analysis of 26S ribosomal DNA sequences. One of the two isolates was identified as Saccharomyces cerevisiae, a direct-fed microbe permitted by the FDA. This isolate was used to prepare GY. The fermentation parameters were optimized through single-factor and orthogonal design methods to maximize the glycerol yield and biomass. The final GY contained 38.7±0.6 g/L glycerol and 12.6±0.5 g/L biomass. In vivo, eight castrated male goats with ruminal fistula were used in a replicated 4×4 Latin square experiment with four consecutive periods of 15 d. Treatments were as follows: control, LGY, MGY, and HGY with 0, 100, 200, and 300 mL GY per goat per day, respectively. The GY was added in two equal portions at 08?00 and 17?00 through ruminal fistula. Samples of blood and ruminal fluid were collected on the last one and two days of each period, respectively. Results showed that the plasma concentrations of triglyceride and total cholesterol were not affected by the supplemented GY. Compared with the control, goats supplemented with MGY and HGY had significantly higher (P<0.05) concentrations of plasma glucose and total protein, ruminal volatile fatty acid and molar proportion of propionate, and significantly lower (P<0.05) ruminal pH and ammonia nitrogen. These parameters changed linearly with increasing GY supplementation level (P<0.05). In conclusion, GY has great potential to be developed as a feed additive with dual effects of glycerol and yeast for ruminants. PMID:24709881

Ye, Gengping; Zhu, Yongxing; Liu, Jin; Chen, Xingxiang; Huang, Kehe

2014-01-01

140

Complete Detoxification of Vinyl Chloride by an Anaerobic Enrichment Culture and Identification of the Reductively Dechlorinating Population as a Dehalococcoides Species  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A major obstacle in the implementation of the reductive dechlorination process at chloroethene-contaminated sites is the accumulation of the intermediate vinyl chloride (VC), a proven human carcinogen. To shed light on the microbiology involved in the final critical dechlorination step, a sediment-free, nonmethanogenic, VC-dechlorinating enrichment culture was derived from tetrachloroethene (PCE)-to-ethene-dechlorinating microcosms established with material from the chloroethene-contaminated ...

2003-01-01

 
 
 
 
141

Assessment of the Accuprobe Listeria monocytogenes culture identification reagent kit for rapid colony confirmation and its application in various enrichment broths.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Accuprobe Listeria monocytogenes Culture Identification Reagent Kit, a nonradioactive probe, was evaluated as a colony confirmation test and in different selective or nonselective enrichment broths. The probe was 100% sensitive and 100% specific when applied to isolated colonies. The minimal detection limit in physiological saline was established to be about 10(5) CFU of L. monocytogenes. Hybridization done directly in broths seeded with L. monocytogenes showed variable results. Three non...

Ninet, B.; Bannerman, E.; Bille, J.

1992-01-01

142

Anaerobic degradation of alkylbenzenes in crude oil. II. Changes of oil composition upon incubation with sulfate-reducing and denitrifying bacteria  

Energy Technology Data Exchange (ETDEWEB)

Various alkylbenzenes in crude oils are degradable by several newly isolated sulfate-reducing and nitrate-reducing bacteria under strictly anoxic conditions. A mesophilic enrichment culture consisting of at least two different types of sulfate-reducing bacteria, depletes toluene, o- and m-xylene, o- and m-ethyltoluene, m-propyltoluene and m-cymene in crude oils at different rates. Experiments with different oils reveal that in general the degradation efficiency seems to depend not very strongly on the composition of the incubated oils. Results of our experiments with nitrate-reducing bacteria show that at least toluene, ethyltoluene and m-, p- and o-xylene in crude oils are biodegradable under denitrifying conditions. All organisms isolated so far exhibit a high substrate specifity. Up to now no indications for the alteration of other oil fractions, i.e. n-alkanes, biomarkers and PAH`s, could be observed with any of the bacteria used in this study. The possible role of alkylbenzene-degrading anaerobic bacteria in biodegradation of petroleums in natural environments will be discussed.

Wilkes, H.; Willsch, H. [Forschungszentrum Juelich (Germany); Rabus, R.; Aeckersberg, F. [Max-Planck-Institut fuer Marine Mikrobiologie, Bremen (Germany)] [and others

1996-10-01

143

Degradation of polycyclic aromatic hydrocarbons at low temperature under aerobic and nitrate-reducing conditions in enrichment cultures from northern soils  

DEFF Research Database (Denmark)

The potential for biodegradation of polycyclic aromatic hydrocarbons (PAHs)at low temperature and under anaerobic conditions is not well understood, but such biodegradation would be very useful for remediation of polluted sites. Biodegradation of a mixture of 11 different PAHs with two to five aromatic rings, each at a concentration of 10 micro g/ml, was studied in enrichment cultures inoculated with samples of four northern soils. Under aerobic conditions, low temperature severely limited PAH biodegradation. After 90 days, aerobic cultures at 20 degrees C removed 52 to 88% of the PAHs. The most extensive PAH degradation under aerobic conditions at 7 degrees C,53% removal, occurred in a culture from creosote-contaminated soil. Low temperature did not substantially limit PAH biodegradation under nitrate-reducing conditions. Under nitrate-reducing conditions,naphthalene, 2-methylnaphthalene, fluorene, and phenanthrene were degraded. The most extensive PAH degradation under nitrate-reducing conditions at 7 degrees C, 39% removal, occurred in a culture from fuel-contaminated Arctic soil. In separate transfer cultures from the above Arctic soil, incubated anaerobically at 7 degrees C, removal of 2-methylnaphthalene and fluorene was stoichiometrically coupled to nitrate removal. Ribosomal intergenic spacer analysis suggested that enrichment resulted in a few predominant bacterial populations,including members of the genera Acidovorax,Bordetella, Pseudomonas, Sphingomonas, and Variovorax. Predominant populations from different soils often included phylotypes with nearly identical partial 16S rRNA gene sequences (i.e., same genus) but never included phylotypes with identical ribosomal intergenic spacers (i.e., different species or subspecies). The composition of the enriched communities appeared to be more affected by presence of oxygen, than by temperature or source of the inoculum.

Eriksson, Mikael; Södersten, Erik Gustaf

2003-01-01

144

Community Composition and Functioning of Denitrifying Bacteria from Adjacent Meadow and Forest Soils  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We investigated communities of denitrifying bacteria from adjacent meadow and forest soils. Our objectives were to explore spatial gradients in denitrifier communities from meadow to forest, examine whether community composition was related to ecological properties (such as vegetation type and process rates), and determine phylogenetic relationships among denitrifiers. nosZ, a key gene in the denitrification pathway for nitrous oxide reductase, served as a marker for denitrifying bacteria. De...

Rich, J. J.; Heichen, R. S.; Bottomley, P. J.; Cromack, K.; Myrold, D. D.

2003-01-01

145

Treatment and electricity harvesting from sulfate/sulfide-containing wastewaters using microbial fuel cell with enriched sulfate-reducing mixed culture  

Energy Technology Data Exchange (ETDEWEB)

Highlights: Black-Right-Pointing-Pointer We started up microbial fuel cell (MFC) using enriched sulfate-reducing mixed culture. Black-Right-Pointing-Pointer Sulfate-reducing bacteria and anode-respiring bacteria were enriched in anodic biofilms. Black-Right-Pointing-Pointer The MFC effectively remove sulfate to elementary sulfur in the presence of lactate. Black-Right-Pointing-Pointer The present device can treat sulfate laden wastewaters with electricity harvesting. - Abstract: Anaerobic treatment of sulfate-laden wastewaters can produce excess sulfide, which is corrosive to pipelines and is toxic to incorporated microorganisms. This work started up microbial fuel cell (MFC) using enriched sulfate-reducing mixed culture as anodic biofilms and applied the so yielded MFC for treating sulfate or sulfide-laden wastewaters. The sulfate-reducing bacteria in anodic biofilm effectively reduced sulfate to sulfide, which was then used by neighboring anode respiring bacteria (ARB) as electron donor for electricity production. The presence of organic carbons enhanced MFC performance since the biofilm ARB were mixotrophs that need organic carbon to grow. The present device introduces a route for treating sulfate laden wastewaters with electricity harvesting.

Lee, Duu-Jong, E-mail: cedean@mail.ntust.edu.tw [Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan (China); Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan (China); Lee, Chin-Yu [Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan (China); Chang, Jo-Shu [Department of Chemical Engineering, National Cheng Kung University, Tainan, Taiwan (China); Center for Bioscience and Biotechnology, National Cheng Kung University, Tainan, Taiwan (China); Research Center for Energy Technology and Strategy, National Cheng Kung University, Tainan, Taiwan (China)

2012-12-15

146

Treatment and electricity harvesting from sulfate/sulfide-containing wastewaters using microbial fuel cell with enriched sulfate-reducing mixed culture  

International Nuclear Information System (INIS)

Highlights: ? We started up microbial fuel cell (MFC) using enriched sulfate-reducing mixed culture. ? Sulfate-reducing bacteria and anode-respiring bacteria were enriched in anodic biofilms. ? The MFC effectively remove sulfate to elementary sulfur in the presence of lactate. ? The present device can treat sulfate laden wastewaters with electricity harvesting. - Abstract: Anaerobic treatment of sulfate-laden wastewaters can produce excess sulfide, which is corrosive to pipelines and is toxic to incorporated microorganisms. This work started up microbial fuel cell (MFC) using enriched sulfate-reducing mixed culture as anodic biofilms and applied the so yielded MFC for treating sulfate or sulfide-laden wastewaters. The sulfate-reducing bacteria in anodic biofilm effectively reduced sulfate to sulfide, which was then used by neighboring anode respiring bacteria (ARB) as electron donor for electricity production. The presence of organic carbons enhanced MFC performance since the biofilm ARB were mixotrophs that need organic carbon to grow. The present device introduces a route for treating sulfate laden wastewaters with electricity harvesting.

2012-12-01

147

Cultured trout gill epithelia enriched in pavement cells or in mitochondria-rich cells provides insights into Na+ and Ca 2+ transport.  

Science.gov (United States)

The lack of a suitable flat epithelial preparation isolated directly from the freshwater fish gill has led, in recent years, to the development of cultured gill epithelia on semipermeable supports. To date, their minimal capacity to actively transport ions has limited their utility as ionoregulatory models. The current study describes a new method of culturing gill epithelia consisting either of an enriched population of pavement (PV) cells or a mixed population of PV cells and mitochondria-rich (MR) cells from the gills of adult rainbow trout. Although the cell culture approach is similar to the double-seeded insert (DSI) technique described previously, it makes use of Percoll density centrifugation to first separate populations of PV and MR cells, which are then seeded on cell culture supports in varying proportions on successive days so as to produce preparations enriched in one or the other cell types. Based on rhodamine staining, the MR cell-rich epithelia exhibited a threefold higher enrichment of MR cells compared to traditional DSI preparations. In general, MR cell-rich epithelia developed extremely high transepithelial resistances (TER; >30 kOmega cm(2)) and positive transepithelial potentials (TEP) under symmetrical conditions (i.e., L15 medium on both apical and basolateral sides). Apical exposure of cell cultures to freshwater reduced TER and produced a negative TEP in all the epithelial preparations, although MR cell-rich epithelia maintained relatively high TER and negative TEP for over 2 d under these asymmetrical conditions. Measurement of unidirectional Na(+) fluxes and application of the Ussing flux ratio criterion demonstrated active Na(+) uptake in PV cell-rich and MR cell-rich epithelia under both symmetrical and asymmetrical conditions. In comparison, Ca(2+) uptake and Na(+)/K(+)-ATPase activity were significantly elevated in MR cell-rich preparations relative to the traditional DSI or PV cell-rich cultures under symmetrical conditions. This new methodology enhances our ability to tailor cultured gill epithelia on semipermeable supports with different proportions of PV cells and MR cells, thereby illuminating the ionoregulatory functions of the two cell types. PMID:18810565

Galvez, Fernando; Tsui, Tommy; Wood, Chris M

2008-01-01

148

Diversity and activity of denitrifiers of Chilean arid soil ecosystems  

Directory of Open Access Journals (Sweden)

Full Text Available The Chilean sclerophyllous matorral is a Mediterranean semiarid ecosystem affected by erosion, with low soil fertility and limited by nitrogen. However, limitation of resources is even more severe for desert soils such as from the Atacama Desert, one of the most extreme arid deserts on Earth. Topsoil organic matter, nitrogen and moisture content were significantly higher in the semiarid soil compared to the desert soil. Although the most significant loss of biologically preferred nitrogen from terrestrial ecosystems occurs via denitrification, virtually nothing is known on the activity and composition of denitrifier communities thriving in arid soils. In this study, we explored denitrifier communities from two soils with profoundly distinct edaphic factors. While denitrification activity in the desert soil was below detection limit, the semiarid soil sustained denitrification activity. To elucidate the genetic potential of the soils to sustain denitrification processes we performed community analysis of denitrifiers based on nitrite reductase (nirK and nirS genes as functional marker genes for this physiological group. Presence of nirK-type denitrifiers in both soils was demonstrated but failure to amplify nirS from the desert soil suggests very low abundance of nirS-type denitrifiers shedding light on the lack of denitrification activity. Phylogenetic analysis showed a very low diversity of nirK with only three distinct genotypes in the desert soil which conditions presumably exert a high selection pressure. While nirK diversity was also limited to only few, albeit distinct genotypes, the semiarid matorral soil showed a surprisingly broad genetic variability of the nirS gene. The Chilean matorral is a shrub land plant community which form vegetational patches stabilizing the soil and increasing its nitrogen and carbon content. These islands of fertility may sustain the development and activity of the overall microbial community and of denitrifiers in particular.

GescheBraker

2012-04-01

149

Rate of denitrification and the accumulation of intermediates in a denitrifying bioreactor  

Science.gov (United States)

Denitrifying bioreactors (DNBRs) are an emerging mechanism to mitigate the impact of excess reactive nitrogen by harnessing the activity of ubiquitous denitrifying soil microbes. DNBRs fundamentally consist of an organic carbon energy source sufficiently saturated to develop anaerobic conditions and support heterotrophic reduction of nitrate to dinitrogen. Although recent research has well established achievable nitrate removal in DNBRs upwards of 90%, few studies experimentally determine the fate of nitrogen in these systems. This study differentiates between denitrification to inert nitrogen gas, which permanently removes reactive nitrogen from an enriched ecosystem, and transformation of nitrate to another bioavailable form (such as N2O or NOX, powerful greenhouse gases). Previous research has failed to make this distinction and as both are perceived as a reduction in nitrate concentration at the outlet, the utility of DNBRs in reducing downstream reactive nitrogen has not been sufficiently established. In order to quantify the rate of nitrate removal and the products produced, dissolved gas samples are collected from the DNBR with passive diffusion gas samplers while the influent and effluent nitrate concentration and chemical oxygen demand are monitored in real time with spectrometer probes. Nitrate removal is compared with the denitrification rate and the ratio of dinitrogen to nitrous oxide is reported. Denitrification is quantified from the proportion of nitrogen gas products produced from the nitrate pool, indicated by the negative congruence of the regression of 15N enrichment in the nitrate pool and temporal depletion in the gaseous products. The proportion of nitrous oxide to dinitrogen is examined with respect to saturation and redox potential. This research informs the interpretation of previous studies as well as advises the focus of long-term system level monitoring that will provide further information on the design and application of DNBRs to mitigate nitrate pollution.

Parsignault, D. R.; Gursky, H.; Kellogg, E. M.; Matilsky, T.; Murray, S.; Schreier, E.; Tananbaum, H.; Giacconi, R.; Brinkman, A. C.

2012-12-01

150

Effects of A2ON Process on Denitrifying Dephosphatation  

Directory of Open Access Journals (Sweden)

Full Text Available In combination with activated sludge process and biomembrance process, based on the principle of denitrifying dephosphatation, A2ON processes for biphase sequencing batch reactor biological nutrient removal (BNR treatment have been developed, with an emphasis on the effects of the ratio of COD to TN (COD/TN variations on the BNR treatment. Results indicated that the process possessed stable effects, showed strong flexibility for water quality, could attenuate the aerobic requirement and decrease the competition of denitrifying and dephosphation for carbon source to a greater degree, and meanwhile guaranteed that nitrifying bacteria about a generation time could grow stably.

Lifang Guo

2010-10-01

151

Optimizing BTEX biodegradation under denitrifying conditions  

International Nuclear Information System (INIS)

Leaking underground storage tanks are a major source of ground water contamination by petroleum hydrocarbons. Gasoline and other fuels contain benzene, toluene, ethylbenzene, and xylenes (collectively known as BTEX), which are hazardous compounds, regulated by the U.S. Environmental Protection Agency (EPA). Laboratory tests were conducted to determine optimum conditions for benzene, toluene, ethylbenzene, and xylene (collectively known as BTEX) biodegradation by aquifer microorganisms under denitrifying conditions. Microcosms, constructed with aquifer samples from Traverse City, Michigan, were amended with selected concentrations of nutrients and one or more hydrocarbons. Toluene, ethylbenzene, m-xylene, and p-xylene, were degraded to below 5 micrograms/L when present as sole source substrates; stoichiometric calculations indicated that nitrate removal was sufficient to account for 70 to 80% of the compounds being mineralized. o-Xylene was recalcitrant when present as a sole source substrate, but was slowly degraded in the presence of the other hydrocarbons. Benzene was not degraded within one year, regardless of whether it was available as a sole source substrate or in combination with toluene, phenol, or catechol. Pre-exposure to low levels of BTEX and nutrients had variable effects, as did the addition of different concentrations of ammonia and phosphate. Nitrate concentrations as high as 500 mg/L NO3-N were slightly inhibitory. These data indicate that nitrate-mediated biodegradation of BTEX at Traverse City can occur under a variety of environmental conditions with rates relatively independent of nutrient concentrations. However, the data reaffirm that benzene is recalcitrant under strictly anaerobic conditions in these samples

1991-01-01

152

Comparison of culture media for enrichment and isolation of Salmonella spp. from frozen Channel catfish and Vietnamese basa fillets.  

Science.gov (United States)

Frozen fillets of Channel catfish and Vietnamese basa fish were used to compare Salmonella spp. recovery effectiveness of selective enrichment in Rappaport-Vassiliadis (RV) broth and tetrathionate broth (TT) and selective isolation on Hekteon enteric (HE) agar, xylose lysine deoxycholate (XLD) agar, and bismuth sulfite (BS) agar. Isolate confirmation was through fatty acid methyl ester analysis. Of 60 samples analyzed, 25 were found contaminated with Salmonella (42% incidence). Salmonella spp. recovery after enrichment in RV medium was 35% on HE agar, 30% on XLD agar, and 42% on BS agar. Similarly, after enrichment in TT broth, HE and XLD agars recovered 22% each and BS agar recovered 37%. No performance difference (p>0.05) was observed in the recovery of Salmonella using the combinations of BS, HE, and XLD agars with RV broth and BS agar with TT broth. The combination of selective enrichment in RV and selective isolation on BS gave numerically greatest isolation of Salmonella from Channel catfish and Vietnamese basa fish compared to other isolation combinations. PMID:19269575

Pal, Amit; Marshall, Douglas L

2009-05-01

153

Comparative Analysis of 16S rRNA and amoA Genes from Archaea Selected with Organic and Inorganic Amendments in Enrichment Culture  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We took advantage of a plant-root enrichment culture system to characterize mesophilic soil archaea selected through the use of organic and inorganic amendments. Comparative analysis of 16S rRNA and amoA genes indicated that specific archaeal clades were selected under different conditions. Three amoA sequence clades were identified, while for a fourth group, identified by 16S rRNA gene analysis alone and referred to as the “root” clade, we detected no corresponding amoA gene. The amoA-co...

Xu, Mouzhong; Schnorr, Jon; Keibler, Brandon; Simon, Holly M.

2012-01-01

154

Nitrate removal, communities of denitrifiers and adverse effects in different carbon substrates for use in denitrification beds.  

Science.gov (United States)

Denitrification beds are containers filled with wood by-products that serve as a carbon and energy source to denitrifiers, which reduce nitrate (NO(3)(-)) from point source discharges into non-reactive dinitrogen (N(2)) gas. This study investigates a range of alternative carbon sources and determines rates, mechanisms and factors controlling NO(3)(-) removal, denitrifying bacterial community, and the adverse effects of these substrates. Experimental barrels (0.2 m(3)) filled with either maize cobs, wheat straw, green waste, sawdust, pine woodchips or eucalyptus woodchips were incubated at 16.8 °C or 27.1 °C (outlet temperature), and received NO(3)(-) enriched water (14.38 mg N L(-1) and 17.15 mg N L(-1)). After 2.5 years of incubation measurements were made of NO(3)(-)-N removal rates, in vitro denitrification rates (DR), factors limiting denitrification (carbon and nitrate availability, dissolved oxygen, temperature, pH, and concentrations of NO(3)(-), nitrite and ammonia), copy number of nitrite reductase (nirS and nirK) and nitrous oxide reductase (nosZ) genes, and greenhouse gas production (dissolved nitrous oxide (N(2)O) and methane), and carbon (TOC) loss. Microbial denitrification was the main mechanism for NO(3)(-)-N removal. Nitrate-N removal rates ranged from 1.3 (pine woodchips) to 6.2 g N m(-3) d(-1) (maize cobs), and were predominantly limited by C availability and temperature (Q(10) = 1.2) when NO(3)(-)-N outlet concentrations remained above 1 mg L(-1). The NO(3)(-)-N removal rate did not depend directly on substrate type, but on the quantity of microbially available carbon, which differed between carbon sources. The abundance of denitrifying genes (nirS, nirK and nosZ) was similar in replicate barrels under cold incubation, but varied substantially under warm incubation, and between substrates. Warm incubation enhanced growth of nirS containing bacteria and bacteria that lacked the nosZ gene, potentially explaining the greater N(2)O emission in warmer environments. Maize cob substrate had the highest NO(3)(-)-N removal rate, but adverse effects include TOC release, dissolved N(2)O release and substantial carbon consumption by non-denitrifiers. Woodchips removed less than half of NO(3)(-) removed by maize cobs, but provided ideal conditions for denitrifying bacteria, and adverse effects were not observed. Therefore we recommend the combination of maize cobs and woodchips to enhance NO(3)(-) removal while minimizing adverse effects in denitrification beds. PMID:21880343

Warneke, Sören; Schipper, Louis A; Matiasek, Michael G; Scow, Kate M; Cameron, Stewart; Bruesewitz, Denise A; McDonald, Ian R

2011-11-01

155

Development of PCR Primer Systems for Amplification of Nitrite Reductase Genes (nirK and nirS) To Detect Denitrifying Bacteria in Environmental Samples  

Science.gov (United States)

A system was developed for the detection of denitrifying bacteria by the amplification of specific nitrite reductase gene fragments with PCR. Primer sequences were found for the amplification of fragments from both nitrite reductase genes (nirK and nirS) after comparative sequence analysis. Whenever amplification was tried with these primers, the known nir type of denitrifying laboratory cultures could be confirmed. Likewise, the method allowed a determination of the nir type of five laboratory strains. The nirK gene could be amplified from Blastobacter denitrificans, Alcaligenes xylosoxidans, and Alcaligenes sp. (DSM 30128); the nirS gene was amplified from Alcaligenes eutrophus DSM 530 and from the denitrifying isolate IFAM 3698. For each of the two genes, at least one primer combination amplified successfully for all of the test strains. Specific amplification products were not obtained with nondenitrifying bacteria or with strains of the other nir type. The specificity of the amplified products was confirmed by subsequent sequencing. These results suggest the suitability of the method for the qualitative detection of denitrifying bacteria in environmental samples. This was shown by applying one generally amplifying primer combination for each nir gene developed in this study to total DNA preparations from aquatic habitats.

Braker, Gesche; Fesefeldt, Andreas; Witzel, Karl-Paul

1998-01-01

156

Use of stable-isotope probing, full-cycle rRNA analysis, and fluorescence in situ hybridization-microautoradiography to study a methanol-fed denitrifying microbial community.  

Science.gov (United States)

A denitrifying microbial consortium was enriched in an anoxically operated, methanol-fed sequencing batch reactor (SBR) fed with a mineral salts medium containing methanol as the sole carbon source and nitrate as the electron acceptor. The SBR was inoculated with sludge from a biological nutrient removal activated sludge plant exhibiting good denitrification. The SBR denitrification rate improved from less than 0.02 mg of NO(3)(-)-N mg of mixed-liquor volatile suspended solids (MLVSS)(-1) h(-1) to a steady-state value of 0.06 mg of NO(3)(-)-N mg of MLVSS(-1) h(-1) over a 7-month operational period. At this time, the enriched microbial community was subjected to stable-isotope probing (SIP) with [(13)C]methanol to biomark the DNA of the denitrifiers. The extracted [(13)C]DNA and [(12)C]DNA from the SIP experiment were separately subjected to full-cycle rRNA analysis. The dominant 16S rRNA gene phylotype (group A clones) in the [(13)C]DNA clone library was closely related to those of the obligate methylotrophs Methylobacillus and Methylophilus in the order Methylophilales of the Betaproteobacteria (96 to 97% sequence identities), while the most abundant clone groups in the [(12)C]DNA clone library mostly belonged to the family Saprospiraceae in the Bacteroidetes phylum. Oligonucleotide probes for use in fluorescence in situ hybridization (FISH) were designed to specifically target the group A clones and Methylophilales (probes DEN67 and MET1216, respectively) and the Saprospiraceae clones (probe SAP553). Application of these probes to the SBR biomass over the enrichment period demonstrated a strong correlation between the level of SBR denitrification and relative abundance of DEN67-targeted bacteria in the SBR community. By contrast, there was no correlation between the denitrification rate and the relative abundances of the well-known denitrifying genera Hyphomicrobium and Paracoccus or the Saprospiraceae clones visualized by FISH in the SBR biomass. FISH combined with microautoradiography independently confirmed that the DEN67-targeted cells were the dominant bacterial group capable of anoxic [(14)C]methanol uptake in the enriched biomass. The well-known denitrification lag period in the methanol-fed SBR was shown to coincide with a lag phase in growth of the DEN67-targeted denitrifying population. We conclude that Methylophilales bacteria are the dominant denitrifiers in our SBR system and likely are important denitrifiers in full-scale methanol-fed denitrifying sludges. PMID:14711691

Ginige, Maneesha P; Hugenholtz, Philip; Daims, Holger; Wagner, Michael; Keller, Jürg; Blackall, Linda L

2004-01-01

157

Cultivo del nematodo Panagrellus redivivus (Goodey, 1945) en un medio de avena enriquecida con Spirulina sp. / Nematode culture of Panagrellus redivivus (Goodey, 1945) with Spirulina sp. - enriched oatmeal  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: Spanish Abstract in spanish El nematodo Panagrellus redivivus se cultivó en dos medios: uno con hojuelas de avena y otro con hojuelas de avena enriquecido con Spirulina sp., en recipientes de plástico de 15x15x5 cm de altura con 200 g de hojuela de avena y 300 mL de agua purificada. Se utilizaron 5 g de Spirulina en el medio. [...] Se utilizó el programa SYSTAT versión 10.2 para el análisis estadístico; para determinar las diferencias significativas entre los tratamientos, se usó un análisis de varianza unidireccional (ANDEVA) con una confiabilidad ?= 0,05. Los resultados obtenidos muestran que el crecimiento de las poblaciones de nematodos en el medio enriquecido con Spirulina presentó la mayor abundancia de individuos a la segunda semana del cultivo, mientras que la población que creció en el medio de avena, presentó su mayor registro a la quinta semana del cultivo y no alcanzó el número de organismos que tuvo la población cultivada en el medio con Spirulina. El contenido de aminoácidos de las poblaciones de ambos medios se comparó y se cotejaron con los reportados para Artemia alimentada con Spirulina, observándose que en la mayoría de los aminoácidos las cantidades fueron mayores en P. redivivus cultivado en el medio con Spirulina. La composición de ácidos grasos en los nematodos cultivados en ambos medios presentó diferencias significativas entre los ácidos grasos linoleico, araquidónico y eicosapentenoico los cuales fueron en mayor porcentaje que los reportados en P. redivivus cultivado en avena con aceite de girasol. Estos datos demuestran que la cianobacteria Spirulina sp. acelera el crecimiento de la población del nematodo y permite la presencia de aminoácidos y ácidos grasos, y hace que estos nematodos puedan cubrir los requerimientos nutritivos de larvas de peces dulceacuícolas, sin embargo, se requieren estudios que lo demuestren Abstract in english The nematode Pangrellus redivivus was cultured in two media: one with oat flakes and the other with Spirulina sp.-enriched oat flakes, in 15x15x5 cm plastic containers with 200 g oat flakes and 300 mL purified water. Five grams of Spirulina was used in the medium. SYSTAT version 10.2 was used for st [...] atistical analysis; to determine the significant differences between treatment a unidirectional analysis of variance (ANOVA) was used with a confidence level of ?= 0.05. The results show that growth of the nematode population in the Spirulina-enriched medium presented the highest abundance of individuals on the second week of culture, whereas the population grown in the oat flakes medium showed the highest abundance on the fifth week of culture and did not reach the number of organisms attained by the population cultured in the Spirulina-enriched medium. The amino acids content of the populations from both media were compared to those reported for Artemia fed with Spirulina, observing that the amounts were higher for most amino acids in P. redivivus cultured in the Spirulina-enriched medium. The composition of fatty acids in the nematode cultures in both media depicted significant differences for the linoleic, arachidonic, and eicosapentaenoic fatty acids, which were found in a higher percentage than reported for P. redivivus cultures in oat flakes supplemented with sunflower oil. These data reveal that the cyanobacterium Spirulina sp. accelerates growth of the nematode populations and allows the presence of amino and fatty acids, making these nematodes suitable to cover the nutritional requirements of freshwater fish larvae, but further studies are needed to demonstrate it

Ramón, de Lara; Thalía, Castro; Jorge, Castro; Germán, Castro.

158

Enriched monolayer precursor cell cultures from micro-dissected adult mouse dentate gyrus yield functional granule cell-like neurons  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Background: Stem cell cultures are key tools of basic and applied research in Regenerative Medicine. In the adult mammalian brain, lifelong neurogenesis originating from local precursor cells occurs in the neurogenic regions of the hippocampal dentate gyrus. Despite widespread interest in adult hippocampal neurogenesis and the use of mouse models to study it, no protocol existed for adult murine long-term precursor cell cultures with hippocampus-specific differentiation potential. Methodology...

Babu, H.; Cheung, G.; Kettenmann, H.; Palmer, T. D.; Kempermann, G.

2007-01-01

159

Rapid in vitro regeneration method for Moringa oleifera and performance evaluation of field grown nutritionally enriched tissue cultured plants  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The present investigations were attempted to develop the rapid in vitro micropropagation protocol of Moringa oleifera (Variety-PKM-1) from nodal sections of young, aseptically grown seedlings. Benzyladenine (BA) at 4.44 ?M was found to be optimal in producing on maximum an average of 9.0 ± 1.0 axillary shoots per explant after 15 days of inoculation. A high multiplication rate was established through routine sub culturing of nodal sections explanted from in vitro shoot cultures. In vitr...

Saini, R. K.; Shetty, N. P.; Giridhar, P.; Ravishankar, G. A.

2012-01-01

160

Uranium enrichment. Enrichment processes  

International Nuclear Information System (INIS)

Despite the remarkable progresses made in the diversity and the efficiency of the different uranium enrichment processes, only two industrial processes remain today which satisfy all of enriched uranium needs: the gaseous diffusion and the centrifugation. This article describes both processes and some others still at the demonstration or at the laboratory stage of development: 1 - general considerations; 2 - gaseous diffusion: physical principles, implementation, utilisation in the world; 3 - centrifugation: principles, elementary separation factor, flows inside a centrifuge, modeling of separation efficiencies, mechanical design, types of industrial centrifuges, realisation of cascades, main characteristics of the centrifugation process; 4 - aerodynamic processes: vortex process, nozzle process; 5 - chemical exchange separation processes: Japanese ASAHI process, French CHEMEX process; 6 - laser-based processes: SILVA process, SILMO process; 7 - electromagnetic and ionic processes: mass spectrometer and calutron, ion cyclotron resonance, rotating plasmas; 8 - thermal diffusion; 9 - conclusion. (J.S.)

2009-01-01

 
 
 
 
161

Relative binding and biochemical effects of heterodimeric and homodimeric isoforms of platelet-derived growth factor in osteoblast-enriched cultures from fetal rat bone  

Energy Technology Data Exchange (ETDEWEB)

Platelet-derived growth factor (PDGF) exists as a homodimer or a heterodimer comprising either PDGF-A or PDGF-B subunits, and each isoform occurs in various tissues, including bone. Although the stimulatory effects of PDGF-BB have been studied in cultures of bone cells and intact bone fragments, the influence of other isoforms that may arise locally or systematically in vivo, has not been reported. Therefore recombinant human PDGF-BB, PDGF-AB, and PDGF-AA were evaluated in osteoblast-enriched cultures from fetal rat bone. Within 24 hours these factors produced a graded response in bone cell DNA and protein synthesis, with half-maximal effects at approximately 0.6, 2.1, and 4.8 nM PDGF-BB, PDGF-AB, and PDGF-AA, respectively. Increases in collagen and noncollagen protein synthesis were abrogated when DNA synthesis was blocked with hydroxyurea. Furthermore, each factor reduced alkaline phosphatase activity, PDGF-BB being the most inhibitory. Binding studies with 125I-PDGF-BB or 125I-PDGF-AA and each unlabeled PDGF isoform produced discrete ligand binding and displacement patterns: 125I-PDGF-BB binding was preferentially displaced by PDGF-BB (Ki approximately 0.7 nM), less by PDGF-AB (Ki approximately 2.3 nM) and poorly by PDGF-AA. In contrast, 125I-PDGF-AA binding was measurably reduced by PDGF-AA (Ki approximately 4.0 nM), but was more effectively displaced by PDGF-BB or PDGF-AB (each with Ki approximately 0.7 nM). These studies indicate that each PDGF isoform produces biochemical effects proportional to binding site occupancy and suggest that receptors that favor PDGF-B subunit binding preferentially mediate these results in osteoblast-enriched bone cell cultures.

Centrella, M.; McCarthy, T.L.; Kusmik, W.F.; Canalis, E. (Department of Research, Saint Francis Hospital and Medical Center, Hartford, CT (USA))

1991-06-01

162

Evidence that the marine-derived multi-mineral Aquamin has anti-inflammatory effects on cortical glial-enriched cultures.  

Science.gov (United States)

It is well established that neuroinflammation contributes to brain aging, and that cortical cells are particularly vulnerable. Lipopolysaccharide stimulates the release of the pro-inflammatory cytokines, tumor necrosis factor-alpha and interleukin-1beta from glial cells which consequently induces an impairment in neuronal cell function. The food supplement, Aquamin, is a natural, multi-mineral derived from the red algae Lithothamnion corallioides, rich in calcium, magnesium and 72 other trace minerals. The aim of this study was to evaluate the anti-inflammatory potential of Aquamin in lipopolysaccharide-stimulated, glial-enriched primary cultures of rat cortex. It is reported that Aquamin prevented lipopolysaccharide-induced secretion of tumor necrosis factor-alpha and interleukin-1beta from cortical glia. These data suggest that nutritional supplements such as Aquamin may play an important role in impeding the detrimental effects of excessive inflammation in the brain. PMID:21520469

Ryan, Sinead; O'Gorman, Denise M; Nolan, Yvonne M

2011-05-01

163

Bacterial diversity of autotrophic enriched cultures from remote, glacial Antarctic, Alpine and Andean aerosol, snow and soil samples  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Four different communities and one culture of autotrophic microbial assemblages were obtained by incubation of samples collected from high elevation snow in the Alps (Mt. Blanc area) and the Andes (Nevado Illimani summit, Bolivia), from Antarctic aerosol (French station Dumont d'Urville) and a maritime Antarctic soil (King George Island, South Shetlands, Uruguay Station Artigas), in a minimal mineral (oligotrophic) media. Molecular analysis of more than 200 16S rRNA gene sequences showed that...

Gonzalez-toril, E.; Amils, R.; J Delmas, Robert; Petit, Jean-robert; Komarek, J.; Elster, J.

2009-01-01

164

Bacterial diversity of autotrophic enriched cultures from remote, glacial Antarctic, Alpine and Andean aerosol, snow and soil samples  

Science.gov (United States)

Four different communities and one culture of autotrophic microbial assemblages were obtained by incubation of samples collected from high elevation snow in the Alps (Mt. Blanc area) and the Andes (Nevado Illimani summit, Bolivia), from Antarctic aerosol (French station Dumont d'Urville) and a maritime Antarctic soil (King George Island, South Shetlands, Uruguay Station Artigas), in a minimal mineral (oligotrophic) media. Molecular analysis of more than 200 16S rRNA gene sequences showed that all cultured cells belong to the Bacteria domain. Phylogenetic comparison with the currently available rDNA database allowed sequences belonging to Proteobacteria Alpha-, Beta- and Gamma-proteobacteria), Actinobacteria and Bacteroidetes phyla to be identified. The Andes snow culture was the richest in bacterial diversity (eight microorganisms identified) and the marine Antarctic soil the poorest (only one). Snow samples from Col du Midi (Alps) and the Andes shared the highest number of identified microorganisms (Agrobacterium, Limnobacter, Aquiflexus and two uncultured Alphaproteobacteria clones). These two sampling sites also shared four sequences with the Antarctic aerosol sample (Limnobacter, Pseudonocardia and an uncultured Alphaproteobacteriaclone). The only microorganism identified in the Antarctica soil (Brevundimonas sp.) was also detected in the Antarctic aerosol. Most of the identified microorganisms had been detected previously in cold environments, marine sediments soils and rocks. Air current dispersal is the best model to explain the presence of very specific microorganisms, like those identified in this work, in environments very distant and very different from each other.

González-Toril, E.; Amils, R.; Delmas, R. J.; Petit, J.-R.; Komárek, J.; Elster, J.

2009-01-01

165

Denitrifying activity of activated sludge in suspension and in biofilm  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A method based on measuring substrate depletion rate was developed to evaluate the denitrifying activity of activated sludge in suspension and in biofilm form in anoxic serum flasks. The adapted activated sludge inoculum was grown as biofilm in an anoxic rotating biological contactor (RBC). Acetate was used as external carbon source to obtain a carbon to nitrogen ratio (C/N) of 2. The results showed that the specific activity of cells in biofilm form was higher than in planktonic for...

Cortez, Susana; Teixeira, P.; Oliveira, R.; Mota, M.

2010-01-01

166

Atypical Polyphosphate Accumulation by the Denitrifying Bacterium Paracoccus denitrificans  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Polyphosphate accumulation by Paracoccus denitrificans was examined under aerobic, anoxic, and anaerobic conditions. Polyphosphate synthesis by this denitrifier took place with either oxygen or nitrate as the electron acceptor and in the presence of an external carbon source. Cells were capable of poly-?-hydroxybutyrate (PHB) synthesis, but no polyphosphate was produced when PHB-rich cells were incubated under anoxic conditions in the absence of an external carbon source. By comparison of th...

Barak, Yoram; Rijn, Jaap

2000-01-01

167

Isolation and Molecular Identification of an Aerobic Denitrifier  

Directory of Open Access Journals (Sweden)

Full Text Available Six bacteria strains of which total nitrogen removal efficiency is over 70% were isolated from the activated sludge after enrichment culture. The strain Z31 with higher nitrogen removal was selected and its characteristic of aerobic denitrification was confirmed by the nitrogen element track. The results showed that the nitrate in the culture could be efficiently removed by strain Z31 and the nitrate nitrogen removal rate was up to above 95%. There was obvious nitrite accumulation during the denitrification process. Moreover, medium pH was increased and medium ORP was decreased as a result of denitrification. According to the morphological observation, physiological biochemical test and sequence analysis of the 16S rDNA, strain Z31 was identified as Pseudomonas stutzeri. And the phylogentic position of the strain was performed based on the phylogenetic tree.

Hongyu Wang

2013-10-01

168

Denitrification characteristics of a marine origin psychrophilic aerobic denitrifying bacterium.  

Science.gov (United States)

A psychrophilic aerobic denitrifying bacterium, strain S1-1, was isolated from a biological aerated filter conducted for treatment of recirculating water in a marine aquaculture system. Strain S1-1 was preliminarily identified as Psychrobacter sp. based on the analysis of its 16S rRNA gene sequence, which showed 100% sequence similarity to that of Psychrobacter sp. TSBY-70. Strain S1-1 grew well either in high nitrate or high nitrite conditions with a removal of 100% nitrate or 63.50% nitrite, and the total nitrogen removal rates could reach to 46.48% and 31.89%, respectively. The results indicated that nitrate was mainly reduced in its logarithmic growth phase with a very low level accumulation of nitrite, suggesting that the aerobic denitrification process of strain S1-1 occurred mainly in this phase. The GC-MS results showed that N2O was formed as the major intermediate during the aerobic denitrifying process of strain S1-1. Finally, factors affecting the growth of strain S1-1 and its aerobic denitrifying ability were also investigated. Results showed that the optimum aerobic denitrification conditions for strain S1-1 were sodium succinate as carbon source, C/N ratio15, salinity 10 g/L NaCl, incubation temperature 20 degrees C and initial pH 6.5. PMID:22432315

Zheng, Haiyan; Liu, Ying; Sun, Guangdong; Gao, Xiyan; Zhang, Qingling; Liu, Zhipei

2011-01-01

169

Thermo-acidophillic biohydrogen production from rice bran de-oiled wastewater by Selectively enriched mixed culture  

Energy Technology Data Exchange (ETDEWEB)

The present study focuses on the biohydrogen production in an anaerobic batch reactor operated at thermophillic (570C) and acidophilic conditions (pH 6) with rice bran de-oiled wastewater (RBOW) as substrate. The hydrogen generating mixed microflora was enriched from slaughter house sludge (SHS) through acid treatment (pH 3-4, for 24h) coupled with heat treatment (1h at 1000C) to eliminate non-spore forming bacteria and to inhibit the growth of methanogenic bacteria (MB) prior to inoculation in the reactor. The hydrogen production rate was maximum at 570C (1861 +- 14ml/L-WW/d) compared to 370C (651 +- 30ml/L-ww/d). The Hydrogen yield increased with temperature from 1.1 to 2.2 molH2/mol of substrate respectively. The optimum pH range for hydrogen production in this system was observed in between 5.5 to 6. Acid-forming pathway with butyric acid as a major metabolite dominated the metabolic flow during the hydrogen production.

Sivaramakrishna, D.; Sreekanth, D.; Himabindu, V. [Centre for Environment, Institute of Science and Technology, Jawaharlal Nehru Technological University Hyderabad, Kukatpally Hyderabad-500 085 (India); Narasu, M. Lakshmi [Centre for Biotechnology, Institute of Science and Technology, Jawaharlal Nehru Technological University Hyderabad, Kukatpally Hyderabad-500 085 (India)

2010-07-01

170

Thermo-acidophillic biohydrogen production from rice bran de-oiled wastewater by Selectively enriched mixed culture  

Directory of Open Access Journals (Sweden)

Full Text Available The present study focuses on the biohydrogen production in an anaerobic batch reactor operated at thermophillic (570C and acidophilic conditions (pH 6 with rice bran de-oiled wastewater (RBOW as substrate. The hydrogen generating mixed microflora was enriched from slaughter house sludge (SHS through acid treatment (pH 3-4, for 24h coupled with heat treatment (1h at 1000C to eliminate non-spore forming bacteria and to inhibit the growth of methanogenic bacteria (MB prior to inoculation in the reactor. The hydrogen production rate was maximum at 570C (1861±14ml/L-WW/d compared to 370C (651±30ml/L-ww/d. The Hydrogen yield increased with temperature from 1.1 to 2.2 molH2/mol of substrate respectively. The optimum pH range for hydrogen production in this system was observed in between 5.5 to 6. Acid-forming pathway with butyric acid as a major metabolite dominated the metabolic flow during the hydrogen production.

D.Sivaramakrishna, D.Sreekanth, V.Himabindu, M.Lakshmi Narasu

2010-07-01

171

Bacterial diversity of autotrophic enriched cultures from remote, glacial Antarctic, Alpine and Andean aerosol, snow and soil samples  

Directory of Open Access Journals (Sweden)

Full Text Available Four different communities and one culture of autotrophic microbial assemblages were obtained by incubation of samples collected from high elevation snow in the Alps (Mt. Blanc area and the Andes (Nevado Illimani summit, Bolivia, from Antarctic aerosol (French station Dumont d'Urville and a maritime Antarctic soil (King George Island, South Shetlands, Uruguay Station Artigas, in a minimal mineral (oligotrophic media. Molecular analysis of more than 200 16S rRNA gene sequences showed that all cultured cells belong to the Bacteria domain. Phylogenetic comparison with the currently available rDNA database allowed sequences belonging to Proteobacteria Alpha-, Beta- and Gamma-proteobacteria, Actinobacteria and Bacteroidetes phyla to be identified. The Andes snow culture was the richest in bacterial diversity (eight microorganisms identified and the marine Antarctic soil the poorest (only one. Snow samples from Col du Midi (Alps and the Andes shared the highest number of identified microorganisms (Agrobacterium, Limnobacter, Aquiflexus and two uncultured Alphaproteobacteria clones. These two sampling sites also shared four sequences with the Antarctic aerosol sample (Limnobacter, Pseudonocardia and an uncultured Alphaproteobacteriaclone. The only microorganism identified in the Antarctica soil (Brevundimonas sp. was also detected in the Antarctic aerosol. Most of the identified microorganisms had been detected previously in cold environments, marine sediments soils and rocks. Air current dispersal is the best model to explain the presence of very specific microorganisms, like those identified in this work, in environments very distant and very different from each other.

E. González-Toril

2009-01-01

172

Determination of the cause of the symptoms on yellow yam (Dioscorea cayenensis Lam.) leaf tissue and their eradication, enriching the culture medium and using techniques of meristem culture, thermo and chemotherapy on in vitro conditions  

International Nuclear Information System (INIS)

Yams (Dioscorea spp) has been cultivated for exportation in Costa Rica, in North Huetar region. In vitro culture technique has been used for multiplying planting material for many advantages. However, cleaning of viruses that affect has been ineffective. Viruses such as: the potyvirus, potexvirus, cucumovirus . Methods like meristem culture, chemotherapy, thermotherapy and combinations of these have been used for the elimination of virus in plant species. The plants were evaluated in indexing assays, observing symptoms, serological methods and electron microscopy, among others. Other problems that have been affecting in vitro plant are deficient culture media in some nutrient. The presence of some abnormal characteristics in leaf tissue was determined whether have been caused by a virus or a nutritional deficiency in the culture medium. The presence of the virus has tried to find using ELISA and electron microscopy. Tests meristem culture, thermotherapy and chemotherapy have been made for the eradication of a possible virus; which have been assessed by observation of symptomatology and ELISA. The efficiency of the culture medium was evaluated to enrich it with nitrogen or excess iron. None of the suspected virus found in ELISA tests. Filaments are presumably viral particles were found through analysis of ultrastructure, as well as alterations in chloroplasts which indicated the presence of a pathogen or toxicity. Thermotherapy and chemotherapy with the concentration of 40 mg/L of ribavirin have been the most effective for the elimination of symptoms in virus eradication treatments. Assessments nutrient concentrations have shown that the differences between the various treatments used were undetectable. The symptoms presented were caused, according to the conclusions, by a virus which should preferably deal with thermotherapy. (author)

2010-01-01

173

Use of Stable-Isotope Probing, Full-Cycle rRNA Analysis, and Fluorescence In Situ Hybridization-Microautoradiography To Study a Methanol-Fed Denitrifying Microbial Community  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A denitrifying microbial consortium was enriched in an anoxically operated, methanol-fed sequencing batch reactor (SBR) fed with a mineral salts medium containing methanol as the sole carbon source and nitrate as the electron acceptor. The SBR was inoculated with sludge from a biological nutrient removal activated sludge plant exhibiting good denitrification. The SBR denitrification rate improved from less than 0.02 mg of NO3?-N mg of mixed-liquor volatile suspended solids (MLVSS)?1 h?1...

Ginige, Maneesha P.; Hugenholtz, Philip; Daims, Holger; Wagner, Michael; Keller, Ju?rg; Blackall, Linda L.

2004-01-01

174

Isotope enrichment  

International Nuclear Information System (INIS)

In this chapter of the textbook for chemists the isotope enrichment methods are overviewed. The subsections are: General characterization of the methods used for isotope enrichment, Distillation and chemical exchange, Electrochemical methods, Diffusion methods, Isotope enrichment through centrifugation, Single-stage methods, Cascades

1987-01-01

175

Azoarcus taiwanensis sp. nov., a denitrifying species isolated from a hot spring.  

Science.gov (United States)

The strain NSC3(T), a novel, facultative, chemolithotrophic, denitrifying, alkaliphilic, sulfide-oxidizing bacterium isolated from a hot spring in Yang-Ming Mountain, Taiwan, was Gram negative, rod shaped, and motile by single polar flagella and grew facultatively by adopting a denitrifying metabolism. The 16S rRNA sequence analysis revealed that strain NSC3(T) belongs to beta subclass of the Proteobacteria and most closely related to Azoarcus evansii KB740(T) (95.44 %), Azoarcus toluvorans Td-21(T) (95.21 %), Azoarcus tolulyticus Tol-4(T) (95.08 %), and Azoarcus toluclasticus MF63(T) (94.94 %). The phylogenetic analyses based on 16S rRNA gene sequences indicated that the strain NSC3(T) formed a distinct lineage in the Betaproteobacteria and that it exhibited the highest level of sequence similarity with species of the genera Azoarcus (95.28-93.13 %). The major fatty acids of the type strain were C16:0 (26.9 %), C16:1w7c (28.9 %), C18:0 (9.6 %), and C18:1w7c/w6c (29.9 %). The DNA G+C content of genomic DNA was 63.7 mol%. On the basis of the 16S rRNA sequence similarity, phenotypic and genotypic characteristics, and chemotaxonomic data, the strain NSC3(T) could be differentiated from other species of the genus Azoarcus. Therefore, strain NSC3(T) (equal to BCRC 80111(T) and DSM 24109(T)) is proposed as a novel species in genus Azoarcus, for which the name Azoarcus taiwanensis sp. nov. is proposed. The strain NSC3(T) is deposited in Bioresource Collection and Research Center, Taiwan, under the reference number BCRC 80111(T), and German Collection of Microorganisms and Cell Cultures, Germany (DSMZ), with DSM 24109(T). PMID:23695778

Lee, Duu-Jong; Wong, Biing-Teo; Adav, Sunil S

2014-02-01

176

Anaerobic degradation of toluene by a denitrifying bacterium.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A denitrifying bacterium, designated strain T1, that grew with toluene as the sole source of carbon under anaerobic conditions was isolated. The type of agar used in solid media and the toxicity of toluene were determinative factors in the successful isolation of strain T1. Greater than 50% of the toluene carbon was oxidized to CO2, and 29% was assimilated into biomass. The oxidation of toluene to CO2 was stoichiometrically coupled to nitrate reduction and denitrification. Strain T1 was toler...

Evans, P. J.; Mang, D. T.; Kim, K. S.; Young, L. Y.

1991-01-01

177

Survival of Denitrifiers in Nitrate-Free, Anaerobic Environments  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Experiments were undertaken to explain the occurrence of a high denitrification capacity in anaerobic, NO3--free habitats. Deep layers of freshwater sediments that were buried more than 40 years ago and digested sludge were the habitats studied. The denitrifier populations were 3.1 × 103 and 3.1 × 105 cells cm-3 in deep sediments from a river and lake, respectively, and 5.3 × 106 cells cm-3 in digested sludge. The denitrification capacities of the samples reflected the population densities...

Jørgensen, Kirsten S.; Tiedje, James M.

1993-01-01

178

Adaptation of Denitrifying Populations to Low Soil pH †  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Natural denitrification rates and activities of denitrifying enzymes were measured in an agricultural soil which had a 20-year past history of low pH (pH ca. 4) due to fertilization with acid-generating ammonium salts. The soil adjacent to this site had been limed and had a pH of ca. 6.0. Natural denitrification rates of these areas were of similar magnitude: 158 ng of N g?1 of soil day?1 for the acid soil and 390 ng of N g?1 of soil day?1 at the neutral site. Estimates of in situ den...

Parkin, Timothy B.; Sexstone, Alan J.; Tiedje, James M.

1985-01-01

179

Enriching Number Knowledge  

Science.gov (United States)

Exploring number systems of other cultures can be an enjoyable learning experience that enriches students' knowledge of numbers and number systems in important ways. It helps students deepen mental computation fluency, knowledge of place value, and equivalent representations for numbers. This article describes how the author designed her…

Mack, Nancy K.

2011-01-01

180

Feeding glycerol-enriched yeast culture improves performance, energy status, and heat shock protein gene expression of lactating Holstein cows under heat stress.  

Science.gov (United States)

This study was conducted to evaluate the effects of supplemental common yeast culture (CY) and glycerol-enriched yeast culture (GY) on performance, plasma metabolites, antioxidant status, and heat shock protein 70 (HSP70) mRNA expression in lactating Holstein cows under heat stress. During summer months, 30 healthy multiparous lactating cows (parity 3.25 ± 0.48; 60 ± 13 d in milk [DIM]; 648 ± 57 kg BW; an average milk yield of 33.8 ± 1.6 kg/d) were blocked by parity, previous milk yield, and DIM and randomly allocated to 3 dietary treatments: no supplemental yeast culture (Control), 1 L/d of CY (33.1 g yeast) per cow, and 2 L/d of GY (153.2 g glycerol and 31.6 g yeast) per cow. During the 60-d experiment, values of air temperature and relative humidity inside the barn were recorded hourly every 3 d to calculate temperature-humidity index (THI). Weekly rectal temperatures (RT) and respiration rates and daily DMI and milk yield were recorded for all cows. Milk and blood samples were taken twice monthly, and BW and BCS were obtained on d 0 and 60. In this experiment, THI values indicated cows experienced a moderate heat stress. Cows supplemented with CY and GY had greater yields of milk, energy-corrected milk and milk fat, and milk fat percent but lower HSP70 mRNA expression in peripheral blood lymphocytes than Control cows (P < 0.05). Supplementing CY and GY tended (P < 0.15) to decrease RT at 1400 h, increase milk protein yield and erythrocyte glutathione, and reduce plasma urea nitrogen compared with Control. Lower plasma NEFA concentration and HSP70 mRNA expression in peripheral blood lymphocytes (P < 0.05) and tendencies towards greater plasma glucose concentration (P = 0.11) but less BW loss (P = 0.14) were observed in GY relative to CY cows. In conclusion, either CY or GY supplementation partially mitigated the negative effects of heat stress on performance and HSP70 mRNA expression of lactating cows, and GY supplementation provided additional improvements in energy status and HSP70 gene expression of lactating cows. PMID:24668959

Liu, J; Ye, G; Zhou, Y; Liu, Y; Zhao, L; Liu, Y; Chen, X; Huang, D; Liao, S F; Huang, K

2014-06-01

 
 
 
 
181

Construction of a consortium comprising ammonia-oxidizing bacteria and denitrifying bacteria isolated from marine sediment.  

Science.gov (United States)

A unique consortium of ammonia-oxidizing bacteria (AOB) and denitrifying bacteria was obtained via a long-term, 3-step cultivation of isolates from organically-enriched marine sediment. We developed this microbial consortium for possible applications in the remediation of degraded habitats in closed aquaculture or other aquatic environments via microbial degradation. Analysis of media components found definitive evidence of nitrogen removal via the coupling of ammonia-oxidation and denitrification. The phylogenetic diversity of the consortium was investigated by performing polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) that targeted the 16S rRNA gene, and the functional genes involved in ammonia-oxidation (amoA) and denitrification (nirS, nirK, norB and nosZ). Consequently, no significant divergence was observed, and thus it is suggested microbial populations were selected via a long-term, 3-step incubation process. All of the 16S rRNA clones fell into three phylogenetic groups, namely, gamma-proteobacteria, Actinobacteria and Flavobacteria. For almost half of the clones, the closest relatives in the database were identified as Alcanivorax spp. and these clones were present at all cultivation stages. The presence of these species as the dominant clones is significant since these bacterial species are known to reduce nitrate to nitrite. Accordingly, their abundance in our microbial consortium may have been responsible for the observed stepwise denitrification. All sequences of the amoA gene were identified to be Nitrosomonas lineage. Half of the nirS clones were identified to be from one major group of well-known denitrifying bacteria, Pseudomonas sp. Furthermore, 70% of the nirK clones were closely related to the nirK sequences of uncultured bacterial clones isolated from arable soil. The qnorB clones consisted of clusters exclusively, and formed a distinct cluster from the novel sequences of cultivated species. The nosZ clones also were not found in any of the closest relatives in the database including the uncultured bacterium from marine sediment. The unique clones obtained from the functional genes were related to each denitrification step. PMID:18839627

Nakano, Miyo; Shimizu, Yasuhiro; Okumura, Hiroyuki; Sugahara, Isawo; Maeda, Hiroto

2008-09-01

182

A Fungal Cytochrome P-450nor Confers Denitrifying Ability to Tobacco By-2 Cells  

Directory of Open Access Journals (Sweden)

Full Text Available Reactive nitrogen gases progressively contribute to the global warming. Development of gas-gas denitrifying plants that can efficiently reduce reactive nitrogen gases to dinitrogen (N2 could help to mitigate the effect of these gases. Taking the advances in gene manipulation technology, tobacco BY-2 cells were transformed with the fungus Cylindrocarpon tonkinense cytochrome P-450nor2 (Cnor2 gene. The product of this gene acts as nitric oxide reductase (nor. Transgenic BY-2 cell clones cultured in 15N-labelled nitrate (15NO3- actively evolved 15N2O gas up to 35-folds compared to the wild-type cells. In 15N-labelled ammonium (15NH4+, the transgenic and wild-type cells produced comparable amounts of 15N2O. This indicates that ammonium is not a direct substrate for nor and the small amount of N2O observed may be due to the nitrification of ammonium to nitrite. Addition of tungstate (a nitrate reductase inhibitor and cyanide to the transgenic cell cultures strongly inhibited 15N2O production. Activity of nor enzyme was also confirmed by in vitro activity assay. These observations together suggest that Cnor2 is actively expressed and enhanced the reduction of nitrate to N2O in plant cells. This finding indicates that plant cells are capable to tackle the denitrification pathway.

Babiker M.A. Abdel-Banat

2008-01-01

183

Enrichment of denitrifying methanotrophic bacteria for application after direct low-temperature anaerobic sewage treatment  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Despite many advantages of anaerobic sewage treatment over conventional activated sludge treatment, it has not yet been applied in temperate zones. This is especially because effluent from low-temperature anaerobic treatment contains nitrogen and dissolved methane. The presence of nitrogen and methane offers the opportunity to develop a reactor in which methane is used as electron donor for denitrification. Such a reactor could be used in a new concept for low-temperature anaerobic sewage tre...

Kampman, C.; Hendrickx, T. L. G.; Luesken, F.; Alen, T. A.; Op Den Camp, H. J. M.; Jetten, M. S. M.; Zeeman, G.; Buisman, C. J. N.; Temmink, B. G.

2012-01-01

184

Uranium enrichment  

International Nuclear Information System (INIS)

Canada is the world's largest producer and exporter of uranium, most of which is enriched elsewhere for use as fuel in LWRs. The feasibility of a Canadian uranium-enrichment enterprise is therefore a perennial question. Recent developments in uranium-enrichment technology, and their likely impacts on separative work supply and demand, suggest an opportunity window for Canadian entry into this international market. The Canadian opportunity results from three particular impacts of the new technologies: 1) the bulk of the world's uranium-enrichment capacity is in gaseous diffusion plants which, because of their large requirements for electricity (more than 2000 kW·h per SWU), are vulnerable to competition from the new processes; 2) the decline in enrichment costs increases the economic incentive for the use of slightly-enriched uranium (SEU) fuel in CANDU reactors, thus creating a potential Canadian market; and 3) the new processes allow economic operation on a much smaller scale, which drastically reduces the investment required for market entry and is comparable with the potential Canadian SEU requirement. The opportunity is not open-ended. By the end of the century the enrichment supply industry will have adapted to the new processes and long-term customer/supplier relationships will have been established. In order to seize the opportunity, Canada must become a credible supplier during this century

1988-06-12

185

Uranium enrichment  

Energy Technology Data Exchange (ETDEWEB)

The separation of uranium isotopes in order to enrich the fuel for light water reactors with the light isotope U-235 is an important part of the nuclear fuel cycle. After the basic principals of isotope separation the gaseous diffusion and the centrifuge process are explained. Both these techniques are employed on an industrial scale. In addition a short review is given on other enrichment techniques which have been demonstrated at least on a laboratory scale. After some remarks on the present situation on the enrichment market the progress in the development and the industrial exploitation of the gas centrifuge process by the trinational Urenco-Centec organisation is presented.

Mohrhauer, H.

1982-10-01

186

Uranium enrichment  

International Nuclear Information System (INIS)

The separation of uranium isotopes in order to enrich the fuel for light water reactors with the light isotope U-235 is an important part of the nuclear fuel cycle. After the basic principals of isotope separation the gaseous diffusion and the centrifuge process are explained. Both these techniques are employed on an industrial scale. In addition a short review is given on other enrichment techniques which have been demonstrated at least on a laboratory scale. After some remarks on the present situation on the enrichment market the progress in the development and the industrial exploitation of the gas centrifuge process by the trinational Urenco-Centec organisation is presented. (orig.)

1982-01-01

187

Uranium enrichment  

International Nuclear Information System (INIS)

Up to a short time ago there was uncertainty about adequate enrichment capacities at the beginning of the 80's. The projects commenced in the western world should however ensure the necessary reliability of supply for the growing nuclear energy programmes. The main problem in uranium enrichment is no longer the technology, but obtaining the considerable investment funds for the construction of the new installations. (orig.)

1975-09-01

188

Greenhouse Gas Emission from In-situ Denitrifying Bioreactors  

Science.gov (United States)

Despite decades of concerted effort to mitigate nonpoint source nitrate (NO3-) pollution from agricultural lands, these efforts have not been sufficient to arrest eutrophication, which continues to be a serious and chronic problem. Two primary processes for removing excess NO3- from water are biological assimilation and denitrification. Denitrifying bacteria use NO3- as the electron acceptor for respiration in the absence of oxygen. Denitrification results in reduced forms of nitrogen, often dinitrogen gas (N2) but also nitrous oxide (N2O), an aggressive greenhouse gas (GHG). A promising solution to NO3- pollution is to intercept agricultural discharges with denitrifying bioreactors (DNBRs), though research has been limited to NO3- level reduction and omitted process mechanisms. DNBRs work by providing an anaerobic environment with plenty of organic matter (commonly woodchips) for denitrifying bacteria to flourish. While, initial results from bioreactor studies show that they can cost-effectively remove NO3-, GHG emission could be an unintended consequence. The study's goal is to determine how bioreactor design promotes microbial denitrification while limiting N2O production. It specifically focuses on expanding the body of knowledge concerning DNBRs in the areas of design implications and internal processes by measuring intermediate compounds and not solely NO3-. Nutrient samples are collected at inflow and outflow structures and tested for NO3- and nitrite (NO2-). Dissolved and headspace gas samples are collected and tested for N2O. Additional gas samples will be analyzed for naturally-occurring isotopic N2 to support proposed pathways. Designs will be analyzed both through the N2O/N2 production ratio and NO2- production caused by various residence times and inflow NO3- concentrations. High GHG ratios and NO2- production suggest non-ideal conditions or flow patterns for complete denitrification. NO3- reduction is used for comparison with previous studies. Few studies have focused on the reactions and products of DNBRs and instead note NO3- reductions in outflows as evidence that this should be used to treat agricultural discharges. It is, however, critical to understand all of the potential impacts that this treatment solution may have, which means identifying processes and design specifications that may affect them. This study addresses this lack of mechanistic understanding of DNBRs by means of sampling for incomplete products. Results will quantify gaseous products and internal processes and present a more complete picture of the potential for widespread use of DNBRs.

Pluer, W.; Walter, M. T.; Geohring, L.

2013-12-01

189

INHIBITION OF ALKYLBENZENE BIODEGRADATION UNDER DENITRIFYING CONDITIONS BY USING THE ACETYLENE BLOCK TECHNIQUE  

Science.gov (United States)

Addition of acetylene to microcosms simultaneously amended with nitrate and alkylbenzenes resulted in inhibition of the rate of alkylbenzene biodegradation under denitrifying conditions. oluene, xylenes, and 1,2,4-trimethylbenzene were recalcitrant, whereas ethylbenzene was degra...

190

Spatial distribution of total, ammonia-oxidizing, and denitrifying bacteria in biological wastewater treatment reactors for bioregenerative life support  

Science.gov (United States)

Bioregenerative life support systems may be necessary for long-term space missions due to the high cost of lifting supplies and equipment into orbit. In this study, we investigated two biological wastewater treatment reactors designed to recover potable water for a spacefaring crew being tested at Johnson Space Center. The experiment (Lunar-Mars Life Support Test Project-Phase III) consisted of four crew members confined in a test chamber for 91 days. In order to recycle all water during the experiment, an immobilized cell bioreactor (ICB) was employed for organic carbon removal and a trickling filter bioreactor (TFB) was utilized for ammonia removal, followed by physical-chemical treatment. In this study, the spatial distribution of various microorganisms within each bioreactor was analyzed by using biofilm samples taken from four locations in the ICB and three locations in the TFB. Three target genes were used for characterization of bacteria: the 16S rRNA gene for the total bacterial community, the ammonia monooxygenase (amoA) gene for ammonia-oxidizing bacteria, and the nitrous oxide reductase (nosZ) gene for denitrifying bacteria. A combination of terminal restriction fragment length polymorphism (T-RFLP), sequence, and phylogenetic analyses indicated that the microbial community composition in the ICB and the TFB consisted mainly of Proteobacteria, low-G+C gram-positive bacteria, and a Cytophaga-Flexibacter-Bacteroides group. Fifty-seven novel 16S rRNA genes, 8 novel amoA genes, and 12 new nosZ genes were identified in this study. Temporal shifts in the species composition of total bacteria in both the ICB and the TFB and ammonia-oxidizing and denitrifying bacteria in the TFB were also detected when the biofilms were compared with the inocula after 91 days. This result suggests that specific microbial populations were either brought in by the crew or enriched in the reactors during the course of operation.

Sakano, Yuko; Pickering, Karen D.; Strom, Peter F.; Kerkhof, Lee J.; Janes, H. W. (Principal Investigator)

2002-01-01

191

Biodegradation of monoaromatic hydrocarbons in groundwater under denitrifying conditions  

Energy Technology Data Exchange (ETDEWEB)

Indigenous subsurface bacteria can degrade a variety of fuel hydrocarbons, including the monoaromatic compounds benzene, toluene, and xylene (BTX), under favorable conditions. Enhanced in-situ biodegradation has received increasing attention for aquifer remediation. The use of denitrification, whereby nitrate (or nitrite) is used as an alternative electron acceptor to oxygen, represents an innovative remediation approach, since nitrate is a very soluble in water and can be easily distributed throughout an aquifer. However, to date, there have only been a few field-scale trials of in-situ bioremediation using denitrification. This report evaluates the effect of nutrients and organic amendments on BTX loss in gasoline-contaminated groundwater incubated anoxially under denitrifying conditions.

Gersberg, R.M.; Bradley, M.D. (San Diego State Univ., CA (United States)); Dawsey, W.J. (San Diego Gas and Electric Co., CA (United States))

1991-08-01

192

Differentiated response of denitrifying communities to fertilization regime in paddy soil.  

Science.gov (United States)

The impact of fertilization regimes on sequential denitrifying communities was investigated in a rice paddy field with 17 years continuous fertilization, located in Taoyuan Agro-ecosystem Research Station (110°72? E, 28°52? N), China. The diversity, community composition, and size of denitrifying genes of narG, qnorB, and nosZ were determined using molecular tools including terminal restriction fragment length polymorphism, quantitative polymerase chain reaction (qPCR), cloning, and sequencing analysis. Soil samples were collected from the plots with no fertilizer (NF), urea (UR), balanced mineral fertilizers (BM), and BM combined with rice straw (BMR). UR and BM caused marked increase in the community size of the denitrifying genes; however, BMR resulted in the highest abundance. The community size of narG was the most affected by the fertilization regimes, while qnorB was the least. Fertilization also induced some shifts in the composition of denitrifying genes, but the responses of different genes varied. However, fertilization regimes caused no significant changes to the diversity of the denitrifying genes. Potential denitrification activity (PDA) was significantly correlated with the abundance of narG and nosZ rather than qnorB, but there were no such correlations between PDA and the composition and diversity of denitrifying communities. Conclusively, long-term fertilization significantly affected denitrifying community size and composition, but not diversity. Among the sequential denitrifying genes, narG was the most, while qnorB was the least sensitive communities to fertilization regimes. PMID:21811796

Chen, Zhe; Liu, Jinbo; Wu, Minna; Xie, Xiaoli; Wu, Jinshui; Wei, Wenxue

2012-02-01

193

Methyl t-Butyl Ether Mineralization in Surface-Water Sediment Microcosms under Denitrifying Conditions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Mineralization of [U-14C]methyl t-butyl ether (MTBE) to 14CO2 without accumulation of t-butyl alcohol (TBA) was observed in surface-water sediment microcosms under denitrifying conditions. Methanogenic activity and limited transformation of MTBE to TBA were observed in the absence of denitrification. Results indicate that bed sediment microorganisms can effectively degrade MTBE to nontoxic products under denitrifying conditions.

2001-01-01

194

Initial reactions in anaerobic ethylbenzene oxidation by a denitrifying bacterium, strain EB1.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Initial reactions in anaerobic oxidation of ethylbenzene were investigated in a denitrifying bacterium, strain EB1. Cells of strain EB1 mineralized ethylbenzene to CO2 under denitrifying conditions, as demonstrated by conversion of 69% of [14C]ethylbenzene to 14CO2. In anaerobic suspensions of strain EB1 cells metabolizing ethylbenzene, the transient formation and consumption of 1-phenylethanol, acetophenone, and an as yet unidentified compound were observed. On the basis of growth experiment...

Ball, H. A.; Johnson, H. A.; Reinhard, M.; Spormann, A. M.

1996-01-01

195

Heterotrophic nitrifying and oxygen tolerant denitrifying bacteria from greenwater system of coastal aquaculture.  

Science.gov (United States)

In this work, herbivorous fish Mugil cephalus has been cultured to secrete protein rich green slime, which helps nitrifying and oxygen tolerant denitrifying bacteria to grow and colonize. Four strains representing Alcaligenaceae family have been isolated from greenwater system and characterized using biochemical test, fatty acid methyl ester (GC-FAME) analysis, 16S rRNA and functional gene approaches. They were tested for an ability to nitrify ammonia and nitrite aerobically. Two strains showed notable nitrification activity, when grown in a mineral salts medium containing ammonium sulfate and potassium nitrite. Functional gene analysis confirmed the presence of nitrous oxide reductase (nosZ) gene showing that they have an oxygen-tolerant denitrification system. It has been proposed that Alcaligenes faecalis strains heterotrophically nitrify ammonia into nitrite via formation of hydroxyl amine, which is oxidized to nitrous oxide using oxygen or nitrite as electron acceptor. These results provide a possible advantage of having nitrification and denitrification capabilities in the same organism, which plays an important role in biological wastewater system. PMID:23354499

Velusamy, Kathiravan; Krishnani, Kishore Kumar

2013-03-01

196

nirS-containing denitrifier communities in the water column and sediment of the Baltic Sea  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this study was to compare structural differences in the nirS-type denitrifying microbial communities along the environmental gradients observed in the water column and coastal sediments of the Baltic Sea. To link community structure and environmental gradients, denitrifier communities were analyzed by terminal restriction fragment length polymorphism (T-RFLP based on nirS as a functional marker gene for denitrification. nirS-type denitrifier community composition was further evaluated by phylogenetic analysis of nirS sequences from clone libraries. T-RFLP analysis indicated some overlap but also major differences between communities from the water column and the sediment. Shifts in community composition along the biogeochemical gradients were observed only in the water column while denitrifier communities were rather uniform within the upper 30 mm of the sediment. Specific terminal restriction fragments (T-RFs indicative of the sulfidic zone suggest the presence of nitrate-reducing and sulfide-oxidizing microorganisms that were previously shown to be important at the suboxic-sulfidic interface in the water column of the Baltic Sea. Phylogenetic analysis of nirS genes from the Baltic Sea and of sequences from marine habitats all over the world indicated distinct denitrifier communities that grouped mostly according to their habitats. We suggest that these subgroups of denitrifiers had developed after selection through several factors, i.e. their habitats (water column or sediment, impact by prevalent environmental conditions and isolation by large geographic distances between habitats.

S. Falk

2007-01-01

197

NirS-containing denitrifier communities in the water column and sediment of the Baltic Sea  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this study was to compare structural differences in the denitrifying microbial communities along the environmental gradients observed in the water column and coastal sediments of the Baltic Sea. To link community structure and environmental gradients, denitrifier communities were analyzed by terminal restriction fragment length polymorphism (T-RFLP based on nirS as a functional marker gene for denitrification. NirS-type denitrifier community composition was further evaluated by phylogenetic analysis of nirS sequences from clone libraries. T-RFLP analysis indicated some overlap but also major differences of communities from the water column and the sediment. Shifts in community composition along the biogeochemical gradients were observed only in the water column while denitrifier communities were rather uniform within the upper 30 mm of the sediment. Specific terminal restriction fragments (T-RFs indicative for the sulfidic zone suggest the presence of nitrate-reducing and sulfide-oxidizing microorganisms that were previously shown to be important at the suboxic-sulfidic interface in the water column of the Baltic Sea. Phylogenetic analysis of nirS genes from the Baltic Sea and of sequences from marine habitats all over the world indicated distinct denitrifier communities that grouped mostly according to their habitat. We suggest that these subgroups of denitrifiers had developed after selection through several factors, i.e. their habitats (water column or sediment, impact by prevalent environmental conditions and isolation by large geographic distances between habitats.

K. Jürgens

2006-06-01

198

Cultivation of Denitrifying Bacteria: Optimization of Isolation Conditions and Diversity Study†  

Science.gov (United States)

An evolutionary algorithm was applied to study the complex interactions between medium parameters and their effects on the isolation of denitrifying bacteria, both in number and in diversity. Growth media with a pH of 7 and a nitrogen concentration of 3 mM, supplemented with 1 ml of vitamin solution but not with sodium chloride or riboflavin, were the most successful for the isolation of denitrifiers from activated sludge. The use of ethanol or succinate as a carbon source and a molar C/N ratio of 2.5, 20, or 25 were also favorable. After testing of 60 different medium parameter combinations and comparison with each other as well as with the standard medium Trypticase soy agar supplemented with nitrate, three growth media were highly suitable for the cultivation of denitrifying bacteria. All evaluated isolation conditions were used to study the cultivable denitrifier diversity of activated sludge from a municipal wastewater treatment plant. One hundred ninety-nine denitrifiers were isolated, the majority of which belonged to the Betaproteobacteria (50.4%) and the Alphaproteobacteria (36.8%). Representatives of Gammaproteobacteria (5.6%), Epsilonproteobacteria (2%), and Firmicutes (4%) and one isolate of the Bacteroidetes were also found. This study revealed a much more diverse denitrifying community than that previously described in cultivation-dependent research on activated sludge.

Heylen, Kim; Vanparys, Bram; Wittebolle, Lieven; Verstraete, Willy; Boon, Nico; De Vos, Paul

2006-01-01

199

Analysis of denitrifier community in a bioaugmented sequencing batch reactor for the treatment of coking wastewater containing pyridine and quinoline  

Energy Technology Data Exchange (ETDEWEB)

The denitrifier community and associated nitrate and nitrite reduction in the bioaugmented and general sequencing batch reactors (SBRs) during the treatment of coking wastewater containing pyridine and quinoline were investigated. The efficiency and stability of nitrate and nitrite reduction in SBR was considerably improved after inoculation with four pyridine- or quinoline-degrading bacterial strains (including three denitrifying strains). Terminal restriction fragment length polymorphism (T-RFLP) based on the nosZ gene revealed that the structures of the denitrifier communities in bioaugmented and non-bioaugmented reactors were distinct and varied during the course of the experiment. Bioaugmentation protected indigenous denitrifiers from disruptions caused by pyridine and quinoline. Clone library analysis showed that one of the added denitrifiers comprised approximately 6% of the denitrifier population in the bioaugmented sludge. (orig.)

Bai, Yaohui; Xing, Rui; Wen, Donghui; Tang, Xiaoyan [Peking Univ., Beijing (CN). Key Lab. of Water and Sediment Sciences (Ministry of Education); Sun, Qinghua [Peking Univ., Beijing (CN). Key Lab. of Water and Sediment Sciences (Ministry of Education); Chinese Center for Disease Control and Prevention, Beijing (China). Inst. of Environmental Health and Related Product Safety

2011-05-15

200

Comparing spatial and temporal dynamics of anammox and denitrifying communities at Cape Fear River Estuary and New River Estuary, North Carolina  

Science.gov (United States)

Anaerobic ammonium oxidation (anammox) and denitrification are two main microbial processes capable of removing fixed nitrogen by conversion into a gaseous species. Both microbial processes are known to occur in anoxic estuarine sediments and are capable of remediating excess nitrogen loadings from anthropogenic activities. In order to understand the importance of anammox and denitrification in estuarine ecosystems, we investigated both processes in two different estuaries of North Carolina to compare sedimentary nitrogen removal capacity and to identify key players of N2 production pathways. Both Cape Fear River Estuary (CFRE) and New River Estuary (NRE) are highly enriched with nitrogen from anthropogenic sources in spite of distinct geomorphological and geochemical characteristics. We conducted seasonal samplings to collect sediments across transects at fifteen stations along each estuary. 15N tracer techniques were used to measure spatial and temporal variations of N2 production by denitrification and anammox in estuarine sediments. Molecular analysis of nitrous oxide reductase (nosZ) and hydrazine oxidase (hzo) genes was conducted to examine community structures of denitrifying and anammox bacteria, respectively. Denitrification was found to be the dominant N2 production processes in both estuaries. Anammox contributed up to 19% and 15 % of total N2 productions in the CFEE and the NRE, respectively. Phylogenetic analysis of hzo genes identified that the anammox bacteria at both estuaries are closely associated with five known genera in the order Brocadiales. Anammox communities at the CFRE showed biogeographical distribution along the estuarine gradients while high seasonal variations were observed in the NRE communities. Spatial and temporal variations of denitrifying communities at both estuaries were also found based on nosZ gene analysis. Multivariate analysis was conducted to define key biogeochemical parameters influencing the community dynamics and activities of anammox and denitrifying bacteria in these ecosystems. Thus, this study reveals the importance of community structure to its function, as well as estimates and compares potential N removal capacity in two geologically distinct estuarine ecosystems.

Lisa, J. A.; Hirsch, M. D.; Duernberger, K. A.; Tobias, C. R.; Song, B.

2010-12-01

 
 
 
 
201

Enriched Uranium  

Science.gov (United States)

This Wikipedia website provides information about the various concentrations of uranium used for different applications. Topics include a brief description of the grades of uranium and methods of isotope separation. There are also links to other aspects of uranium enrichment and related information. This information lays the foundation for informed discussion about the potential of nuclear energy and the risks of nuclear proliferation.

Wikipedia

202

Influence of environmental factors on dissolved nitrate stable isotopes under denitrifying conditions - carbon sources and water isotopes  

Science.gov (United States)

Stable isotopes in dissolved nitrate are regularly used to identify sources of nitrate contamination in aquifers and water bodies. A dual isotope plot of 15N and 18O in nitrate can provide good evidence of the origin of such pollution as various sources have different isotopic signatures. Microbial denitrification changes both isotopic values by removing nitrate with lighter isotopes first, thereby increasing ?18O as well as ?15N. This change can distort the determination of sources but also has the potential to be used to identify and quantify microbial denitrification. Previous studies found a wide range of enrichment factors (?) that did not allow conclusions towards the extent of microbial denitrification. However, it was found that during denitrification at each respective field site or laboratory experiment, there was a constant ratio in increase of the values of ?18O in relation to ?15N. That ratio was, however, not constant across field sites and the values published range from below 0.5 to more than 1.0. The reasons for these variations in enrichment factors and relative enrichment of oxygen compared to nitrogen are yet unknown. We conducted microcosm experiments with three different bacterial species to elucidate possible influences of environmental factors on these parameters. As a result we conclude that the type of carbon source available to denitrifying bacteria can play a role in the value of the enrichment factors, but not in the relative enrichment of the two isotopes. Specifically we found that complex hydrocarbons (toluene, benzoate) produce significantly different enrichment factors in nitrate than a simple hydrocarbon substrate (acetate). The relative enrichment of ?18O compared to ?15N was 0.86. We hypothesise that this influence is based on a variation in process kinetics of cross-membrane nitrate transport in relation to intracellular nitrate reduction. The core of the hypothesis is that nitrate transport into the cell becomes rate limiting as a result of a carbon source induced change in cell membrane composition. The apparent kinetic isotope effect observed outside the cell is then changed as transport-related isotope effects dominate the observations. In addition, a possible effect of water ?18O values on the ?18O of dissolved nitrate was researched. Intermediary nitrite is known to exchange oxygen atoms with water; a reverse reaction of the nitrate reducing step could thus influence the oxygen isotope composition of dissolved nitrate without changing the nitrogen isotopic composition in the same way. Such a process was already shown for sulfate reduction. By adding 18O-labelled water to microcosm experiments, we could show that such an exchange exists for selected microorganisms. The environmental implications of this result is discussed.

Wunderlich, A.; Meckenstock, R.; Einsiedl, F.

2012-04-01

203

Phylogenetic and metabolic diversity of bacteria degrading aromatic compounds under denitrifying conditions, and description of Thauera phenylacetica sp. nov., Thauera aminoaromaticasp. nov., and Azoarcus buckelii sp. nov.  

Science.gov (United States)

Six strains of denitrifying bacteria isolated from various oxic and anoxic habitats on different monocyclic aromatic substrates were characterized by sequencing 16S rRNA genes, determining physiological and morphological traits, and DNA-DNA hybridization. According to these criteria, strains S100, SP and LG356 were identified as members of Thauera aromatica. Strains B5-1 and B5-2 were tentatively affiliated to the species Azoarcus tolulyticus. Strains B4P and S2 were only distantly related to each other and to other described Thauera species. These two strains are proposed as the type strains of two new species, Thauera phenylacetica sp. nov. and Thauera aminoaromaticasp. nov., respectively. By 16S rRNA gene analysis, strain U120 was highly related to the type strains of Azoarcus evansii and Azoarcus anaerobius, whereas corresponding DNA-DNA reassociation values indicated only a low degree of genomic relatedness. Based upon a low DNA similarity value and the presence of distinguishing physiological properties, strain U120 is proposed as the type strain of a new species, Azoarcus buckelii sp. nov. Almost all of the new isolates were obtained with different substrates. The highly varied substrate spectra of the isolates indicates that an even higher diversity of denitrifying bacteria degrading aromatic compounds would be discovered in the different habitats by using a larger spectrum of aromatic substrates for enrichment and isolation. PMID:12070766

Mechichi, Tahar; Stackebrandt, Erko; Gad'on, Nasser; Fuchs, Georg

2002-07-01

204

Denitrifier Community in the Oxygen Minimum Zone of a Subtropical Deep Reservoir  

Science.gov (United States)

Denitrification is an important pathway for nitrogen removal from aquatic systems and this could benefit water quality. However, little is known about the denitrifier community composition and key steps of denitrification in the freshwater environments, and whether different bacteria have a role in multiple processes of denitrification reduction. In this study, quantitative PCR, quantitative RT-PCR, clone library and 454 pyrosequencing were used together to investigate the bacterial and denitrifier community in a subtropical deep reservoir during the strongly stratified period. Our results indicated that the narG gene recorded the highest abundance among the denitrifying genes (2.76×109 copies L?1 for DNA and 4.19×108 copies L?1 for RNA), and the lowest value was nosZ gene (7.56×105 copies L?1 for DNA and undetected for RNA). The RNA: DNA ratios indicated that narG gene was the most active denitrifying gene in the oxygen minimum zone of Dongzhen Reservoir. Further, ?-, ?- and ?- Proteobacteria were the overwhelmingly dominant classes of denitrifier communities. Each functional gene had its own dominant groups which were different at the genus level: the narG gene was dominated by Albidiferax, while nirS gene was dominated by Dechloromonas. The main OTU of nirK gene was Rhodopseudomonas palustris, but for norB and nosZ genes, they were Bacillus and Bradyrhizobium, respectively. These results contribute to the understanding of linkages between denitrifier community, function and how they work together to complete the denitrification process. Studies on denitrifier community and activity may be useful in managing stratified reservoirs for the ecosystem services and aiding in constructing nitrogen budgets.

Yu, Zheng; Yang, Jun; Liu, Lemian

2014-01-01

205

Denitrifier community in the oxygen minimum zone of a subtropical deep reservoir.  

Science.gov (United States)

Denitrification is an important pathway for nitrogen removal from aquatic systems and this could benefit water quality. However, little is known about the denitrifier community composition and key steps of denitrification in the freshwater environments, and whether different bacteria have a role in multiple processes of denitrification reduction. In this study, quantitative PCR, quantitative RT-PCR, clone library and 454 pyrosequencing were used together to investigate the bacterial and denitrifier community in a subtropical deep reservoir during the strongly stratified period. Our results indicated that the narG gene recorded the highest abundance among the denitrifying genes (2.76×109 copies L-1 for DNA and 4.19×108 copies L-1 for RNA), and the lowest value was nosZ gene (7.56×105 copies L-1 for DNA and undetected for RNA). The RNA: DNA ratios indicated that narG gene was the most active denitrifying gene in the oxygen minimum zone of Dongzhen Reservoir. Further, ?-, ?- and ?- Proteobacteria were the overwhelmingly dominant classes of denitrifier communities. Each functional gene had its own dominant groups which were different at the genus level: the narG gene was dominated by Albidiferax, while nirS gene was dominated by Dechloromonas. The main OTU of nirK gene was Rhodopseudomonas palustris, but for norB and nosZ genes, they were Bacillus and Bradyrhizobium, respectively. These results contribute to the understanding of linkages between denitrifier community, function and how they work together to complete the denitrification process. Studies on denitrifier community and activity may be useful in managing stratified reservoirs for the ecosystem services and aiding in constructing nitrogen budgets. PMID:24664112

Yu, Zheng; Yang, Jun; Liu, Lemian

2014-01-01

206

Denitrifying bacteria from the terrestrial subsurface exposed to mixed waste contamination  

International Nuclear Information System (INIS)

In terrestrial subsurface environments where nitrate is a critical groundwater contaminant, few cultivated representatives are available with which to verify the metabolism of organisms that catalyze denitrification. In this study, five species of denitrifying bacteria from three phyla were isolated from subsurface sediments exposed to metal radionuclide and nitrate contamination as part of the U.S. Department of Energy's Oak Ridge Integrated Field Research Challenge (OR-IFRC). Isolates belonged to the genera Afipia and Hyphomicrobium (Alphaproteobacteria), Rhodanobacter (Gammaproteobacteria), Intrasporangium (Actinobacteria) and Bacillus (Firmicutes). Isolates from the phylum Proteobacteria were confirmed as complete denitrifiers, whereas the Gram-positive isolates reduced nitrate to nitrous oxide. Ribosomal RNA gene analyses reveal that bacteria from the genus Rhodanobacter comprise a diverse population of circumneutral to moderately acidophilic denitrifiers at the ORIFRC site, with a high relative abundance in areas of the acidic source zone. Rhodanobacter species do not contain a periplasmic nitrite reductase and have not been previously detected in functional gene surveys of denitrifying bacteria at the OR-IFRC site. Sequences of nitrite and nitrous oxide reductase genes were recovered from the isolates and from the terrestrial subsurface by designing primer sets mined from genomic and metagenomic data and from draft genomes of two of the isolates. We demonstrate that a combination of cultivation, genomic and metagenomic data are essential to the in situ characterization of denitrifiers and that current PCR-based approaches are not suitable for deep coverage of denitrifying microorganisms. Our results indicate that the diversity of denitrifiers is significantly underestimated in the terrestrial subsurface.

2010-05-01

207

Denitrifying bacteria from the terrestrial subsurface exposed to mixed waste contamination  

Energy Technology Data Exchange (ETDEWEB)

In terrestrial subsurface environments where nitrate is a critical groundwater contaminant, few cultivated representatives are available with which to verify the metabolism of organisms that catalyze denitrification. In this study, five species of denitrifying bacteria from three phyla were isolated from subsurface sediments exposed to metal radionuclide and nitrate contamination as part of the U.S. Department of Energy s Oak Ridge Integrated Field Research Challenge (OR-IFRC). Isolates belonged to the genera Afipia and Hyphomicrobium (Alphaproteobacteria), Rhodanobacter (Gammaproteobacteria), Intrasporangium (Actinobacteria) and Bacillus (Firmicutes). Isolates from the phylum Proteobacteria were confirmed as complete denitrifiers, whereas the Gram-positive isolates reduced nitrate to nitrous oxide. Ribosomal RNA gene analyses reveal that bacteria from the genus Rhodanobacter comprise a diverse population of circumneutral to moderately acidophilic denitrifiers at the ORIFRC site, with a high relative abundance in areas of the acidic source zone. Rhodanobacter species do not contain a periplasmic nitrite reductase and have not been previously detected in functional gene surveys of denitrifying bacteria at the OR-IFRC site. Sequences of nitrite and nitrous oxide reductase genes were recovered from the isolates and from the terrestrial subsurface by designing primer sets mined from genomic and metagenomic data and from draft genomes of two of the isolates. We demonstrate that a combination of cultivation, genomic and metagenomic data are essential to the in situ characterization of denitrifiers and that current PCR-based approaches are not suitable for deep coverage of denitrifying microorganisms. Our results indicate that the diversity of denitrifiers is significantly underestimated in the terrestrial subsurface.

Green, Stefan [Florida State University; Prakash, Om [Florida State University; Gihring, Thomas [Florida State University; Akob, Denise M. [Florida State University; Jasrotia, Puja [Florida State University; Jardine, Philip M [ORNL; Watson, David B [ORNL; Brown, Steven D [ORNL; Palumbo, Anthony Vito [ORNL; Kostka, Joel [Florida State University

2010-01-01

208

Denitrifying bacteria isolated from terrestrial subsurface sediments exposed to mixed-waste contamination.  

Science.gov (United States)

In terrestrial subsurface environments where nitrate is a critical groundwater contaminant, few cultivated representatives are available to verify the metabolism of organisms that catalyze denitrification. In this study, five species of denitrifying bacteria from three phyla were isolated from subsurface sediments exposed to metal radionuclide and nitrate contamination as part of the U.S. Department of Energy's Oak Ridge Integrated Field Research Challenge (OR-IFRC). Isolates belonged to the genera Afipia and Hyphomicrobium (Alphaproteobacteria), Rhodanobacter (Gammaproteobacteria), Intrasporangium (Actinobacteria), and Bacillus (Firmicutes). Isolates from the phylum Proteobacteria were complete denitrifiers, whereas the Gram-positive isolates reduced nitrate to nitrous oxide. rRNA gene analyses coupled with physiological and genomic analyses suggest that bacteria from the genus Rhodanobacter are a diverse population of denitrifiers that are circumneutral to moderately acidophilic, with a high relative abundance in areas of the acidic source zone at the OR-IFRC site. Based on genome analysis, Rhodanobacter species contain two nitrite reductase genes and have not been detected in functional-gene surveys of denitrifying bacteria at the OR-IFRC site. Nitrite and nitrous oxide reductase gene sequences were recovered from the isolates and from the terrestrial subsurface by designing primer sets mined from genomic and metagenomic data and from draft genomes of two of the isolates. We demonstrate that a combination of cultivation and genomic and metagenomic data is essential to the in situ characterization of denitrifiers and that current PCR-based approaches are not suitable for deep coverage of denitrifiers. Our results indicate that the diversity of denitrifiers is significantly underestimated in the terrestrial subsurface. PMID:20305024

Green, Stefan J; Prakash, Om; Gihring, Thomas M; Akob, Denise M; Jasrotia, Puja; Jardine, Philip M; Watson, David B; Brown, Steven D; Palumbo, Anthony V; Kostka, Joel E

2010-05-01

209

Denitrifying Bacteria Isolated from Terrestrial Subsurface Sediments Exposed to Mixed-Waste Contamination? †  

Science.gov (United States)

In terrestrial subsurface environments where nitrate is a critical groundwater contaminant, few cultivated representatives are available to verify the metabolism of organisms that catalyze denitrification. In this study, five species of denitrifying bacteria from three phyla were isolated from subsurface sediments exposed to metal radionuclide and nitrate contamination as part of the U.S. Department of Energy's Oak Ridge Integrated Field Research Challenge (OR-IFRC). Isolates belonged to the genera Afipia and Hyphomicrobium (Alphaproteobacteria), Rhodanobacter (Gammaproteobacteria), Intrasporangium (Actinobacteria), and Bacillus (Firmicutes). Isolates from the phylum Proteobacteria were complete denitrifiers, whereas the Gram-positive isolates reduced nitrate to nitrous oxide. rRNA gene analyses coupled with physiological and genomic analyses suggest that bacteria from the genus Rhodanobacter are a diverse population of denitrifiers that are circumneutral to moderately acidophilic, with a high relative abundance in areas of the acidic source zone at the OR-IFRC site. Based on genome analysis, Rhodanobacter species contain two nitrite reductase genes and have not been detected in functional-gene surveys of denitrifying bacteria at the OR-IFRC site. Nitrite and nitrous oxide reductase gene sequences were recovered from the isolates and from the terrestrial subsurface by designing primer sets mined from genomic and metagenomic data and from draft genomes of two of the isolates. We demonstrate that a combination of cultivation and genomic and metagenomic data is essential to the in situ characterization of denitrifiers and that current PCR-based approaches are not suitable for deep coverage of denitrifiers. Our results indicate that the diversity of denitrifiers is significantly underestimated in the terrestrial subsurface.

Green, Stefan J.; Prakash, Om; Gihring, Thomas M.; Akob, Denise M.; Jasrotia, Puja; Jardine, Philip M.; Watson, David B.; Brown, Steven D.; Palumbo, Anthony V.; Kostka, Joel E.

2010-01-01

210

Contrasting denitrifier communities relate to contrasting N2O emission patterns from acidic peat soils in arctic tundra.  

Science.gov (United States)

Cryoturbated peat circles (that is, bare surface soil mixed by frost action; pH 3-4) in the Russian discontinuous permafrost tundra are nitrate-rich 'hotspots' of nitrous oxide (N(2)O) emissions in arctic ecosystems, whereas adjacent unturbated peat areas are not. N(2)O was produced and subsequently consumed at pH 4 in unsupplemented anoxic microcosms with cryoturbated but not in those with unturbated peat soil. Nitrate, nitrite and acetylene stimulated net N(2)O production of both soils in anoxic microcosms, indicating denitrification as the source of N(2)O. Up to 500 and 10??M nitrate stimulated denitrification in cryoturbated and unturbated peat soils, respectively. Apparent maximal reaction velocities of nitrite-dependent denitrification were 28 and 18?nmol N(2)O?g(DW)(-1)?h(-1), for cryoturbated and unturbated peat soils, respectively. Barcoded amplicon pyrosequencing of narG, nirK/nirS and nosZ (encoding nitrate, nitrite and N(2)O reductases, respectively) yielded ?49?000 quality-filtered sequences with an average sequence length of 444?bp. Up to 19 species-level operational taxonomic units were detected per soil and gene, many of which were distantly related to cultured denitrifiers or environmental sequences. Denitrification-associated gene diversity in cryoturbated and in unturbated peat soils differed. Quantitative PCR (inhibition-corrected per DNA extract) revealed higher copy numbers of narG in cryoturbated than in unturbated peat soil. Copy numbers of nirS were up to 1000 × higher than those of nirK in both soils, and nirS nirK(-1) copy number ratios in cryoturbated and unturbated peat soils differed. The collective data indicate that the contrasting N(2)O emission patterns of cryoturbated and unturbated peat soils are associated with contrasting denitrifier communities. PMID:22134649

Palmer, Katharina; Biasi, Christina; Horn, Marcus A

2012-05-01

211

Rapid identification of Salmonella serovars in feces by specific detection of virulence genes, invA and spvC, by an enrichment broth culture-multiplex PCR combination assay.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In order to make a rapid and definite diagnosis of Salmonella enteritis in children, an enrichment broth culture-multiplex PCR combination assay was devised to identify Salmonella serovars directly from fecal samples. Two pairs of oligonucleotide primers were prepared according to the sequences of the chromosomal invA and plasmid spvC genes. PCR with these two primers would produce either one amplicon (from the invA gene) or two amplicons (from the invA and spvC genes), depending on whether o...

1996-01-01

212

[Effect of polycyclic aromatic hydrocarbons on the vertical distribution of denitrifying genes in river sediments].  

Science.gov (United States)

To establish the relationship between polycyclic aromatic hydrocarbons (PAHs) and various stages of denitrification under denitrifying conditions in sediments, we examined the impact of PAHs on the vertical distribution of special denitrifying genes. In March of 2011, sediment samples were collected from three representative locations along the Pearl River. The characteristics of vertical distribution of PAHs as well as denitrifying genes in the sediment samples were analyzed. Based on these vertical characteristics, relationships between PAHs and special denitrifying genes (narG, nirS, nosZ and nrfA) were established using the multivariate method. Results of canonical correspondence analysis (CCA) showed a close correlation between high ring PAHs and dissimilatory nitrate reduction. The impact of PAHs on nosZ was the most significant, namely PAHs imposed strong inhibition on the nitrite reduction stage. Except for the nitrite reduction stage, denitrifying bacteria from other stages of denitrification acclimatized themselves to the high ring PAHs. Especially, bacteria containing nrfA may have the potential to anaerobically degrade high ring PAHs. Besides this, the special role of nirS remains to be studied further. PMID:23233993

Wu, Yan-Yang; Wu, Qun-He; Huang, Shan; Ye, Jia-Xin; Zhang, Heng-Jun; Zhang, Ren-Duo

2012-10-01

213

Anaerobic degradation of toluene by a denitrifying bacterium  

Energy Technology Data Exchange (ETDEWEB)

A denitrifying bacterium, designated strain T1, that grew with toluene as the sole source of carbon under anaerobic conditions was isolated. The type of agar used in solid media and the toxicity of toluene were determinative factors in the successful isolation of strain T1. Greater than 50% of the toluene carbon was oxidized to CO{sub 2}, and 29% was assimilated into biomass. The oxidation of toluene to CO{sub 2} was stoichiometrically coupled to nitrate reduction and denitrification. Strain T1 was tolerant of and grew on 3 mM toluene after a lag phase. The rate of toluene degradation was 1.8 {mu}mol min{sup {minus}1} liter{sup {minus}1} (56 nmol min{sup {minus}1} mg of protein{sup {minus}1}) in a cell suspension. Strain T1 was distinct from other bacteria that oxidize toluene anaerobically, but it may utilize a similar biochemical pathway of oxidation. In addition, o-xylene was transformed to a metabolite in the presence of toluene but did not serve as the sole source of carbon for growth of strain T1. This transformation was dependent on the degradation of toluene.

Evans, P.J.; Mang, D.T.; Kwang Shin Kim; Young, L.Y. (New York Univ. Medical Center, NY (United States))

1991-04-01

214

Genetic characterization of denitrifier communities with contrasting intrinsic functional traits.  

Science.gov (United States)

Microorganisms capable of denitrification are polyphyletic and exhibit distinct denitrification regulatory phenotypes (DRP), and thus, denitrification in soils could be controlled by community composition. In a companion study (Dörsch et al., 2012) and preceding work, ex situ denitrification assays of three organic soils demonstrated profoundly different functional traits including N(2) O/N(2) ratios. Here, we explored the composition of the underlying denitrifier communities by analyzing the abundance and structure of denitrification genes (nirK, nirS, and nosZ). The relative abundance of nosZ (vs. nirK + nirS) was similar for all communities, and hence, the low N(2) O reductase activity in one of the soils was not because of the lack of organisms with this gene. Similarity in community composition between the soils was generally low for nirK and nirS, but not for nosZ. The community with the most robust denitrification (consistently low N(2) O/N(2) ) had the highest diversity/richness of nosZ and nirK, but not of nirS. Contrary results found for a second soil agreed with impaired denitrification (low overall denitrification activity, high N(2) O/N(2) ). In conclusion, differences in community composition and in the absolute abundance of denitrification genes clearly reflected the functional differences observed in laboratory studies and may shed light on differences in in situ N(2) O emission of the soils. PMID:22092293

Braker, Gesche; Dörsch, Peter; Bakken, Lars R

2012-02-01

215

Differential isotopic fractionation during Cr(VI) reduction by an aquifer-derived bacterium under arobic versus denitrifying conditions  

Energy Technology Data Exchange (ETDEWEB)

We studied Cr isotopic fractionation during Cr(VI) reduction by Pseudomonas stutzeri strain RCH2. Despite the fact that strain RCH2 reduces Cr(VI) co-metabolically under both aerobic and denitrifying conditions and at similar specific rates, fractionation was markedly different under these two conditions (ε ~2? aerobically and ~0.4? under denitrifying conditions).

Han, R.; Qin, L.; Brown, S. T.; Christensen, J. N.; Beller, H. R.

2012-02-01

216

Effects of plant biomass on denitrifying genes in subsurface-flow constructed wetlands.  

Science.gov (United States)

The effect of Typha latifolia and its litter on density and abundance of three denitrifying genes (nirS, nirK and nosZ) were investigated in six laboratory-scale SSF CW microcosms. Results showed that the copy numbers of nirS, nirK and nosZ in wetland microcosms were ranged between 10(8)-10(9), 10(6)-10(7) and 10(7)-10(8) copies g(-1), respectively. The presence of T. latifolia encouraged the growth of nirK containing bacteria. Addition of cattail litter could greatly stimulate the growth of bacteria containing nirS and nosZ gene. Path analysis illustrated that the presence of plants and litters had no significant direct impact on denitrifying genes, while it affected the denitrifying genes via alteration of dissolved oxygen and carbon sources. PMID:24565872

Chen, Yi; Wen, Yue; Zhou, Qi; Vymazal, Jan

2014-04-01

217

Spatially tripartite interactions of denitrifiers in arctic ecosystems: activities, functional groups and soil resources.  

Science.gov (United States)

Soil denitrification is one of the most significant contributors to global nitrous oxide (N(2) O) emissions, and spatial patterns of denitrifying communities and their functions may reveal the factors that drive denitrification potential and functional consortia. Although denitrifier spatial patterns have been studied extensively in most soil ecosystems, little is known about these processes in arctic soils. This study aimed to unravel the spatial relationships among denitrifier abundance, denitrification potential and soil resources in 279 soil samples collected from three Canadian arctic ecosystems encompassing 7° in latitude and 27° in longitude. The abundance of nirS (10(6) -10(8) ?copies?g(-1) dry soil), nirK (10(3) -10(7) ?copies?g(-1) dry soil) and nosZ (10(6) -10(7) ?copies?g(-1) dry soil) genes in these soils is in the similar range as non-arctic soil ecosystems. Potential denitrification in Organic Cryosols (1034?ng?N(2) O-N?g(-1) soil) was 5-11 times higher than Static/Turbic Cryosols and the overall denitrification potential in Cryosols was also comparable to other ecosystems. We found denitrifier functional groups and potential denitrification were highly spatially dependent within a scale of 5?m. Functional groups and soil resources were significantly (P?denitrifier activities and the correlations were stronger in Organic Cryosols. Soil moisture, organic carbon and nitrogen content were the predominant controls with nirK abundance also linked to potential denitrification. This study suggests that the dominant control on arctic ecosystem-level denitrification potential is moisture and organic carbon. Further, microbial abundance controls on ecosystem level activity while undoubtedly present, are masked in the nutrient-poor arctic environment by soil resource control on denitrifier ecosystem level activity. PMID:22759091

Banerjee, Samiran; Siciliano, Steven D

2012-09-01

218

Mapping spatial patterns of denitrifiers for bridging community ecology and microbial processes along environmental gradients  

Science.gov (United States)

While there is ample evidence that microbial processes can exhibit large variations at a field scale, very little is known about the spatial distribution of the communities mediating these processes. To explore spatial patterns of size and activity of the denitrifying community, a functional guild involved in N-cycling, in a grassland field subjected to different cattle grazing regimes.We used geostatistical modeling to map the distribution of size and activity of the denitrifier community in the pasture. Size of the denitrifier community was estimated by PCR quantification of the denitrification gene copy numbers while its activity was estimated by measuring potential denitrification activity and potential N2O emissions. Non-random distribution patterns of the size and of the activity of the denitrifier community were observed with a field-scale spatial dependence. The soil properties, which were strongly affected by presence of cattle, imposed significant control on potential denitrification activity, potential N2O production but not on the size of the denitrifier community. The relative abundance of bacteria possessing the nosZ gene encoding the N2O reductase within the total bacterial community was a strong predictor of the N2O/N2 ratio. Our results clearly indicated that patterns of distribution of the abundance of denitrifiers can be modelled at a field scale. Characterization of such pattern at a field-scale constitutes the first step in modelling distribution of functional bacterial communities at a scale compatible with land management strategies. The absolute abundance of most denitrification genes was not correlated with potential denitrification activity or potential N2O production. However, the relative abundance of bacteria possessing the nosZ gene in the total bacterial community was a strong predictor of the N2O/(N2+N2O) ratio, suggesting a relationship between ecosystem processes and bacterial community composition.

Bru, D.; Cuhel, J.; Saby, N.; Cheneby, D.; Chronokova, A.; Arrouays, D.; Martin-Laurent, F.; Simek, M.

2010-12-01

219

Abundance and composition of denitrifiers in response to Spartina alterniflora invasion in estuarine sediment.  

Science.gov (United States)

Nitrite reduction is regulated by nitrite reductase encoded by nirK and nirS genes. This study aimed to investigate the abundance and composition of nirK- and nirS-containing denitrifiers in response to Spartina alterniflora invasion at the Jiulong River estuary, China. The sediment samples (depth: 0-5.0 and 5.1-20 cm) were collected from 3 vegetation zones, 1 dominated by the exotic plant S. alterniflora, 1 dominated by the native plant Kandelia candel, and 1 dominated by the native plant Cyperus malaccensis, and from an unvegetated flat zone. nirK- and nirS-containing denitrifier population sizes were lower in the invaded and nonvegetated zones than in those dominated by native K. candel and C. malaccensis, which were impacted by depth - vegetation species interaction. The ratios of nirS to nirK abundance ranged from 42.10 to 677.27, with the lowest ratio found for the upper layer in the invaded zone. The nirK-containing denitrifier compositions showed a 35% similarity between invaded zone and others. Most of the sequences of nirK genes recovered from the S. alterniflora zone were specific and distinct from those of nirK genes recovered from other vegetation types; nirS genes in the invaded zone were highly divergent. These results reveal that S. alterniflora invasion has a significant effect on the abundance and composition of both nirK- and nirS-containing denitrifiers, and nirS-containing denitrifiers were less responsive to invasion than nirK-containing denitrifiers. PMID:24313455

Zhang, Qiufang; Peng, Jingjing; Chen, Qian; Yang, Xiaoru; Hong, Youwei; Su, Jianqiang

2013-12-01

220

Concurrent Activity of Anammox and Denitrifying Bacteria in the Black Sea  

Directory of Open Access Journals (Sweden)

Full Text Available After the discovery of ANaerobic AMMonium OXidation (anammox in the Black Sea in 2003, the role of heterotrophic denitrification as the main marine pathway for fixed N loss was questioned. A 3 part, 15 month time series investigating Black Sea nitrite reductase (nirS mRNA transcripts at a single location was conducted in order to better understand the activity of anammox and denitrifying bacteria. Here we show that both of these groups were active, as well as being concurrent in the lower suboxic zone over this time span. Their distributions, however, were fundamentally different; denitrification expression was much more variable. Depth profiles covering the suboxic zone showed that the four groups of anammox-type sequences were expressed consistently in the lower suboxic zone, and were consistent with anammox 16S rDNA gene profiles. By contrast, denitrifier-type nirS sequence groups were mixed; half of the groups exhibited consistent expression in the lower suboxic zone, while others varied between season and depth. Co-occurrence of both anammox and denitrifier expression was common and ongoing. Both types of transcripts were also found in samples with low concentrations of sulfide ( >2 ?M. 6 major groups of denitrifier-type nirS transcripts were identified, making these transcripts more diverse than previous DNA clone libraries. Several groups of denitrifier-type nirS transcripts were closely related to sequences from the Baltic Sea. An increase in denitrifier-type nirS transcript diversity and depth range in October 2007 corresponded to an increase in mixed layer net community productivity as measured by O2/Ar gas ratios, as well as to an increase in N2 concentrations in the upper suboxic zone. Taken together, the variations in expression patterns between anammox and denitrification provide one explanation as to how near instantaneous rate measurements, such as isotope spike experiments, may regularly detect anammox activity but underreport denitrification.

JohnB.Kirkpatrick

2012-07-01

 
 
 
 
221

Concurrent activity of anammox and denitrifying bacteria in the Black Sea.  

Science.gov (United States)

After the discovery of ANaerobic AMMonium OXidation (anammox) in the environment, the role of heterotrophic denitrification as the main marine pathway for fixed N loss has been questioned. A 3 part, 15 month time series investigating nitrite reductase (nirS) mRNA transcripts at a single location in the Black Sea was conducted in order to better understand the activity of anammox and denitrifying bacteria. Here we show that both of these groups were active, as well as being concurrent in the lower suboxic zone over this time span. Their distributions, however, differed in that only expression of denitrification-type nirS was seen in the upper suboxic zone, where geochemistry was variable. Depth profiles covering the suboxic zone showed that the four groups of anammox-type sequences were expressed consistently in the lower suboxic zone, and were consistent with anammox 16 S rDNA gene profiles. By contrast, denitrifier-type nirS sequence groups were mixed; some groups exhibited consistent expression in the lower suboxic zone, while others appeared less consistent. Co-occurrence of both anammox and denitrifier expression was common and ongoing. Both types of transcripts were also found in samples with low concentrations of sulfide (>2 ?M). Six major groups of denitrifier-type nirS transcripts were identified, and several groups of denitrifier-type nirS transcripts were closely related to sequences from the Baltic Sea. An increase in denitrifier-type nirS transcript diversity and depth range in October 2007 corresponded to a small increase in mixed layer net community productivity (NCP) as measured by O(2)/Ar gas ratios, as well as to an increase in N(2) concentrations in the suboxic zone. Taken together, the variations in expression patterns between anammox and denitrification provide one possible explanation as to how near instantaneous rate measurements, such as isotope spike experiments, may regularly detect anammox activity but underreport denitrification. PMID:22833740

Kirkpatrick, John B; Fuchsman, Clara A; Yakushev, Evgeniy; Staley, James T; Murray, James W

2012-01-01

222

Cultivation of Denitrifying Bacteria: Optimization of Isolation Conditions and Diversity Study†  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An evolutionary algorithm was applied to study the complex interactions between medium parameters and their effects on the isolation of denitrifying bacteria, both in number and in diversity. Growth media with a pH of 7 and a nitrogen concentration of 3 mM, supplemented with 1 ml of vitamin solution but not with sodium chloride or riboflavin, were the most successful for the isolation of denitrifiers from activated sludge. The use of ethanol or succinate as a carbon source and a molar C/N rat...

2006-01-01

223

Uranium enrichment  

Energy Technology Data Exchange (ETDEWEB)

This paper analyzes under four different scenarios the adequacy of a $500 million annual deposit into a fund to pay for the cost of cleaning up the Department of Energy's (DOE) three aging uranium enrichment plants. These plants are located in Oak Ridge, Tennessee; Paducah, Kentucky; and Portsmouth, Ohio. In summary the following was found: A fixed annual $500 million deposit made into a cleanup fund would not be adequate to cover total expected cleanup costs, nor would it be adequate to cover expected decontamination and decommissioning (D and D) costs. A $500 million annual deposit indexed to an inflation rate would likely be adequate to pay for all expected cleanup costs, including D and D costs, remedial action, and depleted uranium costs.

1991-11-01

224

Effects of dietary ß-cyclodextrin supplemented with a culture of lactobacillus acidophilus on plasma lipid in a cholesterol enriched diet  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Heart disease is a major cause of death for humans. Nutritional studies has indicated that high concentrations of total serum cholesterol and low density lipoprotein (LDL) cholesterol correlate highly with the incidence of coronary heart disease. Several reports have showed that consumption of certain culture dairy products or culture containing dairy products supplemented with Lactobacillus acidophilus reduced concentrations of serum cholesterol. The objective of the present study was to inv...

2012-01-01

225

Enrichment of Prostate Cancer Stem-Like Cells from Human Prostate Cancer Cell Lines by Culture in Serum-Free Medium and Chemoradiotherapy  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The discovery of rare subpopulations of cancer stem cells (CSCs) has created a new focus in cancer research. As CSCs demonstrate resistance to chemoradiation therapy relative to other cancer cells, this allows the enrichment of CSC populations by killing apoptosis-susceptible cancer cells. In this study, three commonly used human prostate cancer (PCa) cell lines (DU145, PC-3 and LNCaP) were examined for their expression of the putative stem cell markers CD133 and CD44 via flow cytometric anal...

Wang, Lei; Huang, Xing; Zheng, Xinmin; Wang, Xinghuan; Li, Shiwen; Zhang, Lin; Yang, Zhonghua; Xia, Zhiping

2013-01-01

226

Use of starter cultures of lactic acid bacteria and yeasts as inoculum enrichment for the production of gowé, a sour beverage from Benin  

DEFF Research Database (Denmark)

Lactobacillus fermentum, Weissella confusa, Kluyveromyces marxianus and Pichia anomala, previously isolated during natural fermentation of traditional gowé, were tested as inoculum enrichment for controlled fermentation of gowé. The final product was subjected to chemical analysis and sensory evaluation. Growth of the lactic acid bacteria (LAB) and yeasts were verified by determination of colony forming units (CFU) and molecular biology techniques. A significant decrease in pH from 6.1 to 3.3, with a concomitant increase in titratable acidity (11 to 60 g/kg as lactic acid, dry weight), was observed after 24 h of fermentation when LAB was used either alone or in combination with yeasts. The LAB count increased significantly from 6.1 to 9.4 log CFU/ml, while the yeast count remained constant throughout fermentation. Repetitive-polymerase chain reaction (rep-PCR) assays performed on isolates during the fermentation confirmed the dominance of the added LAB strains. Sensory evaluation revealed that the product fermented for 7 h with L. fermentum alone or in combination with K. marxianus was as acceptable as the traditional product normally obtained after a minimum of 24 h of fermentation. Consequently, gowé can be obtained by controlled fermentation, using L. fermentum as inoculum enrichment, in a small scale industry.  

Vieira-Dalodé, G.; Madodé, Y.E.

2008-01-01

227

Effect of long-term wastewater irrigation on potential denitrification and denitrifying communities in soils at the watershed scale.  

Science.gov (United States)

Wastewater irrigation mitigates the problem of water shortage but leads to the potential accumulation of pollutants and causes corresponding changes in denitrifying communities and denitrification, hence the potential ecological risk of long-term wastewater irrigation should not be overlooked. We investigated the relative contributions of different environmental factors to the abundance and diversity of denitrifying communities harboring nirK, nirS, and nosZ genes and the relative importance of these biotic and abiotic variables in potential denitrification activity (PDA) in soils with wastewater irrigation for around 25 years at a large watershed scale. Results showed that soil physicochemical properties, pollutants, including heavy metals and PAHs, and vegetation are the major factor groups influencing the abundance and structure of the three denitrifying communities and PDA. NirK-, nirS-, or nosZ-harboring denitrifiers responded in different manners to environmental changes, and were mainly influenced by substrate concentration, carbon source, or pollutants, respectively. The structure of the three denitrifying communities was more relevant to the environmental changes than their abundance. Conversely, the abundance, rather than diversity, was correlated with PDA. Pollutants and vegetation could affect PDA by both direct and indirect paths through soil physicochemical properties including pH, carbon and nitrogen sources, or through the abundance of denitrifying functional genes. The abundance of denitrifying functional genes is a valuable index that integrates potential activity and various environmental factors, and is therefore a good predictor of denitrification in the presence of environmental changes. PMID:23445539

Guo, Guang-Xia; Deng, Huan; Qiao, Min; Yao, Huai-Ying; Zhu, Yong-Guan

2013-04-01

228

Uranium enrichment  

International Nuclear Information System (INIS)

Uranium isotope separation science, technology in the field of industrial applications, and laboratory investigations of uranium isotope separation are treated in this book. Basic concepts for the mathematical treatment of the cascade separation processes and an original presentation of ideal nonsymmetric cascades are treated in the chapter entitled, Cascade theory. The chapter entitled, Gaseous diffusion, discusses this process which is the main industrial process for uranium enrichment today as well as an in depth treatment of the gas flow through the porous barrier and the relevant separation effects. The chapter on the centrifugation process covers essentially the conceptual and theoretical aspects of the process. An overall description of the separation nozzle process including both the physical principle and the technical aspects are discussed. The last two chapters in the book are devoted to new methods of uranium separation which are still in the laboratory stage. The laser method in which separation is obtained through selective photoexcitation of uranium atoms or molecules is treated in one chapter, and the other chapter deals with separation experiments with rotating plasmas and some advanced concepts like using ion cyclotron resonance effects to achieve isotope separation

1979-01-01

229

Post cold-storage conditioning time affects soil denitrifying enzyme activity  

DEFF Research Database (Denmark)

Soil denitrifying enzyme activity (DEA) is often assessed after cold storage. Previous studies using the short-term acetylene inhibition method have not considered conditioning time (post-cold-storage warm-up time prior to soil analysis) as a factor influencing results. We observed fluctuations in DEA following cold storage, suggesting a need to consider conditioning time when planning and interpreting results.

Chirinda, Ngoni; Olesen, Jørgen E

2011-01-01

230

Nitrite reductase genes as functional markers to investigate diversity of denitrifying bacteria during agricultural waste composting.  

Science.gov (United States)

The purpose of this study was to investigate the diversity of denitrifier community during agricultural waste composting. The diversity and dynamics of the denitrifying genes (nirK and nirS) were determined using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). Relationships between physico-chemical parameters and denitrifying genes structures were simultaneously evaluated by redundancy analysis (RDA). Phylogenetic analysis indicated that nirK clones grouped into six clusters and nirS clones into two major clusters, respectively. The results showed a very high diversity of nir gene sequences within composting samples. RDA showed that the nirK and nirS gene structures were significantly related to pH and pile temperature (P?nirS genes, respectively) were explained by pH and pile temperature, suggesting that those two parameters were the most likely ones to influence, or be influenced by the denitrifiers harboring nirK and nirS genes. PMID:24442505

Chen, Yaoning; Zhou, Wei; Li, Yuanping; Zhang, Jiachao; Zeng, Guangming; Huang, Aizhi; Huang, Jingxia

2014-05-01

231

Salinity Decreases Nitrite Reductase Gene Diversity in Denitrifying Bacteria of Wastewater Treatment Systems  

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Investigation of the diversity of nirK and nirS in denitrifying bacteria revealed that salinity decreased the diversity in a nitrate-containing saline wastewater treatment system. The predominant nirS clone was related to nirS derived from marine bacteria, and the predominant nirK clone was related to nirK of the genus Alcaligenes.

Yoshie, Sachiko; Noda, Naohiro; Tsuneda, Satoshi; Hirata, Akira; Inamori, Yuhei

2004-01-01

232

Response of Marine Denitrifying Bacterial Populations to Nitrous Oxide: a Natural Sink?  

Science.gov (United States)

The influence of nitrous oxide upon denitrifying populations was investigated in moderately saline shallow Texas coastal bays. Homogenized sediment samples were incubated under a N2O atmosphere for one week, after which nosZ DNA marker for nitrous oxide reductase enzyme was extracted and analyzed by quantitative polymerase chain reaction (qPCR) and semi-quantitative polymerase chain reaction/denaturing gradient gel electrophoresis (PCR/DGGE). qPCR analysis indicated a significant (over an order of magnitude) increase in nosZ copy number in response to N2O addition, with PCR/DGGE indicating a significant population shift towards a small number of select organisms. Intriguingly, nirK and nirS markers for nitrite reductase enzymes in denitrifying bacteria did not show a corresponding increase, suggesting that observed nosZ peak was not associated with typical denitrifying populations. It is possible that N2O consumption in these sediments might not be driven by normally abundant denitrifiers, but rather by a niche-specific guild of bacteria converting N2O to N2 and naturally present in sediments at low numbers. These organisms are capable of responding rapidly to increased N2O supply. Our results suggest that net biological emission of N2O from the sediments is regulated by bacteria at both production and consumption stage, and disturbance of either could result in enhanced N2O emission.

Sobolev, D.; Brandes, J. A.

2004-12-01

233

"Ultrastructure of the Denitrifying Methanotroph ""Candidatus Methylomirabilis oxyfera,"" a Novel Polygon-Shaped Bacterium"  

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"""Candidatus Methylomirabilis oxyfera"" is a newly discovered denitrifying methanotroph that is unrelated to previously known methanotrophs. This bacterium is a member of the NC10 phylum and couples methane oxidation to denitrification through a newly discovered intra-aerobic pathway. In the present study, we report the first ultrastructural study of ""Ca. Methylomirabilis oxyfera"" using scanning electron microscopy, transmission electron microsc...

Wu, Ming L.; Teeseling, Muriel C. F.; Willems, Marieke J. R.; Donselaar, Elly G.; Klingl, Andreas; Rachel, Reinhard; Geerts, Willie J. C.; Jetten, Mike S. M.; Strous, Marc; Niftrik, Laura

2012-01-01

234

Novel denitrifying bacterium Ochrobactrum anthropi YD50.2 tolerates high levels of reactive nitrogen oxides.  

Science.gov (United States)

Most studies of bacterial denitrification have used nitrate (NO3-) as the first electron acceptor, whereas relatively less is understood about nitrite (NO2-) denitrification. We isolated novel bacteria that proliferated in the presence of high levels of NO2- (72 mM). Strain YD50.2, among several isolates, was taxonomically positioned within the alpha subclass of Proteobacteria and identified as Ochrobactrum anthropi YD50.2. This strain denitrified NO2-, as well as NO3-. The gene clusters for denitrification (nar, nir, nor, and nos) were cloned from O. anthropi YD50.2, in which the nir and nor operons were linked. We confirmed that nirK in the nir-nor operon produced a functional NO2- reductase containing copper that was involved in bacterial NO2- reduction. The strain denitrified up to 40 mM NO2- to dinitrogen under anaerobic conditions in which other denitrifiers or NO3- reducers such as Pseudomonas aeruginosa and Ralstonia eutropha and nitrate-respiring Escherichia coli neither proliferated nor reduced NO2-. Under nondenitrifying aerobic conditions, O. anthropi YD50.2 and its type strain ATCC 49188(T) proliferated even in the presence of higher levels of NO2- (100 mM), and both were considerably more resistant to acidic NO2- than were the other strains noted above. These results indicated that O. anthropi YD50.2 is a novel denitrifier that has evolved reactive nitrogen oxide tolerance mechanisms. PMID:19542343

Doi, Yuki; Takaya, Naoki; Takizawa, Noboru

2009-08-01

235

Nitrous Oxide Reductase Genes (nosZ) of Denitrifying Microbial Populations in Soil and the Earthworm Gut Are Phylogenetically Similar†  

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Earthworms emit nitrous oxide (N2O) and dinitrogen (N2). It has been hypothesized that the in situ conditions of the earthworm gut activates ingested soil denitrifiers during gut passage and leads to these in vivo emissions (M. A. Horn, A. Schramm, and H. L. Drake, Appl. Environ. Microbiol. 69:1662-1669, 2003). This hypothesis implies that the denitrifiers in the earthworm gut are not endemic to the gut but rather are regular members of the soil denitrifier population. To test this hypothesis...

Horn, Marcus A.; Drake, Harold L.; Schramm, Andreas

2006-01-01

236

Nitrous oxide reductase genes (nosZ) of denitrifying populations in soil and the earthworm gut are phylogenetically similar  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Earthworms emit nitrous oxide (N2O) and dinitrogen (N2). It has been hypothesized that the in situ conditions of the earthworm gut activates ingested soil denitrifiers during gut passage and leads to these in vivo emissions (M. A. Horn, A. Schramm, and H. L. Drake, Appl. Environ. Microbiol. 69:1662-1669, 2003). This hypothesis implies that the denitrifiers in the earthworm gut are not endemic to the gut but rather are regular members of the soil denitrifier population. To test this hypothesis...

Horn, Marcus A.; Drake, Harold L.; Schramm, Andreas

2006-01-01

237

Nutrient Cycles and Marine Microbes in a CO2-Enriched Ocean  

Directory of Open Access Journals (Sweden)

Full Text Available The ocean carbon cycle is tightly linked with the cycles of the major nutrient elements nitrogen, phosphorus, and silicon. It is therefore likely that enrichment of the ocean with anthropogenic CO2 and attendant acidification will have large consequences for marine nutrient biogeochemistry, and for the microbes that mediate many key nutrient transformations. The best available evidence suggests that the nitrogen cycle may respond strongly to higher CO2 through increases in global N2 fixation and possibly denitrification, as well as potential decreases in nitrification. These trends could cause nitrification to become a nitrogen cycle “bottleneck,” by increasing the flux of N2 fixed into ammonium while decreasing the fraction being oxidized to nitrite and nitrate. The consequences could include reduced supplies of oxidized nitrogen substrates to denitrifiers, lower levels of nitrate-supported new primary production, and expansion of the regenerated production system accompanied by shifts in current phytoplankton communities. The phosphorus and silicon cycles seem less likely to be directly affected by enhanced CO2 conditions, but will undoubtedly respond indirectly to changing carbon and nitrogen biogeochemistry. A review of culture experiments that examined the effects of increased CO2 on elemental ratios of phytoplankton suggests that for most cyanobacteria and eukaryotes, C:N and N:P ratios will either remain at Redfield values or increase substantially. Natural plankton community CO2 manipulation experiments show much more mixed outcomes, with both increases and decreases in C:N and N:P ratios reported at future CO2 levels. We conclude our review with projections of overall trends in the cycles of nitrogen, phosphorus, and silicon over the next century as they respond to the steady accumulation of fossil-fuel-derived CO2 in a rapidly changing ocean.

David A. Hutchins

2009-12-01

238

RELATIONSHIP BETWEEN THE CONCENTRATION OF DENITRIFIERS AND PSEUDOMONAS SPP. IN SOILS: IMPLICATIONS FOR BTX BIOREMEDIATION (R823420)  

Science.gov (United States)

Aquifer microcosms were used to investigate the effect of stimulating denitrification on microbial population shifts and BTX degradation potential. Selective pressure for facultative denitrifiers was applied to a treatment set by feeding acetate and nitrate, and cycling electr...

239

Regeneration of Ginger Plant from Callus Culture Through Organogenesis and Effect of CO2 Enrichment on the Differentiation of Regenerated Plant  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A efficient and systematic protocol for complete plant regeneration via shoot apical meristem culture has been developed for Zingiber officinale L. Callus was initiated from shoot-tip of young plant on MS-media supplemented with a combination of Naphthalene acetic acid (0.1 mg L-1) and Kinetin (1.0-2.0 mg L-1) and Indole-3-acetic acid (0.1 mg L-1) and 6-Benzylaminopurine (1.0-2.0 mg L-1). Maximum shoot differentiation from callus occurred on ...

Muhammad Jamil; Jin Key Kim; Zahid Akram; Saif Ullah Ajmal; Eui Shik Rha

2007-01-01

240

Changes in Bacterial Denitrifier Community Abundance over Time in an Agricultural Field and Their Relationship with Denitrification Activity?  

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This study measured total bacterial and denitrifier community abundances over time in an agricultural soil cropped to potatoes (Solanum tuberosum L.) by using quantitative PCR. Samples were collected on 10 dates from spring to autumn and from three spatial locations: in the potato “hill” between plants (H), close to the plant (Hp), and in the “furrow” (F). The denitrification rates, N2O emissions, and environmental parameters were also measured. Changes in denitrifier abundance over t...

Dandie, Catherine E.; Burton, David L.; Zebarth, Bernie J.; Henderson, Sherri L.; Trevors, Jack T.; Goyer, Claudia

2008-01-01

 
 
 
 
241

Performance of a reactor containing denitrifying immobilized biomass in removing ethanol and aromatic hydrocarbons (BTEX) in a short operating period  

International Nuclear Information System (INIS)

A horizontal-flow anaerobic immobilized biomass reactor (HAIB) containing denitrifying biomass was evaluated with respect to its ability to remove, separately and in a short operating period (30 days), organic matter, nitrate, and the hydrocarbons benzene (41.4 mg L-1), toluene (27.8 mg L-1), ethylbenzene (31.1 mg L-1), o-xylene (28.5 mg L-1), m-xylene (28.4 mg L-1) and p-xylene (32.1 mg L-1). The purified culture, which was grown in the presence of the specific hydrocarbon, was used as the source of cells to be immobilized in the polyurethane foam. After 30 days of operation, the foam was removed and a new immobilized biomass was grown in the presence of another hydrocarbon. The average hydrocarbon removal efficiency attained was 97%. The organic matter, especially ethanol, was removed with an average efficiency of 83% at a mean influent concentration of 1185.0 mg L-1. A concomitant removal of 97% of nitrate was observed for a mean influent concentration of 423.4 mg L-1. The independent removal of each hydrocarbon demonstrated that these contaminants can be biodegraded separately, without the need for a compound to be the primary substrate for the degradation of another. This study proposes the application of the system for treatment of areas contaminated with these compounds, with substitution and formation of a biofilm in a 30-day period

2007-01-10

242

Simultaneous removal of sulfide, nitrate and acetate under denitrifying sulfide removal condition: Modeling and experimental validation  

Energy Technology Data Exchange (ETDEWEB)

Graphical abstract: Model evaluation applied to case study 1: (A-G) S{sup 2?}, NO{sub 3}{sup ?}-N, NO{sub 2}{sup ?}-N, and Ac{sup ?}-C profiles under initial sulfide concentrations of 156.2 (A), 539 (B), 964 (C), 1490 (D), 342.7 (E), 718 (F), and 1140.7 (G) mg L{sup ?1}. The solid line represents simulated result and scatter represents experimental result. -- Highlights: • This work developed a mathematical model for DSR process. • Kinetics of sulfur–nitrogen–carbon and interactions between denitrifiers were studied. • Kinetic parameters of the model were estimated via data fitting. • The model described kinetic behaviors of DSR processes over wide parametric range. -- Abstract: Simultaneous removal of sulfide (S{sup 2?}), nitrate (NO{sub 3}{sup ?}) and acetate (Ac{sup ?}) under denitrifying sulfide removal process (DSR) is a novel biological wastewater treatment process. This work developed a mathematical model to describe the kinetic behavior of sulfur–nitrogen–carbon and interactions between autotrophic denitrifiers and heterotrophic denitrifiers. The kinetic parameters of the model were estimated via data fitting considering the effects of initial S{sup 2?} concentration, S{sup 2?}/NO{sub 3}{sup ?}-N ratio and Ac{sup ?}-C/NO{sub 3}{sup ?}-N ratio. Simulation supported that the heterotrophic denitratation step (NO{sub 3}{sup ?} reduction to NO{sub 2}{sup ?}) was inhibited by S{sup 2?} compared with the denitritation step (NO{sub 2}{sup ?} reduction to N{sub 2}). Also, the S{sup 2?} oxidation by autotrophic denitrifiers was shown two times lower in rate with NO{sub 2}{sup ?} as electron acceptor than that with NO{sub 3}{sup ?} as electron acceptor. NO{sub 3}{sup ?} reduction by autotrophic denitrifiers occurs 3–10 times slower when S{sup 0} participates as final electron donor compared to the S{sup 2?}-driven pathway. Model simulation on continuous-flow DSR reactor suggested that the adjustment of hydraulic retention time is an efficient way to make the reactor tolerating high S{sup 2?} loadings. The proposed model properly described the kinetic behaviors of DSR processes over wide parametric ranges and which can offer engineers with basis to optimize bioreactor operation to improve the treatment capacity.

Xu, Xijun; Chen, Chuan; Wang, Aijie; Guo, Wanqian; Zhou, Xu [State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090 (China); Lee, Duu-Jong, E-mail: djlee@ntu.edu.tw [State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090 (China); Department of Chemical Engineering, National Taiwan University, Taipei 106, Taiwan (China); Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan (China); Ren, Nanqi, E-mail: rnq@hit.edu.cn [State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090 (China); Chang, Jo-Shu [Research Center for Energy Technology and Strategy, National Cheng Kung University, Tainan, Taiwan (China)

2014-01-15

243

Effect of CO2 enrichment and high photosynthetic photon flux densities (PPFD) on rubisco and PEP-case activities of in vitro cultured strawberry plants  

International Nuclear Information System (INIS)

Standard growing conditions in vitro (low light and CO2) are not conducive to autotrophy. An experiment was conducted to improve photosynthesis in vitro in the hope of increasing survival in acclimatization. A factorial experiment was elaborated where CO2 and PPFD were supplied to in vitro cultured strawberry plants in the rooting stage. Activities of carboxylating enzymes were determined after 4 weeks of culture. The activities of non-activated and activated rubisco and PEP-Case were measured after extraction of the enzymes and a reaction with NaH14CO3 followed by scintillation counting spectroscopy. High CO2 concentration significantly increased net assimilation rates (NAR) by 165% over the control for both 1650 and 3000 ppm CO2. High PPFD only increased NAR by 12 and 35% for 150 and 250 ?mol·m-2·s-1 respectively over the control. Plants grown at 3000 ppm CO2 had the highest level of chlorophyll/g FW with 97% more than the control. The activity of PEP-Case was the highest at high light levels and high CO2 with rates of 1.65 for 1650 ppm versus 1.22 mmol CO2 mg-1 chl. h-1 at 250 ?mol·m-2·s-1. There was no difference in PEP activity at low light levels. The rubisco activity was lower at 1650 and 3000 ppm CO2. Increases in NAR correlate more closely to the PEP-Case than to Rubisco activity. Physiological significance of high activity of PEP-Case over rubisco will be discussed

244

The effect of substrate concentration fluctuation on the performance of high-rate denitrifying reactor.  

Science.gov (United States)

A high-rate denitrifying process is sensitive to the operation conditions and the substrate concentration fluctuation can lead to the deterioration or even collapse of process performance. The results of this study showed that the effect of substrate concentration fluctuation on the high-rate denitrification process was related to the substrate concentration and shock duration. The effect of substrate concentration was greater than that of shock duration and nitrate conversion was more sensitive than methanol conversion. The response of denitrification performance was related to the loading saturation (maximum loading rate/loading capacity ratio). When the loading saturation was lower than 32%, the high-rate denitrification process could stay in pseudo steady state, otherwise it would easily lose stability. The response of denitrification performance could be divided into three periods. The performance deterioration of high-rate denitrifying process could be attributed to the overload trigger and the toxicity of free nitrous acid. PMID:24971944

Li, Wei; Zheng, Ping; Zhang, Jiqiang; Shan, Xiaoyu; Wang, Zhiyao; Zhang, Meng

2014-09-01

245

Cellular and transcriptional response of Pseudomonas stutzeri to quantum dots under aerobic and denitrifying conditions.  

Science.gov (United States)

Pseudomonas stutzeri was exposed to quantum dots (QDs) with three different surface coatings (anionic polymaleic anhydride-alt-1-octadecene (PMAO), cationic polyethylenimine (PEI), and carboxyl QDs) under both aerobic and anaerobic (denitrifying) conditions. Under aerobic conditions, toxicity (assessed per growth inhibition) increased from PMAO to carboxyl to PEI QDs. The positive charge of PEI facilitated direct contact with negatively charged bacteria, which was verified by TEM analysis. Both PMAO and PEI QDs hindered energy transduction (indicated by a decrease in cell membrane potential), and this effect was most pronounced with PEI QDs under denitrifying conditions. Up-regulation of denitrification genes (i.e., nitrate reductase narG, periplasmic nitrate reductase napB, nitrite reductase nirH, and NO reductase norB) occurred upon exposure to subinhibitory PEI QD concentrations (1 nM). Accordingly, denitrification activity (assessed per respiratory nitrate consumption in the presence of ammonia) increased during sublethal PEI QD exposure. However, cell viability (including denitrification) was hindered at 10 nM or higher PEI QD concentrations. Efflux pump genes czcB and czcC were induced by PEI QDs under denitrifying conditions, even though Cd and Se dissolution from QDs did not reach toxic levels (exposure was at pH 7 to minimize hydrolysis of QD coatings and the associated release of metal constituents). Up-regulation of the superoxide dismutase (stress) gene sodB occurred only under aerobic conditions, likely due to intracellular production of reactive oxygen species (ROS). The absence of ROS under denitrifying conditions suggests that the antibacterial activity of QDs was not due to ROS production alone. Overall, this work forewarns about unintended potential impacts to denitrification as a result of disposal and incidental releases of QDs, especially those with positively charged coatings (e.g., PEI QDs). PMID:21526814

Yang, Yu; Zhu, Huiguang; Colvin, Vicki L; Alvarez, Pedro J

2011-06-01

246

Anaerobic toluene oxidation to benzyl alcohol and benzaldehyde in a denitrifying Pseudomonas strain.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The denitrifying Pseudomonas strain K172 was grown with a generation time of 6 h to a cell density of 0.4 g (dry weight) per liter with toluene and nitrate as substrates. We found that anaerobic cell suspensions oxidize [14C]toluene first to [14C]benzyl alcohol and subsequently to [14C]benzaldehyde. This proves that the methyl group of toluene is oxidized without molecular oxygen to a hydroxymethyl group.

Altenschmidt, U.; Fuchs, G.

1992-01-01

247

Anaerobic activation of toluene and o-xylene by addition to fumarate in denitrifying strain T.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Anaerobic assays conducted with strain T, a denitrifying bacterium capable of mineralizing toluene to carbon dioxide, demonstrated that toluene-grown, permeabilized cells catalyzed the addition of toluene to fumarate to form benzylsuccinate. This reaction was not dependent on the presence of coenzyme A (CoA) or ATP. In the presence of CoA, formation of E-phenylitaconate from benzylsuccinate was also observed. Kinetic studies demonstrated that the specific rate of benzylsuccinate formation fro...

Beller, H. R.; Spormann, A. M.

1997-01-01

248

Substrate induction and metabolite accumulation during anaerobic toluene utilization by the denitrifying strain T1.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The denitrifying strain T1 utilizes toluene anaerobically. We now report that anaerobic toluene degradation is inducible in strain T1. Fluoracetate treatment of cell suspensions inhibited both the rate of toluene metabolism and the formation of the toluene dead-end products benzylsuccinate and benzylfumarate, which is consistent with the pathway proposed by Evans et al. (Appl. Environ. Microbiol. 58:496-501, 1992). In addition, when either nitrate was limiting or fluoroacetate was added, benz...

Frazer, A. C.; Ling, W.; Young, L. Y.

1993-01-01

249

Denitrifying Bacterial Communities Affect Current Production and Nitrous Oxide Accumulation in a Microbial Fuel Cell  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The biocathodic reduction of nitrate in Microbial Fuel Cells (MFCs) is an alternative to remove nitrogen in low carbon to nitrogen wastewater and relies entirely on microbial activity. In this paper the community composition of denitrifiers in the cathode of a MFC is analysed in relation to added electron acceptors (nitrate and nitrite) and organic matter in the cathode. Nitrate reducers and nitrite reducers were highly affected by the operational conditions and displayed high diversity. The ...

Vilar Sanz, Ariadna; Puig Broch, Sebastia?; Garci?a Lledo?, Arantzazu; Trias Mansilla, Rosalia; Balaguer I Condom, Maria Dolors; Colprim Galceran, Jesu?s; Ban?eras Vives, Llui?s

2013-01-01

250

Impact of Flood Spates on Denitrifying Bacteria in Low Order Streams  

Science.gov (United States)

The impact of flood events on channel design, macroinvertebrates, and periphyton in stream ecosystems has been well studied. Little is known, however, about how flood spates affect microorganisms found in stream sediments. Denitrifying bacteria are beneficial organisms because they convert nitrates to nitrogen gas. Providing data that describes the impact of flood events on denitrifiers and the time required after the disturbance for the bacteria to recover are crucial in understanding nitrogen dynamics in stream ecosystems. Three low order streams in central Wisconsin, USA are being monitored during several flood spates during July and August of 2011. Discharge is being continuously monitored in all three streams and sediments are being collected before and after several flood events for laboratory assays. Specifically, sediments are being processed for denitrification rates using the acetylene inhibition technique, microbial biomass carbon using chloroform fumigation, and the quantification of denitrifying bacteria (i.e., nirS, nirK, and nosZ genes) using real-time quantitative PCR. Preliminary data show that within 36 hours after a 90 mm rain event, microbial biomass carbon in all three streams (580 ?g C g sediment-1) significantly increased (F1,23 = 650 ± 140; p < 0.001) compared to microbial biomass during baseflow (200 ± 27 ?g C g sediment-1). These initial results suggest that contrary to our expectations flood events enhance bacteria in stream sediments. Denitrification rates and quantification of denitrifying bacteria still need to be analyzed to determine if these specific bacteria follow a similar pattern or if the bacterial recolonization of stream sediments follows a unique pattern.

Herrman, K.; Stokdyk, J.

2011-12-01

251

Algal exudates and stream organic matter influence the structure and function of denitrifying bacterial communities.  

Science.gov (United States)

Within aquatic ecosystems, periphytic biofilms can be hot spots of denitrification, and previous work has suggested that algal taxa within periphyton can influence the species composition and activity of resident denitrifying bacteria. This study tested the hypothesis that algal species composition within biofilms influences the structure and function of associated denitrifying bacterial communities through the composition of organic exudates. A mixed population of bacteria was incubated with organic carbon isolated from one of seven algal species or from one of two streams that differed in anthropogenic inputs. Pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) revealed differences in the organic composition of algal exudates and stream waters, which, in turn, selected for distinct bacterial communities. Organic carbon source had a significant effect on potential denitrification rates (DNP) of the communities, with organics isolated from a stream with high anthropogenic inputs resulting in a bacterial community with the highest DNP. There was no correlation between DNP and numbers of denitrifiers (based on nirS copy numbers), but there was a strong relationship between the species composition of denitrifier communities (as indicated by tag pyrosequencing of nosZ genes) and DNP. Specifically, the relative abundance of Pseudomonas stutzeri-like nosZ sequences across treatments correlated significantly with DNP, and bacterial communities incubated with organic carbon from the stream with high anthropogenic inputs had the highest relative abundance of P. stutzeri-like nosZ sequences. These results demonstrate a significant relationship between bacterial community composition and function and provide evidence of the potential impacts of anthropogenic inputs on the structure and function of stream microbial communities. PMID:22828897

Kalscheur, Kathryn N; Rojas, Miguel; Peterson, Christopher G; Kelly, John J; Gray, Kimberly A

2012-11-01

252

Horizontal Heterogeneity of Denitrifying Bacterial Communities in Marine Sediments by Terminal Restriction Fragment Length Polymorphism Analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Although it is widely believed that horizontal patchiness exists in microbial sediment communities, determining the extent of variability or the particular members of the bacterial community which account for the observed differences among sites at various scales has not been routinely demonstrated. In this study, horizontal heterogeneity was examined in time and space for denitrifying bacteria in continental shelf sediments off Tuckerton, N.J., at the Rutgers University Long-Term Ecosystem O...

Scala, David J.; Kerkhof, Lee J.

2000-01-01

253

Fate of aniline and sulfanilic acid in UASB bioreactors under denitrifying conditions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Two upflow anaerobic sludge blanket (UASB) reactors were operated to investigate the fate of aromatic amines under denitrifying conditions. The feed consisted of synthetic wastewater containing aniline and/or sulfanilic acid and a mixture of volatile fatty acids (VFA) as the primary electron donors. Reactor 1 (R1) contained a stoichiometric concentration of nitrate and Reactor 2 (R2) a stoichiometric nitrate and nitrite mixture as terminal electron acceptors. The R1 results demonstrated that ...

Pereira, Raquel; Pereira, Luciana; Zee, F. P.; Alves, M. M.

2011-01-01

254

Denitrifying Bacteria Isolated from Terrestrial Subsurface Sediments Exposed to Mixed-Waste Contamination? †  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In terrestrial subsurface environments where nitrate is a critical groundwater contaminant, few cultivated representatives are available to verify the metabolism of organisms that catalyze denitrification. In this study, five species of denitrifying bacteria from three phyla were isolated from subsurface sediments exposed to metal radionuclide and nitrate contamination as part of the U.S. Department of Energy's Oak Ridge Integrated Field Research Challenge (OR-IFRC). Isolates belonged to the ...

Green, Stefan J.; Prakash, Om; Gihring, Thomas M.; Akob, Denise M.; Jasrotia, Puja; Jardine, Philip M.; Watson, David B.; Brown, Steven D.; Palumbo, Anthony V.; Kostka, Joel E.

2010-01-01

255

Novel Denitrifying Bacterium Ochrobactrum anthropi YD50.2 Tolerates High Levels of Reactive Nitrogen Oxides? †  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Most studies of bacterial denitrification have used nitrate (NO3?) as the first electron acceptor, whereas relatively less is understood about nitrite (NO2?) denitrification. We isolated novel bacteria that proliferated in the presence of high levels of NO2? (72 mM). Strain YD50.2, among several isolates, was taxonomically positioned within the ? subclass of Proteobacteria and identified as Ochrobactrum anthropi YD50.2. This strain denitrified NO2?, as well as NO3?. The gene cluste...

Doi, Yuki; Takaya, Naoki; Takizawa, Noboru

2009-01-01

256

Coexistence of nitrifying, anammox and denitrifying bacteria in a sequencing batch reactor  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Elevated nitrogen removal efficiencies from ammonium-rich wastewaters have been demonstrated by several applications, that combine nitritation and anammox processes. Denitrification will occur simultaneously when organic carbon is also present. In this study, the activity of aerobic ammonia oxidizing, anammox and denitrifying bacteria in a full scale sequencing batch reactor, treating digester supernatants, was studied by means of batch-assays. AOB and anammox activities were maximum at pH of...

2014-01-01

257

Localization of the cytochrome cd1 and copper nitrite reductases in denitrifying bacteria.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The locations of cytochrome cd1 nitrite reductases in Pseudomonas aeruginosa and Pseudomonas fluorescens and copper nitrite reductases in Achromobacter cycloclastes and Achromobacter xylosoxidans were identified. Immunogold labeling with colloidal-gold probes showed that the nitrite reductases were synthesized exclusively in anaerobically grown (denitrifying) cells. Little immunogold label occurred in the cytoplasm of these four strains; most was found in the periplasmic space or was associat...

Coyne, M. S.; Arunakumari, A.; Pankratz, H. S.; Tiedje, J. M.

1990-01-01

258

Microbial Community Composition and Denitrifying Enzyme Activities in Salt Marsh Sediments?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Denitrifying microbial communities and denitrification in salt marsh sediments may be affected by many factors, including environmental conditions, nutrient availability, and levels of pollutants. The objective of this study was to examine how microbial community composition and denitrification enzyme activities (DEA) at a California salt marsh with high nutrient loading vary with such factors. Sediments were sampled from three elevations, each with different inundation and vegetation pattern...

2008-01-01

259

Microaerobic and anaerobic metabolism of a Methylocystis parvus strain isolated from a denitrifying bioreactor  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An obligate methanotrophic bacterium, strain MTS, was isolated from a methane-fed microaerobic denitrifying bioreactor. 16S rRNA and DNA–DNA hybridization analysis revealed that this organism was most closely related to Methylocystis parvus, a Type II methanotroph, belonging to the ?-subclass of the Proteobacteria. The metabolism of the bacterium under microaerobic and anaerobic conditions was studied by 13C-NMR. 13C-labelled poly-?-hydroxybutyrate (PHB) formation occurred in cell suspens...

Vecherskaya, M.; Dijkema, C.; Ramirez Saad, H.; Stams, A. J. M.

2009-01-01

260

Anaerobic Metabolism of 3-Hydroxybenzoate by the Denitrifying Bacterium Thauera aromatica  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The anaerobic metabolism of 3-hydroxybenzoate was studied in the denitrifying bacterium Thauera aromatica. Cells grown with this substrate were adapted to grow with benzoate but not with 4-hydroxybenzoate. Vice versa, 4-hydroxybenzoate-grown cells did not utilize 3-hydroxybenzoate. The first step in 3-hydroxybenzoate metabolism is a coenzyme A (CoA) thioester formation, which is catalyzed by an inducible 3-hydroxybenzoate–CoA ligase. The enzyme was purified and characterized. Further metabo...

Laempe, Diana; Jahn, Martina; Breese, Klaus; Scha?gger, Hermann; Fuchs, Georg

2001-01-01

 
 
 
 
261

Genetic Diversity of Benzoyl Coenzyme A Reductase Genes Detected in Denitrifying Isolates and Estuarine Sediment Communities  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Benzoyl coenzyme A (benzoyl-CoA) reductase is a central enzyme in the anaerobic degradation of organic carbon, which utilizes a common intermediate (benzoyl-CoA) in the metabolism of many aromatic compounds. The diversity of benzoyl-CoA reductase genes in denitrifying bacterial isolates capable of degrading aromatic compounds and in river and estuarine sediment samples from the Arthur Kill in New Jersey and the Chesapeake Bay in Maryland was investigated. Degenerate primers were developed fro...

Song, Bongkeun; Ward, Bess B.

2005-01-01

262

Nitrogen Redox Metabolism of a Heterotrophic, Nitrifying-Denitrifying Alcaligenes sp. from Soil  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Metabolic characteristics of a heterotrophic, nitrifier-denitrifier Alcaligenes sp. isolated from soil were further characterized. Pyruvic oxime and hydroxylamine were oxidized to nitrite aerobically by nitrification-adapted cells with specific activities (Vmax) of 0.066 and 0.003 ?mol of N × min?1 × mg of protein?1, respectively, at 22°C. Km values were 15 and 42 ?M for pyruvic oxime and hydroxylamine, respectively. The greater pyruvic oxime oxidation activity relative to hydroxylam...

Castignetti, Domenic; Hollocher, Thomas C.

1982-01-01

263

A Fungal Cytochrome P-450nor Confers Denitrifying Ability to Tobacco By-2 Cells  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Reactive nitrogen gases progressively contribute to the global warming. Development of gas-gas denitrifying plants that can efficiently reduce reactive nitrogen gases to dinitrogen (N2) could help to mitigate the effect of these gases. Taking the advances in gene manipulation technology, tobacco BY-2 cells were transformed with the fungus Cylindrocarpon tonkinense cytochrome P-450nor2 (Cnor2) gene. The product of this gene acts as nitric oxide reductase (nor). Transgenic BY-...

Abdel-banat, Babiker M. A.; Adam, Suaad E. H.; Misa Takahashi; Atsushi Sakamoto; Hirofumi Shoun; Hiromichi Morikawa

2008-01-01

264

Solvent Stress Response of the Denitrifying Bacterium “Aromatoleum aromaticum” Strain EbN1? †  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The denitrifying betaproteobacterium “Aromatoleum aromaticum” strain EbN1 degrades several aromatic compounds, including ethylbenzene, toluene, p-cresol, and phenol, under anoxic conditions. The hydrophobicity of these aromatic solvents determines their toxic properties. Here, we investigated the response of strain EbN1 to aromatic substrates at semi-inhibitory (about 50% growth inhibition) concentrations under two different conditions: first, during anaerobic growth with ethylbenzene (0....

Trautwein, Kathleen; Ku?hner, Simon; Wo?hlbrand, Lars; Halder, Thomas; Kuchta, Kenny; Steinbu?chel, Alexander; Rabus, Ralf

2008-01-01

265

Sediment denitrifier community composition and nirS gene expression investigated with functional gene microarrays  

DEFF Research Database (Denmark)

A functional gene microarray was used to investigate denitrifier community composition and nitrite reductase (nirS) gene expression in sediments along the estuarine gradient in Chesapeake Bay, USA. The nirS oligonucleotide probe set was designed to represent a sequence database containing 539 Chesapeake Bay clones, as well as sequences from many other environments. Greatest nirS diversity was detected at the freshwater station at the head of the bay and least diversity at the higher salinity station near the mouth of the Bay. The most common OTUs from the sequence database were detected on the array with high signal strength in most samples. One of the most abundant OTUs, CB2-S-138, was identified as dominant at the mid-bay site by both microarray and quantitative PCR assays, but it comprised a much smaller fraction of the assemblage in the north and south bay samples. cDNA (transcribed from total RNA extracts) targets were hybridized to the same array to compare the profiles of community composition at the DNA (relative abundance) and mRNA (gene expression) levels. Only the three dominant denitrifying groups (in terms of relative strength of DNA hybridization signal) were detected at the mRNA level. These results suggest that the most actively denitrifying groups are responsible for most nirS expression as well Udgivelsesdato: 2008/11

Francis, C.A.; Jackson, G.A.

2008-01-01

266

Characterizations of denitrifying polyphosphate-accumulating bacterium Paracoccus sp. Strain YKP-9.  

Science.gov (United States)

A denitrifying polyphosphate-accumulating bacterium (YKP-9) was isolated from activated sludge of a 5-stage biological nutrient removal process with step feed system. This organism was a Gram-negative, coccus-shaped, facultative aerobic chemoorganotroph. It had a respiratory type of metabolism with oxygen, nitrate, and nitrite as terminal electron acceptors. The 16S rRNA gene sequence of strain YKP-9 was most similar to the 16S rRNA gene sequence of Paracoccus sp. OL18 (AY312056) (similarity level, 97%). Denitrifying polyphosphate accumulation by strain YKP-9 was examined under anaerobicanoxic and anaerobic-oxic batch conditions. It was able to use external carbon sources for polyhydroxyalkanoates (PHA) synthesis and to release phosphate under anaerobic condition. It accumulated polyphosphate and grew a little on energy provided by external carbon sources under anoxic condition, but did neither accumulate polyphosphate nor grow in the absence of external carbon sources under anoxic condition. Cells with intracellular PHA cannot accumulate polyphosphate in the absence of external carbon sources under anoxic condition. Under oxic condition, it grew but could not accumulate polyphosphate with external carbon sources. Based on the results from this study, strain YKP-9 is a new-type denitrifying polyphosphate-accumulating bacterium that accumulates polyphosphate only under anoxic condition, with nitrate and nitrite as the electron acceptors in the presence of external carbon sources. PMID:19131700

Lee, Han Woong; Park, Yong Keun

2008-12-01

267

Bioavailability and biodegradation of weathered diesel fuel in aquifer material under denitrifying conditions  

International Nuclear Information System (INIS)

During the in situ bioremediation of a diesel fuel-contaminated aquifer in Menziken, Switzerland, aquifer material containing weathered diesel fuel (WDF) and indigenous microorganisms was excavated. This material was used to identify factors limiting WDF biodegradation under denitrifying conditions. Incubations of this material for 360 to 390 d under denitrifying conditions resulted in degradation of 23% of the WDF with concomitant consumption of NO3- and production of inorganic carbon. The biodegradation of WDF and the rate of NO3- consumption was stimulated by agitation of the microcosms. Biodegradation was not stimulated by the addition of a biosurfactant (rhamnolipids) or a synthetic surfactant (Triton X-100) at concentrations above their critical micelle concentrations. The rhamnolipids were biodegraded preferentially to WDF, whereas Triton X-100 was not degraded. Both surfactants reduced the surface tension of the growth medium from 72 to <35 dynes/cm and enhanced the apparent aqueous solubility of the model hydrocarbon n-hexadecane by four orders of magnitude. Solvent-extracted WDF, added at a concentration equal to that already present in the aquifer material, was also biodegraded by the microcosms, but not at a higher rate than the WDF already present in the material. The results show that the denitrifying biodegradation of WDF is not necessarily limited by bioavailability but rather by the inherent recalcitrance of WDF

1998-07-01

268

Tropomyosin-enriched and alpha-actinin-enriched microfilaments isolated from chicken embryo fibroblasts by monoclonal antibodies  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Antitropomyosin and anti-alpha-actinin monoclonal antibodies have been used to isolate two classes of microfilaments, i.e., tropomyosin- enriched and alpha-actinin-enriched microfilaments, respectively, from cultured chicken embryo fibroblasts. Electron microscopic studies of the isolated tropomyosin-enriched microfilaments showed periodic localization of tropomyosin along the microfilaments, with a 35-nm repeat. On the contrary, the isolated alpha-actinin-enriched microfilaments showed no ob...

1984-01-01

269

Primers for overlooked nirK, qnorB, and nosZ genes of thermophilic Gram-positive denitrifiers.  

Science.gov (United States)

Although efforts have been made the past few years, knowledge on genomic and phenotypic diversity and occurrence of the denitrification ability in Gram-positive bacteria are still fragmentary. Many environmental monitoring approaches have used nir, nor, and nos genes as marker genes for detection of denitrification or denitrifying bacteria. However, primers used in these methods often fail to detect the genes in specific bacterial taxa, such as Gram-positive denitrifiers. In this study, novel primer sets specifically targeting nirK, qnorB, and nosZ genes of the Firmicute genus Geobacillus were developed by genomic mining and tested in parallel with commonly used primers on a set of phylogenetically closely related denitrifying geobacilli. Novel nirK and qnorB sequences were recovered from all strains tested, whereas nosZ was detected in part of the strain set, which was in agreement with observed phenotypes. Interspecies and modest intraspecies variations in amplified fragment length polymorphism (AFLP) patterns were observed, verifying presence of genomic variation within the strain set. Our study shows that closely related Gram-positive denitrifiers may differ in denitrification phenotype and genotype. But foremost, novel primers targeting very divergent nirK, qnorB, and nosZ gene sequences of Gram-positive denitrifiers, are now available for cultivation-independent environmental surveys. PMID:24784780

Verbaendert, Ines; Hoefman, Sven; Boeckx, Pascal; Boon, Nico; De Vos, Paul

2014-07-01

270

Effect of nitrogen and waterlogging on denitrifier gene abundance, community structure and activity in the rhizosphere of wheat.  

Science.gov (United States)

Microbial denitrification plays a key role in determining the availability of soil nitrogen (N) to plants. However, factors influencing the structure and function of denitrifier communities in the rhizosphere remain unclear. Waterlogging can result in root anoxia and increased denitrification, leading to significant N loss from soil and potential nitrous oxide (N(2)O) emissions. This study investigated denitrifier gene abundance, community structure and activity in the rhizosphere of wheat in response to anoxia and N limitation. Denitrifier community structure in the rhizosphere differed from that in bulk soil, and denitrifier gene copy numbers (nirS, nirK, nosZ) and potential denitrification activity were greater in the rhizosphere. Anoxia and N limitation, and in particular a combination of both, reduced the magnitude of this effect on gene abundance (in particular nirS) and activity, with N limitation having greater impact than waterlogging in rhizosphere soil, in contrast to bulk soil where the impact of waterlogging was greater. Increased N supply to anoxic plants improved plant health and increased rhizosphere soil pH, which resulted in enhanced reduction of N(2)O. Both anoxia and N limitation significantly influenced the structure and function of denitrifier communities in the rhizosphere, with reduced root-derived carbon postulated to play an important role. PMID:23006139

Hamonts, Kelly; Clough, Tim J; Stewart, Alison; Clinton, Peter W; Richardson, Alan E; Wakelin, Steven A; O'Callaghan, Maureen; Condron, Leo M

2013-03-01

271

High-efficient nitrogen removal by coupling enriched autotrophic-nitrification and aerobic-denitrification consortiums at cold temperature.  

Science.gov (United States)

This study paid particular attention to total nitrogen removal at low temperature (10°C) by excellent coupling of enriched autotrophic nitrifying and heterotrophic denitrifying consortiums at sole aerobic condition. The maximum specific nitrifying rate of the nitrifying consortium reached 8.85mgN/(gSSh). Further test in four identical lab-scale sequencing batch reactors demonstrated its excellent performance for bioaugmentation in potential applications. On the other hand, the aerobic denitrifying consortium could achieve a specific denitrifying rate of 32.93mgN/(gSSh) under dissolved oxygen of 1.0-1.5mg/L at 10°C. Coupling both kinds of consortiums was proved very successful for a perfect total nitrogen (TN) removal at COD/N of 4 and dissolved oxygen of 1.5-4.5mg/L, which was hardly reached by any single consortium reported previously. The encouraging results from coupling aerobic consortiums implied a huge potential in practical treatment of low-strength domestic wastewater (200-300mg/L COD) during wintertime. PMID:24717321

Zou, Shiqiang; Yao, Shuo; Ni, Jinren

2014-06-01

272

Characteristics of self-alkalization in high-rate denitrifying automatic circulation (DAC) reactor fed with methanol and sodium acetate.  

Science.gov (United States)

Denitrification is a self-alkalization process. In this experiment, the characteristics of self-alkalization in high-rate heterotrophic denitrifying automatic circulation (DAC) reactor fed with methanol and sodium acetate were investigated, respectively. The results showed that, (1) The self-alkalization of high-rate denitrifying reactors was remarkably strong both with methanol and sodium acetate as carbon sources, while the effluent pH was much lower than the stoichiometric values and the malfunction from self-alkalization of denitrification was far less serious than expected. (2) The self-adaptation of the reactors was attributed to the neutralization of carbon dioxide (oxidization product of organic matter) and the self-adaptation of denitrifying sludge. The formation and discharge of calcium carbonate precipitates gave rise to lower effluent pH and alkalinity than the stoichiometric values. PMID:24380825

Li, Wei; Zheng, Ping; Guo, Jun; Ji, Junyuan; Zhang, Meng; Zhang, Zonghe; Zhan, Enchao; Abbas, Ghulam

2014-02-01

273

Uranium Enrichment, an overview  

International Nuclear Information System (INIS)

This general presentation on uranium enrichment will be followed by lectures on more specific topics including descriptions of enrichment processes and assessments of the prevailing commercial and industrial situations. I shall therefore avoid as much as possible duplications with these other lectures, and rather dwell on: some theoretical aspects of enrichment in general, underlying the differences between statistical and selective processes, a review and comparison between enrichment processes, remarks of general order regarding applications, the proliferation potential of enrichment. It is noteworthy that enrichment: may occur twice in the LWR fuel cycle: first by enriching natural uranium, second by reenriching uranium recovered from reprocessing, must meet LWR requirements, and in particular higher assays required by high burn up fuel elements, bears on the structure of the entire front part of the fuel cycle, namely in the conversion/reconversion steps only involving UF_6 for the moment. (author). tabs., figs., 4 refs

1994-02-07

274

Biotransformation of BTEX under anaerobic, denitrifying conditions: Field and laboratory observations  

Science.gov (United States)

Three natural-gradient injection experiments in the Borden aquifer (Ontario, Canada) (˜ 100-300 days in duration) and a 452-day laboratory microcosm experiment were performed to evaluate the biotransformation of BTEX (benzene, toluene, ethylbenzene and o-, m-, p-xylenes) derived from gasoline under anaerobic, denitrifying conditions. Both NO 3-- amended and unamended control (i.e. no NO 3- added) experiments were performed. In the unamended control injection experiment, toluene biotransformed between 1 and 5 m from the injection well. All other aromatic compounds were recalcitrant in this field experiment and all aromatic compounds were recalcitrant in unamended control microcosms. After an acclimatization period, toluene biotransformed relatively rapidly in the presence of NO 3- in both the laboratory and field to a residual level of ˜ 100 ?g L -1. In the presence of NO 3- the xylene isomers and ethylbenzene biotransformed to a lesser degree. Benzene was recalcitrant in all experiments. The acetylene blockage technique was used to demonstrate that denitrifying bacteria were active in the presence of NO 3-. In the NO 3--amended injection experiments, little BTEX mass loss occurred beyond the 1-m multilevel-piezometer fence. However, NO 3- continued to decline downgradient, suggesting that other sources of carbon were being utilized by denitrifying bacteria in preference to residual BTEX. In addition to observations on mass loss, these experiments provided evidence of inhibition of BTEX biotransformation in the presence of acetylene, and competitive utilization between toluene, ethylbenzene and the xylene isomers. Given the recalcitrance of benzene and high thresholds of the compounds that did biotransform, the addition of NO 3- as an alternate electron acceptor would not be successful in this aquifer as a remedial measure.

Barbaro, J. R.; Barker, J. F.; Lemon, L. A.; Mayfield, C. I.

1992-11-01

275

Association of Novel and Highly Diverse Acid-Tolerant Denitrifiers with N2O Fluxes of an Acidic Fen? †  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Wetlands are sources of denitrification-derived nitrous oxide (N2O). Thus, the denitrifier community of an N2O-emitting fen (pH 4.7 to 5.2) was investigated. N2O was produced and consumed to subatmospheric concentrations in unsupplemented anoxic soil microcosms. Total cell counts and most probable numbers of denitrifiers approximated 1011 cells·gDW?1 (where DW is dry weight) and 108 cells·gDW?1, respectively, in both 0- to 10-cm and 30- to 40-cm depths. Despite this uniformity, depth-re...

Palmer, Katharina; Drake, Harold L.; Horn, Marcus A.

2010-01-01

276

Inhibition by sulfide of nitric and nitrous oxide reduction by denitrifying Pseudomonas fluorescens.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The influence of low redox potentials and H2S on NO and N2O reduction by resting cells of denitrifying Pseudomonas fluorescens was studied. Hydrogen sulfide and Ti(III) were added to achieve redox potentials near -200 mV. The control without reductant had a redox potential near +200 mV. Production of 13NO, [13N]N2O, and [13N]N2 from 13NO3- and 13NO2- was followed. Total gas production was similar for all three treatments. The accumulation of 13NO was most significant in the presence of sulfid...

1980-01-01

277

Activity and Composition of the Denitrifying Bacterial Community Respond Differently to Long-Term Fertilization  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The objective of this study was to explore the long-term effects of different organic and inorganic fertilizers on activity and composition of the denitrifying and total bacterial communities in arable soil. Soil from the following six treatments was analyzed in an experimental field site established in 1956: cattle manure, sewage sludge, Ca(NO3)2, (NH4)2SO4, and unfertilized and unfertilized bare fallow. All plots but the fallow were planted with corn. The activity was measured in terms of p...

Enwall, Karin; Philippot, Laurent; Hallin, Sara

2005-01-01

278

Concurrent activity of anammox and denitrifying bacteria in the Black Sea  

Digital Repository Infrastructure Vision for European Research (DRIVER)

After the discovery of ANaerobic AMMonium OXidation (anammox) in the environment, the role of heterotrophic denitrification as the main marine pathway for fixed N loss has been questioned. A 3 part, 15 month time series investigating nitrite reductase (nirS) mRNA transcripts at a single location in the Black Sea was conducted in order to better understand the activity of anammox and denitrifying bacteria. Here we show that both of these groups were active, as well as being concurrent in the l...

2012-01-01

279

Quantity-activity relationship of denitrifying bacteria and environmental scaling in streams of a forested watershed  

Science.gov (United States)

The spatial variability of subreach denitrification rates in streams was evaluated with respect to controlling environmental conditions, molecular examination of denitrifying bacteria, and dimensional analysis. Denitrification activities ranged from 0 and 800 ng-N gsed-1 d-1 with large variations observed within short distances (dissolved oxygen flux. Buckingham's pi theorem was used to generate dimensionless groupings and field data were used to determine scaling parameters. The resulting expressions between dimensionless NO3- flux and dimensionless groupings of environmental variables showed consistent scaling, which indicates that the subreach variability in denitrification rates can be predicted by the controlling physical, chemical, and microbiological conditions.

O'Connor, Ben L.; Hondzo, Miki; Dobraca, Dina; Lapara, Timothy M.; Finlay, Jacques C.; Brezonik, Patrick L.

2006-12-01

280

Pseudomonas yangmingensis sp. nov., an alkaliphilic denitrifying species isolated from a hot spring.  

Science.gov (United States)

This study isolated and identified a facultative, alkaliphilic, denitrifying Pseudomonas strain designed as CRS1 from a hot spring, Yang-Ming Mountain, Taiwan. The biochemical characterization, phenotypic characteristics and phylogenetic relationship of strain CRS1 were studied. On the basis of the 16S rRNA sequence similarity, phenotypic and genotypic characteristics and chemotaxonomic data, the strain CRS1 represents a novel species of the genus Pseudomonas, for which the name Pseudomonas yangmingensis sp. nov., is proposed. The strain CRS1 is a facultative autotrophic bacterium that has capability of mixotrophic and heterotrophic denitrification. PMID:23849745

Wong, Biing-Teo; Lee, Duu-Jong

2014-01-01

 
 
 
 
281

Advanced enrichment techniques  

International Nuclear Information System (INIS)

BNFL is in a unique position in that it has commercial experience of diffusion enrichment, and of centrifuge enrichment through its associate company Urenco. In addition BNFL is developing laser enrichment techniques as part of a UK development programme in this area. The paper describes the development programme which led to the introduction of competitive centrifuge enrichment technology by Urenco and discusses the areas where improvements have and will continue to be made in the centrifuge process. It also describes the laser development programme currently being undertaken in the UK. The paper concludes by discussing the relative merits of the various methods of uranium enrichment, with particular reference to the enrichment market likely to obtain over the rest of the century. (author)

1987-09-07

282

Advanced enrichment techniques  

International Nuclear Information System (INIS)

BNFL is in a unique position in that it has commercial experience of diffusion enrichment, and of centrifuge enrichment through its associate company Urenco. In addition BNFL is developing laser enrichment techniques as part of a UK development programme in this area. The paper describes the development programme which led to the introduction of competitive centrifuge enrichment technology by Urenco and discusses the areas where improvements have and will continue to be made in the centrifuge process. It also describes the laser development programme currently being undertaken in the UK. The paper concludes by discussing the relative merits of the various methods of uranium enrichment, with particular reference to the enrichment market likely to obtain over the rest of the century

1987-09-07

283

Molecular approaches to understand the regulation of N2O emission from denitrifying bacteria - model strains and soil communities (Invited)  

Science.gov (United States)

Emissions of N2O from agricultural soils are largely caused by denitrifying bacteria. Field measurements of N2O fluxes show large variations and depend on several environmental factors, and possibly also on the composition of the denitrifying microbial community. The temporal and spatial variation of fluxes are not adequately captured by biogeochemical models, and few options for mitigations have been invented, which underscores the need to understand the mechanisms underlying the emissions of N2O. Analyses of denitrification genes and transcripts extracted from soils are important for describing the system, but may have limited value for prediction of N2O emissions. In contrast, phenotypic analyses are direct measures of the organisms’ responses to changing environmental conditions. Our approach is to combine phenotypic characterizations using high-resolution gas kinetics, with gene transcription analyses to study denitrification regulatory phenotypes (DRP) of bacterial strains or complex microbial communities. The rich data sets obtained provide a basis for refinement of biochemical and physiological research on this key process in the nitrogen cycle. The strength of this combined approach is illustrated by a series of experiments investigating effects of soil pH on denitrification. Soil pH emerges as a master variable determining the microbial community composition as well as its denitrification product ratio (N2O/N2), with higher ratio in acid than in alkaline soil. It is therefore likely that emissions of N2O from agro-ecosystems will increase in large parts of the world where soil pH is decreasing due to intensified management and increased use of chemical fertilizers. Considering its immense implications, surprisingly few attempts have been made to unravel the mechanisms involved in the pH-control of the product stoichiometry of denitrification. We investigated the kinetics of gas transformations (O2, NO, N2O and N2) and transcription of functional genes in intact soil samples from long-term liming experiments. Expression of nirS (encoding nitrite reductase) and nosZ (encoding N2OR) was generally lower at pH6 compared to pH8, but the nosZ/nirS transcript ratios were similar or even higher at pH6. These results were largely corroborated in refined experiments using extracted bacterial communities from the same soils, which allowed us to better control the pH levels experienced by the cells. The findings indicated that the higher N2O/N2 product ratios at pH6 were due to a post-transcriptional effect. Pure culture experiments using Paracoccus denitrificans demonstrated very low N2O/N2 ratios at pH7 while N2O reduction was severely inhibited by suboptimal pH, and that this inhibition occurred during protein synthesis/assembly rather than at the transcription level. The results are important for the understanding of main factors affecting N2O emissions from terrestrial ecosystems.

Frostegard, A.; Bakken, L. R.

2010-12-01

284

Alternative isotope enrichment processes  

Energy Technology Data Exchange (ETDEWEB)

Alternative processes such as gas centrifugation, plasma separation, and laser excited separation are evaluated for use at the ORNL Stable Isotope Enrichment Facility. The applicabiliy of each process to the isotopic enrichment of the calutron feed material and to the selective production of isotopes is determined. The process energy demands are compared to those of the existing facilities. The isotopic enrichment of the feed material prior to a first-pass through the calutrons can result in a significant saving in energy.

Terry, J.W.

1983-01-01

285

Sensitive detection of a novel class of toluene-degrading denitrifiers, Azoarcus tolulyticus, with small-subunit rRNA primers and probes.  

Science.gov (United States)

Azoarcus tolulyticus is a new class of widely distributed toluene-degrading denitrifiers of potential importance in remediating benzene, toluene, ethylbenzene, and xylene (BTEX)-contaminated environments. To detect these organisms in the environment, 16S rRNA gene-based phylogenetic probes were developed. Two sets of specific PCR amplification primers and two oligonucleotide hybridization probes were designed and tested against both closely and distantly related environmental isolates. All of these primers and probes were specific to the species A. tolulyticus. The sensitivity of the PCR amplification primer sets was evaluated with DNA isolated from A. tolulyticus Tol-4 pure culture and from sterile soils seeded with a known number of Tol-4 and Escherichia coli cells. These primer sets were able to detect 1 fg to 1 pg of template DNA from the pure culture and 1.11 x 10(2) to 1.1 x 10(8) Tol-4 cells per g of soil in the presence of 1.56 x 10(10) E. coli cells. These two PCR amplification primers were also successfully tested at two field sites. The primers identified the A. tolulyticus strains among the toluene-degrading bacteria isolated from a low-O2-high-NO(3)- aquifer at Moffett Field, Calif. Also, the presence of A. tolulyticus was detected in the groundwater samples from a BTEX-contaminated aquifer at an industrial site in Detroit, Mich., which showed anaerobic toluene degradation. PMID:9172359

Zhou, J; Palumbo, A V; Tiedje, J M

1997-06-01

286

Uranium enrichment and conversion  

International Nuclear Information System (INIS)

This report mainly refers to uranium enrichment. Following points are dealt with: The present situation on the world market for separation activities; Decision of DOE regarding the future enrichment techniques in the USA; Start-up of the new enrichment plant of URENCO DEUTSCHLAND in Gronau; Successes of the Urenco-centrifuge techniques; Present level of laser enrichment from the standpoint of Uranit. This is followed by a brief survey of the market for conversion. The conversion of uranium recovered from the reprocessing of LWR-fuel is dealt with more closely. (orig./UA)

1986-02-01

287

Digital enrichment monitor  

International Nuclear Information System (INIS)

A nondestructive method of measuring the enrichment of uranium bearing materials via 186 keV gamma rays from 235U is described. The monitoring system consists of a NaI scintillation detector, preamplifier, amplifier, channel-analyser and scaler-timer units. The system is operational at the Nuclear Fuel Complex, Hyderabad, and is used as a quality control tool to monitor enrichment of fuel pellets in fuel rods before making fuel bundles. The enrichment of the rods presently being monitored are 1.6, 2.1 and 2.66. The monitor system can also be used for freshly enriched UF6 and recycled uranium. (A.K.)

1976-12-23

288

Identification of active denitrifiers in rice paddy soil by DNA- and RNA-based analyses.  

Science.gov (United States)

Denitrification occurs markedly in rice paddy fields; however, few microbes that are actively involved in denitrification in these environments have been identified. In this study, we used a laboratory soil microcosm system in which denitrification activity was enhanced. DNA and RNA were extracted from soil at six time points after enhancing denitrification activity, and quantitative PCR and clone library analyses were performed targeting the 16S rRNA gene and denitrification functional genes (nirS, nirK and nosZ) to clarify which microbes are actively involved in denitrification in rice paddy soil. Based on the quantitative PCR results, transcription levels of the functional genes agreed with the denitrification activity, although gene abundance did not change at the DNA level. Diverse denitrifiers were detected in clone library analysis, but comparative analysis suggested that only some of the putative denitrifiers, especially those belonging to the orders Neisseriales, Rhodocyclales and Burkholderiales, were actively involved in denitrification in rice paddy soil. PMID:22972387

Yoshida, Megumi; Ishii, Satoshi; Fujii, Daichi; Otsuka, Shigeto; Senoo, Keishi

2012-01-01

289

Evaluation of the microbial diversity of denitrifying bacteria in batch reactor  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Microbial communities in an industrial activated sludge plant may contribute to the denitrification process, but the information on the microorganisms present in denitrifying reactors is still scarce. Removal of inorganic nitrogen compounds can be accomplished by the addition of carbon sources to th [...] e biological process of denitrification. Ethanol is an economically viable alternative as a carbon source in tropical countries like Brazil, with large-scale production from sugarcane. This paper reports the successful aplication of activated sludge with nitrate and ethanol in a batch anaerobic reactor. The operation lasted 61.5 h with total consumption of nitrate in 42.5 h, nitrite generation (2.0 mg/L) and ethanol consumption (830.0 mg/L) in 23.5 h. Denitrifying cell counts by the most probable number at the start of the operation were lower than at the end, confirming the ability of the inoculum from activated sludge for the denitrification process. The samples from cell counts were identified as Acidovorax sp., Acinetobacter sp., Comamonas sp. and uncultured bacteria. Therefore, these species may be involved in nitrate reduction and ethanol consumption in the batch reactor.

Maintinguer, S. I.; Sakamoto, I. K.; Adorno, M. A. T.; Varesche, M. B. A..

290

Many forms of culture.  

Science.gov (United States)

Psychologists interested in culture have focused primarily on East-West differences in individualism-collectivism, or independent-interdependent self-construal. As important as this dimension is, there are many other forms of culture with many dimensions of cultural variability. Selecting from among the many understudied cultures in psychology, the author considers three kinds of cultures: religion, socioeconomic status, and region within a country. These cultures vary in a number of psychologically interesting ways. By studying more types of culture, psychologists stand to enrich how they define culture, how they think about universality and cultural specificity, their views of multiculturalism, how they do research on culture, and what dimensions of culture they study. Broadening the study of culture will have far-reaching implications for clinical issues, intergroup relations, and applied domains. PMID:19348520

Cohen, Adam B

2009-04-01

291

Actinobacterial nitrate reducers and proteobacterial denitrifiers are abundant in N2O-metabolizing palsa peat.  

Science.gov (United States)

Palsa peats are characterized by elevated, circular frost heaves (peat soil on top of a permanently frozen ice lens) and are strong to moderate sources or even temporary sinks for the greenhouse gas nitrous oxide (N(2)O). Palsa peats are predicted to react sensitively to global warming. The acidic palsa peat Skalluvaara (approximate pH 4.4) is located in the discontinuous permafrost zone in northwestern Finnish Lapland. In situ N(2)O fluxes were spatially variable, ranging from 0.01 to -0.02 ?mol of N(2)O m(-2) h(-1). Fertilization with nitrate stimulated in situ N(2)O emissions and N(2)O production in anoxic microcosms without apparent delay. N(2)O was subsequently consumed in microcosms. Maximal reaction velocities (v(max)) of nitrate-dependent denitrification approximated 3 and 1 nmol of N(2)O per h per gram (dry weight [g(DW)]) in soil from 0 to 20 cm and below 20 cm of depth, respectively. v(max) values of nitrite-dependent denitrification were 2- to 5-fold higher than the v(max) nitrate-dependent denitrification, and v(max) of N(2)O consumption was 1- to 6-fold higher than that of nitrite-dependent denitrification, highlighting a high N(2)O consumption potential. Up to 12 species-level operational taxonomic units (OTUs) of narG, nirK and nirS, and nosZ were retrieved. Detected OTUs suggested the presence of diverse uncultured soil denitrifiers and dissimilatory nitrate reducers, hitherto undetected species, as well as Actino-, Alpha-, and Betaproteobacteria. Copy numbers of nirS always outnumbered those of nirK by 2 orders of magnitude. Copy numbers of nirS tended to be higher, while copy numbers of narG and nosZ tended to be lower in 0- to 20-cm soil than in soil below 20 cm. The collective data suggest that (i) the source and sink functions of palsa peat soils for N(2)O are associated with denitrification, (ii) actinobacterial nitrate reducers and nirS-type and nosZ-harboring proteobacterial denitrifiers are important players, and (iii) acidic soils like palsa peats represent reservoirs of diverse acid-tolerant denitrifiers associated with N(2)O fluxes. PMID:22660709

Palmer, Katharina; Horn, Marcus A

2012-08-01

292

Long-term effect of temperature on N2O emission from the denitrifying activated sludge.  

Science.gov (United States)

The long-term effect of various temperature (4°C, 12°C, 20°C, 25°C and 34°C) on nitrous oxide (N2O) emission from lab-scale denitrifying activated sludge was studied in terms of activation energy, abundance of functional gene nosZ and its transcription. Results showed that temperature had a positive effect on N2O emissions as well as the maximum biomass-specific reduction rates of N2O and NO3(-), ranging from 0.006% to 0.681% of (N2O + N2), 17.3-116.2 and 5.2-66.2 mg N g(-1) VSS h(-1), respectively. The activation energies (Ea) for N2O and NO3(-) reduction of 44.1 kJ mol(-1) and 54.9 kJ mol(-1), shed light on differences in denitrifying rate variation. The maximum NO3(-) reduction rates were more sensitive to temperature variation than the corresponding N2O reduction rates under long-term acclimation. As a result, the ratio between N2O and NO3(-) reduction rates declined to 1.87 at 34°C from 3.31 at 4°C, suggesting great potential capacity for N2O losses at high temperature. The copy numbers of denitrifiers as nosZ gene (×10(8) copies mL(-1)) and total bacteria as 16S rRNA gene (×10(10) copies mL(-1)) did not show obvious relationship with temperature, having relative abundance of 0.42% on average. The transcriptional regulation of nosZ gene, in the range of 10(8)-10(5) copies mL(-1), was affected by reductase activity, substrate concentration as well as its duration. The active nosZ gene expression was accompanied with low reductase capacity, high dissolved N2O and the duration of N2O accumulation. These results provide insights into activation energy and gene expression responsible for N2O emission. PMID:24480748

Wang, Xiaojun; Yang, Xiaoru; Zhang, Zhaoji; Ye, Xin; Kao, Chih Ming; Chen, Shaohua

2014-03-01

293

Developments in uranium enrichment  

International Nuclear Information System (INIS)

The enrichment services market is still characterized by overcapacities. While consumption worldwide will rise by some 15% to 39,000 t SWU/a over the next ten years, capacities amount to nearly 50,000 t SWU/a. The price for enrichment services probably has reached its all time low. Prices below U.S. $ 100/kg SWU are not likely to cover costs even of the economically most advanced enrichment processes. Urenco has prepared for the difficult enrichment business in the years to come by streamlining and cost cutting measures. The company intends to hold and increase its share of more than 10% in the world market. The uranium enrichment plant of Gronau will be expanded further. Expansion beyond 1000 t is subject to another permit being granted under the Atomic Energy Act, an application for which was filed in December 1994. Centrifuge technology is the superior enrichment technology, i.e., there is still considerable potential for further development. Construction of enrichment plants employing the centrifuge technology in the United States and in France is being pursued in various phases, from feasibility studies to licensing procedures. Before these plants could be implemented, however, considerable problems of organization would have to be solved, and the market would have to change greatly, respectively. The laser process, at the present time, does not seem to be able to develop into a major industrial competitor. (orig.)

294

TRIGA low enrichment fuel  

International Nuclear Information System (INIS)

Sixty TRIGA reactors have been sold and the earliest of these are now passing twenty years of operation. All of these reactors use the uranium-zirconium hydride fuel (UZrH) which provides certain unique advantages arising out of its large prompt negative temperature coefficient, very low fission product release, and high temperature capability. Eleven of these Sixty reactors are conversions from plate fuel to TRIGA fuel which were made as a result of these advantages. With only a few exceptions, TRIGA reactors have always used low-enriched-uranium (LEU) fuel with an enrichment of 19.9%. The exceptions have either been converted from the standard low-enriched fuel to the 70% enriched FLIP fuel in order to achieve extended lifetime, or are higher powered reactors which were designed for long life using 93%-enriched uranium during the time when the use and export of highly enriched uranium (HEU) was not restricted. The advent of international policies focusing attention on nonproliferation and safeguards made the HEU fuels obsolete. General Atomic immediately undertook a development effort (nearly two years ago) in order to be in a position to comply with these policies for all future export sales and also to provide a low-enriched alternative to fully enriched plate-type fuels. This important work was subsequently partially supported by the U.S. Department of Energy. The laboratory and production tests have shown that higher uranium densities can be achieved to compensate for reducing the enrichment to 20%, and that the fuels maintain the characteristics of the very thoroughly proven standard TRIGA fuels. In May of 1978, General Atomic announced that these fuels were available for TRIGA reactors and for plate-type reactors with power levels up to 15 MW with GA's standard commercial warranty

1993-08-01

295

TRIGA low enrichment fuel  

International Nuclear Information System (INIS)

Sixty TRIGA reactors have been sold and the earliest of these are now passing twenty years of operation. All of these reactors use the uranium zirconium hydride fuel (UZrH) which provides certain unique advantages arising out of its large prompt negative temperature coefficient, very low fission product release, and high temperature capability. Eleven of these Sixty reactors are conversions from plate fuel to TRIGA fuel which were made as a result of these advantages. With only a few exceptions, TRIGA reactors have always used low-enriched uranium (LEU) fuel with an enrichment of 19.9%. The exceptions have either been converted from the standard low-enriched fuel to the 70% enriched FLIP fuel in order to achieve extended lifetime, or are higher powered reactors which were designed for long life using 93%-enriched uranium during the time when the use and export of highly enriched uranium (HEU) was not restricted. The advent of international policies focusing attention on nonproliferation and safeguards made the HEU fuels obsolete. General Atomic immediately undertook a development effort (nearly two years ago) in order to be in a position to comply with these policies for all future export sales and also to provide a low-enriched alternative to fully enriched plate-type fuels. This important work was subsequently partially supported by the U.S. Department of Energy. The laboratory and production tests have shown that higher uranium densities can be achieved to compensate for reducing the enrichment to 20%, and that the fuels maintain the characteristics of the very thoroughly proven standard TRIGA fuels. In May of 1978, General Atomic announced that these fuels were available for TRIGA reactors and for plate-type reactors with power levels up to 15 MW with General Atomic's standard commercial warranty

1993-08-01

296

Denitrifying sulfide removal and nitrososulfide complex: Azoarcus sp. NSC3 and Pseudomonas sp. CRS1 mix.  

Science.gov (United States)

Denitrifying sulfide removal (DSR) process simultaneously removes nitrate, sulfide and organic matters in the same reactor. This study applied Azoarcus sp. NSC3 and Pseudomonas sp. CRS1 mix for DSR tests in autotrophic, heterotrophic and mixotrophic growths. Negligible NO-compounds were noted in heterotrophic or mixotrophic growths, while most cells were damaged and bound with NO-compounds in autotrophic growth. Nitroprusside (SNP) ions were applied as model compound to reveal the formation of nitrososulfide complex (RSNO) by nitroso (NO(+)) and excess sulfide (S(2-)), rather than the previously proposed mechanism by direct reaction between nitric oxide (NO) and S(2-). We speculated that RSNO was then abiotically decomposed to NO and elemental sulfur in the presence of biological cells. A revised nitrogen cycle considering interactions with sulfur compounds was proposed. We also speculated that SNO and NO were inhibitory to the functional strains, whose efficient removals were essential to reach high-rate DSR performance. PMID:24929301

Lee, Duu-Jong; Wong, Biing-Teo

2014-08-01

297

Tolerance of an aerobic denitrifier (Pseudomonas stutzeri) to high O2 concentrations.  

Science.gov (United States)

An aerobic denitrifier was isolated from activated sludge and the isolate possessed an average removal rate of 5.7 mg NO3 (-)-N l(-1) h(-1) without accumulation of NO2 (-)-N (less than 2.1 mg l(-1)). The average removal efficiency of nitrate was 93.7 % in 24 h, when the dissolved oxygen (DO) concentrations ranged from 3.2 to 17.5 mg l(-1). The activity of both nap (periplasmic nitrate reductase) and nir (nitrite reductase), whose corresponding genes (napA and nirS) were amplified by touchdown PCR, could be responsible for the tolerance of DO concentrations. Other three genes relating to narG, norB and nosZ were noted to involve in isolate strain. PMID:24347061

Ji, Bin; Wang, Hongyu; Yang, Kai

2014-04-01

298

Anaerobic metabolism of phthalate and other aromatic compounds by a denitrifying bacterium. [Pseudomonas sp  

Energy Technology Data Exchange (ETDEWEB)

The anaerobic metabolism of phthalate and other aromatic compounds by the denitrifying bacterium Pseudomonas sp. strain P136 was studied. Benzoate, cyclohex-1-ene-carboxylate, 2-hydroxycyclohexanecarboxylate, and pimelate were detected as predominant metabolic intermediates during the metabolism of three isomers of phthalate, m-hydroxybenzoate, p-hydroxybenzoate, and cyclohex-3-ene-carboxylate. Inducible acyl-coeznyme A synthetase activities for phthalates, benzoate, cyclohex-1-ene-carboxylate, and cyclohex-3-ene-carboxylate were detected in the cells grown on aromatic compounds. Simultaneous adaptation to these aromatic compounds also occurred. A similar phenomenon was observed in the aerobic metabolism of aromatic compounds by this strain. A new pathway for the anaerobic metabolism of phthalate and a series of other aromatic compounds by this strain was proposed. Some properties of the regulation of this pathway were also discussed.

Nozawa, T.; Maruyama, Y. (Univ. of Tokyo (Japan))

1988-12-01

299

Characterization of denitrifying polyphosphate-accumulating organisms in activated sludge based on nitrite reductase gene.  

Science.gov (United States)

Nitrite reductase gene (nirS) fragments in the activated sludge obtained from a sequencing batch reactor (SBR) under anaerobic-aerobic condition were cloned and classified by restriction fragment length polymorphism (RFLP) analysis, and representative fragments were sequenced. One of the nirS clones was approximately 70% of all nirS clones in anaerobic/aerobic (existing oxygen and nitrate) cycle operation in which a large amount of anoxic phosphate uptake was observed. Although the activated sludge samples analyzed might contain bacteria that did not accumulate polyphosphate, it was likely that this nirS fragment sequence was that from denitrifying polyphosphate-accumulating organisms (DNPAOs) which can utilize both oxygen and nitrate as electron acceptors. The sequence was similar to the nirS sequences of Thauera mechernichensis (83% similarity) and Azoarcus tolulyticus (83% similarity) both of which belong to the Rhodocyclus group. PMID:16233809

Tsuneda, Satoshi; Miyauchi, Ryuki; Ohno, Takashi; Hirata, Akira

2005-04-01

300

Floatation of granular sludge and its mechanism: a key approach for high-rate denitrifying reactor.  

Science.gov (United States)

A high-rate denitrifying automatic circulate (DAC) reactor has been developed recently, and it is promising to become an alternative in nitrogen removal from wastewaters. However, the performance of DAC reactor was disturbed by the floatation of granular sludge at high-loads. The results showed that: the floatation of granular sludge led to a serious biomass washout and a sharp decrease of biomass concentration. The floatation of granular sludge was ascribed to a low sludge density originated from the holdup of gaseous products. The average density and average gas holdup ratio of floated granular sludge were 913 kg m(-3) and 11.8% (by volume), respectively. The floatation of granular sludge could disappear by releasing gas when sludge was in the state of elastic expansion, but it would become worse by holding gas when it entered the plastic expansion state. The plastic expansion of granules was significantly correlated with the less content of extracellular polymeric substances. PMID:24316483

Li, Wei; Zheng, Ping; Ji, Junyuan; Zhang, Meng; Guo, Jun; Zhang, Jiqiang; Abbas, Ghulam

2014-01-01

 
 
 
 
301

[Screening and denitrification characteristics of a heterotrophic nitrification-aerobic denitrifier bacteria].  

Science.gov (United States)

A heterotrophic nitrification-aerobic denitrifier bacteria CPZ24 was isolated form the livestock wastewater by way of the limiting dilution combined with the chromogenic medium screening methods. This bacterium was Gram positive, rod. The colonies of the strain were orange-red.It was identified as Rhodococuus pyridinivorans according to its morphological and physiological properties and the analysis of its 16S rDNA gene. Studied on its function of heterotrophic nitrification and aerobic denitrification,the results show that all NH4+ -N is removed and the removal rate of TN is 98.70% in heterotrophic nitrification; the removal rate of NO3- -N by this strain is 66.74% and the removal rate of TN is 64.27%. This high effective microorganisms with nitrogen removed is able to realize simultaneous nitrification and denitrification. It can perform the whole process of bacteria denitrification independently. PMID:20187396

Chen, Pei-zhen; Wang, Li-gang; Wang, Ying-chun; Li, Ji; Ding, Wei; Ren, Tian-zhi; Li, Shao-peng

2009-12-01

302

Uranium conversion and enrichment  

International Nuclear Information System (INIS)

A description is given of the Atomic Energy Corporation's uranium conversion and enrichment plants at Valinda ba, including a brief discussion of problems encountered and plans for future developments. (author)

1990-06-01

303

Nitrite Reductase Genes (nirK and nirS) as Functional Markers To Investigate Diversity of Denitrifying Bacteria in Pacific Northwest Marine Sediment Communities  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Genetic heterogeneity of denitrifying bacteria in sediment samples from Puget Sound and two sites on the Washington continental margin was studied by PCR approaches amplifying nirK and nirS genes. These structurally different but functionally equivalent single-copy genes coding for nitrite reductases, a key enzyme of the denitrification process, were used as a molecular marker for denitrifying bacteria. nirS sequences could be amplified from samples of both sampling sites, whereas nirK sequen...

Braker, Gesche; Zhou, Jizhong; Wu, Liyou; Devol, Allan H.; Tiedje, James M.

2000-01-01

304

The Role of plant type and salinity in the selection for the denitrifying community structure in the rhizosphere of wetland vegetation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Coastal wetlands, as transient links from terrestrial to marine environments, are important for nitrogen removal by denitrification. Denitrification strongly depends on both the presence of emergent plants and the denitrifier communities selected by different plant species. In this study, the effects of vegetation and habitat heterogeneity on the community of denitrifying bacteria were investigated in nine coastal wetlands in two preserved areas of Spain. Sampling locations were selected to c...

Ban?eras Vives, Llui?s; Ruiz Rueda, Olaya; Lo?pez I Flores, Roci?o; Quintana Pou, Xavier; Hallin, Sara

2012-01-01

305

The role of plant type and salinity in the selection for the denitrifying community structure in the rhizosphere of wetland vegetation.  

Science.gov (United States)

Coastal wetlands, as transient links from terrestrial to marine environments, are important for nitrogen removal by denitrification. Denitrification strongly depends on both the presence of emergent plants and the denitrifier communities selected by different plant species. In this study, the effects of vegetation and habitat heterogeneity on the community of denitrifying bacteria were investigated in nine coastal wetlands in two preserved areas of Spain. Sampling locations were selected to cover a range of salinity (0.81 to 31.3 mS/cm) and nitrate concentrations (0.1 to 303 ?M NO3-), allowing the evaluation of environmental variables that select for denitrifier communities in the rhizosphere of Phragmites sp., Ruppia sp., and Paspalum sp. Potential nitrate reduction rates were found to be dependent on the sampling time and plant species and related to the denitrifier community structure, which was assessed by terminal restriction fragment length polymorphism analysis of the functional genes nirS, nirK and nosZ. The results showed that denitrifier community structure was also governed by plant species and salinity, with significant influences of other variables, such as sampling time and location. Ruppia sp. and Phragmites sp. selected for certain communities, whereas this was not the case for Paspalum sp. The plant species effect was strongest on nirK-type denitrifiers, whereas water carbon content was a significant factor defining the structure of the nosZ-harboring community. The differences recognized using the three functional gene markers indicated that different drivers act on denitrifying populations capable of complete denitrification, compared to the overall denitrifier community. This finding may have implications for emissions of the greenhouse gas nitrous oxide. PMID:22847270

Bañeras, Luís; Ruiz-Rueda, Olaya; López-Flores, Rocío; Quintana, Xavier D; Hallin, Sara

2012-06-01

306

Impact of Plant Functional Group, Plant Species, and Sampling Time on the Composition of nirK-Type Denitrifier Communities in Soil? †  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We studied the influence of eight nonleguminous grassland plant species belonging to two functional groups (grasses and forbs) on the composition of soil denitrifier communities in experimental microcosms over two consecutive years. Denitrifier community composition was analyzed by terminal restriction fragment length polymorphism (T-RFLP) of PCR-amplified nirK gene fragments coding for the copper-containing nitrite reductase. The impact of experimental factors (plant functional group, plant ...

2007-01-01

307

In situ analysis of denitrifying toluene- and m-xylene-degrading bacteria in a diesel fuel-contaminated laboratory aquifer column.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A diesel fuel-contaminated aquifer was bioremediated in situ by the injection of oxidants (O2 and NO3-) and nutrients in order to stimulate microbial activity. After 3.5 years of remediation, an aquifer sample was excavated and the material was used (i) to isolate bacterial strains able to grow on selected hydrocarbons under denitrifying conditions and (ii) to construct a laboratory aquifer column in order to simulate the aerobic and denitrifying remediation processes. Five bacterial strains ...

1997-01-01

308

Denitrifying Bacterial Communities Affect Current Production and Nitrous Oxide Accumulation in a Microbial Fuel Cell  

Science.gov (United States)

The biocathodic reduction of nitrate in Microbial Fuel Cells (MFCs) is an alternative to remove nitrogen in low carbon to nitrogen wastewater and relies entirely on microbial activity. In this paper the community composition of denitrifiers in the cathode of a MFC is analysed in relation to added electron acceptors (nitrate and nitrite) and organic matter in the cathode. Nitrate reducers and nitrite reducers were highly affected by the operational conditions and displayed high diversity. The number of retrieved species-level Operational Taxonomic Units (OTUs) for narG, napA, nirS and nirK genes was 11, 10, 31 and 22, respectively. In contrast, nitrous oxide reducers remained virtually unchanged at all conditions. About 90% of the retrieved nosZ sequences grouped in a single OTU with a high similarity with Oligotropha carboxidovorans nosZ gene. nirS-containing denitrifiers were dominant at all conditions and accounted for a significant amount of the total bacterial density. Current production decreased from 15.0 A·m?3 NCC (Net Cathodic Compartment), when nitrate was used as an electron acceptor, to 14.1 A·m?3 NCC in the case of nitrite. Contrarily, nitrous oxide (N2O) accumulation in the MFC was higher when nitrite was used as the main electron acceptor and accounted for 70% of gaseous nitrogen. Relative abundance of nitrite to nitrous oxide reducers, calculated as (qnirS+qnirK)/qnosZ, correlated positively with N2O emissions. Collectively, data indicate that bacteria catalysing the initial denitrification steps in a MFC are highly influenced by main electron acceptors and have a major influence on current production and N2O accumulation.

Vilar-Sanz, Ariadna; Puig, Sebastia; Garcia-Lledo, Arantzazu; Trias, Rosalia; Balaguer, M. Dolors; Colprim, Jesus; Baneras, Lluis

2013-01-01

309

Nitrogen cycling and relationships between ammonia oxidizers and denitrifiers in a clay-loam soil.  

Science.gov (United States)

This study investigated the effect of municipal solid waste (MSW) compost (0, 50, and 100 t/ha) on N cycling and the microorganisms involved in it, in a clay-loam soil. After a release of nitrates (NO3(-)-N) in the first 6 days after compost incorporation, soil NO3(-)-N content remained constant in all the treatments until day?62, suggesting N immobilization induced by the soil used in this study. Then, soil NO3(-)-N content increased in all treatments and especially in the highest compost dose, providing evidence that immobilization effect has been at least partially relieved. amoA gene copies of ammonia-oxidizing archaea (AOA) and bacteria (AOB) followed the overall pattern of soil NO3(-)-N content; however, no differences were found in amoA gene copies among treatments, except in the last sampling, an effect attributed to the slight differences in the potential nitrification rate among them. Ammonia oxidizer pattern provided evidence that both groups were involved in ammonia oxidation and changes in their abundance can be used as 'indicator' to predict changes in soil nitrification status. Moreover, the strong correlation between AOA and AOB amoA copies (R(2)?=?0.94) and the high slope (13) of the curve suggest that AOA had probably an important role on ammonia oxidation. Denitrifying genes (nirS, nirK, nosZ) also followed the general pattern of soil NO3(-)-N, and they were strongly correlated with both groups of ammonia oxidizers, and particularly AOA, suggesting strong interrelationships among them. Losses of N through denitrification, as they were estimated by total nitrogen, were inversely related to soil NO3(-)-N content. Similar to ammonia oxidizers, denitrifying gene copies did not differ among compost treatments an effect that could be probably explained by the low availability of organic-C in the MSW compost and hence the competition with aerobic heterotrophs. PMID:23435941

Paranychianakis, N V; Tsiknia, M; Giannakis, G; Nikolaidis, N P; Kalogerakis, N

2013-06-01

310

[Denitrifying bacteria of constructed wetland system based on nitrous oxide reductase gene (nosZ)].  

Science.gov (United States)

A horizontal subsurface flow constructed wetland was used to treat micro-pollution surface water and its effluent flowed into a landscape river as the water supplement. The abundance of the nitrous oxide reductase gene nosZ and 16S rDNA was investigated for the rhizosphere soil of the constructed wetland and the sediment of the landscape river by quantitive PCR. The diversity and similarity of denitrifiers were studied by using PCR-DGGE technique targeting the functional gene nosZ. The quantitive PCR results showed that the copy number of 16S rDNA and nosZ gene of the rhizosphere soil of the constructed wetland and the sediment of the landscape river were 1.91E + 07, 1.26E + 06 and 2.68E + 07, 8.37E + 05 copies x ng(-1) (by DNA), and 1.45E + 11, 9.31E + 09 and 5.31E + 11, 1.45E + 10 copies x g(-1) (by dry soil), respectively. Generally, the total bacterial count and denitrifiers in the sediment of the landscape river was higher than that of the constructed wetland, but the relative abundance of nosZ of the latter (3.8% - 10.1%) was significantly higher than that of the former (1.7% - 4.1%). There was low similarity between the two niches in cluster analysis. The predominant species of rhizosphere soil were mainly contained Rhodobacearales, Rhizobiales and Burkholderiales, although the predominant species of sediment were uncultured bacteria. PMID:22720582

Wang, Xiao-Jun; Chen, Shao-Hua; Zhang, Zhao-Ji; Xiao, Jun-Chao

2012-04-01

311

Isolation and functional analysis of denitrifiers in an aquifer with high potential for denitrification.  

Science.gov (United States)

Aquifers are among the main freshwater sources. The Raigón aquifer is susceptible to contamination, mainly by nitrate and pesticides, such as atrazine, due to increasing agricultural activities in the area. The capacity of indigenous bacteria to attenuate nitrate contamination in different wells of this aquifer was assessed by measuring denitrification rates with either acetate plus succinate or nitrate amendments. Denitrification activity in nitrate-amended assays was significantly higher than in unamended assays, particularly in groundwater from wells where nitrate concentration was 33.5 mg L(-1) or lower. Furthermore, groundwater denitrifiers capable of using acetate or succinate as electron donors were isolated, identified by 16S rRNA gene sequencing and evaluated for functional denitrification genes (nirS, nirK and nosZ). Phylogenetic affiliation of 54 isolates showed that all members belonged to nine different genera within the Proteobacteria (Bosea, Ochrobactrum, Azospira, Zoogloea, Acidovorax, Achromobacter, Vogesella, Stenotrophomonas and Pseudomonas). In addition, isolate AR28 that clustered separately from validly described species could potentially belong to a new genus. The majority of the isolates were related to species belonging to previously reported denitrifying genera. However, the phylogeny of the nirS and nosZ genes revealed new sequences of these functional genes. To our knowledge, this is the first isolation and sequencing of the nirS gene from the genus Vogesella, as well as the nosZ gene from the genera Acidovorax and Zoogloea. The results indicated that indigenous bacteria in the Raigón aquifer had the capacity to overcome high nitrate contamination and exhibited functional gene diversity. PMID:23972399

Bellini, M Inés; Gutiérrez, Lucía; Tarlera, Silvana; Scavino, Ana Fernández

2013-10-01

312

Coexistence of nitrifying, anammox and denitrifying bacteria in a sequencing batch reactor.  

Science.gov (United States)

Elevated nitrogen removal efficiencies from ammonium-rich wastewaters have been demonstrated by several applications, that combine nitritation and anammox processes. Denitrification will occur simultaneously when organic carbon is also present. In this study, the activity of aerobic ammonia oxidizing, anammox and denitrifying bacteria in a full scale sequencing batch reactor, treating digester supernatants, was studied by means of batch-assays. AOB and anammox activities were maximum at pH of 8.0 and 7.8-8.0, respectively. Short term effect of nitrite on anammox activity was studied, showing nitrite up to 42 mg/L did not result in inhibition. Both denitrification via nitrate and nitrite were measured. To reduce nitrite-oxidizing activity, high NH3-N (1.9-10 mg NH3-N/L) and low nitrite (3-8 mg TNN/L) are required conditions during the whole SBR cycle. Molecular analysis showed the nitritation-anammox sludge harbored a high microbial diversity, where each microorganism has a specific role. Using ammonia monooxygenase ?-subunit (amoA) gene as a marker, our analyses suggested different macro- and micro-environments in the reactor strongly affect the AOB community, allowing the development of different AOB species, such as N. europaea/eutropha and N. oligotropha groups, which improve the stability of nitritation process. A specific PCR primer set, used to target the 16S rRNA gene of anammox bacteria, confirmed the presence of the "Ca. Brocadia fulgida" type, able to grow in presence of organic matter and to tolerate high nitrite concentrations. The diversity of denitrifiers was assessed by using dissimilatory nitrite reductase (nirS) gene-based analyses, who showed denitifiers were related to different betaproteobacterial genera, such as Thauera, Pseudomonas, Dechloromonas and Aromatoleum, able to assist in forming microbial aggregates. Concerning possible secondary processes, no n-damo bacteria were found while NOB from the genus Nitrobacter was detected. PMID:24550899

Langone, Michela; Yan, Jia; Haaijer, Suzanne C M; Op den Camp, Huub J M; Jetten, Mike S M; Andreottola, Gianni

2014-01-01

313

Coexistence of nitrifying, anammox and denitrifying bacteria in a sequencing batch reactor  

Directory of Open Access Journals (Sweden)

Full Text Available Elevated nitrogen removal efficiencies from ammonium-rich wastewaters have been demonstrated by several applications, that combine nitritation and anammox processes. Denitrification will occur simultaneously when organic carbon is also present. In this study, the activity of aerobic ammonia oxidizing, anammox and denitrifying bacteria in a full scale Sequencing Batch Reactor, treating digester supernatants, was studied by means of batch-assays. AOB and anammox activities were maximum at pH of 8.0 and 7.8-8.0, rispectively. Short term effect of nitrite on anammox activity was studied, showing nitrite up to 42 mg/L did not result in inhibition. Both denitrification via nitrate and nitrite were measured. To reduce nitrite-oxidizing activity, high of NH3 – N (1.9-10 mg N-NH3/L and low nitrite (3-8 mg TNN/L are required conditions during the whole SBR cycle.Molecular analysis showed the nitritation-anammox sludge harbored a high microbial diversity, where each microorganism has a specific role. Using ammonia monooxygenase ? –subunit (amoA gene as a marker, our analyses suggested different macro- and micro-environments in the reactor strongly affect the AOB community, allowing the development of different AOB species, such as N. europaea/eutropha and N. oligotropha groups, which improve the stability of nitritation process. A specific PCR primer set, used to target the 16S rRNA gene of anammox bacteria, confirmed the presence of the “Ca. Brocadia fulgida” type, able to grow in precence of organic matter and to tolerate high nitrite concentrations. The diversity of denitrifiers was assessed by using dissimilatory nitrite reductase (nirS gene-based analyses, who showed denitifiers were related to different betaproteobacterial genera, such as Thauera, Pseudomonas, Dechloromonas and Aromatoleum, able to assist in forming microbial aggregates. Concerning possible secondary processes, no n-damo bacteria were found while NOB from the genus of Nitrobacter was detected.

MichelaLangone

2014-02-01

314

Modeling of Cr(VI) Bioreduction Under Fermentative and Denitrifying Conditions  

Science.gov (United States)

The mechanisms of bioreductive immobilization of Cr(VI) were investigated by reactive transport modeling of a set of flow-through column experiments performed using natural Hanford 100H aquifer sediment. The columns were continuously eluted with 5 ?M Cr(VI), 5 mM lactate as the electron donor, and selected electron acceptors (tested individually). Here we focus on the two separate experimental conditions that showed the most removal of Cr(VI) from solution: fermentation and denitrification. In each case, a network of enzymatic and abiotic reaction pathways was considered to interpret the rate of chromate reduction. The model included biomass growth and decay, and thermodynamic limitations on reaction rates, and was constrained by effluent concentrations measured by IC and ICP-MS and additional information from bacterial isolates from column effluent. Under denitrifying conditions, Cr(VI) reduction was modeled as co-metabolic with nitrate reduction based on experimental observations and previous studies on a denitrifying bacterium derived from the Hanford 100H aquifer. The reactive transport model results supported this interpretation of the reaction mechanism and were used to quantify the efficiency of the process. The models results also suggest that biomass growth likely relied on a nitrogen source other than ammonium (e.g. nitrate). Under fermentative conditions and based on cell suspension studies performed on a bacterial isolate from the columns, the model assumes that Cr(VI) reduction is carried out directly by fermentative bacteria that convert lactate into acetate and propionate. The evolution to complete lactate fermentation and Cr(VI) reduction took place over a week's time and simulations were used to determine an estimate for a lower limit of the rate of chromate reduction by calibration with the flow-through column experimental results. In spite of sulfate being added to these columns, sulfate reduction proceeded at a slow rate and was not well constrained.

Molins, S.; Steefel, C.; Yang, L.; Beller, H. R.

2011-12-01

315

Reduced nitrate leaching and enhanced denitrifier activity and efficiency in organically fertilized soils.  

Science.gov (United States)

Conventional agriculture has improved in crop yield but at large costs to the environment, particularly off-site pollution from mineral N fertilizers. In response to environmental concerns, organic agriculture has become an increasingly popular option. One component of organic agriculture that remains in question is whether it can reduce agricultural N losses to groundwater and the atmosphere relative to conventional agriculture. Here we report reduced N pollution from organic and integrated farming systems compared with a conventional farming system. We evaluated differences in denitrification potential and a suite of other soil biological and chemical properties in soil samples taken from organic, integrated, and conventional treatments in an experimental apple orchard. Organically farmed soils exhibited higher potential denitrification rates, greater denitrification efficiency, higher organic matter, and greater microbial activity than conventionally farmed soils. The observed differences in denitrifier function were then assessed under field conditions after fertilization. N(2)O emissions were not significantly different among treatments; however, N(2) emissions were highest in organic plots. Annual nitrate leaching was 4.4-5.6 times higher in conventional plots than in organic plots, with the integrated plots in between. This study demonstrates that organic and integrated fertilization practices support more active and efficient denitrifier communities, shift the balance of N(2) emissions and nitrate losses, and reduce environmentally damaging nitrate losses. Although this study specifically examines a perennial orchard system, the ecological and biogeochemical processes we evaluated are present in all agroecosystems, and the reductions in nitrate loss in this study could also be achievable in other cropping systems. PMID:16537377

Kramer, Sasha B; Reganold, John P; Glover, Jerry D; Bohannan, Brendan J M; Mooney, Harold A

2006-03-21

316

What is Enrichment For (?)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

It has long been held that schooling, the curriculum (hidden or otherwise), and the pedagogical practices pertaining to them are the perpetrators of social and economic inequalities in Western society. My interest surrounds the role of ‘enrichment’, as an auxiliary of education, in perpetuating or restricting social justice. As the enrichment coordinator within an inner city Sixth Form college, it became part of my remit to research the dispositions held by our largely underprivileged stu...

Matsangos, P.

2011-01-01

317

Evaluation of different culture media and enrichment in orange juice upon the growth of Alicyclobacillus spp. / Avaliação de diferentes meios de cultura e enriquecimento em suco de laranja sobre o crescimento de Alicyclobacillus spp.  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese As bactérias do gênero Alicyiclobacillus spp. formam esporos e se desenvolvem em meios ácidos, podendo causar deterioração em sucos cítricos. O Brasil é o maior exportador de suco de laranja concentrado do mundo e, assim, este gênero vem sendo estudado por causar alterações de odor e sabor. Vários e [...] studos relatam diferentes meios de culturas empregados para a detecção e enumeração de Alicyclobacillus spp. Este estudo teve como objetivo avaliar a recuperação de esporos de Alicyclobacillus spp. nos meios ALI, BAT, K ágar e YSG, utilizando a metodologia indicada pela ABECitrus. Cinco inóculos diferentes foram utilizados, sendo dois de linhagens-referência e os outros três isolados de suco concentrado de laranja pasteurizado. Também foi verificada a recuperação das células após o enriquecimento em suco de laranja reconstituído. Foi inoculada uma população inicial de 6 log UFC/mL. Os meios ALI, BAT e YSG conseguiram recuperar esta população nos diferentes inóculos, não existindo diferenças significativas entre os resultados. Contudo, devido à facilidade do preparo, os meios ALI e YSG mostraram-se mais vantajosos quando comparados ao meio BAT. O meio K ágar apresentou recuperação inferior aos outros meios para todos os inóculos, porém, houve diferença significativa apenas para Alicyclobacillus acidocaldarius 0298 T (3,66 log UFC/mL) e Alicyclobacillus pomorum-like CBMAI 0278 (4,11 log UFC/mL). Abstract in english Bacteria of the genus Alicyiclobacillus spp. form spores and develop in acid media, leading to the spoilage of citrus juices. Brazil is the largest exporter of orange juice concentrate, and yet, it has been extensively studied due to changes in taste and smell. Several investigations have reported d [...] ifferent culture media used to detect and enumerate Alicyiclobacillus spp. The objective of the present study was to evaluate the recovery of Alicyiclobacillus spp. spores grown in ALI, BAT, K agar and YSG media using the methodology suggested by ABECitrus. Five inocula were used, two from reference strains and three from pasteurized concentrated orange juice. Cell recovery after the enrichment in reconstituted orange juice was also analyzed. An initial population of 6 log CFU/mL was inoculated. ALI, BAT and YSG media were able to recover the initial population of all different inocula, with no significant differences between the results. When compared to BAT, however, the preparation of ALI and YSG media was simpler and had more advantages. The recovery with K agar medium was lower than the other media for all the tested inocula, with significant differences found for Alicyclobacillus acidocaldarius 0298T (3.66 log CFU/mL) and Alicyclobacillus pomorum-like CBMAI 0278 (4.11 log CFU/mL).

Márcia Maria, Anjos; Suelen Pereira, Ruiz; Benício Alves, Abreu Filho.

318

Isolation of the ?-caprolactam denitrifying bacteria from a wastewater treatment system manufactured with acrylonitrile-butadiene-styrene resin  

International Nuclear Information System (INIS)

?-Caprolactam has high COD and toxicity, so its discharge to natural water and soil systems may lead to an adverse environmental effect on water quality, endangering public health and welfare. This investigation attempts to isolate ?-caprolactam denitrifying bacteria from a wastewater treatment system manufactured with acrylonitrile-butadiene-styrene (ABS) resin. The goal is to elucidate the effectiveness of isolated pure strain and ABS mixed strains in treating ?-caprolactam from synthetic wastewater. The results reveal that Paracoccus versutus MDC-3 was isolated from the wastewater treatment system manufactured with ABS resin. The ABS mixed strains and P. versutus MDC-3 can consume up to 1539 mg/l ?-caprolactam to denitrify from synthetic wastewater. Complete ?-caprolactam removal depended on the supply of sufficient electron acceptors (nitrate). Strain P. versutus MDC-3, Hyphomicrobium sp. HM, Methylosinus pucelana and Magnetospirillum sp. CC-26 are related closely, according to the phylogenetic analyses of 16S rDNA sequences

2007-06-25

319

Enrichment of nitrous oxide reducing bacteria from coastal marsh sediments  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We attempted to recover organisms capable of respiratory nitrous oxide reduction with acetate as an electron donor from a variety of coastal marine sediments from Lavaca Bay area, Texas by use of liquid enrichment cultures. Putative positive cultures were analyzed by amplifying eubacterial and archaeal 16S rRNA gene fragments and analyzing their diversity by separating them by a denaturing ...

Nguyen, Khuong B. T.; Dmitri Sobolev

2013-01-01

320

Metabolic Profiles and Genetic Diversity of Denitrifying Communities in Activated Sludge after Addition of Methanol or Ethanol†  

Digital Repository Infrastructure Vision for European Research (DRIVER)

External carbon sources can enhance denitrification rates and thus improve nitrogen removal in wastewater treatment plants. The effects of adding methanol and ethanol on the genetic and metabolic diversity of denitrifying communities in activated sludge were compared using a pilot-scale plant with two parallel lines. A full-scale plant receiving the same municipal wastewater, but without external carbon source addition, was the reference. Metabolic profiles obtained from potential denitrifica...

Hallin, Sara; Throba?ck, Ingela Noredal; Dicksved, Johan; Pell, Mikael

2006-01-01

 
 
 
 
321

Association of Earthworm-Denitrifier Interactions with Increased Emission of Nitrous Oxide from Soil Mesocosms Amended with Crop Residue  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Earthworm activity is known to increase emissions of nitrous oxide (N2O) from arable soils. Earthworm gut, casts, and burrows have exhibited higher denitrification activities than the bulk soil, implicating priming of denitrifying organisms as a possible mechanism for this effect. Furthermore, the earthworm feeding strategy may drive N2O emissions, as it determines access to fresh organic matter for denitrification. Here, we determined whether interactions between earthworm feeding strategy a...

Nebert, L. D.; Bloem, J.; Lubbers, I. M.; Groenigen, J. W.

2011-01-01

322

Association of Earthworm-Denitrifier Interactions with Increased Emission of Nitrous Oxide from Soil Mesocosms Amended with Crop Residue? †  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Earthworm activity is known to increase emissions of nitrous oxide (N2O) from arable soils. Earthworm gut, casts, and burrows have exhibited higher denitrification activities than the bulk soil, implicating priming of denitrifying organisms as a possible mechanism for this effect. Furthermore, the earthworm feeding strategy may drive N2O emissions, as it determines access to fresh organic matter for denitrification. Here, we determined whether interactions between earthworm feeding strategy a...

Nebert, Lucas D.; Bloem, Jaap; Lubbers, Ingrid M.; Groenigen, Jan Willem

2011-01-01

323

Structure and function of microbial communities in constructed wetlands - influence of environmental parameters and pesticides on denitrifying bacteria  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This thesis addresses the interactions and relationships between natural aquatic bacterial communities, environmental parameters, anthropogenic chemicals and the denitrification pathway in the habitat of agricultural constructed wetlands. The main aim was to gain fundamental knowledge of the drivers behind the processes of the denitrification (i.e. nitrogen removal) in constructed wetlands, hence, the structure and function of the denitrifying bacterial community as efficient nitrogen removal...

Milenkovski, Susann

2009-01-01

324

Impacts of nitrogen application rates on the activity and diversity of denitrifying bacteria in the Broadbalk Wheat Experiment  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Bacterial denitrification results in the loss of fertilizer nitrogen and greenhouse gas emissions as nitrous oxides, but ecological factors in soil influencing denitrifier communities are not well understood, impeding the potential for mitigation by land management. Communities vary in the relative abundance of the alternative dissimilatory nitrite reductase genes nirK and nirS, and the nitrous oxide reductase gene nosZ; however, the significance for nitrous oxide emissions is unclear. We ass...

Clark, Ian M.; Buchkina, Natalya; Jhurreea, Deveraj; Goulding, Keith W. T.; Hirsch, Penny R.

2012-01-01

325

Impacts of different N management regimes on nitrifier and denitrifier communities and N cycling in soil microenvironments  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Real-time quantitative PCR assays, targeting part of the ammonia-monooxygenase (amoA), nitrous oxide reductase (nosZ), and 16S rRNA genes were coupled with 15N pool dilution techniques to investigate the effects of long-term agricultural management practices on potential gross N mineralization and nitrification rates, as well as ammonia-oxidizing bacteria (AOB), denitrifier, and total bacterial community sizes within different soil microenvironments. Three soil microenvironments [coarse parti...

Kong, Angela Y. Y.; Hristova, Krassimira; Scow, Kate M.; Six, Johan

2010-01-01

326

Anaerobic Mineralization of Quaternary Carbon Atoms: Isolation of Denitrifying Bacteria on Pivalic Acid (2,2-Dimethylpropionic Acid)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The degradability of pivalic acid was established by the isolation of several facultative denitrifying strains belonging to Zoogloea resiniphila, to Thauera and Herbaspirillum, and to Comamonadaceae, related to [Aquaspirillum] and Acidovorax, and of a nitrate-reducing bacterium affiliated with Moraxella osloensis. Pivalic acid was completely mineralized to carbon dioxide. The catabolic pathways may involve an oxidation to dimethylmalonate or a carbon skeleton rearrangement, a putative 2,2-dim...

2003-01-01

327

Short exposure to acetylene to distinguish between nitrifier and denitrifier nitrous oxide production in soil and sediment samples  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The contribution of nitrifiers and denitrifiers to the nitrous oxide production in slurries of calcareous silt loam and river bank sediment at different oxygen concentrations was determined using acetylene as nitrification inhibitor. The addition of 10 Pa acetylene resulted in inhibition of nitrous oxide production at oxic conditions, but strongly enhanced the nitrous oxide production at oxygen-poor and anoxic conditions. Inhibition of nitrification by short exposure (1 to 24 h) to h...

Kester, R. A.; Boer, W.; Laanbroek, H. J.

1996-01-01

328

Population analysis in a denitrifying sand filter: conventional and in situ identification of Paracoccus spp. in methanol-fed biofilms.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The microbial community of a denitrifying sand filter in a municipal wastewater treatment plant was examined by conventional and molecular techniques to identify the bacteria actively involved in the removal of nitrate. In this system, denitrification is carried out as the last step of water treatment by biofilms growing on quartz grains with methanol as a supplemented carbon source. The biofilms are quite irregular, having a median thickness of 13 to 20 microns. Fatty acid analysis of 56 den...

Neef, A.; Zaglauer, A.; Meier, H.; Amann, R.; Lemmer, H.; Schleifer, K. H.

1996-01-01

329

Uranium enrichment in Europe  

International Nuclear Information System (INIS)

Until the mid 1970's, the USA had a monopoly of separation work. There is now sufficient capacity at the Eurodif and Urenco plants for fully servicing Europe, but the Americans still have a large proportion of the European market. In 1984/85, the international market was determined by a series of basic decisions by the American market leader, which in turn were determined by the world-wide marketing activities of the European concerns Eurodif and Urenco. The author deals with the present situation in the world market for separation work, the recent decisions by the US Department of Energy (DOE) in enrichment technology, the setting to work of the enrichment plant at Urenco Germany at Gronau, the successes of the Urenco centrifuge technique and the state of laser enrichment. (orig.)

1985-01-01

330

Oxygen enrichment incineration  

Energy Technology Data Exchange (ETDEWEB)

Oxygen enriched combustion technology has recently been used in waste incineration. To apply the oxygen enrichment on alpha-bearing waste incineration, which is being developed, a state-of-an-art review has been performed. The use of oxygen or oxygen-enriched air instead of air in incineration would result in increase of combustion efficiency and capacity, and reduction of off-gas product. Especially, the off-gas could be reduced below a quarter, which might reduce off-gas treatment facilities, and also increase an efficiency of off-gas treatment. However, the use of oxygen might also lead to local overheating and high nitrogen oxides (NOx) formation. To overcome these problems, an application of low NOx oxy-fuel burner and recycling of a part of off-gas to combustion chamber have been suggested.

Kim, Jeong Guk; Yang, Hee Chul; Park, Geun Il; Kim, Joon Hyung

2000-10-01

331

Oxygen enrichment incineration  

International Nuclear Information System (INIS)

Oxygen enriched combustion technology has recently been used in waste incineration. To apply the oxygen enrichment on alpha-bearing waste incineration, which is being developed, a state-of-an-art review has been performed. The use of oxygen or oxygen-enriched air instead of air in incineration would result in increase of combustion efficiency and capacity, and reduction of off-gas product. Especially, the off-gas could be reduced below a quarter, which might reduce off-gas treatment facilities, and also increase an efficiency of off-gas treatment. However, the use of oxygen might also lead to local overheating and high nitrogen oxides (NOx) formation. To overcome these problems, an application of low NOx oxy-fuel burner and recycling of a part of off-gas to combustion chamber have been suggested

2000-01-01

332

NLOSS: A mechanistic model of denitrified N{sub 2}O and N{sub 2} evolution from soil  

Energy Technology Data Exchange (ETDEWEB)

Soil microbial denitrification is a significant source of atmospheric nitrous oxide (N{sub 2}O), a trace gas important in global climate change and stratospheric ozone depletion. In this paper the authors describe a mechanistic submodel, which is incorporated in the model NLOSS, designed to predict the soil biogenic source and efflux of N{sub 2}O and N{sub 2} during denitrification. NLOSS simulates transient soil moisture and temperature, decomposition, soil anaerobicity, denitrifying bacterial biomass, rates of soil nitrogen transformations, soil trace-gas transport, and gas efflux to the atmosphere. Uncertainty in predicted N gas effluxes is computed using a Monte Carlo approach. The authors test NLOSS's denitrification estimates by comparing predictions with results from a {sup 15}N tracer experiment in a Mexican agricultural system. The model accurately predicted the measured soil moisture and denitrified N{sub 2}O and N{sub 2} fluxes during the experiment. They also apply NLOSS to compute denitrified N trace-gas speciation curves as a function of soil hydrologic properties and moisture content. These speciation curves will be used in future work to extrapolate the plot-scale modeling results presented here to field and regional estimates of N trace-gas emissions. The results presented here suggest that NLOSS can be used to identify the processes most important for trace-gas losses and to facilitate efforts to scale plot-level modeling results to regional estimates of N trace-gas emissions.

Riley, W.J.; Matson, P.A.

2000-03-01

333

Thermal diffusion enrichment  

International Nuclear Information System (INIS)

A static thermal diffusion enrichment system is described which is run in a mode like a feed-back amplifier, i.e. nearly all tritium contained in the hydrogen that is admitted to the system, is transferred into a sampling column, and the content of this column is then transferred quantitatively into the gas counter. The system is designed to accommodate approximately 1 mol of hydrogen, and to achieve the desired sensitivity is run in combination with electrolytical enrichment. The columns are of the hot-wire type and the outer wall is glass holding a glass cooling jacket

1981-05-01

334

Enrichment of amino acid-oxidizing, acetate-reducing bacteria.  

Science.gov (United States)

In anaerobic condition, amino acids are oxidatively deaminated, and decarboxylated, resulting in the production of volatile fatty acids. In this process, excess electrons are produced and their consumption is necessary for the accomplishment of amino acid degradation. In this study, we anaerobically constructed leucine-degrading enrichment cultures from three different environmental samples (compost, excess sludge, and rice field soil) in order to investigate the diversity of electron-consuming reaction coupled to amino acid oxidation. Constructed enrichment cultures oxidized leucine to isovalerate and their activities were strongly dependent on acetate. Analysis of volatile fatty acids (VFAs) profiles and community structure analysis during batch culture of each enrichment indicated that Clostridium cluster I coupled leucine oxidation to acetate reduction in the enrichment from the compost and the rice field soil. In these cases, acetate was reduced to butyrate. On the other hand, Clostridium cluster XIVb coupled leucine oxidation to acetate reduction in the enrichment from the excess sludge. In this case, acetate was reduced to propionate. To our surprise, the enrichment from rice field soil oxidized leucine even in the absence of acetate and produced butyrate. The enrichment would couple leucine oxidation to reductive butyrate synthesis from CO2. The coupling reaction would be achieved based on trophic link between hydrogenotrophic acetogenic bacteria and acetate-reducing bacteria by sequential reduction of CO2 and acetate. Our study suggests anaerobic degradation of amino acids is achieved yet-to-be described reactions. PMID:24630616

Ato, Makoto; Ishii, Masaharu; Igarashi, Yasuo

2014-08-01

335

Uranium enrichment techniques  

International Nuclear Information System (INIS)

This article includes an introduction about the isotopes of natural uranium, their existence and the difficulty of the separation between them. Then it goes to the details of a number of methods used to enrich uranium: Gaseous Diffusion method, Electromagnetic method, Jet method, Centrifugal method, Chemical method, Laser method and Plasma method.

2007-01-01

336

Enrichment: Dealing with overcapacity  

Energy Technology Data Exchange (ETDEWEB)

Today`s surplus of enrichment capacity will continue until at least the end of this century. This will challenge the ingenuity of the SWU suppliers as they attempt to keep market share and remain profitable in a very competitive marketplace. The utilities will be faced with attractive choices, but making the best choice will require careful analysis and increased attention to market factors. National markets served by many government-controlled enrichment suppliers have replaced the international market dominance that the US Government once enjoyed. Today customers give their national suppliers special preference. A customer`s loyalty may arise out of equity participation in the producer, nationalistic feelings, a position as a subcontractor, or simply a preference for firms serving the local area. The suppliers with relatively secure national markets include URANSERVICE in the USSR and in the eastern European countries; China Nuclear Energy Industry Corporation in the Peoples Republic of China; EURODIF in France, Italy, Spain, and Belgium; URENCO in the United Kingdom, The Netherlands, and Germany; and the domestic suppliers in Japan, Argentina, Brazil, and South Africa. Competition in the SWU market is concentrated in the USA where the US DOE may not be able to maintain its traditional share of its domestic market, and in countries that are not self-sufficient in enrichment. Competition also exists in the countries served by EURODIF and URENCO, but the uncommitted market is smaller and the enrichment suppliers are maintaining a high degree of customer loyalty.

NONE

1988-12-01

337

Promotion of uranium enrichment business  

International Nuclear Information System (INIS)

The Committee on Nuclear Power has studied on the basic nuclear power policy, establishing its five subcommittees, entrusted by the Ministry of Nternational Trade and Industry. The results of examination by the subcommittee on uranium enrichment business are given along with a report in this connection by the Committee. In order to establish the nuclear fuel cycle, the aspect of uranium enrichment is essential. The uranium enrichment by centrifugal process has proceeded steadily in Power Reactor and Nuclear Fuel Development Corporation. The following matters are described: the need for domestic uranium enrichment, the outlook for overseas enrichment services and the schedule for establishing domestic enrichment business, the current state of technology development, the position of the prototype enrichment plant, the course to be taken to establish enrichment business the main organization operating the prototype and commercial plants, the system of supplying centrifuges, the domestic conversion of natural uranium the subsidies for uranium enrichment business. (J.P.N.)

1981-01-01

338

Correlating denitrifying catabolic genes with N2O and N2 emissions from swine slurry composting.  

Science.gov (United States)

This work evaluated N dynamics that occurs over time within swine slurry composting piles. Real-time quantitative PCR (qPCR) analyzes were conducted to estimate concentrations of bacteria community harboring specific catabolic nitrifying-ammonium monooxygenase (amoA), and denitrifying nitrate- (narG), nitrite- (nirS and nirG), nitric oxide- (norB) and nitrous oxide reductases (nosZ) genes. NH3-N, N2O-N, N2-N emissions represented 15.4 ± 1.9%, 5.4 ± 0.9%, and 79.1 ± 2.0% of the total nitrogen losses, respectively. Among the genes tested, temporal distribution of narG, nirS, and nosZ concentration correlated significantly (pnosZ ? 100 was indicative of N2O emission potential from the compost pile. Considering our current empirical limitations to accurately measure N2 emissions from swine slurry composting at field scale the use of these catabolic genes could represent a promising monitoring tool to aid minimize our uncertainties on biological N mass balances in these systems. PMID:23711942

Angnes, G; Nicoloso, R S; da Silva, M L B; de Oliveira, P A V; Higarashi, M M; Mezzari, M P; Miller, P R M

2013-07-01

339

Responses of activities, abundances and community structures of soil denitrifiers to short-term mercury stress.  

Science.gov (United States)

The responses of activities, abundances and community structures of soil denitrifiers to mercury (Hg) stress were investigated through a short-term incubation experiment. Four soil treatments with different concentrations of Hg (CK, Hg25, Hg50, and Hg 100, denoted as 0, 25, 50, and 100 mg Hg/kg dry soil, respectively) were incubated for 28 days. Soil denitrification enzyme activity (DEA) was measured at day 3, 7 and 28. The abundances and community structures of two denitrification concerning genes, nirS (cd(1)-nitrite reductase gene) and nosZ (nitrous oxide reductase gene), were analyzed using real-time PCR and denaturing gradient gel electrophoresis (DGGE). Results showed that soil DEA was significantly stimulated in the treatments of Hg25 and Hg50 compared with others at day 7. Meanwhile, no difference in the abundances of soil nirS and nosZ was found between Hg spiked treatments and CK, except the lower abundance of nirS (P nosZ gene. The results indicated that Hg (Hg25 and Hg50) had a strongly short-term stimulation on soil DEA, and nirS gene is more sensitive than nosZ gene to Hg stress. PMID:22655348

Zhou, Zhifeng; Zheng, Yuanming; Shen, Jupei; Zhang, Limei; Liu, Yurong; He, Jizheng

2012-01-01

340

Tertiary Denitrification of the Secondary Effluent by Denitrifying Biofilters Packed with Different Sizes of Quartz Sand  

Directory of Open Access Journals (Sweden)

Full Text Available Tertiary denitrification of the secondary effluent in wastewater treatment plants is necessary to control the eutrophication of receiving water bodies. Two denitrifying biofilters (DNBF, one packed with quart sand with sizes of 2–4 mm (DNBFS and the other of 4–6 mm (DNBFL, were operated for tertiary denitrification under empty bed retention times (EBRTs of 30 min, 15 min and 7.5 min, respectively. Under EBRTs of 30 min, 15 min and 7.5 min, the NO3?-N removal percentages were 93%, 82% and 83% in DNBFS, and were 92%, 68% and 36% in DNBFL, respectively. The nitrogen removal loading rates increased with decreasing EBRTs, and at the EBRT of 7.5 min, the rate was 2.15 kg/(m3·d in DNBFS and 1.08 kg/(m3·d in DNBFL. The half-order denitrification coefficient of DNBFS increased from 0.42 (mg/L1/2/min at the EBRT of 30 min to 0.70 (mg/L1/2/min at the EBRT of 7.5 min, while did not vary much in DNBFL with values from 0.22 to 0.25 (mg/L1/2/min. The performance of both DNBFs was stable within each backwashing cycle, with the NO3?-N removal percentage variation within 5%. Better denitrification was achieved in DNBFS but with a slightly high decreased flow rate during the operation.

Nan Wei

2014-05-01

 
 
 
 
341

The effect of urban landfill leachate characteristics on the coexistence of anammox bacteria and heterotrophic denitrifiers.  

Science.gov (United States)

Heterotrophic denitrification coexists with the anammox process contributing to N removal owing to the biodegradable organic matter supply from urban landfill leachate and the decay of microorganisms. Both biomasses consumed nitrite increasing the nitrite requirements of the system. The aim of this paper is the study of the causes which induce the system to decrease nitrogen removal efficiency. In this study, urban landfill leachate has been treated in an anammox Sequencing Batch Reactor (SBR) for 360 days. The anammox reactor treated on average 0.24 kgN m(-3) d(-1) obtaining nitrogen removal efficiencies up to 89%. The results demonstrated that i) a suitable influent nitrite to ammonium molar ratio is a crucial factor to avoid troubles in the anammox reactor performance; ii) an excess of nitrite implied nitrite accumulation in the reactor; iii) a lower nitrite supply than the necessary for the system could force a loss of specific anammox activity due to nitrite competition with denitrifiers. These results pointed out the importance of the previous partial-nitritation process control in order to obtain a correct influent nitrite to ammonium molar ratio for the anammox reactor. In addition, sudden variation of the leachate characteristics must be avoided. PMID:20182087

Ruscalleda, M; Puig, S; Mora, X; López, H; Ganigué, R; Balaguer, M D; Colprim, J

2010-01-01

342

Thermal characterization during dehydration of nitrifying and denitrifying microbiological mud encapsulated in silica gel  

Energy Technology Data Exchange (ETDEWEB)

An alternative method to diminish the nitrogen pollutant levels in waste waters is to encapsulate microorganisms whitin ceramic materials. The sol-gel method has been extensively used for the preparation of such kind of materials permitting a higher stability and viability of useful organisms. In this work, the thermal characterization during dehydration of nitrifying and denitrifying aqueous emulsions of mud encapsulated in sol-gel silica is presented during the process of dehydration in ambient conditions and as a function of temperature. The characterization was performed by a photopyroelectric (PPE) technique, whose detector was made with a 110 mm polyvinyldifluoride (PVDF). The cell was constructed in such a way that the sample was inside the cell, and the bottom of the cell was closed by the PVDF foil. Thermal effusivity as a function of temperature was obtained illuminating the PVDF directly by a modulated 1W tungsten lamp. The sample is enclosed inside a chamber, using a Peltier cell that controls temperature in a range from 40 to 27 deg. C. The sample is on top of the PVDF, which is illuminated by the modulated tungsten lamp.

Aguirre, G.; Arriola, G.; Gomez-Hernandez, J.; Lopez, T.; Picquart, M.; Aguilar, D.H.; Quintana, P.; Alvarado-Gil, J.J

2004-11-01

343

A biofilm model to understand the onset of sulfate reduction in denitrifying membrane biofilm reactors.  

Science.gov (United States)

This work presents a multispecies biofilm model that describes the co-existence of nitrate- and sulfate-reducing bacteria in the H(2)-based membrane biofilm reactor (MBfR). The new model adapts the framework of a biofilm model for simultaneous nitrate and perchlorate removal by considering the unique metabolic and physiological characteristics of autotrophic sulfate-reducing bacteria that use H(2) as their electron donor. To evaluate the model, the simulated effluent H(2), UAP (substrate-utilization-associated products), and BAP (biomass-associated products) concentrations are compared to experimental results, and the simulated biomass distributions are compared to real-time quantitative polymerase chain reaction (qPCR) data in the experiments for parameter optimization. Model outputs and experimental results match for all major trends and explain when sulfate reduction does or does not occur in parallel with denitrification. The onset of sulfate reduction occurs only when the nitrate concentration at the fiber's outer surface is low enough so that the growth rate of the denitrifying bacteria is equal to that of the sulfate-reducing bacteria. An example shows how to use the model to design an MBfR that achieves satisfactory nitrate reduction, but suppresses sulfate reduction. PMID:23055395

Tang, Youneng; Ontiveros-Valencia, Aura; Feng, Liang; Zhou, Chen; Krajmalnik-Brown, Rosa; Rittmann, Bruce E

2013-03-01

344

Development of enrichment techniques  

International Nuclear Information System (INIS)

The experience accumulated in operating the older uranium enrichment plants in Almelo and Capenhurst was the basis for the construction of the Gronau centrifuge plant commissioned in August 1985 after three and a half years of construction. The total capacity of the three Urenco plants as of late 1992 is 2750 t SWU/a. The goal set at the beginning of centrifuge development, i.e. to achive troublefree operation of the centrifuges for more than ten years, has been attained. Enrichment by centrifuges on the whole consumes less than one permil of the electric power generated. Economic calculations show that a laser plant is hardly able to underrun the costs of separative work of a centrifuge plant. (orig.)

1993-01-01

345

ENRICHMENT OF OBO ONTOLOGIES  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper describes a frame-based integration of the three GO subontologies, the Chemicals of Biological Interest ontology (ChEBI), and the Cell Type Ontology (CTO) in which relationships between elements of the ontologies are modeled in a way that better captures the relational semantics between biological concepts represented by the terms, rather than between the terms themselves, than previous frame-based efforts. We also describe a methodology for creating suggested enriching assertions ...

Bada, Michael; Hunter, Lawrence

2007-01-01

346

Enrich Project Final Report  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Enrich project was a 12 month JISC project funded as part of the Inf11 Programme (2009-11). It was conducted in partnership by the Library, Research and Enterprise and IT Services – with additional technical support from EPrints Services. This interdepartmental approach was critical to the success of the project and the repository’s long term sustainability as an institutional [not simply Library] service.

Nixon, William

2010-01-01

347

Organic wheatgrass as environmental enrichment.  

Science.gov (United States)

Environmental enrichment must be provided for the various animal species that are housed in laboratory animal facilities. Wheatgrass can be used as a natural form of enrichment that requires minimal preparation and effort. Wheatgrass is appropriate enrichment for cats, rabbits, guinea pigs, rodents and birds. PMID:20164947

Brown, Cyndi

2010-03-01

348

Centrifugal enrichment of sulfur isotopes  

International Nuclear Information System (INIS)

This work contains the results of the research for the complete cycle of the centrifuge enrichment process of all sulfur isotopes. As a result of this work there was obtained, and made available (by centrifuge enrichment process), for the first time hundreds of grams of all the isotopes of sulfur to high enrichment. (author)

2014-02-01

349

Characterization of a murine neuron-enriched model of primary trigeminal ganglia cultures to study the interferon- ? antiviral effect against Herpes Simplex Virus type 1 / Caracterización de un modelo murino de cultivos primarios de ganglio trigeminal enriquecido en neuronas para el estudio del efecto antiviral del interferón- ? frente al virus Herpes simple tipo 1  

Scientific Electronic Library Online (English)

Full Text Available SciELO Colombia | Language: English Abstract in spanish Objetivo: Caracterizar un cultivo primario de ganglio trigeminal (GT) enriquecido en neuronas y evaluar la expresión de interferón- y su actividad frente a la infección con Herpes simple tipo 1 (HSV-1). Materiales y métodos: El porcentaje de neuronas fue determinado por inmunocitoquímica para neurof [...] ilamento. Los cultivos fueron tratados con interferón- ? e infectados con HSV-1, y se cuantificaron las células positivas para antígeno viral por inmunocitoquímica y la expresión de interferón- ? por PCR cuantitativa. Resultados: El cultivo presentó un 15% de neuronas y 85% de células no neuronales. Se encontró efecto citopático, asociado a una alta diseminación de la infección (72,9% neuronas y 48,3% de células no neuronales positivas para antígeno viral). El interferón- ? evitó la aparición de efecto citopático y disminuyó las células infectadas a 16,7% en neuronas y a 7,8% las células no neuronales. La infección viral incrementó la expresión de transcritos de interferón- ? 18,2 veces a las 6 h de infección, mientras que a las 18 h post infección el tratamiento con interferón incrementó esta expresión 3,7 veces. Discusión: Los cultivos presentaron un 15% de neuronas, lo cual es 10 veces más que en otros cultivos reportados. Las células no neuronales representan el 85% de las células del cultivo, y se evidenció que todos los tipos de células se infectaron; similar a lo que ha sido reportado durante infecciones agudas in vivo . Adicionalmente, el interferón- ? disminuyó el porcentaje de células infectadas y evitó la aparición de efecto citopático, similar a lo que ha sido reportado en cultivos de GT porcino. Conclusiones: Se caracterizó un modelo de cultivo primario de GT enriquecido en neuronas. Interferón- ? protegió las células del efecto citopático y la diseminación viral mientras que la infección viral incrementó la expresión de interferón- ?. Por lo tanto, el interferón- ? ejerció un papel antiviral importante frente al HSV-1 en estos cultivos. Abstract in english Objective: To characterize a neuron-enriched primary TG culture and evaluate interferon- ? expression and activity after HSV-1 infection. Materials and methods: The percentage of neurons present in cultures was assessed by neurofilament immunocytochemistry. Cultures were treated with interferon- ? a [...] nd infected with HSV-1, then viral antigen positive cells were counted and interferon- ?expression was assessed by quantitative PCR. Results: The culture contained 15% neurons and 85% non-neuronal cells. A cytopathic effect was observed, associated with high viral spread (72.9% neurons and 48.3% non-neuronal cells were positive for viral antigen). Interferon- ? treatment impaired the cytopathic effect and decreased the infected neurons to 16.7% and infected non-neuronal cells to 7.8%. Viral infection at 6 h postinfection significantly increased the interferon- ? transcripts by 18.2 fold, while at 18 h postinfection Interferon pre-treatment in infected cultures increased interferon- ? transcription by 3.7 fold. Discussion: This culture model contained 15% neurons, which is 10 times higher compared to other reported cultures, and non-neuronal cells comprised 85% of cells in this culture. All types of cells were found to be infected, which is similar to that reported during acute infections in vivo . Additionally, interferon- ?decreased the infected cells, avoiding the cytopathic effect, which is similar to that reported in swine TG cultures. Conclusions: A neuron-enriched primary TG model was characterized. Interferon- ? treatment protected cells from cytopathic effects and viral spread, while viral infection up-regulated interferon- ? expression. This result means that interferon- ? exerts an important antiviral effect against HSV-1 in these cultures.

Ana Maria, Low-Calle; Jeanette, Prada-Arismendy; Jaime E., Castellanos.

350

[Effects of different fertilization regimes on abundance and community structure of the nirK-type denitrifying bacteria in greenhouse vegetable soils].  

Science.gov (United States)

The community structure and abundance of nirK-type denitrifying bacteria in different soil layers (0-20 cm and 20-40 cm) under various fertilization regimes in Wuwei, Gansu Province were investigated by the combination of terminal restriction fragment length polymorphism (T-RFLP) and real-time quantitative PCR. Results showed that the nirK-type denitrifying bacteria community structure was significantly affected by fertilization regimes, especially for 70, 156 and 190 bp T-RFs that represented the dominant populations in greenhouse soil. Fertilization regimes significantly influenced the abundance of nirK gene in the 0-20 cm soil layer with the highest abundance of nirK gene copy number (2.16 x 10(7) copies x g(-1) soil) detected in the manure treatment (M), which was 2.04 and 2.02 times of that in the control (CK) and chemical fertilizer (NPK) treatments, respectively. Both the dominant population and abundance of nirK-type denitrifying bacteria in the greenhouse soil were significantly different between the 0-20 cm and 20-40 cm soil layers, and the nirK-type denitrifying bacteria community structure and abundance in the greenhouse soil were obviously different from that in the field. Soil pH, soil organic matter content and nitrate-N content had the greatest influence on the bacterial community composition. Phylogenetic analysis indicated that there were not only anaerobic nirK-type denitrifying bacteria in greenhouse soil, but also aerobic denitrifying bacteria, such as Rhizobium, Ochrobactrum, Agrobacterium. PMID:24830252

Zeng, Xi-Bai; Wang, Ya-Nan; Wang, Yu-Zhong; Bai, Ling-Yu; Li, Lian-Fang; Duan, Ran; Su, Shi-Ming; Wu, Cui-Xia

2014-02-01

351

Denitrifiers in the surface zone are primarily responsible for the nitrous oxide emission of dairy manure compost  

Energy Technology Data Exchange (ETDEWEB)

Highlights: ? Nitrous oxide (N{sub 2}O) productions of each compost zones were compared. ? The pile surface emitted significant fluxes of N{sub 2}O. ? The isotopic signature of N{sub 2}O from surface and NO{sub 2}{sup ?} amended core were different. ? The denitrifying gene abundance was significantly higher in pile surface than the pile core. -- Abstract: During the dairy manure composting process, significant nitrous oxide (N{sub 2}O) emissions occur just after the pile turnings. To understand the characteristics of this N{sub 2}O emission, samples were taken from the compost surface and core independently, and the N{sub 2}O production was monitored in laboratory incubation experiments. Equal amounts of surface and core samples were mixed to simulate the turning, and the {sup 15}N isotope ratios within the molecules of produced N{sub 2}O were analyzed by isotopomer analysis. The results showed that the surface samples emitted significant levels of N{sub 2}O, and these emissions were correlated with NO{sub x}{sup ?}-N accumulation. Moreover, the surface samples and surface-core mixed samples incubated at 30 °C produced N{sub 2}O with a low site preference (SP) value (?0.9 to 7.0‰) that was close to bacteria denitrification (0‰), indicating that denitrifiers in the surface samples are responsible for this N{sub 2}O production. On the other hand, N{sub 2}O produced by NO{sub 2}{sup ?}-amended core samples and surface samples incubated at 60 °C showed unrecognized isotopic signatures (SP = 11.4–20.3‰). From these results, it was revealed that the N{sub 2}O production occurring just after the turnings was mainly derived from bacterial denitrification (including nitrifier denitrification) of NO{sub x}{sup ?}-N under mesophilic conditions, and surface denitrifying bacteria appeared to be the main contributor to this process.

Maeda, Koki, E-mail: k_maeda@affrc.go.jp [Dairy Research Division, National Agricultural Research Center for Hokkaido Region, National Agricultural and Food Research Organization, 1 Hitsujigaoka, Sapporo 062-8555 (Japan); Department of Environmental Chemistry and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502 (Japan); Toyoda, Sakae [Department of Environmental Chemistry and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502 (Japan); Hanajima, Dai [Dairy Research Division, National Agricultural Research Center for Hokkaido Region, National Agricultural and Food Research Organization, 1 Hitsujigaoka, Sapporo 062-8555 (Japan); Yoshida, Naohiro [Department of Environmental Chemistry and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502 (Japan)

2013-03-15

352

Diaphorobacter nitroreducens gen nov, sp nov, a poly(3-hydroxybutyrate)-degrading denitrifying bacterium isolated from activated sludge.  

Science.gov (United States)

Three denitrifying strains of bacteria capable of degrading poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) were isolated from activated sludge and characterized. All of the isolates had almost identical phenotypic characteristics. They were motile gram-negative rods with single polar flagella and grew well with simple organic compounds, as well as with PHB and PHBV, as carbon and energy sources under both aerobic and anaerobic denitrifying conditions. However, none of the sugars tested supported their growth. The cellular fatty acid profiles showed the presence of C16:1omega7cis and C16:0 as the major components and of 3-OH-C10:0 as the sole component of hydroxy fatty acids. Ubiquinone-8 was detected as the major respiratory quinone. A 16S rDNA sequence-based phylogenetic analysis showed that all the isolates belonged to the family Comamonadaceae, a major group of beta-Proteobacteria, but formed no monophyletic cluster with any previously known species of this family. The closest relative to our strains was an unidentified bacterium strain LW1 (=DSM 13225) (99.9% similarity), reported previously as a 1-chloro-4-nitrobenzene degrading bacterium. DNA-DNA hybridization levels among the new isolates were more than 60%, whereas those between our isolates and strain DSM 13225 were less than 50%. The G+C content of genomic DNA of the new strains was 64 to 65 mol%. Based on these results, we concluded that the PHBV-degrading denitrifying isolates should be classified as a new genus and a new species, for which we propose the name Diaphorobacter nitroreducens. The type strain is strain NA10B (=JCM 11421=CIP 107294). We also propose to classify strain DSM 13225 as a genospecies of Diaphorobacter. PMID:12682868

Khan, Shams Tabrez; Hiraishi, Akira

2002-12-01

353

Denitrifiers in the surface zone are primarily responsible for the nitrous oxide emission of dairy manure compost  

International Nuclear Information System (INIS)

Highlights: ? Nitrous oxide (N2O) productions of each compost zones were compared. ? The pile surface emitted significant fluxes of N2O. ? The isotopic signature of N2O from surface and NO2? amended core were different. ? The denitrifying gene abundance was significantly higher in pile surface than the pile core. -- Abstract: During the dairy manure composting process, significant nitrous oxide (N2O) emissions occur just after the pile turnings. To understand the characteristics of this N2O emission, samples were taken from the compost surface and core independently, and the N2O production was monitored in laboratory incubation experiments. Equal amounts of surface and core samples were mixed to simulate the turning, and the 15N isotope ratios within the molecules of produced N2O were analyzed by isotopomer analysis. The results showed that the surface samples emitted significant levels of N2O, and these emissions were correlated with NOx?-N accumulation. Moreover, the surface samples and surface-core mixed samples incubated at 30 °C produced N2O with a low site preference (SP) value (?0.9 to 7.0‰) that was close to bacteria denitrification (0‰), indicating that denitrifiers in the surface samples are responsible for this N2O production. On the other hand, N2O produced by NO2?-amended core samples and surface samples incubated at 60 °C showed unrecognized isotopic signatures (SP = 11.4–20.3‰). From these results, it was revealed that the N2O production occurring just after the turnings was mainly derived from bacterial denitrification (including nitrifier denitrification) of NOx?-N under mesophilic conditions, and surface denitrifying bacteria appeared to be the main contributor to this process

2013-03-15

354

Beta activity of enriched uranium  

International Nuclear Information System (INIS)

Use of enriched uranium as reactor fuel necessitates its handling in various forms. For purposes of planning and organising radiation protection measures in enriched uranium handling facilities, it is necessary to have a basic knowledge of the radiation status of enriched uranium systems. The theoretical variations in beta activity and energy with U"2"3"5 enrichment are presented. Depletion is considered separately. Beta activity build up is also studied for two specific enrichments, in respect of which experimental values for specific alpha activity are available. (author)

1975-01-01

355

Functional diversity in the denitrifying biofilm of the methanol-fed marine denitrification system at the Montreal Biodome.  

Science.gov (United States)

Nitrate is a serious problem in closed-circuit public aquariums because its accumulation rapidly becomes toxic to many lifeforms. A moving bed biofilm denitrification reactor was installed at the Montreal Biodome to treat its 3,250-m(3) seawater system. Naturally occurring microorganisms from the seawater affluent colonized the reactor carriers to form a denitrifying biofilm. Here, we investigated the functional diversity of this biofilm by retrieving gene sequences related to narG, napA, nirK, nirS, cnorB, and nosZ. A total of 25 sequences related to these genes were retrieved from the biofilm. Among them, the corresponding napA1, nirK1, cnorB9, and nosZ3 sequences were identical to the corresponding genes found in Hyphomicrobium sp. NL23 while the narG1 and narG2 sequences were identical to the two corresponding narG genes found in Methylophaga sp. JAM1. These two bacterial strains were previously isolated from the denitrifying biofilm. To assess the abundance of denitrifiers and nitrate respirers in the biofilm, the gene copy number of all the narG, napA, nirS, and nirK sequences found in biofilm was determined by quantitative PCR. napA1, nirK1, narG1, and narG2, which were all associated with either Methylophaga sp. JAM1 or Hyphomicrobium sp. NL23, were the most abundant genes. The other genes were 10 to 10,000 times less abundant. nirK, cnorB, and nosZ but not napA transcripts from Hyphomicrobium sp. NL23 were detected in the biofilm, and only the narG1 transcripts from Methylophaga sp. JAM1 were detected in the biofilm. Among the 19 other genes, the transcripts of only two genes were detected in the biofilm. Our results show the predominance of Methylophaga sp. JAM1 and Hyphomicrobium sp. NL23 among the denitrifiers detected in the biofilm. The results suggest that Hyphomicrobium sp. NL23 could use the nitrite present in the biofilm generated by nitrate respirers such as Methylophaga sp. JAM1. PMID:22006549

Auclair, Julie; Parent, Serge; Villemur, Richard

2012-05-01

356

Uranium enrichment by gas centrifuge  

International Nuclear Information System (INIS)

After recalling the physical principles and the techniques of centrifuge enrichment the report describes the centrifuge enrichment programmes of the various countries concerned and compares this technology with other enrichment technologies like gaseous diffusion, laser, aerodynamic devices and chemical processes. The centrifuge enrichment process is said to be able to replace with advantage the existing enrichment facilities in the short and medium term. Future prospects of the process are also described, like recycled uranium enrichment and economic improvements; research and development needs to achieve the economic prospects are also indicated. Finally the report takes note of the positive aspect of centrifuge enrichment as far as safeguards and nuclear safety are concerned. 27 figs, 113 refs

1988-01-01

357

Availability of enrichment services  

Energy Technology Data Exchange (ETDEWEB)

Within one decade, uranium enrichment services have changed from a monopoly supplier's market to a diversified supply situation allowing buyers to satisfy their needs in an optimal way. In 1970, the medium term possibility to meet requirements still appeared to be uncertain, with the U.S. Atomic Energy Commission acting practically as the only supplier, or even endangered by orders to stop deliveries, which the U.S. administration could have issued at any time, but already by the late seventies there were at least four potential suppliers with considerable aggregate excess capacities, the range of services of which the utilities were able to exploit for their own advantage. The position of companies offering separative work services is rendered even more difficult by existing excess quantities held partly in government stockpiles, partly by the utilities, and by good chances to buy on the secondary market. Thanks to their high flexibility the operators of centrifuge plants are best equipped to meet this situation; for this reason they think they will be able to maintain or even improve their competitiveness in the future. In August 1979, Urenco Deutschland GmbH was founded with the British and Netherlands partners of Urenco. Uranit GmbH is engaged in building for the German company a centrifuge uranium enrichment plant at Gronau, Westphalia, with a design capacity of 1000 t SWU/a.

Mohrhauer, H.

358

Availability of enrichement services  

International Nuclear Information System (INIS)

Within one decade, uranium enrichment services have changed from a monopoly supplier's market to a diversified supply situation allowing buyers to satisfy their needs in an optimal way. In 1970, the medium term possibility to meet requirements still appeared to be uncertain, with the U.S. Atomic Energy Commission acting practically as the only supplier, or even endangered by orders to stop deliveries, which the U.S. administration could have issued at any time, but already by the late seventies there were at least four potential suppliers with considerable aggregate excess capacities, the range of services of which the utilities were able to exploit for their own advantage. The position of companies offering separative work services is rendered even more difficult by existing excess quantities held partly in government stockpiles, partly by the utilities, and by good chances to buy on the secondary market. Thanks to their high flexibility the operators of centrifuge plants are best equipped to meet this situation; for this reason they think they will be able to maintain or even improve their competitiveness in the future. In August 1979, Urenco Deutschland GmbH was founded with the British and Netherlands partners of Urenco. Uranit GmbH is engaged in building for the German company a centrifuge uranium enrichment plant at Gronau, Westphalia, with a design capacity of 1000 t SWU/a. (orig.)

1984-05-22

359

Impacts of nitrogen application rates on the activity and diversity of denitrifying bacteria in the Broadbalk Wheat Experiment.  

Science.gov (United States)

Bacterial denitrification results in the loss of fertilizer nitrogen and greenhouse gas emissions as nitrous oxides, but ecological factors in soil influencing denitrifier communities are not well understood, impeding the potential for mitigation by land management. Communities vary in the relative abundance of the alternative dissimilatory nitrite reductase genes nirK and nirS, and the nitrous oxide reductase gene nosZ; however, the significance for nitrous oxide emissions is unclear. We assessed the influence of different long-term fertilization and cultivation treatments in a 160-year-old field experiment, comparing the potential for denitrification by soil samples with the size and diversity of their denitrifier communities. Denitrification potential was much higher in soil from an area left to develop from arable into woodland than from a farmyard manure-fertilized arable treatment, which in turn was significantly higher than inorganic nitrogen-fertilized and unfertilized arable plots. This correlated with abundance of nirK but not nirS, the least abundant of the genes tested in all soils, showing an inverse relationship with nirK. Most genetic variation was seen in nirK, where sequences resolved into separate groups according to soil treatment. We conclude that bacteria containing nirK are most probably responsible for the increased denitrification potential associated with nitrogen and organic carbon in this soil. PMID:22451109

Clark, Ian M; Buchkina, Natalya; Jhurreea, Deveraj; Goulding, Keith W T; Hirsch, Penny R

2012-05-01

360

Denitrifying bacteria from the genus Rhodanobacter dominate bacterial communities in the highly contaminated subsurface of a nuclear legacy waste site  

Energy Technology Data Exchange (ETDEWEB)

The effect of long-term mixed-waste contamination, particularly uranium and nitrate, on the microbial community in the terrestrial subsurface was investigated at the field scale at the Oak Ridge Integrated Field Research Challenge (ORIFRC) site in Oak Ridge, TN. The abundance, community composition, and distribution of groundwater microorganisms were examined across the site during two seasonal sampling events. At representative locations, subsurface sediment was also examined from two boreholes, one sampled from the most heavily contaminated area of the site and another from an area with low contamination. A suite of DNA- and RNA-based molecular tools were employed for community characterization, including quantitative PCR of ribosomal RNA and nitrite reductase genes, community composition fingerprinting analysis, and high-throughput pyrotag sequencing of rRNA genes. The results demonstrate that pH is a major driver of the subsurface microbial community structure, and denitrifying bacteria from the genus Rhodanobacter (class Gammaproteobacteria) dominate at low pH. The relative abundance of bacteria from this genus was positively correlated with lower pH conditions, and these bacteria were abundant and active in the most highly contaminated areas. Other factors, such as concentration of nitrogen species, oxygen and sampling season did not appear to strongly influence the distribution of Rhodanobacter. Results indicate that these organisms are acid-tolerant denitrifiers, well suited to the acidic, nitrate-rich subsurface conditions, and pH is confirmed as a dominant driver of bacterial community structure in this contaminated subsurface environment.

Green, Stefan [Florida State University; Prakash, Om [Florida State University; Jasrotia, Puja [Florida State University; Overholt, Will [Florida State University; Cardenas, Erick [Michigan State University, East Lansing; Hubbard, Daniela [Florida State University; Tiedje, James M. [Michigan State University, East Lansing; Watson, David B [ORNL; Schadt, Christopher Warren [ORNL; Brooks, Scott C [ORNL; Kostka, Joel [Florida State University

2011-01-01

 
 
 
 
361

Isolation of the {epsilon}-caprolactam denitrifying bacteria from a wastewater treatment system manufactured with acrylonitrile-butadiene-styrene resin  

Energy Technology Data Exchange (ETDEWEB)

{epsilon}-Caprolactam has high COD and toxicity, so its discharge to natural water and soil systems may lead to an adverse environmental effect on water quality, endangering public health and welfare. This investigation attempts to isolate {epsilon}-caprolactam denitrifying bacteria from a wastewater treatment system manufactured with acrylonitrile-butadiene-styrene (ABS) resin. The goal is to elucidate the effectiveness of isolated pure strain and ABS mixed strains in treating {epsilon}-caprolactam from synthetic wastewater. The results reveal that Paracoccus versutus MDC-3 was isolated from the wastewater treatment system manufactured with ABS resin. The ABS mixed strains and P. versutus MDC-3 can consume up to 1539 mg/l {epsilon}-caprolactam to denitrify from synthetic wastewater. Complete {epsilon}-caprolactam removal depended on the supply of sufficient electron acceptors (nitrate). Strain P. versutus MDC-3, Hyphomicrobium sp. HM, Methylosinus pucelana and Magnetospirillum sp. CC-26 are related closely, according to the phylogenetic analyses of 16S rDNA sequences.

Wang, C.-C. [Department of Environmental Engineering, Hungkuang University, Shalu, Taichung 433, Taiwan (China)]. E-mail: chunchin@sunrise.hk.edu.tw; Lee, C.-M. [Department of Environmental Engineering, National Chung Hsing University, Taichung 402, Taiwan (China)

2007-06-25

362

Gronau uranium enrichment plant  

Energy Technology Data Exchange (ETDEWEB)

The German uranium enrichment plant at Gronau is part of British-German-Netherlands cooperation in the field of uranium isotope separation. The three companies of Urenco had an aggregate capacity of some 1500 t SWU/a in operation in late 1985, which is to be doubled in order to meet requirements. The delivery contracts entered into by Urenco make it necessary that the German plant, operating at 150 t SWU/a at the moment, go beyond the presently licensed capacity of 400 t SWU/a already around mid-1988 and attain its full capacity of 1000 t SWU/a around 1992. The steady improvement in performance of the centrifuges and their high availability ensures the international competitiveness of the Urenco facilities.

Mohrhauer, H.

1986-07-01

363

Stem cell enrichment approaches.  

Science.gov (United States)

Adult somatic tissue, and the tumours that arise therein, are maintained by a small population of stem cells. In addition to the self-renewal potential and pluripotency, these stem cells express several phenotypic traits that can be used in isolation and enrichment strategies. Since most of the traits are not exclusive to the stem cells however, the resultant populations are typically heterogeneous and variable from one isolation to another. In this article, we review the strategies for isolation of stem cells, and the limitations thereof, with emphasis on mesenchymal tissue and bone tumours. The emerging evidence suggests that stem cell is not a distinct entity, but rather an indefinite state along a spectrum, characterized by phenotypic traits, epigenetic factors and the microenvironment. PMID:16814562

Park, Paul C; Selvarajah, Shamini; Bayani, Jane; Zielenska, Maria; Squire, Jeremy A

2007-06-01

364

Enrichment of boron 10  

International Nuclear Information System (INIS)

A isotopic separation pilot plant with five ion exchange columns interconnected in series were designed and built in the IEN. The columns are charged with a strong anionic resin in its alkaline form. The boric acid solution is introduced in the separation columns until it reaches a absorbing zone length which is sufficient to obtain the desired boron-10 isotopic concentration. The boric acid absorbing zone movement is provided by the injection of a diluted hydrochloric acid solution, which replace the boric acid throughout the columns. The absorbing zone equilibrium length is proportional to its total length. The enriched boron-10 and the depleted boron are located in the final boundary and in the initial position of the absorbing zones, respectively. (author)

1990-04-22

365

Uranium enrichment device  

International Nuclear Information System (INIS)

A device for enriching uranium by the separating-nozzle process is claimed. The device includes a plurality of separating-stage units, upstream coolers, associated compressors and duct means for supplying the starting gas and for incorporating the separating-stage units into a cascade. A vacuum-tight vessel having a circular cross-section is divided by radial partitions into sectors for the individual stages in cascade. The duct means include gas ducts disposed centrally in the sectors and in the lower part of the vessel. The vessel is spherical in shape, strengthened by the radial partitions and mounted on a central cruciform support defining four cross-sectional regions, the separating-stage units and the coolers being disposed in the sectors. The compressors are divided into four sets forming independent structures and are removably disposed in the cross-sectional regions beneath the vessel

1978-03-17

366

Uranium enrichment device  

International Nuclear Information System (INIS)

A device for enriching uranium by the separating-nozzle process, is claimed. It inlcudes a plurality of separating-element units; a plurality of heat-exchangers including tubes and constructed as coolers positioned upstream of the separating-element units; a corresponding number of associated compressors; and gas ducts for supplying the starting gas and for incorporating the separating-element units into cascades during operation. The individual separating-element units and heat exchangers form individual components of a cascade stage, each component being disposed in a compartment of a vessel having a substantially circular cross-section. The compressors are removably mounted under the vessel. The vessel is horizontally disposed on supports and the compartments are formed by diametrical partitions in the vessels. The heat exchangers have tubes which extend through the compartments and diametrical partitions. The device further includes a distribution chamber connected upstream and a header connected downstream of the vessel

1978-03-17

367

Effects of elevated CO2 concentrations on denitrifying and nitrifying popualtions at terrestrial CO2 leakeage analogous sites  

Science.gov (United States)

CO2 capture and geological storage (CCS) is recognized to be an important option for carbon abatement in Europe. One of the risks of CCS is the leakage from storage site. A laboratory was conducted on soil samples sampled near-surface from a CO2 leakage analogous site (Latera, Italy) in order to evaluate the impact of an elevated soil CO2 concentration on terrestrial bacterial ecosystems form near surface terrestrial environments and to determine a potential bacterial indicator of CO2 leakage from storage site. Surveys were conducted along a 50m long transect across the vent centre, providing a spectrum of CO2 flux rates, soil gas concentrations and compositions (Beaubien et al., 2007). A bacterial diversity studies, performed by CE-SSCP technique, on a soil profile with increasing CO2 soil concentrations (from 0.3% to 100%) showed that a change on bacterial diversity was noted when CO2 concentration was above 50 % of CO2. From this result, 3 soil samples were taken at 70 cm depth in 3 distinct zones (background soil CO2 content, soil CO2 content of 20% and soil CO2 content of 50%). Then theses soil samples were incubated under closed jars flushed with different air atmospheres (20, 50 and 90 % of CO2) during 18 months. At initial, 3, 6, 12 and 18 months, some soil samples were collected in order to estimate the denitrifying, nitrifying activities as a function of CO2 concentration content and times. Theses enzymatic activities were chosen because one occurs under anaerobic conditions (denitrification) and the other occurs under aerobic conditions (nitrification). Both of them were involved in the nitrogen cycle and are major actors of soil function and groundwater quality preservation. Metabolic diversity using BIOLOG Ecoplates was determined on every soil samples. Physico-chemical parameters (e.g. pH, bulk chemistry, mineralogy) were analyzed to have some information about the evolution of the soil during the incubation with increasing soil CO2 concentrations. Statistical analyses were performed to correlate microbiological measures and physico-chemical parameters. For the soil sampled in a zone with background CO2 content, incubation under an atmosphere with 20% of CO2, induce a sharp decrease of denitrifying activity after 6 months of incubation and only after 3 months with an atmosphere of 50% of CO2. On the contrary, concerning the soil sampled in a zone with 25.5% of CO2, incubation with an atmosphere of 50% has no effect on denitrifying activity and moreover this activity was stimulated with an atmosphere of 90% of CO2.Last, with the soil sampled in an area with 65.8% of CO2, denitrifying activity was negatively impacted from the 3th month of incubation with 90% CO2.and the activity was 2 fold lower after 12th of incubation. Concerning the nitrifying activity, soil sampled in an area with background CO2 content, this one remains little affected by increasing CO2 incubation. At initial times, soil sampled in the areas with 25.5 and 65.8 % of CO2 showed low level of nitrifying activities and further CO2 incubations have no effect on these activities. At the end, denitrifying activities seems to be more sensitive to CO2 concentrations evolution in the soil. More studies need to be done as incubation with lower CO2 content (threshold of CO2 that can affect the near-surface bacterial activities and identify a possible candidate of CO2 leakage from deep reservoirs.

Christine, Dictor Marie; Catherine, Joulian; Valerie, Laperche; Stephanie, Coulon; Dominique, Breeze

2010-05-01

368

Marriage Enrichment: Friend or Foe?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Marriage enrichment programs seem to have particular appeal to couples who hope to improve their relationship in their middle years. These programs usually take the form of a weekend retreat, and are limited to and usually led by married couples. Marriage enrichment programs should not be confused with encounter groups which flourished in the 1950s and 1960s. Some encounter groups deliberately used confrontation to bring anger or fear to the surface; enrichment programs emphasize the positive...

Bader, Edward

1984-01-01

369

Enrichment of live foods.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Live foods such rotifers and Artemia are still indispensable for mass propagation of larval fish. At present, more than 20 fish and crustacean species are mass produced in Japanese governmental fish farming centres and private hatcheries. Fry are either released into the coastal areas or used for commercial cultivation. This culture technology is rapidly developing with new species being introduced each year and larval rearing is increasingly identified as the number one constraint. Artemia i...

1989-01-01

370

Enrichment of Thermophilic Propionate-Oxidizing Bacteria in Syntrophy with Methanobacterium thermoautotrophicum or Methanobacterium thermoformicicum  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Thermophilic propionate-oxidizing, proton-reducing bacteria were enriched from the granular methanogenic sludge of a bench-scale upflow anaerobic sludge bed reactor operated at 55°C with a mixture of volatile fatty acids as feed. Thermophilic hydrogenotrophic methanogens had a high decay rate. Therefore, stable, thermophilic propionate-oxidizing cultures could not be obtained by using the usual enrichment procedures. Stable and reproducible cultivation was possible by enrichment in hydrogen-...

Stams, Alfons J. M.; Grolle, Katja C. F.; Frijters, Carla T. M.; Lier, Jules B.

1992-01-01

371

Distribution of typical denitrifying functional genes and diversity of the nirS-encoding bacterial community related to environmental characteristics of river sediments  

Science.gov (United States)

Denitrification in river sediments leads to nitrate removal from the aquatic system; therefore, it is necessary to understand functional diversity of denitrifier communities in the system. Sediment samples (0-25 cm depth) were collected from three typical locations along the Pearl River. The real-time PCR approach was used to measure the abundance of nitrate (narG), nitrite (nirS, nirK and nrfA), and nitrous oxide (nosZ) reductase genes from the sediment samples. Assemblages of nirS, nirK and nosZ indicated that complete denitrification occurred in sediment cores, with the greatest number of gene copies from 5-15 cm depth. Dissimilatory nitrate reduction appeared to be important below 15 cm depth, based on increasing gene copies of narG and nrfA with sediment depth. There was a close match (78-94 %) between the nirS sequences recovered from the Pearl River sediment and those detected in estuarine and marine sediments as well as active sludge, suggesting that the nitrogen source in the Pearl River sediment was affected by domestic sewage inputs and irregular tides. Canonical correspondence analysis indicated that the spatial distribution of denitrifying bacteria was highly correlated with dissolved inorganic nitrogen (including NH4+, NO2- and NO3-) concentrations in sediment. It was concluded that the difference in dissolved inorganic nitrogen concentrations along the sediment profile influenced the distribution of denitrifying genes and the nirS-encoding denitrifier community in the river sediment. In addition, a variety of novel denitrifying bacteria were revealed in the river sediment.

Huang, S.; Chen, C.; Yang, X.; Wu, Q.; Zhang, R.

2011-10-01

372

Distribution of typical denitrifying functional genes and diversity of the nirS-encoding bacterial community related to environmental characteristics of river sediments  

Directory of Open Access Journals (Sweden)

Full Text Available Denitrification in river sediments leads to nitrate removal from the aquatic system; therefore, it is necessary to understand functional diversity of denitrifier communities in the system. Sediment samples (0–25 cm depth were collected from three typical locations along the Pearl River. The real-time PCR approach was used to measure the abundance of nitrate (narG, nitrite (nirS, nirK and nrfA, and nitrous oxide (nosZ reductase genes from the sediment samples. Assemblages of nirS, nirK and nosZ indicated that complete denitrification occurred in sediment cores, with the greatest number of gene copies from 5–15 cm depth. Dissimilatory nitrate reduction appeared to be important below 15 cm depth, based on increasing gene copies of narG and nrfA with sediment depth. There was a close match (78–94 % between the nirS sequences recovered from Pearl River sediment and those detected in estuarine and marine sediments as well as active sludge, suggesting that domestic sewage inputs and irregular tides. Canonical correspondence analysis indicated that the spatial distribution of denitrifying bacteria was highly correlated with dissolved inorganic N (DIN: NH4+, NO2 and NO3? concentrations in sediment. We conclude that changes in DIN within the sediment profile influences the distribution of denitrifying genes and the nirS-encoding denitrifier community in the river sediment. Our results also reveal a variety of novel denitrifying bacteria in the river sediment.

X. Yang

2011-05-01

373

Distribution of typical denitrifying functional genes and diversity of the nirS-encoding bacterial community related to environmental characteristics of river sediments  

Directory of Open Access Journals (Sweden)

Full Text Available Denitrification in river sediments leads to nitrate removal from the aquatic system; therefore, it is necessary to understand functional diversity of denitrifier communities in the system. Sediment samples (0–25 cm depth were collected from three typical locations along the Pearl River. The real-time PCR approach was used to measure the abundance of nitrate (narG, nitrite (nirS, nirK and nrfA, and nitrous oxide (nosZ reductase genes from the sediment samples. Assemblages of nirS, nirK and nosZ indicated that complete denitrification occurred in sediment cores, with the greatest number of gene copies from 5–15 cm depth. Dissimilatory nitrate reduction appeared to be important below 15 cm depth, based on increasing gene copies of narG and nrfA with sediment depth. There was a close match (78–94 % between the nirS sequences recovered from the Pearl River sediment and those detected in estuarine and marine sediments as well as active sludge, suggesting that the nitrogen source in the Pearl River sediment was affected by domestic sewage inputs and irregular tides. Canonical correspondence analysis indicated that the spatial distribution of denitrifying bacteria was highly correlated with dissolved inorganic nitrogen (including NH4+, NO2? and NO3? concentrations in sediment. It was concluded that the difference in dissolved inorganic nitrogen concentrations along the sediment profile influenced the distribution of denitrifying genes and the nirS-encoding denitrifier community in the river sediment. In addition, a variety of novel denitrifying bacteria were revealed in the river sediment.

R. Zhang

2011-10-01

374

Effects of temperatures near the freezing point on N2O emissions, denitrification and on the abundance and structure of nitrifying and denitrifying soil communities.  

Science.gov (United States)

Climate warming in temperate regions may lead to decreased soil temperatures over winter as a result of reduced snow cover. We examined the effects of temperatures near the freezing point on N(2)O emissions, denitrification, and on the abundance and structure of soil nitrifiers and denitrifiers. Soil microcosms supplemented with NO3 - and/or NO3 - plus red clover residues were incubated for 120 days at -4 °C, -1 °C, +2 °C or +5 °C. Among microcosms amended with residues, N(2)O emission and/or denitrification increased with increasing temperature on Days 2 and 14. Interestingly, N(2)O emission and/or denitrification after Day 14 were the greatest at -1 °C. Substantial N(2) O emissions were only observed on Day 2 at +2 °C and +5 °C, while at -1 °C, N(2)O emissions were consistently detected over the duration of the experiment. Abundances of ammonia oxidizing bacteria (AOB) and archaea (AOA), Nitrospira-like bacteria and nirK denitrifiers were the lowest in soils at -4 °C, while abundances of Nitrobacter-like bacteria and nirS denitrifiers did not vary among temperatures. Community structures of nirK and nirS denitrifiers and Nitrobacter-like bacteria shifted between below-zero and above-zero temperatures. Structure of AOA and AOB communities also changed but not systematically among frozen and unfrozen temperatures. Results indicated shifts in some nitrifier and denitrifier communities with freezing and a surprising stimulation of N(2)O emissions at -1 °C when NO3 - and C are present. PMID:22882277

Wertz, Sophie; Goyer, Claudia; Zebarth, Bernie J; Burton, David L; Tatti, Enrico; Chantigny, Martin H; Filion, Martin

2013-01-01

375

Phylogenetic analyses of a new group of denitrifiers capable of anaerobic growth of toluene and description of Azoarcus tolulyticus sp. nov.  

Science.gov (United States)

To understand the phylogeny and taxonomy of eight new toluene-degrading denitrifying isolates, we performed a 16S rRNA sequence analysis and a gas chromatographic analysis of their cellular fatty acids and examined some of their biochemical and physiological features. These isolates had 16s rRNA sequence signatures identical to those of members of the beta subclass of the Proteobacteria. The levels of similarity were as follows: 97.9 to 99.9% among the new isolates; 91.2 to 92.4% between the new isolates and Azoarcus sp. strain S5b2; 95.3 to 96.2% between the new isolates and Azoarcus sp. strain BH72; and 94.8 to 95.3% between the new isolates and Azoarcus indigens VB32T (T = type strain). Phylogenetic trees constructed by using the distance matrix, maximum-parsimony, and maximum-likelihood methods showed that our eight denitrifying isolates form a phylogenetically coherent cluster which represents a sister lineage of the previously described Azoarcus species. Furthermore, the fatty acid profiles, the cell morphology, and several physiological and nutritional characteristics of the eight isolates and the previously described members of the genus Azoarcus were also similar. In contrast to the previously described members of the genus Azoarcus, the eight new isolates were capable of degrading toluene under denitrifying conditions. We concluded that these toluene-degrading denitrifiers are members of a new species of the novel nitrogen-fixing genus Azoarcus. We propose the name Azoarcus tolulyticus for these toluene-degrading denitrifying isolates and designate strain Tol-4 the type strain. PMID:8590677

Zhou, J; Fries, M R; Chee-Sanford, J C; Tiedje, J M

1995-07-01

376

Inhibition of bacteriochlorophyll synthesis in Rhodobacter sphaeroides subsp. denitrificans grown in light under denitrifying conditions.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The inclusion of nitrate or nitrite in cultures of Rhodobacter spaeroides subsp. denitrificans grown heterotrophically in light depressed the formation of bacteriochlorophyll a. The pigment biosynthesis was inhibited at the stage of the reduction of chlorophyllide (chlorin) to bacteriochlorophyllide (tetrahydroporphyrin) since 3-hydroxyethylchlorophyllide a accumulated in the culture medium. The addition of exogenous 5-aminolevulinic acid to these cultures resulted in a complete restoration o...

Michalski, W. P.; Nicholas, D. J.

1987-01-01

377

Homotopy locally presentable enriched categories  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We develop a homotopy theory of categories enriched in a monoidal model category V. In particular, we deal with homotopy weighted limits and colimits, and homotopy local presentability. The main result, which was known for simplicially-enriched categories, links homotopy locally presentable V-categories with combinatorial model V-categories, in the case where has all objects of V are cofibrant.

Lack, Stephen; Rosicky, Jiri

2013-01-01

378

Industrial aspects in uranium enrichment  

International Nuclear Information System (INIS)

Characteristics of isotope separation processes in operation and under development are discussed. These include the number of stages in series, the number of components, the component unit capacity and enery requirements. The implementation of an enrichment process and the question of an enrichment plant in Australia are also considered

1982-05-14

379

Uranium enrichment by centrifuges  

International Nuclear Information System (INIS)

After having built the pilot plants and industrial demonstration plants in Great Britain and the Netherlands, now, besides the British and Dutch plants being built, another plant with an annual capacity of 1000 t UTA with centrifuge is planned on a German site. After having examined a number of potential sites, Gronau in the region Muensterland was selected. In March 1979, a settling contract was signed by the city of Gronau and the Uranit Company for the Urenco Deutschland oHG and the M.A.N.-Uranit Gronau GmbH. By the end of 1980, within the frame of the licensing procedure the expert's report on the 1st TEG covering the conventional technique and the operational part was finished. According to the time schedule, the 1st TEG is expected in the second quarter of 1981. Thus, the start-up might take place in the first quarter of 1984. The plant concept which the uranium enrichment plant Gronau was based on and which is dealt with closely allows a step-by-step construction with the first section of 400 t UTA possibly ready for start-up by the mid eighties. The development potential of the centrifuges seems to allow an essential reduction in the plant expenses from the mid of the eighties on. (orig./UA)

1981-01-00

380

Enrichment operations outlook  

International Nuclear Information System (INIS)

The U. S. gaseous diffusion plants have achieved an admirable record of performance and reliability, and there is confidence it can be maintained through the rest of this century. In addition to aggressive regular maintenance, three specific programs are combined to maximize the reliability of the plants: A Deferred Maintenance Program to restore production equipment and associated auxiliary systems; a Cascade Improvement Program (CIP) to install new and improved technology such as rebuilt and more efficient compressors, piping and control valves with better aerodynamic characteristics, and new and improved barrier; and a Cascade Uprating Program (CUP) to refurbish and add capacity to electrical and process cooling systems. A three-plant steering committee has been formed to examine in detail all aspects of enrichment facilities not already covered by these three specific programs, and task forces have been assigned to investigate in depth long-term reliability in these areas. In many cases, specific testing programs have been designed to evaluate the potential life of components, and information from commercial industries is routinely used. Where deficiencies are found, capital budget items are submitted and corrective action planned. Existing experience is available to those industries concerned with new plant ventures, and the Industrial Participation Program is one example where private industry can take full advantage of this existing experience. (U.S.)

1975-03-18

 
 
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