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1

Enrichment of Denitrifying Methane-Oxidizing Microorganisms Using Up-Flow Continuous Reactors and Batch Cultures  

Science.gov (United States)

Denitrifying anaerobic methane oxidizing (DAMO) microorganisms were enriched from paddy field soils using continuous-flow and batch cultures fed with nitrate or nitrite as a sole electron acceptor. After several months of cultivation, the continuous-flow cultures using nitrite showed remarkable simultaneous methane oxidation and nitrite reduction and DAMO bacteria belonging to phylum NC10 were enriched. A maximum volumetric nitrite consumption rate of 70.4±3.4 mg-N·L?1·day?1 was achieved with very short hydraulic retention time of 2.1 hour. In the culture, about 68% of total microbial cells were bacteria and no archaeal cells were detected by fluorescence in situ hybridization. In the nitrate-fed continuous-flow cultures, 58% of total microbial cells were bacteria while archaeal cells accounted for 7% of total cell numbers. Phylogenetic analysis of pmoA gene sequence showed that enriched DAMO bacteria in the continuous-flow cultivation had over 98% sequence similarity to DAMO bacteria in the inoculum. In contrast, for batch culture, the enriched pmoA gene sequences had 89–91% sequence similarity to DAMO bacteria in the inoculum. These results indicate that electron acceptor and cultivation method strongly affect the microbial community structures of DAMO consortia. PMID:25545013

Hatamoto, Masashi; Kimura, Masafumi; Sato, Takafumi; Koizumi, Masato; Takahashi, Masanobu; Kawakami, Shuji; Araki, Nobuo; Yamaguchi, Takashi

2014-01-01

2

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

3

Simultaneous enrichment of denitrifying methanotrophs and anammox bacteria.  

Science.gov (United States)

Interaction between denitrifying anaerobic methane oxidation (DAMO) and anaerobic ammonium oxidation (anammox) processes may play an important role in global carbon and nitrogen cycles. In this study, a coculture of denitrifying methanotrophs (DAMO archaea and DAMO bacteria) and anammox bacteria, initially sourced from the environment, was enriched with a supply of methane, nitrate, and ammonium. After a 4.5-month enrichment, simultaneous oxidation of methane and ammonium and reduction of nitrate were observed. The highest rate of nitrate reduction in the suspended DAMO culture was 4.84 mmol/L/day, and simultaneously, the highest ammonium removal rate was 4.07 mmol/L/day. Fluorescence in situ hybridization and analysis of 16S rRNA gene clone libraries revealed the coexistence of DAMO archaea, DAMO bacteria, and anammox bacteria. The development of anammox bacteria might reduce the enrichment time of DAMO microorganisms and promote the activity of DAMO archaea. The activity of the reactor fluctuated during the long-term operation, which might be caused by the formation of microbial clusters whereby DAMO archaea grew in aggregates that were surrounded by anammox and DAMO bacteria. This study is the first to demonstrate that it is feasible to establish a coculture of DAMO archaea, DAMO bacteria, and anammox bacteria from environmental inocula. PMID:25056292

Ding, Zhao-Wei; Ding, Jing; Fu, Liang; Zhang, Fang; Zeng, Raymond J

2014-12-01

4

Rapid succession of uncultured marine bacterial and archaeal populations in a denitrifying continuous culture.  

Science.gov (United States)

Marine denitrification constitutes an important part of the global nitrogen cycle and the diversity, abundance and process rates of denitrifying microorganisms have been the focus of many studies. Still, there is little insight in the ecophysiology of marine denitrifying communities. In this study, a heterotrophic denitrifying community from sediments of a marine intertidal flat active in nitrogen cycling was selected in a chemostat and monitored over a period of 50 days. The chemostat enabled the maintenance of constant and well-defined experimental conditions over the time-course of the experiment. Analysis of the microbial community composition by automated ribosomal intergenic spacer analysis (ARISA), Illumina sequencing and catalyzed reporter deposition fluorescence in situ hybridization (CARD-FISH) revealed strong dynamics in community composition over time, while overall denitrification by the enrichment culture was stable. Members of the genera Arcobacter, Pseudomonas, Pseudovibrio, Rhodobacterales and of the phylum Bacteroidetes were identified as the dominant denitrifiers. Among the fermenting organisms co-enriched with the denitrifiers was a novel archaeon affiliated with the recently proposed DPANN-superphylum. The pan-genome of populations affiliated to Pseudovibrio encoded a NirK as well as a NirS nitrite reductase, indicating the rare co-occurrence of both evolutionary unrelated nitrite reductases within coexisting subpopulations. PMID:24976559

Kraft, Beate; Tegetmeyer, Halina E; Meier, Dimitri; Geelhoed, Jeanine S; Strous, Marc

2014-10-01

5

Impact of mercury on denitrification and denitrifying microbial communities in nitrate enrichments of subsurface sediments.  

Science.gov (United States)

The contamination of groundwater with mercury (Hg) is an increasing problem worldwide. Yet, little is known about the interactions of Hg with microorganisms and their processes in subsurface environments. We tested the impact of Hg on denitrification in nitrate reducing enrichment cultures derived from subsurface sediments from the Oak Ridge Integrated Field Research Challenge site, where nitrate is a major contaminant and where bioremediation efforts are in progress. We observed an inverse relationship between Hg concentrations and onset and rates of denitrification in nitrate enrichment cultures containing between 53 and 1.1 ?M of inorganic Hg; higher Hg concentrations increasingly extended the time to onset of denitrification and inhibited denitrification rates. Microbial community complexity, as indicated by terminal restriction fragment length polymorphism (tRFLP) analysis of the 16S rRNA genes, declined with increasing Hg concentrations; at the 312 nM Hg treatment, a single tRFLP peak was detected representing a culture of Bradyrhizobium sp. that possessed the merA gene indicating a potential for Hg reduction. A culture identified as Bradyrhizobium sp. strain FRC01 with an identical 16S rRNA sequence to that of the enriched peak in the tRFLP patterns, reduced Hg(II) to Hg(0) and carried merA whose amino acid sequence has 97 % identity to merA from the Proteobacteria and Firmicutes. This study demonstrates that in subsurface sediment incubations, Hg may inhibit denitrification and that inhibition may be alleviated when Hg resistant denitrifying Bradyrhizobium spp. detoxify Hg by its reduction to the volatile elemental form. PMID:22678127

Wang, Yanping; Wiatrowski, Heather A; John, Ria; Lin, Chu-Ching; Young, Lily Y; Kerkhof, Lee J; Yee, Nathan; Barkay, Tamar

2013-02-01

6

Selenite reduction by a denitrifying culture: batch- and packed-bed reactor studies.  

Science.gov (United States)

Selenite reduction by a bacterial consortium enriched from an oil refinery waste sludge was studied under denitrifying conditions using acetate as the electron donor. Fed-batch studies with nitrate as the primary electron acceptor showed that accumulation of nitrite led to a decrease in the extent of selenite reduction. Also, when nitrite was added as the primary electron acceptor, rapid selenite reduction was observed only after nitrite was significantly depleted from the medium. These results indicate that selenite reduction was inhibited at high nitrite concentrations. In addition to batch experiments, continuous-flow selenite reduction experiments were performed in packed-bed columns using immobilized enrichment cultures. These experiments were carried out in three phases: in phase I, a continuous nitrate feed with different inlet selenite concentration was applied; in phase II, nitrate was fed in a pulsed fashion; and in phase III, nitrate was fed in a continuous mode but at much lower concentrations than the other two phases. During the phase I experiments, little selenite was removed from the influent. However, when the column was operated in the pulse feed strategy (phase II) or in the continuous mode with low nitrate levels (phase III), significant quantities of selenium were removed from solution and retained in the immobilization matrix in the column. Thus, immobilized denitrifying cultures can be effective in removing selenium from waste streams, but nitrate-limited operating conditions might be required. PMID:16432744

Viamajala, Sridhar; Bereded-Samuel, Yared; Apel, William A; Petersen, James N

2006-08-01

7

Selenite Reduction by a Denitrifying Culture: Batch- and Packed-Bed- Reactor Studies  

Energy Technology Data Exchange (ETDEWEB)

Selenite reduction by a bacterial consortium enriched from an oil refinery waste sludge was studied under denitrifying conditions using acetate as the electron donor. Fed-batch studies with nitrate as the primary electron acceptor showed that accumulation of nitrite led to a decrease in the extent of selenite reduction. Also, when nitrite was added as the primary electron acceptor, rapid selenite reduction was observed only after nitrite was significantly depleted from the medium. These results indicate that selenite reduction was inhibited at high nitrite concentrations. In addition to batch experiments, continuous flow selenite reduction experiments were performed in packed-bed columns using immobilized enrichment cultures. These experiments were carried out in three phases: In phase-I, a continuous nitrate feed with different inlet selenite concentration was applied; in phase-II, nitrate was fed in a pulsed fashion; and in phase-III, nitrate was fed in a continuous mode but at much lower concentrations than the other two phases. During the phase-I experiments, little selenite was removed from the influent. However, when the column was operated in the pulse feed strategy (phase II), or in the continuous mode with low nitrate levels (phase-III), significant quantities of selenium was removed from solution and retained in the immobilization matrix in the column. Thus, immobilized denitrifying cultures can be effective in removing selenium from waste streams, but nitrate-limited operating conditions might be required.

William A. Apel; Sridhar Viamajala; Yared Bereded-Samuel; James N. Petersen

2006-08-01

8

Selenite reduction by a denitrifying culture: batch- and packed-bed reactor studies  

Energy Technology Data Exchange (ETDEWEB)

Selenite reduction by a bacterial consortium enriched from an oil refinery waste sludge was studied under denitrifying conditions using acetate as the electron donor. Fed-batch studies with nitrate as the primary electron acceptor showed that accumulation of nitrite led to a decrease in the extent of selenite reduction. Also, when nitrite was added as the primary electron acceptor, rapid selenite reduction was observed only after nitrite was significantly depleted from the medium. These results indicate that selenite reduction was inhibited at high nitrite concentrations. In addition to batch experiments, continuous-flow selenite reduction experiments were performed in packed-bed columns using immobilized enrichment cultures. These experiments were carried out in three phases: in phase I, a continuous nitrate feed with different inlet selenite concentration was applied; in phase II, nitrate was fed in a pulsed fashion; and in phase III, nitrate was fed in a continuous mode but at much lower concentrations than the other two phases. During the phase I experiments, little selenite was removed from the influent. However, when the column was operated in the pulse feed strategy (phase II) or in the continuous mode with low nitrate levels (phase III), significant quantities of selenium were removed from solution and retained in the immobilization matrix in the column. Thus, immobilized denitrifying cultures can be effective in removing selenium from waste streams, but nitrate-limited operating conditions might be required. (orig.)

Viamajala, S. [National Bioenergy Center, Golden, CO (United States). National Renewable Energy Lab.; Bereded-Samuel, Y.; Petersen, J.N. [Washington State Univ., Pullman, WA (United States). Dept. of Chemical Engineering; Apel, W.A. [Idaho National Lab., Idaho Falls, ID (United States). Biological Sciences Dept.

2006-08-15

9

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

Energy Technology Data Exchange (ETDEWEB)

Highlights: Black-Right-Pointing-Pointer A new concept for low-temperature anaerobic sewage treatment is proposed. Black-Right-Pointing-Pointer In this concept, denitrification and methane oxidation are performed by Methylomirabilis oxyfera. Black-Right-Pointing-Pointer The bacteria were enriched from fresh water sediment using sequencing fed-batch reactors. Black-Right-Pointing-Pointer The volumetric consumption rate has to be increased by an order of magnitude for practical application. Black-Right-Pointing-Pointer Further research should focus on systems with improved biomass retention. - Abstract: 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 treatment, consisting of a UASB-digester system, a reactor for denitrification coupled to anaerobic methane oxidation, and a nitritation reactor. In the present study denitrifying methanotrophic bacteria similar to 'Candidatus Methylomirabilis oxyfera' were enriched. Maximum volumetric nitrite consumption rates were 33.5 mg NO{sub 2}{sup -}-N/L d (using synthetic medium) and 37.8 mg NO{sub 2}{sup -}-N/L d (using medium containing effluent from a sewage treatment plant), which are similar to the maximum rate reported so far. Though the goal was to increase the rates, in both reactors, after reaching these maximum rates, volumetric nitrite consumption rates decreased in time. Results indicate biomass washout may have significantly decelerated enrichment. Therefore, to obtain higher volumetric consumption rates, further research should focus on systems with complete biomass retention.

Kampman, Christel, E-mail: christel.kampman@wur.nl [Sub-department of Environmental Technology, Wageningen University, P.O. Box 17, 6700 AA, Wageningen (Netherlands); Hendrickx, Tim L.G. [Sub-department of Environmental Technology, Wageningen University, P.O. Box 17, 6700 AA, Wageningen (Netherlands); Luesken, Francisca A.; Alen, Theo A. van; Op den Camp, Huub J.M.; Jetten, Mike S.M. [Department of Microbiology, Institute for Water and Wetland Research, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen (Netherlands); Zeeman, Grietje; Buisman, Cees J.N.; Temmink, Hardy [Sub-department of Environmental Technology, Wageningen University, P.O. Box 17, 6700 AA, Wageningen (Netherlands)

2012-08-15

10

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

International Nuclear Information System (INIS)

Highlights: ? A new concept for low-temperature anaerobic sewage treatment is proposed. ? In this concept, denitrification and methane oxidation are performed by Methylomirabilis oxyfera. ? The bacteria were enriched from fresh water sediment using sequencing fed-batch reactors. ? The volumetric consumption rate has to be increased by an order of magnitude for practical application. ? Further research should focus on systems with improved biomass retention. - Abstract: 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 treatment, consisting of a UASB-digester system, a reactor for denitrification coupled to anaerobic methane oxidation, and a nitritation reactor. In the present study denitrifying methanotrophic bacteria similar to ‘Candidatus Methylomirabilis oxyfera’ were enriched. Maximum volumetric nitrite consumption rates were 33.5 mg NO2?-N/L d (using synthetic medium) and 37.8 mg NO2?-N/L d (using medium containing effluent from a sewage treatment plant), which are sment plant), which are similar to the maximum rate reported so far. Though the goal was to increase the rates, in both reactors, after reaching these maximum rates, volumetric nitrite consumption rates decreased in time. Results indicate biomass washout may have significantly decelerated enrichment. Therefore, to obtain higher volumetric consumption rates, further research should focus on systems with complete biomass retention.

11

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

12

Acute and chronic responses of denitrifying culture to diclofenac.  

Science.gov (United States)

Acute and chronic effect as well as biodegradation potential at different sludge retention times (SRTs) of a priority pollutant, diclofenac on denitrification process was assessed. The continuous amendment of the culture for 6months with 1?g/L diclofenac resulted in 30% decrease in gas production. The average diclofenac removal observed in the diclofenac-acclimated culture was less than 15%. Batch tests showed that nitrate was removed in diclofenac free-control reactor at a higher rate compared to diclofenac amended reactor. Although, SRT did not have any progressive effect on diclofenac degradation, the system operated at low SRT was more sensitive to diclofenac and resulted in an increase in N2O emission. Wastewater treatment plants (WWTPs) operated at higher SRTs may tolerate and recover from the adverse effects of such micropollutants. The study can lead to other researchers to understand the fate and effect of other emerging pollutants in the anoxic unit of WWTPs. PMID:25460991

Ozdemir, Gamze; Aydin, Egemen; Topuz, Emel; Yangin-Gomec, Cigdem; Okutman Tas, Didem

2015-01-01

13

Analysis of denitrification genes and comparison of nosZ, cnorB and 16S rDNA from culturable denitrifying bacteria in potato cropping systems.  

Science.gov (United States)

Bacterial denitrification in agricultural soils is a major source of nitrous oxide, a potent greenhouse gas. This study examined the culturable bacterial population of denitrifiers in arable field soils in potato (Solanum tuberosum L.) production and denitrification genes (nir, nor and nos) and 16S rDNA in those isolates. Enrichments for culturable denitrifiers yielded 31 diverse isolates that were then analysed for denitrification genes. The nitrous oxide reductase (nosZ) gene was found in all isolates. The majority of isolates ( approximately 90%) contained the cnorB nitric oxide reductase gene, with the remainder containing the qnorB gene. Nitrite reductase genes (nirS and nirK) were amplifiable from most of the isolates, and were segregated between species similar to previously isolated denitrifiers. Isolated strains were preliminarily identified using fatty acid methyl ester analysis and further identified using 16S rDNA sequencing. The majority of isolates (21) were classified as Pseudomonas sp., with smaller groups of isolates being most similar to Bosea spp. (4), Achromobacter spp. (4) and two isolates closely related to Sinorhizobium/Ensifer spp. Phylogenetic trees were compared among nosZ, cnorB and 16S rDNA genes for a subset of Pseudomonas strains. The trees were mostly congruent, but some Pseudomonas sp. isolates grouped differently depending on the gene analysed, indicating potential horizontal gene transfer of denitrification genes. Although Bosea spp. are known denitrifiers, to the best of our knowledge this is the first report of isolation and sequencing of denitrification genes from this bacterial genus. PMID:16793234

Dandie, C E; Burton, D L; Zebarth, B J; Trevors, J T; Goyer, C

2007-03-01

14

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

15

Production of NO and N(inf2)O by Pure Cultures of Nitrifying and Denitrifying Bacteria during Changes in Aeration  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Peak emissions of NO and N(inf2)O are often observed after wetting of soil. The reactions to sudden changes in the aeration of cultures of nitrifying and denitrifying bacteria with respect to NO and N(inf2)O emissions were compared to obtain more information about the microbiological aspects of peak emissions. In continuous culture, the nitrifier Nitrosomonas europaea and the denitrifiers Alcaligenes eutrophus and Pseudomonas stutzeri were cultured at different levels of aeration (80 to 0% ai...

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

1997-01-01

16

Enrichment of high ammonia tolerant methanogenic culture  

DEFF Research Database (Denmark)

Ammonia is the major toxicant in full scale anaerobic digesters of animal wastes which are rich in proteins and/or urea, such as pig or poultry wastes. Ammonia inhibition decreases methane production rates, increases volatile fatty acids concentration and leads to economic losses for the biogas plants. The methods used today to counteract ammonia inhibition are slow and costexpensive. A new biological approach to avoid or counteract ammonia inhibition by using ammonia tolerant methanogens, could provide a sustainable solution for cost-effective digestion of abundant ammonia-rich wastes. The aim of the current study was to isolate and identify methanogenic cultures tolerant to high ammonia concentrations. A mixed methanogenic population was stepwise exposed to ammonia concentrations (1 to 9.26 g NH4+-N L-1) during an enrichment process with successive batch cultivations. The methanogenic population was derived from a full scale biogas reactor (Hashøj, Denmark), fed with 75% animal manure and 25% food industries organic waste. Basal anaerobic medium was used for the enrichment along with sodium acetate (1 g HAc L-1) as a carbon source. Fluorescence insitu hybridization (FISH) was used to determine microbial community composition. The outcome of the enrichment process was a mesophilic aceticlastic methanogenic enriched culture able to withstand high ammonia loads and utilize acetate and form methane stoichiometrically. FISH analysis showed that the methanogens of the enriched culture belonged exclusively to strict aceticlastic methanogens. Results obtained in this study, demonstrated for the first time that strictly aceticlastic methanogens, derived from an enriched culture, can efficiently produce methane under high ammonia levels.

Fotidis, Ioannis; Karakashev, Dimitar Borisov

17

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

18

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

2014-01-01

19

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

20

Methanogenic degradation of acetone by an enrichment culture  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An anaerobic enrichment culture degraded 1 mol of acetone to 2 tool of methane and 1 tool of carbon dioxide. Two microorganisms were involved in this process, a filament-forming rod similar to Methanothrix sp. and an unknown rod with round to slightly pointed ends. Both organisms formed aggregates up to 300 gm in diameter. No fluorescing bacteria were observed indicating that hydrogen or formate-utilizing methanogens are not involved in this process. Acetate was utilized in this culture by th...

Platen, Harald; Schink, Bernhard

1987-01-01

 
 
 
 
21

Substrate versatility of polyhydroxyalkanoate producing glycerol grown bacterial enrichment culture.  

Science.gov (United States)

Waste-based polyhydroxyalkanoate (PHA) production by bacterial enrichments generally follows a three step strategy in which first the wastewater is converted into a volatile fatty acid rich stream that is subsequently used as substrate in a selector and biopolymer production units. In this work, a bacterial community with high biopolymer production capacity was enriched using glycerol, a non-fermented substrate. The substrate versatility and PHA production capacity of this community was studied using glucose, lactate, acetate and xylitol as substrate. Except for xylitol, very high PHA producing capacities were obtained. The PHA accumulation was comparable or even higher than with glycerol as substrate. This is the first study that established a high PHA content (?70 wt%) with glucose as substrate in a microbial enrichment culture. The results presented in this study support the development of replacing pure culture based PHA production by bacterial enrichment cultures. A process where mixtures of substrates can be easily handled and the acidification step can potentially be avoided is described. PMID:25213684

Moralejo-Gárate, Helena; Kleerebezem, Robbert; Mosquera-Corral, Anuska; Campos, José Luis; Palmeiro-Sánchez, Tania; van Loosdrecht, Mark C M

2014-12-01

22

Immunological identification and distribution of dissimilatory heme cd1 and nonheme copper nitrite reductases in denitrifying bacteria.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Polyclonal antibodies were used to identify heme or copper nitrite reductases in the following groups: 23 taxonomically diverse denitrifiers from culture collections, 100 numerically dominant denitrifiers from geographically diverse environments, and 51 denitrifiers from a culture collection not selected for denitrification. Antisera were raised against heme nitrite reductases from Pseudomonas aeruginosa and Pseudomonas stutzeri and against copper nitrite reductase from Achromobacter cyclocla...

Coyne, M. S.; Arunakumari, A.; Averill, B. A.; Tiedje, J. M.

1989-01-01

23

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

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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

24

Respiration and respiratory enzyme activity in aerobic and anaerobic cultures of the marine denitrifying bacterium, Pseudomonas perfectomarinus  

Science.gov (United States)

Oxygen consumption, nitrate reduction, respiratory electron transport activity, and nitrate reductase activity were measured in aerobic and anaerobic cultures of the marine bacterium, Pseudomonas perfectomarinus. The respiratory electron transport activity was closely correlated with oxygen consumption ( r = 0.98) in aerobic cultures and nearly as well correlated with nitrate reductase activity ( r = 0.91) and nitrate reduction ( r = 0.85) in anaerobic cultures. It was also well correlated with biomass in both aerobic ( r = 0.99) and anaerobic ( r = 0.94) cultures supporting the use of tetrazolium reduction as an index of living biomass. Time courses of nitrate and nitrate in the anaerobic cultures demonstrated that at nitrate concentrations above 1 mM, denitrification proceeds stepwise. Time courses of pH in anaerobic cultures revealed a rise from 7 to 8.5 during nitrite reduction indicating net proton utilization. This proton utilization is predicted by the stoichiometry of denitrification. Although the experiments were not under 'simulated in situ' conditions, the results are relevant to studies of denitrification, to bacterial ATP production, and to the respiratory activity of marine plankton in the ocean.

Packard, T. T.; Garfield, P. C.; Martinez, R.

1983-03-01

25

Isolation, genetic and functional characterization of novel soil nirK-type denitrifiers.  

Science.gov (United States)

Denitrification, the reduction of nitrogen oxides (NO(3)(-) and NO(2)(-)) to N(2) via the intermediates NO and N(2)O, is crucial for nitrogen turnover in soils. Cultivation-independent approaches that applied nitrite reductase genes (nirK/nirS) as marker genes to detect denitrifiers showed a predominance of genes presumably derived from as yet uncultured organisms. However, the phylogenetic affiliation of these organisms remains unresolved since the ability to denitrify is widespread among phylogenetically unrelated organisms. In this study, denitrifiers were cultured using a strategy to generally enrich soil microorganisms. Of 490 colonies screened, eight nirK-containing isolates were phylogenetically identified (16S rRNA genes) as members of the Rhizobiales. A nirK gene related to a large cluster of sequences from uncultured bacteria mainly retrieved from soil was found in three isolates classified as Bradyrhizobium sp. Additional isolates were classified as Bradyrhizobium japonicum and Bosea sp. that contained nirK genes also closely related to the nirK from these strains. These isolates denitrified, albeit with different efficiencies. In Devosia sp., nirK was the only denitrification gene detected. Two Mesorhizobium sp. isolates contained a nirK gene also related to nirK from cultured Mesorhizobia and uncultured soil bacteria but no gene encoding nitric oxide or nitrous oxide reductase. These isolates accumulated NO under nitrate-reducing conditions without growth, presumably due to the lethal effects of NO. This showed the presence of a functional nitrite reductase but lack of a nitric oxide reductase. In summary, similar nirK genotypes recurrently detected mainly in soils likely originated from Rhizobia, and functional differences were presumably strain-dependent. PMID:20675088

Falk, Silke; Liu, Binbin; Braker, Gesche

2010-10-01

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Identification of toluene degraders in a methanogenic enrichment culture.  

Science.gov (United States)

Methanogenic biodegradation involves the cooperative metabolism of syntrophic bacteria that catalyse the initial attack and subsequent degradation of hydrocarbons, and methanogens that convert intermediates such as hydrogen and carbon dioxide, formate, and/or acetate to methane. The identity of syntrophic microbes and the nature of their interactions with other syntrophs and methanogens are not well understood. Furthermore, it is difficult to isolate the organisms responsible for the initial activation and subsequent degradation of hydrocarbon substrates under methanogenic conditions due to the thermodynamic relationships that exist among microbes in methanogenic communities. We used time-resolved RNA stable isotope probing and RT-qPCR to identify the organisms involved in the initial attack on toluene and subsequent degradation reactions in a highly enriched toluene-degrading methanogenic culture. Our results reveal the importance of a Desulfosporosinus sp. in anaerobic toluene activation in the culture. Other organisms that appear to play roles in toluene degradation include Syntrophaceae, Desulfovibrionales and Chloroflexi. The high bacterial diversity observed in this culture and the extensive labelling of different phylogenetic groups over the course of the stable isotope probing experiment highlight the complexity of the relationships that exist in methanogenic ecosystems. PMID:24910080

Fowler, S Jane; Gutierrez-Zamora, Maria-Luisa; Manefield, Mike; Gieg, Lisa M

2014-09-01

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Novel detoxification of the trichothecene mycotoxin deoxynivalenol by a soil bacterium isolated by enrichment culture.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A mixed microbial culture capable of metabolizing deoxynivalenol was obtained from soil samples by an enrichment culture procedure. A bacterium (strain E3-39) isolated from the enrichment culture completely removed exogenously supplied deoxynivalenol from culture medium after incubation for 1 day. On the basis of morphological, physiological, and phylogenetic studies, strain E3-39 was classified as a bacterium belonging to the Agrobacterium-Rhizobium group. Thin-layer chromatographic analysis...

Shima, J.; Takase, S.; Takahashi, Y.; Iwai, Y.; Fujimoto, H.; Yamazaki, M.; Ochi, K.

1997-01-01

28

Role of chemotaxis in the ecology of denitrifiers  

Science.gov (United States)

It has been recognized that the process of denitrification represents a major sequence in the nitrogen cycle. It involves the anaerobic reduction of nitrate or nitrite to nitrous oxide or elemental nitrogen. This process is responsible for significant losses of nitrogen from agricultural soils. Up to now, little attention has been paid to the ecology of the organisms responsible for denitrification. It is pointed out that chemotaxis would probably offer a strong competitive mechanism for denitrifiers, since chemotaxis would allow denitrifiers to actively reach nitrate by directed motility, rather than by random movement or diffusion of nitrate. The present investigation was initiated to examine the chemotactic responses of several denitrifiers to nitrate and nitrite. Attention is given to bacterial strains, culture media and cell preparation, chemotaxis assays, and competition experiments. It was found that several denitrifiers, including P. aeruginosa, P. fluorescens, and P. Stutzeri, were strongly attracted to NO3(-) and NO2(-).

Kennedy, M. J.; Lawless, J. G.

1985-01-01

29

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

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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

30

Evaluation of culture enrichment procedures for use with Salmonella detection immunoassay.  

Science.gov (United States)

To design efficient culture strategies for use with immunoassays to detect Salmonella in food, the growth of these organisms was investigated according to the Bacteriological Analytical Manual (BAM) and enrichment-immunoassay (EI) culture procedures. The cultures were further evaluated using a commercial enzyme-linked immunosorbent assay (ELISA) kit. The BAM procedure includes pre-enrichment in nutrient broth (NB) for 16 h followed by selective enrichment in either Rappaport-Vassiliadis (RV) or tetrathionate brilliant green (TBG) broth for 16 h. The EI procedure includes pre-enrichment in NB for 4 h, selective enrichment in RV for 16 h and post-enrichment in NB for 4 h. The effects of different incubation times for pre- and post-enrichment, and different culture media for selective enrichment (TBG and RV) and post-enrichment in NB and Brain Heart Infusion broth (BHI) on the growth of the bacteria and ELISA titers in the EI procedure were also investigated. Salmonella enteritidis and S. typhimurium inoculated at different initial concentrations between 0.1 and 35 CFU/ml grew to similar concentrations of 10(7) to 10(8) colony forming unit (CFU)/ml in pure culture and generally 2 to 4 fold lower concentrations (PRV was higher (PRV were generally negative. In the EI procedure, the ELISA titers from cultures post-enriched in NB or BHI were higher (PRV, was used for selective enrichment. Post-enrichment in BHI yielded higher numbers of Salmonella and higher ELISA titers than those in NB (Pdetectable by most ELISAs, and that the type of the culture media used may have a significant impact on ELISA results. PMID:10574084

Huang, H; Garcia, M M; Brooks, B W; Nielsen, K; Ng, S P

1999-10-15

31

Changes in Bacterial Species Composition in Enrichment Cultures with Various Dilutions of Inoculum as Monitored by Denaturing Gradient Gel Electrophoresis  

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Denaturing gradient gel electrophoresis revealed changes in the bacterial species obtained from enrichment cultures with different inoculum dilutions. This inoculum dilution enrichment approach may facilitate the detection and isolation of a greater number of bacterial species than traditional enrichment techniques.

Jackson, Colin R.; Roden, Eric E.; Churchill, Perry F.

1998-01-01

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A strict anaerobic extreme thermophilic hydrogen-producing culture enriched from digested household waste  

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The aim of this study was to enrich, characterize and identify strict anaerobic extreme thermophilic hydrogen (H-2) producers from digested household solid wastes. A strict anaerobic extreme thermophilic H-2 producing bacterial culture was enriched from a lab-scale digester treating household wastes at 70 degrees C. The enriched mixed culture consisted of two rod-shaped bacterial members growing at an optimal temperature of 80 degrees C and an optimal pH 8.1. The culture was able to utilize g...

Karakashev, Dimitar Borisov; Kotay, Shireen Meher; Trably, Eric; Angelidaki, Irini

2009-01-01

33

Tetrachloroethene transformation to trichloroethene and cis-1,2-dichloroethene by sulfate-reducing enrichment cultures.  

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Tetrachloroethene, also known as perchloroethylene, was reductively dechlorinated to trichloroethene and cis-1,2-dichloroethene by laboratory sulfate-reducing enrichment cultures. The causative organism or group was not identified. However, tetrachloroethene was dechlorinated to trichloroethene in 50 mM bromoethane-sulfonate-inhibited enrichments and to trichloroethene and cis-1,2-dichloroethene in 3 mM fluoroacetate-inhibited enrichments. Overall transformation varied from 92% tetrachloroeth...

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

1990-01-01

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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

35

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.

36

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

37

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

38

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 yeum 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.

39

Characteristics of enriched cultures for bio-huff-`n`-puff tests at Jilin oil field  

Energy Technology Data Exchange (ETDEWEB)

Three enriched cultures (48, 15a, and 26a), selected from more than 80 soil and water samples, could grow anaerobically in the presence of crude oil at 30{degrees}C and could ferment molasses to gases and organic acids. Oil recovery by culture 48 in the laboratory model experiment was enhanced by 25.2% over the original reserves and by 53.7% over the residual reserves. Enriched culture 48 was composed of at least 4 species belonging to the genera Eubacterium, Fusobacterium, and Bacteroides. This enriched culture was used as inoculum for MEOR field trials at Jilin oil field with satisfactory results. The importance of the role of these isolates in EOR was confirmed by their presence and behavior in the fluids produced from the microbiologically treated reservoir.

Xiu-Yuan Wang; Gang Dai; Yan-Fen Xue; Shu-Hua Xie [Institute of Microbiology, Beijing (China)] [and others

1995-12-31

40

A strict anaerobic extreme thermophilic hydrogen-producing culture enriched from digested household waste  

DEFF Research Database (Denmark)

The aim of this study was to enrich, characterize and identify strict anaerobic extreme thermophilic hydrogen (H-2) producers from digested household solid wastes. A strict anaerobic extreme thermophilic H-2 producing bacterial culture was enriched from a lab-scale digester treating household wastes at 70 degrees C. The enriched mixed culture consisted of two rod-shaped bacterial members growing at an optimal temperature of 80 degrees C and an optimal pH 8.1. The culture was able to utilize glucose, galactose, mannose, xylose, arabinose, maltose, sucrose, pyruvate and glycerol as carbon sources. Growth on glucose produced acetate, H-2 and carbon dioxide. Maximal H-2 production rate on glucose was 1.1 mmol l(-1) h(-1) with a maximum H-2 yield of 1.9 mole H-2 per mole glucose. 16S ribosomal DNA clone library analyses showed that the culture members were phylogenetically affiliated to the genera Bacillus and Clostridium. Relative abundance of the culture members, assessed by fluorescence in situ hybridization, were 87 +/- 5% and 13 +/- 5% for Bacillus and Clostridium, respectively. An extreme thermophilic, strict anaerobic, mixed microbial culture with H-2-producing potential was enriched from digested household wastes. This study provided a culture with a potential to be applied in reactor systems for extreme thermophilic H-2 production from complex organic wastes.

Karakashev, Dimitar Borisov; Kotay, Shireen Meher

2009-01-01

 
 
 
 
41

Enrichment Culture of Hydrogen Fermentation Microorganisms and Analysis of Microbial Communities  

Science.gov (United States)

The present study was aimed at enrichment of hydrogen fermentative microflora that can utilize garbage as fermentation substrate. It was shown that stable hydrogen fermentation was performed using enriched microbes from sewage sludge compost. During the enrichment culture, the microflora were analyzed by the FISH method and the PCR-DGGE method. As a result, predominant microbes of hydrogen production were determined to be from the genus Clostridium belonging to a Gram positive Low G+C group. Furthermore, it was supposed that genus Bacillus contributed to the stability of hydrogen productivity from garbage by genus Clostridium. In the batch culture, under pH control at 6.0, it was ascertained that enriched microflora obtained from sewage sludge compost had sufficient hydrogen productivity using garbage, and yielded 2.03mol-H2/mol-hexose. It is supposed that the microflora of sewage sludge compost is effective as inoculum of the hydrogen fermentation system when using garbage as substrate.

Huang, Xiaoyu; Matsumoto, Akiko; Ohnishi, Akihiro; Sakamoto, Masaru; Fujimoto, Naoshi; Suzuki, Masaharu

42

Differential gene expression profiling of enriched human spermatogonia after short- and long-term culture.  

Science.gov (United States)

This study aimed to provide a molecular signature for enriched adult human stem/progenitor spermatogonia during short-term (<2 weeks) and long-term culture (up to more than 14 months) in comparison to human testicular fibroblasts and human embryonic stem cells. Human spermatogonia were isolated by CD49f magnetic activated cell sorting and collagen(-)/laminin(+) matrix binding from primary testis cultures obtained from ten adult men. For transcriptomic analysis, single spermatogonia-like cells were collected based on their morphology and dimensions using a micromanipulation system from the enriched germ cell cultures. Immunocytochemical, RT-PCR and microarray analyses revealed that the analyzed populations of cells were distinct at the molecular level. The germ- and pluripotency-associated genes and genes of differentiation/spermatogenesis pathway were highly expressed in enriched short-term cultured spermatogonia. After long-term culture, a proportion of cells retained and aggravated the "spermatogonial" gene expression profile with the expression of germ and pluripotency-associated genes, while in the majority of long-term cultured cells this molecular profile, typical for the differentiation pathway, was reduced and more genes related to the extracellular matrix production and attachment were expressed. The approach we provide here to study the molecular status of in vitro cultured spermatogonia may be important to optimize the culture conditions and to evaluate the germ cell plasticity in the future. PMID:24738045

Conrad, Sabine; Azizi, Hossein; Hatami, Maryam; Kubista, Mikael; Bonin, Michael; Hennenlotter, Jörg; Renninger, Markus; Skutella, Thomas

2014-01-01

43

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

44

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

45

Anaerobic 4-chlorophenol mineralization in an enriched culture under iron-reducing conditions.  

Science.gov (United States)

We enriched an anaerobic, soil-free 4-chlorophenol (4-CP)-degrading culture under iron-reducing conditions. The [ring-(14)C(U)]4-CP tracer experiment showed that 65 ?M 4-CP mineralized to CO2 and CH4 through phenol, 4-hydroxybenzoate, and benzoate intermediates over 60 days. 16S rRNA gene analyses suggested the involvement of Dehalobacterium in the 4-CP dechlorination in the culture. PMID:24794625

Li, Zhiling; Suzuki, Daisuke; Zhang, Chunfang; Yang, Suyin; Nan, Jun; Yoshida, Naoko; Wang, Aijie; Katayama, Arata

2014-11-01

46

Dichloromethane Fermentation by a Dehalobacter sp. in an Enrichment Culture Derived from Pristine River Sediment  

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Dichloromethane (DCM) as the sole substrate supported growth of a Dehalobacter sp. in an enrichment culture derived from noncontaminated river sediment. DCM was not reductively dechlorinated, and acetate was produced, indicating DCM fermentation and further suggesting Dehalobacter growth is not limited to organohalide respiration.

Justicia-leon, Shandra D.; Ritalahti, Kirsti M.; Mack, E. Erin; Lo?ffler, Frank E.

2012-01-01

47

Oxygen regulation of nitrate uptake in denitrifying Pseudomonas aeruginosa.  

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Oxygen had an immediate and reversible inhibitory effect on nitrate respiration by denitrifying cultures of Pseudomonas aeruginosa. Inhibition of nitrate utilization by oxygen appeared to be at the level of nitrate uptake, since nitrate reduction to nitrite in cell extracts was not affected by oxygen. The degree of oxygen inhibition was dependent on the concentration of oxygen, and increasing nitrate concentrations could not overcome the inhibition. The inhibitory effect of oxygen was maximal...

Hernandez, D.; Rowe, J. J.

1987-01-01

48

Enrichment and characterization of chlorinated organophosphate ester-degrading mixed bacterial cultures.  

Science.gov (United States)

Chlorinated organophosphate ester (OPE)-degrading enrichment cultures were obtained using tris(2-chloroethyl) phosphate (TCEP) or tris(1,3-dichloro-2-propyl) phosphate (TDCPP) as the sole phosphorus source. In cultures with 46 environmental samples, significant TCEP and TDCPP degradation was observed in 10 and 3 cultures, respectively, and successive subcultivation markedly increased their degradation rates. 67E and 45D stable enrichment cultures obtained with TCEP and TDCPP, respectively, completely degraded 20 muM of the respective compounds within 6 h and also the other, although the degradation rate of TCEP by 45D was relatively slow. We confirmed chloride ion generation on degradation in both cases and the generation of 2-chloroethanol (2-CE) and 1,3-dichloro-2-propanol (1,3-DCP) as metabolites of TCEP and TDCPP, respectively. 67E and 45D also showed dehalogenation ability toward 2-CE and 1,3-DCP, respectively. Addition of inorganic phosphate did not significantly influence their ability to degrade the chlorinated OPEs but markedly increased their dehalogenation ability, which was maximum at 0.2 mM of inorganic phosphate and decreased at a higher concentration. Denaturing gradient gel electrophoresis analysis showed that dominant bacteria in 67E are related to Acidovorax spp. and Sphingomonas spp. and those in 45D are Acidovorax spp., Aquabacterium spp., and Sphingomonas spp. This analysis indicated the relationship of the Sphingomonas- and Acidovorax-related bacteria with the cleavage of the phosphoester bond and dehalogenation, respectively, in both cultures. This is the first report on bacterial enrichment cultures capable of degrading both TCEP and TDCPP. PMID:18691527

Takahashi, Shouji; Kawashima, Koji; Kawasaki, Manami; Kamito, Jun; Endo, Yusuke; Akatsu, Kumiko; Horino, Sadatoshi; Yamada, Ryo-Hei; Kera, Yoshio

2008-07-01

49

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

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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

50

Enrichment of prostate cancer stem cells from primary prostate cancer cultures of biopsy samples  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This study was to enrich prostate cancer stem cells (PrCSC) from primary prostate cancer cultures (PPrCC). Primary prostate cancer cells were amplified in keratinocyte serum-free medium with epidermal growth factor (EGF) and bovine pituitary extract (BPE), supplemented with leukemia inhibitory factor (LIF), stem cell factor (SCF) and cholera toxin. After amplification, cells were transferred into ultra-low attachment dishes with serum-free DMEM/F12 medium, supplemented with EGF, basic fibrobl...

Wang, Shunqi; Huang, Shengsong; Zhao, Xin; Zhang, Qimin; Wu, Min; Sun, Feng; Han, Gang; Wu, Denglong

2013-01-01

51

Metabolic by-products of anaerobic toluene degradation by sulfate-reducing enrichment cultures.  

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Two dead-end metabolites of anaerobic toluene transformation, benzylsuccinic acid and benzylfumaric acid, accumulated in sulfate-reducing enrichment cultures that were fed toluene as the sole carbon source. Stable isotope-labeled toluene and gas chromatography-mass spectrometry were used to confirm that the compounds resulted from toluene metabolism. The two metabolites constituted less than 10% of the toluene carbon (over 80% was mineralized to carbon dioxide, according to a previous study)....

Beller, H. R.; Reinhard, M.; Grbic?-galic?, D.

1992-01-01

52

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

Blo?the, Marco; Roden, Eric E.

2009-01-01

53

The characteristics of enriched nitrifier culture in the degradation of selected pharmaceutically active compounds.  

Science.gov (United States)

The biodegradation of 10 selected pharmaceuticals by enriched nitrifier cultures with ammonia oxidizing activity of 30mg NH(4)-N/gMLVSSh was investigated under various initial operating conditions such as in the presence of different growth substrates and inhibitors. The enriched nitrifier culture showed higher degradation of the target pharmaceuticals than the conventional activated sludge. The degradation efficiency of persistent pharmaceuticals such as clofibric acid (CA), diclofenac (DCF), carbamazepine (CBZ), and propyphenazone (PPZ) was increased with the increase in the ammonium concentration. A higher removal efficiency of CA, DCF, CBZ and PPZ was obtained when organic substrates were added. The contribution of autotrophs and heterotrophs in the biotransformation of the pharmaceuticals by the enriched nitrifier culture was successfully estimated by the addition of inhibitors. Experimental results showed that the high degradation of IBP and partial degradation of other selected pharmaceuticals were observed in the presence of allylthiourea (ATU), an ammonia monooxygenase inhibitor, reflecting the activity of heterotrophic bacteria, while the results with and without ATU addition showed that the contribution of the nitrification in the degradation of most pharmaceuticals was also dominant. The results suggest that nitrification can enhance the biotransformation of pharmaceutical substances. PMID:19615816

Tran, Ngoc Han; Urase, Taro; Kusakabe, Osamu

2009-11-15

54

[Mass spectrometry assay for denitrifying enzyme activity measurement].  

Science.gov (United States)

Nitrification inhibitors exert inhibition function in soil nitrification process (NH4(+)-N to NO3(-)-N) and are widely applied in order to improve N fertilizer use efficiency. Before the new nitrification inhibitor is used, its effects on denitrification process must be investigated and denitrifying enzyme activity (DEA) is an effective indicator to show this process. In the present paper, a mass spectrometery (MS) method was taken to measure the denitrifying enzyme activity in the new nitrification inhibitor 3, 4-dimethylpyrazole phosphate (DMPP) incubation system. The results showed that the method measured the concentration of N2O in the incubation system accurately and the concentration measured by MS had marked correlation with that measured by gas chromatogram (GC) (MS(N2O) = -0.45 + 1.03GC(N2O, R2 = 0.995). At the same time, enrichment of 15 N2O and 15 N2 was measured to discriminate the nitrate reductase and N2O reductase. Differed with traditional method, the enzymatic inhibitor-acetylene was not appended. The results showed that DMPP had no influence on the denitrifying enzyme activity and indicated that the denitrification process was not influenced by DMPP. PMID:20828021

Zhang, Li-li; Wu, Zhi-jie; Song, Yu-chao

2010-07-01

55

Biodegradation of munitions compounds by a sulfate reducing bacterial enrichment culture  

Energy Technology Data Exchange (ETDEWEB)

The degradation of several munitions compounds was studied. The compounds included 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetraazocine, 2,4,6-trinitrobenzene (TNB), and 2,4-dinitrotoluene. All of the compounds studied were degraded by the sulfate reducing bacterial (SRB) enrichment culture. The SRB culture did not use the munitions compounds as their sole source of carbon. However, all the munitions compounds tested served as the sole source of nitrogen for the SRB culture. Degradation of munitions compounds was achieved by a co-metabolic process. The SRB culture used a variety of carbon sources including pyruvate, ethanol, formate, lactate, and H{sub 2}-CO{sub 2}. The SRB culture was an incomplete oxidizer, unable to carry out the terminal oxidation of organic substrates to CO{sub 2} as the sole product, and it did not use acetate or methanol as a carbon source. In addition to serving as nitrogen sources, the munitions compounds also served as electron acceptors in the absence of sulfate. A soil slurry experiment with 5% and 10% munitions compounds-contaminated soil showed that the contaminant TNT was metabolized by the SRB culture in the presence of pyruvate as electron donor. This culture may be useful in decontaminating munitions compounds-contaminated soil and water under anaerobic conditions.

Boopathy, R.; Manning, J. [Argonne National Lab., IL (United States). Environmental Research Div.

1997-08-01

56

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2012-01-01

57

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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, I.; Ahring, B. K.

1995-01-01

58

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

59

Immunochromatographic Detection of the Group B Streptococcus Antigen from Enrichment Cultures  

Science.gov (United States)

Group B Streptococcus (GBS; Streptococcus agalactiae) is a leading cause of serious neonatal infections. The Centers for Disease Control and Prevention recommends GBS screening for all pregnant women during the 35th to 37th weeks of gestation. Although GBS screening has been performed mainly by the culture-based method, it takes several days to obtain a reliable result. In this study, we developed a rapid immunochromatographic test (ICT) for the detection of GBS-specific surface immunogenic protein in 15 min using an overnight enrichment culture. The ICT was prepared using two anti-Sip monoclonal antibodies. This ICT was able to detect recombinant Sip levels of 0.5 ng/ml, or about 106 CFU/ml of GBS cells, in tests with 9 GBS strains of different serotypes. The cross-reactivity test using 26 species of microorganism showed no detectable false-positive result. Reactivity of the ICT with 229 GBS strains showed one false-negative result that was attributable to the production of truncated Sip. Among 260 enrichment cultures of vaginal swabs, 17 produced red to orange pigments in Granada medium, and they were all GBS and Sip positive. Among 219 pigment-negative cultures, 12 were GBS positive and 10 were Sip positive. Two Sip-negative cultures contained GBS cells below the limit of detection by the ICT. Among 207 GBS-negative cultures, only one was Sip positive, which was attributable to GBS cell debris. Thus, the sensitivity and specificity of the ICT appeared to be 93.1% and 99.6%, respectively. The newly developed ICT is readily applicable to clinical use in the detection of GBS. PMID:23825191

Matsui, Hidehito; Kimura, Juri; Higashide, Masato; Takeuchi, Yoshio; Okue, Kuniyuki; Cui, Longzhu; Nakae, Taiji; Sunakawa, Keisuke

2013-01-01

60

Integrated biogas upgrading and hydrogen utilization in an anaerobic reactor containing enriched hydrogenotrophic methanogenic culture  

DEFF Research Database (Denmark)

Biogas produced by anaerobic digestion, is mainly used in a gas motor for heat and electricity production. However, after removal of CO2, biogas can be upgraded to natural gas quality, giving more utilization possibilities, such as utilization as autogas, or distant utilization by using the existing natural gas grid. The current study presents a new biological method for biogas upgrading in a separate biogas reactor, containing enriched hydrogenotrophic methanogens and fed with biogas and hydrogen. Both mesophilic- and thermophilic anaerobic cultures were enriched to convert CO2 to CH4 by addition of H2. Enrichment at thermophilic temperature (55°C) resulted in CO2 and H2 bioconversion rate of 320?mL CH4/(gVSS?h), which was more than 60% higher than that under mesophilic temperature (37°C). Different dominant species were found at mesophilic- and thermophilic-enriched cultures, as revealed by PCR–DGGE. Nonetheless, they all belonged to the order Methanobacteriales, which can mediate hydrogenotrophic methanogenesis. Biogas upgrading was then tested in a thermophilic anaerobic reactor under various operation conditions. By continuous addition of hydrogen in the biogas reactor, high degree of biogas upgrading was achieved. The produced biogas had a CH4 content, around 95% at steady-state, at gas (mixture of biogas and hydrogen) injection rate of 6?L/(L?day). The increase of gas injection rate to 12?L/(L?day) resulted in the decrease of CH4 content to around 90%. Further study showed that by decreasing the gas–liquid mass transfer by increasing the stirring speed of the mixture the CH4 content was increased to around 95%. Finally, the CH4 content around 90% was achieved in this study with the gas injection rate as high as 24?L/(L?day). Biotechnol. Bioeng. 2012; 109: 2729–2736. © 2012 Wiley Periodicals, Inc.

Luo, Gang; Angelidaki, Irini

2012-01-01

 
 
 
 
61

Enrichment of prostate cancer stem cells from primary prostate cancer cultures of biopsy samples.  

Science.gov (United States)

This study was to enrich prostate cancer stem cells (PrCSC) from primary prostate cancer cultures (PPrCC). Primary prostate cancer cells were amplified in keratinocyte serum-free medium with epidermal growth factor (EGF) and bovine pituitary extract (BPE), supplemented with leukemia inhibitory factor (LIF), stem cell factor (SCF) and cholera toxin. After amplification, cells were transferred into ultra-low attachment dishes with serum-free DMEM/F12 medium, supplemented with EGF, basic fibroblast growth factor (bFGF), bovine serum albumin (BSA), insulin, and N2 nutrition. Expression of cell-type-specific markers was determined by RT-qPCR and immunostaining. Tumorigenicity of enriched PrCSC was determined by soft agar assay and xenograft assay in NOD/SCID mice. Biopsy samples from 19 confirmed prostate cancer patients were used for establishing PPrCC, and 18 cases (95%) succeeded. Both basal marker (CK5) and luminal markers (androgen receptor and CK8) strongly co-expressed in most of PPrCC, indicating their basal epithelial origin. After amplification under adherent culture condition in vitro, transient amplifying cells were the dominant cells. Sphere formation efficiency (SFE) of passaged PPrCC was about 0.5%, which was 27 times lower than SFE of LNCaP (13.67%) in the same condition. Compared with adherent cells from PPrCC, prostasphere from PPrCC showed up regulated stem cell markers and increased tumorigenic potential in soft-agar assay. However, spheroid cells from PPrCC prostasphere failed to initiate tumor in xenograft assay in 6 months. Thus, PPrCC can be established and amplified from prostate cancer biopsy samples. Our modified sphere culture system can enrich PrCSC from PPrCC. PMID:24427338

Wang, Shunqi; Huang, Shengsong; Zhao, Xin; Zhang, Qimin; Wu, Min; Sun, Feng; Han, Gang; Wu, Denglong

2014-01-01

62

Biological enrichment of Mycoplasma agents by cocultivation with permissive cell cultures.  

Science.gov (United States)

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-1, EBTr, WI-38, R9ab, MDCK, and High Five) used in the study, only MDCK cell culture was found to support the efficient growth of all the tested mycoplasmas (Mycoplasma arginini, M. bovis, M. fermentans, M. gallinaceum, M. gallisepticum, M. synoviae, M. hominis, M. hyorhinis, M. orale, M. salivarium, and Acholeplasma laidlawii) known to be most frequently associated with contamination of cell substrates and cell lines in research laboratories or manufacturing facilities. The infection of MDCK cells with serial dilutions of each mycoplasma species demonstrated that these common cell line contaminants can be detected reliably after 7-day enrichment in MDCK cell culture at contamination levels of 0.05 to 0.25 CFU/ml. The High Five insect cell line was also found to be able to support the efficient growth of most mycoplasma species tested, except for M. hyorhinis strain DBS1050. However, mycoplasma growth in insect cell culture was demonstrated to be temperature dependent, and the most efficient growth was observed when the incubation temperature was increased from 28 degrees C to between 35 and 37 degrees C. We believe that this type of mycoplasma enrichment is one of the most promising approaches for improving the purity and safety testing of cell substrates and other cell-derived biologics and pharmaceuticals. PMID:18606798

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

2008-09-01

63

Visualization and direct counting of individual denitrifying bacterial cells in soil by nirK-targeted direct in situ PCR.  

Science.gov (United States)

The abundance of denitrifying bacteria in soil has been determined primarily by the conventional most probable number (MPN) method. We have developed a single-cell identification technique that is culture-independent, direct in situ PCR, to enumerate denitrifying bacteria in soils. The specificity of this method was evaluated with six species of denitrifying bacteria using nirK as the target gene; Escherichia coli was used as a negative control. Almost all (97.3%-100%) of the nirK-type denitrifying bacteria (Agromonas oligotrophica, Alcaligenes faecalis, Achromobacter denitrificans, Bradyrhizobium japonicum, and Pseudomonas chlororaphis) were detected by direct in situ PCR, whereas no E. coli cells and only a few cells (2.4%) of nirS-type denitrifying bacteria (Pseudomonas aeruginosa) were detected. Numbers of denitrifying bacteria in upland and paddy soil samples quantified by this method were 3.3 × 10(8) to 2.6 × 10(9) cells g(-1) dry soil. These values are approximately 1,000 to 300,000 times higher than those estimated by the MPN method. These results suggest that direct in situ PCR is a better tool for quantifying denitrifying bacteria in soil than the conventional MPN method. PMID:21487206

Ryuda, Noriko; Hashimoto, Tomoyoshi; Ueno, Daisuke; Inoue, Koichi; Someya, Takashi

2011-01-01

64

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

65

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

66

Pathway of indole metabolism by a denitrifying microbial community  

Energy Technology Data Exchange (ETDEWEB)

The metabolism of indole in a mineral-salts medium inoculated with 9% anaerobically digested nitrate-reducing sewage sludge was studied. The sequential occurrence of four structurally-related compounds - oxindole, isatin, dioxindole, and anthranilic acid - was detected using high-performance liquid or thin-layer chromatography. Mass spectrometry and proton nuclear resonance were used to identify isatin and dioxindole isolated from the culture fluids. Prior exposure of the microorganisms to indole, oxindole, isatin, or anthranilic acid resulted in accelerated decomposition of these compounds in a pattern that was consistent with a proposed pathway for the metabolism of indole under denitrifying conditions.

Madsen, E.L.; Bollag, J.M. (Pennsylvania State Univ., University Park (United States))

1989-01-01

67

Evidence that elevated CO2 levels can indirectly increase rhizosphere denitrifier activity  

Science.gov (United States)

We examined the influence of elevated CO2 concentration on denitrifier enzyme activity in wheat rhizoplanes by using controlled environments and solution culture techniques. Potential denitrification activity was from 3 to 24 times higher on roots that were grown under an elevated CO2 concentration of 1,000 micromoles of CO2 mol-1 than on roots grown under ambient levels of CO2. Nitrogen loss, as determined by a nitrogen mass balance, increased with elevated CO2 levels in the shoot environment and with a high NO3- concentration in the rooting zone. These results indicated that aerial CO2 concentration can play a role in rhizosphere denitrifier activity.

Smart, D. R.; Ritchie, K.; Stark, J. M.; Bugbee, B.

1997-01-01

68

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

69

Fermentative bio-hydrogen production from cellulose by cow dung compost enriched cultures  

Energy Technology Data Exchange (ETDEWEB)

The performance of hydrogen production from cellulose by the cow dung compost enriched continuously in defined medium containing cellulose was investigated. In the initial experiments, batch-fermentation was carried out to observe the effects of different substrate concentration conditions on the rate of cellulose-degrading, growth of bacteria and the capability of hydrogen-producing from cellulose. The result showed that the cellulose degradation decreased from 55% at 5 g/l to 22% at 30 g/l. The maximum cumulative hydrogen production and the rate of hydrogen production first increased from 828 ml/l at 5 g/l to 1251 ml/l at 10 g/l then remained constant beyond 10 g/l. The maximum hydrogen production potential, the rate of hydrogen production and the yield of hydrogen was 1525 ml/l, 33 ml/l.h, and 272 ml/g-cellulose (2.09 mol/mol-hexose) was obtained at substrate concentration 10 g/l, the hydrogen concentration in biogas was 47-50%(v/v) and there was no methane observed. During the conversion of cellulose into hydrogen, acetate and butyrate were main liquid end-products in the metabolism of hydrogen fermentation. These results proposed that cow dung compost enriched cultures were ideal microflora for hydrogen production from cellulose. (author)

Ren, Nan-Qi; Xu, Ji-Fei; Gao, Ling-Fang; Xin, Liang; Qiu, Jie; Su, Dong-Xia [State Key Laboratory of Urban Water Resources and Environment, Harbin Institute of Technology, Harbin 150090 (China)

2010-04-15

70

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

Directory of Open Access Journals (Sweden)

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

71

Growth and denitrifying activity of Xanthobacter autotrophicus CECT 7064 in the presence of selected pesticides.  

Science.gov (United States)

The effects of the application of nine pesticides used commonly in agriculture (aldrin, lindane, dimetoate, methylparathion, methidation, atrazine, simazine, captan and diflubenzuron) on growth, CO2 production, denitrifying activity [as nitrous oxide (N2O) released] and nitrite accumulation in the culture medium by Xanthobacter autotrophicus strain CECT 7064 (Spanish Type Culture Collection) (a micro-organism isolated from a submerged fixed-film) were studied. The herbicide atrazine and the insecticide dimetoate totally inhibited growth and biological activity of X. autotrophicus at 10 mg l(-1), while the rest of the tested pesticides delayed the growth of strain CECT 7064 but did not drastically affect the bacterial growth after 96 h of culture. The denitrifying activity of X. autotrophicus was negatively affected by the pesticides application with the exception of fungicide captan. The release of N2O was strongly inhibited by several pesticides (aldrin, lindane, methylparathion, methidation and diflubenzuron), while dimetoate, atrazine and simazine inhibited totally the denitrifying activity of the strain. The effects of the pesticides on denitrifying submerged fixed-film reactor are discussed. PMID:16249877

Sáez, Florentina; Pozo, Clementina; Gómez, Miguel Angel; Martínez-Toledo, Maria Victoria; Rodelas, Belén; Gónzalez-López, Jesús

2006-07-01

72

Co-metabolic degradation of diazo dye- reactive blue 160 by enriched mixed cultures BDN.  

Science.gov (United States)

Mixed cultures BDN (BDN) proficient in decolourizing diazo dye-reactive blue 160 (RB160) consist of eight bacterial strains, was developed through culture enrichment method from soil samples contaminated with anthropogenic activities. The synthrophic interactions of BDN have led to complete decolourization and degradation of RB160 (100mg/L) within 4h along with co-metabolism of yeast extract (0.5%) in minimal medium. BDN microaerophilicaly decolourized even 1500mg/L of RB160 under high saline conditions (20g/L NaCl) at 37°C and pH 7.0. BDN exhibited broad substrate specificity and decolourized 27 structurally different dyes. The reductase enzymes symmetrically cleaved RB160 and oxidative enzymes further metabolised the degraded products and five different intermediates were identified using FTIR, (1)HNMR and GC-MS. The phytotoxicity assay confirmed that intact RB160 was more toxic than dye degraded intermediates. The BDN was able to colonize and decolourized RB160 in soil model system in presence of indigenous miocroflora as well as in sterile soil without any amendment of additional nutrients, which signifies it useful and potential application in bioremediation. PMID:25043700

Balapure, Kshama H; Jain, Kunal; Chattaraj, Sananda; Bhatt, Nikhil S; Madamwar, Datta

2014-08-30

73

Enrichment and characterization of MTBE-degrading cultures under iron and sulfate reducing conditions  

Energy Technology Data Exchange (ETDEWEB)

Methyl tert-butyl ether (MTBE) is widely used as an additive to gasoline. It has been exposed to the environment as a result of releases from underground storage tanks and pipelines. MTBE has been banned or limited in many areas of North America because of its high aqueous solubility and slow biodegradation rate. The aim of this study was to obtain highly enriched consortia capable of the anaerobic biodegradation of MTBE. Amplified 16S rDNA restriction-digest analysis (ARDRA) was used to identify the sequencing of unique 16S rRNA genes. The study examined sulfate- and iron-reducing conditions as electron acceptors in groundwater. The aqueous cultures were inoculated in 3 different growth media to examine the effect of biodegradation. Between 5 to 8 members were identified in 3 consortia. A clone was detected in cultures containing iron. Results indicated that the buildup of intermediates and the presence of sulfides inhibited biodegradation. The results may provide biomarkers to support current anaerobic MTBE biodegradation field studies. 80 refs., 1 tab., 3 figs.

Raynal, M. [Univ. Nacional Autonoma de Mexico, Mexico City (Mexico). Inst. de Ingenieria; Crimi, B. [Delft Univ. of Technology (Netherlands). Dept. of Biotechnology; Pruden, A. [Virginia Tech, Blacksburg, VA (United States). Dept. of Civil and Environmental Engineering

2010-04-15

74

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

75

Kinetics of 1,2-dichloroethane and 1,2-dibromoethane biodegradation in anaerobic enrichment cultures.  

Science.gov (United States)

1,2-Dichloroethane (1,2-DCA) and 1,2-dibromoethane (ethylene dibromide [EDB]) contaminate groundwater at many hazardous waste sites. The objectives of this study were to measure yields, maximum specific growth rates (?), and half-saturation coefficients (K(S)) in enrichment cultures that use 1,2-DCA and EDB as terminal electron acceptors and lactate as the electron donor and to evaluate if the presence of EDB has an effect on the kinetics of 1,2-DCA dehalogenation and vice versa. Biodegradation was evaluated at the high concentrations found at some industrial sites (>10 mg/liter) and at lower concentrations found at former leaded-gasoline sites (1.9 to 3.7 mg/liter). At higher concentrations, the Dehalococcoides yield was 1 order of magnitude higher when bacteria were grown with 1,2-DCA than when they were grown with EDB, while ?'s were similar for the two compounds, ranging from 0.19 to 0.52 day(-1) with 1,2-DCA to 0.28 to 0.36 day(-1) for EDB. K(S) was larger for 1,2-DCA (15 to 25 mg/liter) than for EDB (1.8 to 3.7 mg/liter). In treatments that received both compounds, EDB was always consumed first and adversely impacted the kinetics of 1,2-DCA utilization. Furthermore, 1,2-DCA dechlorination was interrupted by the addition of EDB at a concentration 100 times lower than that of the remaining 1,2-DCA; use of 1,2-DCA did not resume until the EDB level decreased close to its maximum contaminant level (MCL). In lower-concentration experiments, the preferential consumption of EDB over 1,2-DCA was confirmed; both compounds were eventually dehalogenated to their respective MCLs (5 ?g/liter for 1,2-DCA, 0.05 ?g/liter for EDB). The enrichment culture grown with 1,2-DCA has the advantage of a more rapid transition to 1,2-DCA after EDB is consumed. PMID:23263950

Yu, Rong; Peethambaram, Hari S; Falta, Ronald W; Verce, Matthew F; Henderson, James K; Bagwell, Christopher E; Brigmon, Robin L; Freedman, David L

2013-02-01

76

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

77

Role of sulfate concentration in dechlorination of 3,4,5-trichlorocatechol by stable enrichment cultures grown with coumarin and flavanone glycones and aglycones.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Metabolically stable anaerobic enrichment cultures have been obtained from sediment samples contaminated with chlorophenolic compounds. Enrichment was carried out with esculin, esculetin, naringin, naringenin, fraxin, quercetin, and acetate in media with two sulfate concentrations. These cultures were used to examine the O-demethylation of 4,5,6-trichloroguaiacol and the dechlorination of 3,4,5-trichlorocatechol. Whereas O-demethylation was observed in all cultures, the occurrence of dechlori...

Allard, A. S.; Hynning, P. A.; Remberger, M.; Neilson, A. H.

1992-01-01

78

Nitrogen and oxygen isotope-ratio analysis of nitrate by the denitrifier method using continuous flow isotope-ratio mass spectrometry  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The total isotopic composition of nitrate is used for identifying the origin and fate of nitrate in atmospheric, terrestrial and aquatic systems. The analysis of ?18O and ?15N values each give important and unique information about the sources and sinks of nitrate in these systems. This denitrifier method is based on the isotope ratio analysis of nitrous oxide generated through reduction of nitrate by cultured denitrifying bacteria. Here, preliminary data is presented on ? 15N and ?18O ge...

Crawley, Lindsey R.

2010-01-01

79

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

80

Enrichment and Molecular Characterization of a Bacterial Culture That Degrades Methoxy-Methyl Urea Herbicides and Their Aniline Derivatives  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Soil treated with linuron for more than 10 years showed high biodegradation activity towards methoxy-methyl urea herbicides. Untreated control soil samples taken from the same location did not express any linuron degradation activity, even after 40 days of incubation. Hence, the occurrence in the field of a microbiota having the capacity to degrade a specific herbicide was related to the long-term treatment of the soil. The enrichment culture isolated from treated soil showed specific degrada...

El-fantroussi, Said; Verstraete, Willy; Top, Eva M.

2001-01-01

 
 
 
 
81

PCR amplification of Bartonella koehlerae from human blood and enrichment blood cultures  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Cats appear to be the primary reservoir host for Bartonella koehlerae, an alpha Proteobacteria that is most likely transmitted among cat populations by fleas (Ctenocephalides felis. Bartonella koehlerae has caused endocarditis in a dog and in one human patient from Israel, but other clinically relevant reports involving this bacterium are lacking. Despite publication of numerous, worldwide epidemiological studies designed to determine the prevalence of Bartonella spp. bacteremia in cats, B. koehlerae has never been isolated using conventional blood agar plates. To date, successful isolation of B. koehlerae from cats and from the one human endocarditis patient has consistently required the use of chocolate agar plates. Results In this study, Bartonella koehlerae bacteremia was documented in eight immunocompetent patients by PCR amplification and DNA sequencing, either prior to or after enrichment blood culture using Bartonella alpha Proteobacteria growth medium. Presenting symptoms most often included fatigue, insomnia, joint pain, headache, memory loss, and muscle pain. Four patients were also infected with Bartonella vinsonii subsp. berkhoffii genotype II. After molecular documentation of B. koehlerae infection in these patients, a serological test was developed and serum samples were tested retrospectively. Bartonella koehlerae antibodies were not detected (titers B. koehlerae antibody titers of 1:64 or greater. Conclusions Although biased by a study population consisting of individuals with extensive arthropod and animal exposure, the results of this study suggest that B. koehlerae bacteremia is more common in immunocompetent people than has been previously suspected. Future studies should more thoroughly define modes of transmission and risk factors for acquiring infection with B. koehlerae. In addition, studies are needed to determine if B. koehlerae is a cause or cofactor in the development of arthritis, peripheral neuropathies or tachyarrhythmias in patients.

Breitschwerdt Edward B

2010-08-01

82

Degradation of polycyclic aromatic hydrocarbons by microbial consortia enriched from three soils using two different culture media  

International Nuclear Information System (INIS)

A consortium composed of many different bacterial species is required to efficiently degrade polycyclic aromatic hydrocarbons (PAH) in oil-contaminated soil. We obtained six PAH-degrading microbial consortia from three oil-contaminated soils using two different isolation culture media. Denaturing gradient gel electrophoresis (DGGE) and sequence analyses of amplified 16s rRNA genes confirmed the bacterial community was greatly affected by both the culture medium and the soil from which the consortia were enriched. Three bacterial consortia enriched using malt yeast extract (MYE) medium showed higher degradation rates of PAHs than consortia enriched using Luria broth (LB) medium. Consortia obtained from a soil and then added back to that same soil was more effective in degrading PAHs than adding, to the same soil, consortia isolated from other, unrelated soils. This suggests that inoculum used for bioremediation should be from the same, or very similar nearby soils, as the soil that is actually being bioremediated. -- Highlights: •Six PAH-degrading microbial consortia were isolated from three oil-contaminated soils. •The bacterial community by 16s rRNA genes was affected by culture media and source soil. •Inoculum should be from the same or similar soil as the soil being bioremediated. -- Bioremediation of oil-contaminated soils was most effective when using inoculum of microbial consortia from the same or similar soil as the soil being bioremediated

83

Aerobic and anaerobic degradation of a range of alkyl sulfides by a denitrifying marine bacterium.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A pure culture of a bacterium was obtained from a marine microbial mat by using an anoxic medium containing dimethyl sulfide (DMS) and nitrate. The isolate grew aerobically or anaerobically as a denitrifier on alkyl sulfides, including DMS, dimethyl disulfide, diethyl sulfide (DES), ethyl methyl sulfide, dipropyl sulfide, dibutyl sulfide, and dibutyl disulfide. Cells grown on an alkyl sulfide or disulfide also oxidized the corresponding thiols, namely, methanethiol, ethanethiol, propanethiol,...

Visscher, P. T.; Taylor, B. F.

1993-01-01

84

Addition of novobiocin in pre-enrichment step can improve Salmonella culture protocol of modified semisolid Rappaport-Vassiliadis  

DEFF Research Database (Denmark)

The aim was to investigate the effect of addition of Novobiocin to the non-selective buffered peptone water (BPW) for pre-enrichment of Salmonella in connection with plating on modified semisolid Rappaport-Vassiliadis (MSRV). In a semi-quantitative study, the level of Salmonella following pre-enrichment of 32 presumably naturally contaminated swine fecal samples were assessed for BPW with and without addition of Novobiocin (22 mug/ml). In another experiment, a total of 400 swine fecal samples were screened for the presence of Salmonella spp., in order to compare the performance of the nonselective pre-enrichment broth with BPW made semi-selective by addition of Novobiocin. The semi-quantitative assessment of the Salmonella level showed that addition of Novobiocin in the pre-enrichment step on average increased the level of Salmonella 1.2 log dilution steps. When growth was scored at five levels, 90 samples opposed to 50 yielded a strong positive reading (+++) when Novobiocin was applied. Growth was on average0.3 scores higher when pre-enriched with Novobiocin. The difference in growth score medians of the two methods was highly significant (Sign test; p <0.001). Despite the increased sensitivity, 13 culture-positive samples were missed when using the Novobiocin-containing BPW. In conclusion, a simple addition of Novobiocin in the BPW pre-enrichment step of fecal samples may facilitate reading and thereby detection of Salmonella on MSRV. The increase of Salmonella in the semi-quantitative study may be caused by a reduction in the number of competitive microorganisms.

Jensen, Annette Nygaard; SØrensen, Gitte

2003-01-01

85

Enrichment strategy to select functional consortium from mixed cultures: Consortium from rumen liquor for simultaneous cellulose degradation and hydrogen production  

Energy Technology Data Exchange (ETDEWEB)

Strain isolation using conventional roll tube/plating technique is time consuming and is able to culture in vitro only a small fraction of existing microbes in a natural microflora. This paper proposed a simple and rapid method to select the as-simple-as-possible biological consortium by serially diluting the original mixed culture. The diluted which remains, while the one diluted in serial loses the target function, is defined as the functional consortium of the original mixed culture. Since the microbial structure and the reaction pathway incorporated with the functional consortium is much simpler than its original mother liquor, detailed analysis on the strain interaction is possible without the risk of losing key functional strains as often caused from conventional isolation method. The rumen liquor that can degrade cellulose and produce hydrogen is used as a demonstration example. A ''rumen cellulose-degrading bacterial consortium'' (RCBC) was identified using the proposed enrichment strategy. (author)

Wang, Aijie; Ren, Nanqi [State Key Lab of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090 (China); School of Environmental and Municipal Engineering, Harbin Institute of Technology, Harbin 150090 (China); Gao, Lingfang; Xu, Jifei; Liu, Chong; Lee, Duu-Jong [School of Environmental and Municipal Engineering, Harbin Institute of Technology, Harbin 150090 (China)

2010-12-15

86

[Denitrifying phosphorus removal in MUCT-MBR].  

Science.gov (United States)

The self-designed MUCT-MBR simplifies the MUCT process with reducing reactors from 5 to 2, which greatly reduces land occupied by equipment. Instead of secondary sedimentation tank, the membrane effluent quality is quite safe, and the operation is simple. In the investigation about simultaneous phosphorus and nitrogen removal of MUCT-MBR, the results showed that: when the proportions of C, N and P in the influent were 33.3/5/1-25/5.5/1, the average removal rate of COD, TN and TP in the whole experimental process were 89.3%, 75.4% and 79.2%, respectively. And the sludge settling capacity had no influence on the membrane effluent quality. The key factor of N and P removal rates is denitrifying phosphorus removal in anoxic condition. The proportion of denitrifying phosphate accumulating organisms (DPAOs) and the rate of denitrifying phosphorous removal were 84.2% and 67.07% on the 58th day, respectively. PMID:19774998

Liu, Peng-Xiao; Zhang, Han-Min; Wang, Xiao-Lin; Xiao, Jing-Ni; Yang, Feng-Lin

2009-07-15

87

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 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

88

Potential effect of matrix stiffness on the enrichment of tumor initiating cells under three-dimensional culture conditions.  

Science.gov (United States)

Cancer stem cell (CSC) or tumor initiating cell (TIC) plays an important role in tumor progression and metastasis. Biophysical forces in tumor microenvironment have an important effect on tumor formation and development. In this study, the potential effect of matrix stiffness on the biological characteristics of human head and neck squamous cell carcinoma (HNSCC) TICs, especially the enrichment of HNSCC TICs, was investigated under three-dimensional (3D) culture conditions by means of alginate gel (ALG) beads with different matrix stiffnesses. ALG beads with soft (21kPa), moderate (70kPa) and hard (105kPa) stiffness were generated by changing alginate concentration. It was found that significant HNSCC TIC enrichment was achieved in the ALG beads with moderate matrix stiffness (70kPa). The gene expression of stemness markers Oct3/4 and Nanog, TIC markers CD44 and ABCG2 was enhanced in cells under this moderate (70kPa) stiffness. HNSCC TIC proportion was also highly enriched under moderate matrix stiffness, accompanying with higher tumorigenicity, metastatic ability and drug resistance. And it was also found that the possible molecular mechanism underlying the regulated TIC properties by matrix stiffness under 3D culture conditions was significantly different from 2D culture condition. Therefore, the results achieved in this study indicated that 3D biophysical microenvironment had an important effect on TIC characteristics and alginate-based biomimetic scaffolds could be utilized as a proper platform to investigate the interaction between tumor cells and 3D microenvironment. PMID:25108138

Liu, Chang; Liu, Yang; Xu, Xiao-Xi; Wu, Hao; Xie, Hong-Guo; Chen, Li; Lu, Ting; Yang, Li; Guo, Xin; Sun, Guang-Wei; Wang, Wei; Ma, Xiao-Jun; He, Xin

2015-01-01

89

Fermentative degradation of acetone by an enrichment culture in membrane-separated culture devices and in cell suspensions  

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A mixed culture, WoAct, growing on acetone, consisted of two dominant morphotypes: a rod-shaped acetone-fermenting bacterium producing acetate, and an acetate-utilizing Methanosaeta species. Dense cell suspensions, largely free of the aceticlastic methanogen and supplemented with bromoethanesulfonate, were able to degrade acetone and grow in small volumes in membrane-separated culture devices in which the acetate produced could diffuse into a large volume of medium. Acetone degradation and gr...

Platen, Harald; Janssen, Peter H.; Schink, Bernhard

1994-01-01

90

Microbial and metabolic characterization of a denitrifying phosphorus-uptake/side stream phosphorus removal system for treating domestic sewage.  

Science.gov (United States)

In this study, an advanced wastewater treatment process, the denitrifying phosphorus/side stream phosphorus removal system (DPR-Phostrip), was developed for the purpose of enhancing denitrifying phosphorus removal. The enrichment of denitrifying phosphorus-accumulating organisms (DPAOs) and the microbial community structure of DPR-Phostrip were evaluated by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), and the metabolic activity of seed sludge and activated sludge collected after 55 days of operation were evaluated by Biolog™ analysis. This experimental study of DPR-Phostrip operation showed that nutrients were removed effectively, and denitrifying phosphorus removal was observed during the pre-anoxic period. PCR-DGGE analysis indicated that DPR-Phostrip supported DPAO growth while inhibiting PAOs and GAOs. The major dominant species in DPR-Phostrip were Bacteroidetes bacterium, Saprospiraceae bacterium, and Chloroflexi bacterium. Moreover, the functional diversity indices calculated on the basis of Biolog analysis indicated that DPR-Phostrip had almost no effect on microbial community diversity but was associated with a shift in the dominant species, which confirms the results of the PCR-DGGE analysis. The results for average well color development, calculated via Biolog analysis, showed that DPR-Phostrip had a little impact on the metabolic activity of sludge. Further principal component analysis suggested that the ability to utilize low-molecular-weight organic compounds was reduced in DPR-Phostrip. PMID:25073616

Jin, Zhan; Ji, Fang-Ying; Xu, Xuan; Xu, Xiao-Yi; Chen, Qing-Kong; Li, Qi

2014-11-01

91

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 (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

92

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

93

Effects of CO2 enrichment and nutrients supply intermittency on batch cultures of Isochrysis galbana.  

Science.gov (United States)

Aiming at enhanced performance to increase economic feasibility of microalgae based processes, Isochrysis galbana was grown in three modes of cultivation: batch, intermittent fed batch and semi-continuous. The batch mode was conducted under two regimes of aeration: conventional aeration and CO2 enriched aeration (5% v/v in air). Increased biomass productivity without significant impact on lipid accumulation was observed for CO2 enriched aeration relatively to cultivation aerated with air only. The intermittent fed batch cultivation policy was proven to be useful for lipid accumulation, increasing the lipid content by 19.8%. However, the semi-continuous mode resulted in higher productivity due to increased biomass concentration; the biomass productivity reached 0.51 g/(Ld). Fluorescence measurements were performed; the calculated low electron transport rate showed the need to increase the irradiance. The results showed that I. galbana can be grown in semi-continuous condition at high levels of biomass productivity. PMID:23800629

Picardo, Marta C; de Medeiros, José Luiz; Araújo, Ofélia de Queiroz F; Chaloub, Ricardo Moreira

2013-09-01

94

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

95

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

96

Applicability of a Lactobacillus amylovorus strain as co-culture for natural folate bio-enrichment of fermented milk.  

Science.gov (United States)

The ability of 55 strains from different Lactobacillus species to produce folate was investigated. In order to evaluate folic acid productivity, lactobacilli were cultivated in the folate-free culture medium (FACM). Most of the tested strains needed folate for growth. The production and the extent of vitamin accumulation were distinctive features of individual strains. Lactobacillus amylovorus CRL887 was selected for further studies because of its ability to produce significantly higher concentrations of vitamin (81.2 ± 5.4 ?g/L). The safety of this newly identified folate producing strain was evaluated through healthy experimental mice. No bacterial translocation was detected in liver and spleen after consumption of CRL887 during 7 days and no undesirable side effects were observed in the animals that received this strain. This strain in co-culture with previously selected folate producing starter cultures (Lactobacillus bulgaricus CRL871, and Streptococcus thermophilus CRL803 and CRL415) yielded a yogurt containing high folate concentrations (263.1 ± 2.4 ?g/L); a single portion of which would provide 15% of the recommended dietary allowance. This is the first report where a Lactobacillus amylovorus strain was successfully used as co-culture for natural folate bio-enrichment of fermented milk. PMID:25217720

Laiño, Jonathan Emiliano; Juarez del Valle, Marianela; Savoy de Giori, Graciela; LeBlanc, Jean Guy Joseph

2014-11-17

97

Bone-like tissue formation by three-dimensional culture of MG63 osteosarcoma cells in gelatin hydrogels using calcium-enriched medium.  

Science.gov (United States)

The aim of this study was to investigate the effect of Ca(2+) concentration in culture medium on the promotion of osteogenesis by MG63 osteoblast-like cells and to prepare bone-like tissues by supplying Ca(2+)-enriched medium to MG63 cells immobilized in three-dimensional gelatin hydrogels. Human osteosarcoma MG63 cells were cultured on tissue culture dish under various Ca(2+) concentrations to evaluate the effect of Ca(2+) concentration on calcium deposition. When Ca(2+) concentration was 8 mM, the maximum calcium deposition was obtained at day 28. Then MG63 cells were entrapped in gelatin hydrogels cross-linked by transglutaminase and cultured for 28 days, either in a standard culture medium or in medium containing 8 mM Ca(2+). Effects of Ca(2+)-enriched medium on osteoblastic phenotype of MG63 cells in gelatin hydrogels were analyzed in terms of cell number, calcium deposition content, and alkaline phosphatase (ALP) activity. The characteristics of calcified gelatin hydrogels were evaluated by x-ray diffraction (XRD), histological analysis, and scanning electron microscopy (SEM). After 28 days of culture, no significant difference in cell numbers was found between the different culture conditions. However, calcium content of gelatin hydrogels with cells cultured in Ca(2+)-enriched media was significantly higher than that of hydrogels with cells cultured in standard Ca(2+) concentration medium. After 14 days of culture, ALP activity of cells cultured in Ca(2+)-enriched media was down-regulated compared with that of cells cultured in standard Ca(2+) concentration media. XRD analysis indicated the formation of hydroxyapatite in gelatin hydrogels cultured in the Ca(2+)-enriched media at day 14, and the XRD pattern of the composite at day 21 was almost similar to that of mouse tibia. Moreover, histological analysis and SEM analysis revealed that cross-sections of hydrogels cultured in Ca(2+)-enriched media had an organic/mineral layer structure analogous to that of mouse tibia. PMID:16674304

Takagishi, Yoshiyuki; Kawakami, Takashi; Hara, Yusuke; Shinkai, Masashige; Takezawa, Toshiaki; Nagamune, Teruyuki

2006-04-01

98

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

Energy Technology Data Exchange (ETDEWEB)

Oil spills are fairly common in polar tundra regions, including remote locations, and are a threat to the relatively fragile ecosystem. Remediation must be done economically and with minimum additional damage. Bioremediation is considered to be the appropriate technology, although its application in polar tundra regions is not well documented. Most studies of hydrocarbon remediation in polar regions have concerned marine oil spills, while a few studies have demonstrated on-site polar tundra soil remediation. A few of these demonstrated the presence of psychrotolerant hydrocarbon-degrading bacteria in polar tundra soils. Because fuels are complex mixtures of hydrocarbons, microbial consortia rather than pure cultures may be the most effective agents in degrading fuels. Despite their potential advantages for bioaugmentation applications, consortia are difficult to characterize and monitor. Molecular methods based on DNA analysis partially address these difficulties. One such approach is to randomly clone rRNA gene (rDNA) fragments and to sequence as a set of clones. The relative abundance of individual sequences in the clone library is related to the relative abundance of the corresponding organism in the community. In this study a psychrotolerant, fuel-degrading consortium was enriched with Arctic tundra soil. The enrichment substrate for the consortium was Jet A-1 fuel, which is very similar to Arctic diesel fuel, a common contaminant in the region. The objectives of the study were to (1) characterize thr consortium by DNA- and culture-based methods, (2) develop quantitative polymerase chain reaction assays for populations of predominant consortium members, and (3) determine the dynamics of those populations during incubation of the consortium. Result showed that is possible to quantitatively monitor members of a microbial consortium, with potential application for bioremediation of Arctic tundra soil. The relative abundance of consortium members was found to vary in laboratory culture; even greater variance may be expected in the soil environment. 37 refs., 3 tabs., 3 figs.

Thomassin-Lacroix, E. J. M.; Reimer, K. J. [Royal Military College, Dept. of Chemistry and Chemical Engineering, Kingston, On (Canada); Yu, Z.; Mohn, W. W. [British Columbia Univ., Dept. of Microbiology and Immunology, Vancouver, BC (Canada); Eriksson, M. [Royal Inst. of Technology, Dept. of Biotechnology, Stockholm (Sweden)

2001-12-01

99

Atrazine biodegradation efficiency, metabolite detection, and trzD gene expression by enrichment bacterial cultures from agricultural soil.  

Science.gov (United States)

Atrazine is a selective herbicide used in agricultural fields to control the emergence of broadleaf and grassy weeds. The persistence of this herbicide is influenced by the metabolic action of habituated native microorganisms. This study provides information on the occurrence of atrazine mineralizing bacterial strains with faster metabolizing ability. The enrichment cultures were tested for the biodegradation of atrazine by high-performance liquid chromatography (HPLC) and mass spectrometry. Nine cultures JS01.Deg01 to JS09.Deg01 were identified as the degrader of atrazine in the enrichment culture. The three isolates JS04.Deg01, JS07.Deg01, and JS08.Deg01 were identified as efficient atrazine metabolizers. Isolates JS04.Deg01 and JS07.Deg01 produced hydroxyatrazine (HA) N-isopropylammelide and cyanuric acid by dealkylation reaction. The isolate JS08.Deg01 generated deethylatrazine (DEA), deisopropylatrazine (DIA), and cyanuric acid by N-dealkylation in the upper degradation pathway and later it incorporated cyanuric acid in their biomass by the lower degradation pathway. The optimum pH for degrading atrazine by JS08.Deg01 was 7.0 and 16S rDNA phylogenetic typing identified it as Enterobacter cloacae strain JS08.Deg01. The highest atrazine mineralization was observed in case of isolate JS08.Deg01, where an ample amount of trzD mRNA was quantified at 72 h of incubation with atrazine. Atrazine bioremediating isolate E. cloacae strain JS08.Deg01 could be the better environmental remediator of agricultural soils and the crop fields contaminated with atrazine could be the source of the efficient biodegrading microbial strains for the environmental cleanup process. PMID:24302716

Solomon, Robinson David Jebakumar; Kumar, Amit; Satheeja Santhi, Velayudhan

2013-12-01

100

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

 
 
 
 
101

Anaerobic degradation of 3-aminobenzoate by a newly isolated sulfate reducer and a methanogenic enrichment culture  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A new rod-shaped, gram-negative, non-sporing sulfate reducer, strain mAB1, was enriched and isolated from marine sediment samples with 3-aminobenzoate as sole electron and carbon source. Strain mAB1 degraded 3-aminobenzoate completely to CO 2 and NH 3 with stoichiometric reduction of sulfate to sulfide. Ceils contained carbon monoxide dehydrogenase, cytochromes, and sulfite reductase P582. Strain mAB1 degraded also benzoate, 4-aminobenzoate, hydroxybenzoates, and some aliphatic compounds. Bes...

Schnell, Sylvia; Schink, Bernhard

1992-01-01

102

Characterization of extracellular polymeric substances from denitrifying organism Comamonas denitrificans.  

Science.gov (United States)

Extracellular polymeric substances (EPS) play an important role in the formation and activity of biofilms in wastewater treatment (WWT). The EPS of the denitrifying biomarker Comamonas denitrificans strain 110, produced in different culture media and growth modes, were characterized. The EPS mainly contained protein (3-37%), nucleic acids (9-50%), and carbohydrates (3-21%). The extracellular DNA was found to be important for initial biofilm formation since biofilm, but not planktonic growth, was inhibited in the presence of DNase. The polysaccharide fraction appeared to consist of at least two distinct polymers, one branched fraction (A) made up of glucose and mannose with a molecular weight around 100 kDa. The other fraction (B) was larger and consisted of ribose, mannose, glucose, rhamnose, arabinose, galactose, and N-acetylglucosamine. Fraction B polysaccharides were mainly found in capsular EPS which was the dominant type in biofilms and agar-grown colonies. Fraction A was abundant in the released EPS, the dominant type in planktonic cultures. Biofilm and agar-grown EPS displayed similar overall properties while planktonic EPS showed clear compositional disparity. This study presents results on the physiology of a key WWT organism, which may be useful in the future development of improved biofilm techniques for WWT purposes. PMID:19123000

Andersson, Sofia; Dalhammar, Gunnel; Land, Carl Johan; Kuttuva Rajarao, Gunaratna

2009-03-01

103

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

104

One health from a social-ecological systems perspective: enriching social and cultural dimensions.  

Science.gov (United States)

This chapter offers insights from the environmental management paradigm of 'social-ecological systems' and related bodies of theory on people-environment relationships to assist the evolution of the One Health interdisciplinary endeavour of health promotion across human-animal ecosystem relationships. It also seeks to expand thinking about the social and cultural dimensions that are likely to prove important in the development of thinking and practice in the One Health field. It advocates consideration of cultural and economic relationships affecting people's interactions with domesticated and wild animal species and ecosystems, and exploration of the cognitive and behavioural aspects of these interactions. PMID:23124939

Ross, Helen

2013-01-01

105

Stable acetate production in extreme-thermophilic (70°C) mixed culture fermentation by selective enrichment of hydrogenotrophic methanogens  

Science.gov (United States)

The control of metabolite production is difficult in mixed culture fermentation. This is particularly related to hydrogen inhibition. In this work, hydrogenotrophic methanogens were selectively enriched to reduce the hydrogen partial pressure and to realize efficient acetate production in extreme-thermophilic (70°C) mixed culture fermentation. The continuous stirred tank reactor (CSTR) was stable operated during 100 days, in which acetate accounted for more than 90% of metabolites in liquid solutions. The yields of acetate, methane and biomass in CSTR were 1.5 +/- 0.06, 1.0 +/- 0.13 and 0.4 +/- 0.05 mol/mol glucose, respectively, close to the theoretical expected values. The CSTR effluent was stable and no further conversion occurred when incubated for 14 days in a batch reactor. In fed-batch experiments, acetate could be produced up to 34.4 g/L, significantly higher than observed in common hydrogen producing fermentations. Acetate also accounted for more than 90% of soluble products formed in these fed-batch fermentations. The microbial community analysis revealed hydrogenotrophic methanogens (mainly Methanothermobacter thermautotrophicus and Methanobacterium thermoaggregans) as 98% of Archaea, confirming that high temperature will select hydrogenotrophic methanogens over aceticlastic methanogens effectively. This work demonstrated a potential application to effectively produce acetate as a value chemical and methane as an energy gas together via mixed culture fermentation.

Zhang, Fang; Zhang, Yan; Ding, Jing; Dai, Kun; van Loosdrecht, Mark C. M.; Zeng, Raymond J.

2014-06-01

106

Transformation capacities of chlorinated organics by mixed cultures enriched on methane, propane, toluene, or phenol.  

Science.gov (United States)

The degradation of trichloroethylene (TCE), chloroform (CF), and 1,2-dichloroethane (1,2-DCA) by four aerobic mixed cultures (methane, propane, toluene, and phenol oxidizers) grown under similar chemostat conditions was measured. Methane and propane oxidizers were capable of degrading both saturated and unsaturated chlorinated organics (TCE, CF, and 1,2-DCA). Toluene and phenol oxidizers degraded TCE but were not able to degrade CF, 1,2-DCA, or other saturated organics. None of the cultures tested were able to degrade perchloroethylene (PCE) or carbon tetrachloride (CC(4)). For the four cultures tested, degradation of each of the chlorinated organics resulted in cell inactivation due to product toxicity. In all cases, the toxic products were rapidly depleted, leaving no toxic residues in solution. Among the four tested cultures, the resting cells of methane oxidizers exhibited the highest transformation capacities (T(c)) for TCE, CF, and 1,2-DCA. The T(c) for each chlorinated organic was observed to be inversely proportional to the chlorine carbon ratio (Cl/C). The addition of low concentrations of growth substrate or some catabolic intermediates enhanced TCE transformation capacities and degradation rates, presumably due to the regeneration of reducing energy (NADH); however, addition of higher concentrations of most amendments reduced TCE transformation capacities and degradation rates. Reducing energy limitations and amendment toxicity may significantly affect T(c) measurements, causing a masking of the toxicity associated with chlorinated organic degradation. PMID:18623237

Chang, H L; Alvarez-Cohen, L

1995-03-01

107

Effects of the antimicrobial sulfamethoxazole on groundwater bacterial enrichment  

Science.gov (United States)

The effects of "trace" (environmentally relevant) concentrations of the antimicrobial agent sulfamethoxazole (SMX) on the growth, nitrate reduction activity, and bacterial composition of an enrichment culture prepared with groundwater from a pristine zone of a sandy drinking-water aquifer on Cape Cod, MA, were assessed by laboratory incubations. When the enrichments were grown under heterotrophic denitrifying conditions and exposed to SMX, noticeable differences from the control (no SMX) were observed. Exposure to SMX in concentrations as low as 0.005 ??M delayed the initiation of cell growth by up to 1 day and decreased nitrate reduction potential (total amount of nitrate reduced after 19 days) by 47% (p = 0.02). Exposure to 1 ??M SMX, a concentration below those prescribed for clinical applications but higher than concentrations typically detected in aqueous environments, resulted in additional inhibitions: reduced growth rates (p = 5 ?? 10-6), lower nitrate reduction rate potentials (p = 0.01), and decreased overall representation of 16S rRNA gene sequences belonging to the genus Pseudomonas. The reduced abundance of Pseudomonas sequences in the libraries was replaced by sequences representing the genus Variovorax. Results of these growth and nitrate reduction experiments collectively suggest that subtherapeutic concentrations of SMX altered the composition of the enriched nitrate-reducing microcosms and inhibited nitrate reduction capabilities. ?? 2011 American Chemical Society.

Underwood, J.C.; Harvey, R.W.; Metge, D.W.; Repert, D.A.; Baumgartner, L.K.; Smith, R.L.; Roane, T.M.; Barber, L.B.

2011-01-01

108

Enrichment culture and microscopy conceal diverse thermophilic Synechococcus populations in a single hot spring microbial mat habitat.  

Science.gov (United States)

Recent molecular studies have shown a great disparity between naturally occurring and cultivated microorganisms. We investigated the basis for disparity by studying thermophilic unicellular cyanobacteria whose morphologic simplicity suggested that a single cosmopolitan species exists in hot spring microbial mats worldwide. We found that partial 16S rRNA sequences for all thermophilic Synechococcus culture collection strains from diverse habitats are identical. Through oligonucleotide probe analysis and cultivation, we provide evidence that this species is strongly selected for in laboratory culture to the exclusion of many more-predominant cyanobacterial species coexisting in the Octopus Spring mat in Yellowstone National Park. The phylogenetic diversity among Octopus Spring cyanobacteria is of similar magnitude to that exhibited by all cyanobacteria so far investigated. We obtained axenic isolates of two predominant cyanobacterial species by diluting inocula prior to enrichment. One isolate has a 16S rRNA sequence we have not yet detected by cloning. The other has a 16S rRNA sequence identical to a new cloned sequence we report herein. This is the first cultivated species whose 16S rRNA sequence has been detected in this mat system by cloning. We infer that biodiversity within this community is linked to guild structure. PMID:11536748

Ferris, M J; Ruff-Roberts, A L; Kopczynski, E D; Bateson, M M; Ward, D M

1996-03-01

109

Antitumoural activity of viniferin-enriched extracts from Vitis vinifera L. cell cultures.  

Science.gov (United States)

The aim of this work was to evaluate the effect of stilbenes from different cultivars of Vitis vinifera on tumour proliferation. Extracts were obtained from elicited V. vinifera cell cultures and characterised by HPLC/DAD/MS. Cell growth was evaluated in four human cancer cell lines and in normal human fibroblasts. The cells were exposed to the extracts or to trans-resveratrol, used as reference molecule, for 48 h, at 1-10 ?M concentrations of total stilbenoids. All the extracts exhibited antiproliferative activity, mediated by modulation of the cell cycle and induction of cytotoxicity in cancer but not in normal cell lines, and positively correlated with the content in dimeric stilbenoids. The Alphonse Lavallée extract was the most active, and the obtained stilbenoid fraction resulted 8-10 times more active than trans-resveratrol. Extracts from V. vinifera cell cultures could represent new sources of active stilbenoid compounds to be further assayed in in vivo studies for their antitumoural properties. PMID:24949881

Giovannelli, L; Innocenti, M; Santamaria, A R; Bigagli, E; Pasqua, G; Mulinacci, N

2014-01-01

110

Growth and nitrate reduction of Beggiatoa filaments studied in enrichment cultures  

DEFF Research Database (Denmark)

In this thesis, several aspects of the gliding, filamentous, colourless sulphur bacteria Beggiatoa were investigated. The first part of this thesis addressed the growth mode, breakage of filaments for multiplication, and movement directions of filaments of Beggiatoa. Marine Beggiatoa were enriched in oxygen-sulphide gradient tubes, and observed with a camera system. Growth mode, breakage, and movement directions of Beggiatoa filaments were documented via time-lapse video recording. The initial doubling time of cells was 15.7 ±1.3 h (mean ±SD; room temperature). Filaments grew up to an average length of 1.7 ±0.2 mm, but filaments of up to ca. 6 mm were also present. First breakages of filaments occurred ca. 19 h after inoculation, and time-lapse movies illustrated that a parent filament could break into several daughter filaments within a few hours. In many cases, filament breakage occurred at the same point at which the tip of a forming loop of the filament had been observed before. As it is known that filament breakage is accomplished by the formation of a sacrificial cell, it was hypothesised that sacrificial cells interrupt the communication between two parts of one filament. As a consequence, the two parts of one filament can move towards each other forming the tip of a loop at the sacrificial cell. The second part of this thesis focused on the physiology of Beggiatoa. The sulphur bacteria Beggiatoa can reach high biomass in many aquatic habitats, e.g. in and on freshwater and marine sediments, and affect the benthic sulphur cycle. In addition, Beggiatoa may influence the nitrogen cycle when they use nitrate anaerobically as an alternative electron acceptor in place of oxygen. The ability of freshwater and marine Beggiatoa to oxidise sulphide anaerobically with nitrate has been studied for some time. However, for freshwater Beggiatoa, the anaerobic sulphide oxidation with nitrate has not been unequivocally documented, and was therefore a special focal point of this thesis. In a first study, the general ability of freshwater Beggiatoa to oxidise sulphide with nitrate as alternative electron acceptor was investigated. A freshwater Beggiatoa strain was highly enriched in oxygen-sulphide gradient tubes. The gradient tubes contained different nitrate concentrations, and the chemotactic response of the Beggiatoa mats was observed. The effects of the Beggiatoa on vertical gradients of nitrate, sulphide, oxygen, and pH were determined with microsensors. The more nitrate that was added to the agar, the deeper the Beggiatoa filaments glided into anoxic agar layers, suggesting that the Beggiatoa used nitrate to oxidise sulphide at depths below the depth that oxygen penetrated. In the presence of nitrate, Beggiatoa formed thick mats (>8 mm), compared to the thin mats (ca. 0.4 mm) that were formed when no nitrate was added. These thick mats spatially separated oxygen and sulphide, but not nitrate and sulphide, and therefore nitrate must have served as the electron acceptor for sulphide oxidation. This interpretation is consistent with a fourfold-lower oxygen flux and a twofold- higher sulphide flux into the nitrate-exposed mats compared to the fluxes for controls without nitrate. Additionally, a pronounced pH maximum was observed within the Beggiatoa mat; such a pH maximum is known to occur when sulphide is oxidised to elemental sulphur with nitrate as the electron acceptor. In a second study, a freshwater Beggiatoa strain was phylogenetically analysed and investigated with respect to the capability of intracellular nitrate storage and the dissimilatory use of nitrate. The 16S rDNA sequence retrieved from the filaments revealed the affiliation with the genus Beggiatoa and with a confined cluster of freshwater strains. Intracellular nitrate storage was found with concentrations of 35 ±32 mmol L-1. To follow the metabolic pathway of the possible dissimilatory use of nitrate by this freshwater Beggiatoa strain, the filaments were highly enriched in oxygen-sulphide gradient tubes in which experiments with 15N-labelled nitrate wer

Kamp, Anja

2007-01-01

111

Stable Nitrogen and Oxygen Isotope Analysis of Nitrate using Denitrifying Bacteria  

Science.gov (United States)

The total isotopic composition of nitrate is used for identifying the origin and fate of nitrate in atmospheric, terrestrial and aquatic systems. The analysis of ? 18O, ?15N, and ?17O values each give important and unique information about the sources and sinks of nitrate in these systems. Currently, there is no published method that allows for the simultaneous determination of ?18O, ?15N, and ?17O of nitrate. Cascotti designed a novel method for measurement of ?18O and ?15N in nitrate but not ?17O. This denitrifier method is based on the isotope ratio analysis of nitrous oxide generated by reduction of nitrate by cultured denitrifying bacteria. Kaiser then altered Cascotti's denitrifier method by converting N2O into O2 followed by the quantitative measurement ?18O and ?17O, however ?15N was not measured. Here we present preliminary data on ?15N, ?18O, ?17O values of N2 and O2 generated by the disproportionation of bacterial produced N2O. During the process of denitrification, nitrates are converted to nitrogen gas via a series of intermediate gaseous nitrogen oxide products. This is possible due to the presence of heterotrophic bacteria or autotrophic denitrifiers in select bacteria. Thus, we have chosen three distinct bacteria for the investigation of nitrate reduction for this study: Pseudomonas aureofaciens, Bacillus halodenitrificans, and Achromobacter cycloclastes. They each contain the copper-containing nitrite reductase necessary for the catalyzation of nitrate in order to complete the nitrogen cycle by returning N2 to the atmosphere. Bacillus halodenitrificans has the advantage of being an anaerobic halotolerant (salt-tolerant) denitrifier. Many of our samples have a high saline content; also, pre-concentration techniques using anion resin require elution using high ionic strength solutions. Further, high saline growth solutions limit contamination from other bacteria or organisms. Our efforts also focus on the conversion of N2O over a gold tube into both O2 and N2 using techniques adapted from Cascotti and Kaiser. Our instrument utilizes an extended 11-cup multi-collector feature which does not require a peak jump during analysis on the continuous flow IRMS. Although this is not the first method to study independent measurements of ?18O, ?17O, ?15N, or ?17O, this is first technique that simultaneously detects the stable isotope composition of oxygen and nitrogen in a given nitrate sample. Tests of the impact on isotopic composition by pre-concentration methods have been performed including freeze-drying/evaporation, column chromatography and ion chromatography.

Edenburn, L.; Michalski, G. M.

2009-12-01

112

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

113

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

114

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

Science.gov (United States)

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. PMID:23891624

Terra, Letícia F; Teixeira, Priscila C; Wailemann, Rosangela A M; Zelanis, André; Palmisano, Giuseppe; Cunha-Neto, Edecio; Kalil, Jorge; Larsen, Martin R; Labriola, Leticia; Sogayar, Mari C

2013-12-01

115

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

116

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

117

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

118

A Novel Reductive Dehalogenase, Identified in a Contaminated Groundwater Enrichment Culture and in Desulfitobacterium dichloroeliminans Strain DCA1, Is Linked to Dehalogenation of 1,2-Dichloroethane?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A mixed culture dechlorinating 1,2-dichloroethane (1,2-DCA) to ethene was enriched from groundwater that had been subjected to long-term contamination. In the metagenome of the enrichment, a 7-kb reductive dehalogenase (RD) gene cluster sequence was detected by inverse and direct PCR. The RD gene cluster had four open reading frames (ORF) showing 99% nucleotide identity with pceB, pceC, pceT, and orf1 of Dehalobacter restrictus strain DSMZ 9455T, a bacterium able to dechlorinate chlorinated e...

Marzorati, Massimo; Ferra, Francesca; Raemdonck, Hilde; Borin, Sara; Allifranchini, Elena; Carpani, Giovanna; Serbolisca, Luca; Verstraete, Willy; Boon, Nico; Daffonchio, Daniele

2007-01-01

119

N-acyl homoserine lactone-degrading microbial enrichment cultures isolated from Penaeus vannamei shrimp gut and their probiotic properties in Brachionus plicatilis cultures.  

Science.gov (United States)

Three bacterial enrichment cultures (ECs) were isolated from the digestive tract of Pacific white shrimp Penaeus vannamei, by growing the shrimp microbial communities in a mixture of N-acyl homoserine lactone (AHL) molecules. The ECs, characterized by denaturing gradient gel electrophoresis analysis and subsequent rRNA sequencing, degraded AHL molecules in the degradation assays. Apparently, the resting cells of the ECs also degraded one of the three types of quorum-sensing signal molecules produced by Vibrio harveyi in vitro [i.e. harveyi autoinducer 1 (HAI-1)]. The most efficient AHL-degrading ECs, EC5, was tested in Brachionus experiments. EC5 degraded the V. harveyi HAI-1 autoinducer in vivo, neutralizing the negative effect of V. harveyi autoinducer 2 (AI-2) mutant, in which only the HAI-1- and CAI-1-mediated components of the quorum-sensing system are functional on the growth of Brachionus. This suggests that EC5 interferes with HAI-1-regulated metabolism in V. harveyi. These AHL-degrading ECs need to be tested in other aquatic systems for their probiotic properties, preferably in combination with specific AI-2-degrading bacteria. PMID:17784866

Tinh, Nguyen Thi Ngoc; Asanka Gunasekara, R A Y S; Boon, Nico; Dierckens, Kristof; Sorgeloos, Patrick; Bossier, Peter

2007-10-01

120

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

 
 
 
 
121

Inhibitory Effect of Gamma-Irradiated Chitosan on the Growth of Denitrifiers  

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Full Text Available In order to find an environmentally benign substitute to hazardous inhibitory agents, the inhibitory effect of ?-irradiated chitosans against a mixed culture of denitrifying bacteria was experimentally evaluated. Unlike other studies using pure aerobic cultures, the observed effect was not a complete inhibition but a transient inhibition reflected by prolonged lag phases and reduced growth rates. Raw chitosan under acid conditions (pH 6.3 exerted the strongest inhibition followed by the 100?kGy and 500?kGy irradiated chitosans, respectively. Therefore, because the molecular weight of chitosan decreases with the degree of ?-irradiation, the inhibitory properties of chitosan due to its high molecular weight were more relevant than the inhibitory properties gained due to the modification of the surface charge and/or chemical structure by ?-irradiation. High dosage of ?-irradiated appeared to increase the growth of mixed denitrifying bacteria in acid pH media. However, in neutral pH media, high dosage of ?-irradiation appeared to enhance the inhibitory effect of chitosan.

Javier Vilcáez

2009-01-01

122

Role of the denitrifying Haloarchaea in the treatment of nitrite-brines.  

Science.gov (United States)

Haloferax mediterranei is a denitrifying halophilic archaeon able to reduce nitrate and nitrite under oxic and anoxic conditions. In the presence of oxygen, nitrate and nitrite are used as nitrogen sources for growth. Under oxygen scarcity, this haloarchaeon uses both ions as electron acceptors via a denitrification pathway. In the present work, the maximal nitrite concentration tolerated by this organism was determined by studying the growth of H. mediterranei in minimal medium containing 30, 40 and 50 mM nitrite as sole nitrogen source and under initial oxic conditions at 42 degrees C. The results showed the ability of H. mediterranei to withstand nitrite concentrations up to 50 mM. At the beginning of the incubation, nitrate was detected in the medium, probably due to the spontaneous oxidation of nitrite under the initial oxic conditions. The complete removal of nitrite and nitrate was accomplished in most of the tested conditions, except in culture medium containing 50 mM nitrite, suggesting that this concentration compromised the denitrification capacity of the cells. Nitrite and nitrate reductases activities were analyzed at different growth stages of H. mediterranei. In all cases, the activities of the respiratory enzymes were higher than their assimilative counterparts; this was especially the case for NirK. The denitrifying and possibly detoxifying role of this enzyme might explain the high nitrite tolerance of H. mediterranei. This archaeon was also able to remove 60% of the nitrate and 75% of the nitrite initially present in brine samples collected from a wastewater treatment facility. These results suggest that H. mediterranei, and probably other halophilic denitrifying Archaea, are suitable candidates for the bioremediation of brines with high nitrite and nitrate concentrations. PMID:23847815

Nájera-Fernández, Cindy; Zafrilla, Basilio; Bonete, María José; Martínez-Espinosa, Rosa María

2012-09-01

123

Degradative capacities and 16S rRNA-targeted whole-cell hybridization of sulfate-reducing bacteria in an anaerobic enrichment culture utilizing alkylbenzenes from crude oil.  

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A mesophilic sulfate-reducing enrichment culture growing anaerobically on crude oil was used as a model system to study which nutritional types of sulfate-reducing bacteria may develop on original petroleum constituents in oil wells, tanks, and pipelines. Chemical analysis of oil hydrocarbons during growth revealed depletion of toluene and o-xylene within 1 month and of m-xylene, o-ethyltoluene, m-ethyltoluene, m-propyltoluene, and m-isopropyltoluene within approximately 2 months. In anaerobi...

Rabus, R.; Fukui, M.; Wilkes, H.; Widdle, F.

1996-01-01

124

Diversity and activity of denitrifiers of Chilean arid soil ecosystems  

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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

125

Effects of A2ON Process on Denitrifying Dephosphatation  

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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

126

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

127

Evidence for cooperative mineralization of diuron by Arthrobacter sp. BS2 and Achromobacter sp. SP1 isolated from a mixed culture enriched from diuron exposed environments.  

Science.gov (United States)

Diuron was found to be mineralized in buffer strip soil (BS) and in the sediments (SED) of the Morcille river in the Beaujolais vineyard repeatedly treated with this herbicide. Enrichment cultures from BS and SED samples led to the isolation of three bacterial strains transforming diuron to 3,4-dichloroaniline (3,4-DCA) its aniline derivative. 16S rRNA sequencing revealed that they belonged to the genus Arthrobacter (99% of similarity to Arthrobacter globiformis strain K01-01) and were designated as Arthrobacter sp. BS1, BS2 and SED1. Diuron-degrading potential characterized by sequencing of the puhA gene, characterizing the diuron-degradaing potential, revealed 99% similarity to A. globiformis strain D47 puhA gene isolated a decade ago in the UK. These isolates were also able to use chlorotoluron for their growth. Although able to degrade linuron and monolinuron to related aniline derivatives they were not growing on them. Enrichment cultures led to the isolation of a strain from the sediments entirely degrading 3,4-DCA. 16S rRNA sequence analysis showed that it was affiliated to the genus Achromobacter (99% of similarity to Achromobacter sp. CH1) and was designated as Achromobacter sp. SP1. The dcaQ gene encoding enzyme responsible for the transformation of 3,4-DCA to chlorocatechol was found in SP1 with 99% similarity to that of Comamonas testosteroni WDL7. This isolate also used for its growth a range of anilines (3-chloro-4-methyl-aniline, 4-isopropylaniline, 4-chloroaniline, 3-chloroaniline, 4-bromoaniline). The mixed culture composed of BS2 and SP1 strains entirely mineralizes (14)C-diuron to (14)CO2. Diuron-mineralization observed in the enrichment culture could result from the metabolic cooperation between these two populations. PMID:25061887

Devers-Lamrani, Marion; Pesce, Stéphane; Rouard, Nadine; Martin-Laurent, Fabrice

2014-12-01

128

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.

129

Development of PCR primer systems for amplification of nitrite reductase genes (nirK and nirS) to detect denitrifying bacteria in environmental samples  

Energy Technology Data Exchange (ETDEWEB)

A system was developed for the detection of denitrifying bacteria by the application 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 wit h 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 the generally amplifying primer combination for each nir gene developed in this study to total DNA preparations from aquatic habitats.

Braker, G.; Witzel, K.P. [Max-Planck-Inst. fuer Limnologie, Ploen (Germany); Fesefeldt, A. [Univ. Kiel (Germany). Inst. fuer Allgemeine Mikrobiologie

1998-10-01

130

Clustering and nonlinear regression analysis applied to the in vitro growing of Leucoagaricus gongylophorus (Singer Möller in a culture environment enriched with different botanical extracts  

Directory of Open Access Journals (Sweden)

Full Text Available The study aimed to evaluate the in vitro growing of Leucoagaricus gongylophorus in a culture environment enriched with different extracts from botanical species, via multivariate statistical analysis of data clustering, besides identifying the fungus behavior through nonlinear regression equations. The fungus was inoculated into a BDA medium enriched with eight botanical extracts, along with two controls (with and without the addition of 20mL distilled water, in Petri plates. The plates were kept in a climatized chamber at a 25±1ºC temperature in the dark, during a 42 days period and the fungus growing was evaluated at weekly intervals. It was proved that the clustering analysis and the Chapman-Richards model are effi cient to verify the similarity of different botanical extracts in the fungus development, as well as to estimate and describe the growing of L. gongylophorus.

Marcelo Dias de Souza

2011-12-01

131

Enrichment of umbilical cord blood mononuclears with hemopoietic precursors in co-culture with mesenchymal stromal cells from human adipose tissue.  

Science.gov (United States)

We demonstrated the possibility of enrichment of umbilical cord blood mononuclear fraction with early non-differentiated precursors under conditions of co-culturing with mesenchymal stromal cells from the human adipose tissue. It was established that umbilical cord blood mononuclear cells adhered to mesenchymal stromal cell feeder and then proliferate and differentiate into hemopoietic cells. In comparison with the initial umbilical cord blood mononuclear fraction, the cell population obtained after 7-day expansion contained 2-fold more CFU and 33.4 ± 9.5 and 24.2 ± 11.2% CD34(+) and CD133(+) cells, respectively, which corresponds to enrichment of precursor cell population by 148 ± 60. The proposed scheme of expansion of hemopoietic cells from umbilical cord blood is economically expedient and can widely used in biology and medicine. PMID:24771453

Maslova, E V; Andreeva, E R; Andrianova, I V; Bobyleva, P I; Romanov, Yu A; Kabaeva, N V; Balashova, E E; Ryaskina, S S; Dugina, T N; Buravkova, L B

2014-02-01

132

Characterization of Fe(III)-reducing enrichment cultures and isolation of Fe(III)-reducing bacteria from the Savannah River site, South Carolina.  

Science.gov (United States)

The Savannah River site, South Carolina (SRS), has been subjected to heavy metal and radionuclide contamination. Dissimilatory Fe(III)-reducing bacteria, by reducing insoluble Fe(III) to soluble Fe(II), may enhance contaminant mobility through subsurface environments. In order to investigate populations of the indigenous iron-reducing microbes from the SRS, duplicate enrichment cultures were initiated using a 10% inoculum of 7 sediment/soil samples, and serial dilutions were made into Wolfe's minimal salts media amended with 50 mM Fe(III) floc, 10 mM acetate and 0.01% yeast extract. Terminal restriction fragment length polymorphism (T-RFLP) analysis was used to generate fingerprints of the cultures and track changes in the microbial communities through the dilutions. Cluster analysis determined the relatedness of individual fingerprints. Initial enrichment cultures exhibited complex fingerprints consisting of many individual T-RF peaks, and demonstrated low similarity between sites. After four serial dilutions the fingerprints were less complex and clustered at higher similarities. Several individual T-RF peaks became dominant in a majority of the fingerprints. Cloning and sequence analysis revealed the presence of microbes closely related to Clostridium and Bacillus species and to known iron reducers such as Geobacter species and Pantoea agglomerans. Several Fe(III)-reducing isolates related to Aeromonas, Bacillus and Clostridium species were obtained. PMID:16730954

Scala, David J; Hacherl, Eric L; Cowan, Robert; Young, Lily Y; Kosson, David S

2006-10-01

133

Isolation and Molecular Identification of an Aerobic Denitrifier  

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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

134

Nitric oxide-dependent proton translocation in various denitrifiers.  

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Respiration of NO resulted in transient proton translocation in anaerobically grown cells of four physiologically diverse denitrifiers. Paracoccus denitrificans, Rhodopseudomonas sphaeroides subsp. denitrificans, "Achromobacter cycloclastes," and Rhizobium japonicum gave, respectively, H+/NO ratios of 3.65, 4.96, 1.94, and 1.12. Antimycin A completely inhibited NO-dependent proton translocation in P. denitrificans and severely restricted translocation in the R. sphaeroides strain. Proton upta...

Shapleigh, J. P.; Payne, W. J.

1985-01-01

135

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.

2007-04-01

136

Diversity of Denitrifying Bacteria in the San Francisco Bay  

Science.gov (United States)

We compared the diversity of communities of denitrifying bacteria from the San Francisco Bay to investigate whether environmental factors affect diversity. To do this, we studied the sequence diversity of the marker gene nirK. nirK codes for the enzyme nitrite reductase which helps reduce nitrite to nitric oxide, an important step in denitrification. Sediment samples were collected spatially from five different locations and temporally during the four different seasons along a salinity gradient in the bay. After collecting samples and extracting DNA from them, we used PCR to amplify our gene of interest, created clone libraries for sequencing, and compared phylogenetic trees from the different communities. Based on several phylogenetic analyses on our tree and environments, we saw that denitrifying bacteria from the North and Central Bay form distinct spatial clusters; Central Bay communities are very similar to each other, while communities from the North Bay are more distinct from each other and from communities in the Central Bay. Bacteria from site 8.1M (Carquinez Strait) showed the most cm-scale spatial diversity, and there was the most species richness during the winter. All this suggests that diversity of communities of denitrifying bacteria may be affected by spatial and temporal environmental factors.

Atluri, A.; Lee, J.; Francis, C. A.

2012-12-01

137

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

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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

138

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

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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

139

[Effect of dissolved oxygen on diversity of ammonia-oxidizing microorganisms in enrichment culture from estuarine wetland surface sediments and ammonia-oxidizing rate].  

Science.gov (United States)

Dissolved oxygen (DO) is one of the important environmental factors influencing the ammonia oxidation process. In order to examine the effects of DO on ammonia oxidation process and its potential mechanisms, surface sediments from Jiulong River Estuarine Wetland were collected and cultured to obtain enrichment cultures. Then the enrichment cultures were inoculated under different levels of DO, and the diversity of ammonia-oxidizing microorganisms was analyzed using PCR-DGGE technique to determine the effect of DO on the ammonia oxidation rate and the ammonia-oxidizing microorganism diversity. Results showed that the Shannon index was 2. 00 and 2.05 for ammonia-oxidizing bacteria (AOB) under saturated and aerobic conditions, respectively, and the values were 2.49 (saturated) and 2.03 (aerobic) for ammonia-oxidizing archaea (AOA). However, this index was 1.76 and 1.80 for AOB under hypoxia and anaerobic condition, and 1.27 and 2. 21 for AOA. Under saturated and aerobic conditions ( higher DO level), the ammonia-oxidizing rates were 14.20 mg.(L.d)-1 and 13.36 mg.(L.d)-1 and the related conversation rates of NH+4 -N were 93.8% and 88. 2% , respectively. In comparison, under hypoxia and anaerobic conditions (lower DO level), the ammonia-oxidizing rates were 7.82 mg.(L.d) -1 and 5.66 mg.(L.d)-1 and the related conversation rates of NH+4 -N were 51.7% and 37.4% , respectively. The correlation analysis showed that DO concentration was highly significantly positively correlated with the ammonia oxidation rate, and was significantly positively correlated with the AOB diversity index; DO and ammonia oxidation rate had no correlation with indices of AOA community. PMID:23668119

Qiu, Zhao-Zheng; Luo, Zhuan-Xi; Zhao, Yan-Ling; Yan, Chang-Zhou

2013-02-01

140

Molecular and Stable Isotope Investigation of Nitrite Respiring Bacterial Communities Capable of Anaerobic Ammonium Oxidation (ANAMMOX) and Denitrifying Anaerobic Methane Oxidation (DAMO) in Nitrogen Contaminated Groundwater  

Science.gov (United States)

Anaerobic ammonium oxidation (ANAMMOX) and denitrifying anaerobic methane oxidation (DAMO) are two recently discovered N2 production pathways in the microbial nitrogen cycle. ANAMMOX has been relatively well investigated in various aquatic ecosystems, while DAMO has been examined only in freshwater wetlands. However, neither ANAMMOX nor DAMO have been studied in groundwater ecosystems as microbial N removal processes where they could compliment or compete with denitrification to remediate N contaminated aquifers. Thus, we conducted molecular and stable isotope analyses to detect and measure ANAMMOX and DAMO in a nitrogen contaminated aquifer on Cape Cod, Massachusetts. The study site has a plume of nitrogen contaminated groundwater as a result of continuous discharge of treated wastewater over 60 years. Groundwater was collected from multiport sampling devices installed at two sites, near the waste-water disposal location (A) and more than 3 km down gradient (B) along the contamination plume. Biomass was collected from water samples for DNA extraction and 15N tracer incubation experiments. PCR with specific 16S rRNA gene primers detected the presence of ANAMMOX and DAMO bacteria at both sites. Phylogenetic analysis of 16S rRNA genes revealed that the ANAMMOX community at site A was most associated with Kuenenia spp. while site B had a community more closely related to Brocadia spp. The DAMO communities at the two sites were quite different based on 16S rRNA gene analysis. The communities at site B are closely associated with Candidatus “Methylomirabilis oxyfera”, which is the first enriched DAMO culture. Most of the 16S rRNA sequences detected in site A were related to those found in other DAMO enrichment cultures established from a eutrophic ditch sediment. In order to determine active members of ANAMMOX communities, the transcriptional expression of hydrazine oxidase (hzo) and hydrazine hydrolase (hh) genes was examined at both sites. In addition, 15N tracer incubation experiments were used to measure the rates of ANAMMOX and denitrification. ANAMMOX was found to be higher than denitrification at site A where ANAMMOX accounted for 60% of the 15N2 production. In contrast, denitrification was higher than ANAMMOX at site B where Methylomirabilis spp. were found. Thus, this study clearly demonstrates the potential importance of ANAMMOX and DAMO in the nitrogen removal from groundwater and suggests that detailed characterization of the processes under in situ subsurface conditions could provide new information regarding the ecology of these microbes.

Song, B.; Hirsch, M.; Taylor, J.; Smith, R. L.; Repert, D.; Tobias, C. R.

2010-12-01

 
 
 
 
141

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

D Sivaramakrishna, D. Sreekanth

2010-01-01

142

Cytokine-dependent long-term culture of highly enriched precursors of hematopoietic progenitor cells from human bone marrow.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Human marrow cells positive for the CD34 antigen but not expressing HLA-DR, CD15, or CD71 antigens were isolated. In a liquid culture system supplemented with 48-hourly additions of recombinant interleukins IL-1 alpha, IL-3, IL-6, or granulocyte/macrophage colony-stimulating factor (GM-CSF), these cells were capable of sustaining in vitro hematopoiesis for up to eight weeks. The establishment of an adherent cell layer was never observed. Cultures containing no exogenous cytokine produced clon...

Brandt, J.; Srour, E. F.; Besien, K.; Briddell, R. A.; Hoffman, R.

1990-01-01

143

Investigation of an Acetate-Fed Denitrifying Microbial Community by Stable Isotope Probing, Full-Cycle rRNA Analysis, and Fluorescent In Situ Hybridization-Microautoradiography  

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The acetate-utilizing microbial consortium in a full-scale activated sludge process was investigated without prior enrichment using stable isotope probing (SIP). [13C]acetate was used in SIP to label the DNA of the denitrifiers. The [13C]DNA fraction that was extracted was subjected to a full-cycle rRNA analysis. The dominant 16S rRNA gene phylotypes in the 13C library were closely related to the bacterial families Comamonadaceae and Rhodocyclaceae in the class Betaproteobacteria. Seven oligo...

Ginige, Maneesha P.; Keller, Ju?rg; Blackall, Linda L.

2005-01-01

144

A Novel Reductive Dehalogenase, Identified in a Contaminated Groundwater Enrichment Culture and in Desulfitobacterium dichloroeliminans Strain DCA1, Is Linked to Dehalogenation of 1,2-Dichloroethane?  

Science.gov (United States)

A mixed culture dechlorinating 1,2-dichloroethane (1,2-DCA) to ethene was enriched from groundwater that had been subjected to long-term contamination. In the metagenome of the enrichment, a 7-kb reductive dehalogenase (RD) gene cluster sequence was detected by inverse and direct PCR. The RD gene cluster had four open reading frames (ORF) showing 99% nucleotide identity with pceB, pceC, pceT, and orf1 of Dehalobacter restrictus strain DSMZ 9455T, a bacterium able to dechlorinate chlorinated ethenes. However, dcaA, the ORF encoding the catalytic subunit, showed only 94% nucleotide and 90% amino acid identity with pceA of strain DSMZ 9455T. Fifty-three percent of the amino acid differences were localized in two defined regions of the predicted protein. Exposure of the culture to 1,2-DCA and lactate increased the dcaA gene copy number by 2 log units, and under these conditions the dcaA and dcaB genes were actively transcribed. A very similar RD gene cluster with 98% identity in the dcaA gene sequence was identified in Desulfitobacterium dichloroeliminans strain DCA1, the only known isolate that selectively dechlorinates 1,2-DCA but not chlorinated ethenes. The dcaA gene of strain DCA1 possesses the same amino acid motifs as the new dcaA gene. Southern hybridization using total genomic DNA of strain DCA1 with dcaA gene-specific and dcaB- and pceB-targeting probes indicated the presence of two identical or highly similar dehalogenase gene clusters. In conclusion, these data suggest that the newly described RDs are specifically adapted to 1,2-DCA dechlorination. PMID:17351102

Marzorati, Massimo; de Ferra, Francesca; Van Raemdonck, Hilde; Borin, Sara; Allifranchini, Elena; Carpani, Giovanna; Serbolisca, Luca; Verstraete, Willy; Boon, Nico; Daffonchio, Daniele

2007-01-01

145

A novel reductive dehalogenase, identified in a contaminated groundwater enrichment culture and in Desulfitobacterium dichloroeliminans strain DCA1, is linked to dehalogenation of 1,2-dichloroethane.  

Science.gov (United States)

A mixed culture dechlorinating 1,2-dichloroethane (1,2-DCA) to ethene was enriched from groundwater that had been subjected to long-term contamination. In the metagenome of the enrichment, a 7-kb reductive dehalogenase (RD) gene cluster sequence was detected by inverse and direct PCR. The RD gene cluster had four open reading frames (ORF) showing 99% nucleotide identity with pceB, pceC, pceT, and orf1 of Dehalobacter restrictus strain DSMZ 9455(T), a bacterium able to dechlorinate chlorinated ethenes. However, dcaA, the ORF encoding the catalytic subunit, showed only 94% nucleotide and 90% amino acid identity with pceA of strain DSMZ 9455(T). Fifty-three percent of the amino acid differences were localized in two defined regions of the predicted protein. Exposure of the culture to 1,2-DCA and lactate increased the dcaA gene copy number by 2 log units, and under these conditions the dcaA and dcaB genes were actively transcribed. A very similar RD gene cluster with 98% identity in the dcaA gene sequence was identified in Desulfitobacterium dichloroeliminans strain DCA1, the only known isolate that selectively dechlorinates 1,2-DCA but not chlorinated ethenes. The dcaA gene of strain DCA1 possesses the same amino acid motifs as the new dcaA gene. Southern hybridization using total genomic DNA of strain DCA1 with dcaA gene-specific and dcaB- and pceB-targeting probes indicated the presence of two identical or highly similar dehalogenase gene clusters. In conclusion, these data suggest that the newly described RDs are specifically adapted to 1,2-DCA dechlorination. PMID:17351102

Marzorati, Massimo; de Ferra, Francesca; Van Raemdonck, Hilde; Borin, Sara; Allifranchini, Elena; Carpani, Giovanna; Serbolisca, Luca; Verstraete, Willy; Boon, Nico; Daffonchio, Daniele

2007-05-01

146

Uranium enrichment  

Energy Technology Data Exchange (ETDEWEB)

This article deals with the demand for and supply of enriched uranium. The demand for enriched uranium is closely related to the development of new nuclear power plants. The enrichment programmes in various countries including USA, France, United Kingdom, West-Germany, Netherlands and Japan, as well as the different processes that they use for uranium enrichment (e.g. centrifuges and gaseous diffusion) are disscussed. South Africa's UCOR-process for uranium enrichment is also discussed.

Grant, W.L. (Uranium Enrichment Corp. of South Africa, Ltd., Pretoria)

1983-02-01

147

Uranium enrichment  

International Nuclear Information System (INIS)

This article deals with the demand for and supply of enriched uranium. The demand for enriched uranium is closely related to the development of new nuclear power plants. The enrichment programmes in various countries including USA, France, United Kingdom, West-Germany, Netherlands and Japan, as well as the different processes that they use for uranium enrichment (e.g. centrifuges and gaseous diffusion) are disscussed. South Africa's UCOR-process for uranium enrichment is also discussed

148

Enrichment culture and microscopy conceal diverse thermophilic Synechococcus populations in a single hot spring microbial mat habitat.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Recent molecular studies have shown a great disparity between naturally occurring and cultivated microorganisms. We investigated the basis for disparity by studying thermophilic unicellular cyanobacteria whose morphologic simplicity suggested that a single cosmopolitan species exists in hot spring microbial mats worldwide. We found that partial 16S rRNA sequences for all thermophilic Synechococcus culture collection strains from diverse habitats are identical. Through oligonucleotide probe an...

Ferris, M. J.; Ruff-roberts, A. L.; Kopczynski, E. D.; Bateson, M. M.; Ward, D. M.

1996-01-01

149

Anaerobic degradation of toluene by a denitrifying bacterium.  

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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

150

Characterization of denitrifying activity by the alphaproteobacterium, Sphingomonas wittichii RW1  

Directory of Open Access Journals (Sweden)

Full Text Available Sphingomonas wittichii RW1 has no reported denitrifying activity yet encodes nitrite and nitric oxide reductases. The aims of this study were to determine conditions under which S. wittichii RW1 consumes nitrite (NO2- and produces nitrous oxide (N2O, examine expression of putative genes for N-oxide metabolism, and determine the functionality of chromosomal (ch and plasmid (p encoded quinol-dependent nitric oxide reductases (NorZ. Batch cultures of wildtype (WT and a norZch mutant of S. wittichii RW1 consumed NO2- and produced N2O during stationary phase. The norZch mutant produced N2O, although at significantly lower levels (c.a. 66-87% relative to the WT. Rates of N2O production were 2-3 times higher in cultures initiated at low relative to atmospheric O2 per unit biomass, although rates of NO2- consumption were elevated in cultures initiated with atmospheric O2 and 1 mM NaNO2. Levels of mRNA encoding nitrite reductase (nirK, plasmid-encoded nitric oxide dioxygenase (hmpp and plasmid-encoded nitric oxide reductase (norZp were significantly higher in the norZch mutant over a growth curve relative to WT. The presence of NO2- further increased levels of nirK and hmpp mRNA in both the WT and norZch mutant; levels of norZp mRNA compensated for the loss of norZch expression in the norZch mutant. Together, the results suggest that S. wittichii RW1 denitrifies NO2- to N2O and expresses gene products predicted to detoxify N-oxides. So far, only S. wittichii strains within four closely related taxa have been observed to encode both nirK and norZ genes, indicating a species-specific lateral gene transfer that may be relevant to the niche preference of S. wittichii.

LisaYStein

2014-08-01

151

Physiological and transcriptional studies of Cr(VI) reduction under aerobic and denitrifying conditions by an aquifer-derived pseudomonad.  

Science.gov (United States)

Cr(VI) is a widespread groundwater contaminant that is a potent toxin, mutagen, and carcinogen. In situ reductive immobilization is a favored approach for Cr(VI) bioremediation, and Cr(VI) reduction has been reported in a variety of aerobic, facultative, and anaerobic bacteria, including a number of pseudomonads. However, studies comparing Cr(VI) reduction under aerobic and denitrifying conditions in the same organism are not available. We have conducted studies with strain RCH2, a bacterium similar to Pseudomonas stutzeri that we isolated from a Cr-contaminated aquifer. Cell suspension studies with lactate demonstrated that Cr(VI) reduction could occur under either denitrifying or aerobic conditions (at comparable specific rates) and that reduction was at least 20-fold more rapid when the terminal electron acceptor (i.e., nitrate or O(2)) was present. Our results suggest that Cr(VI) reduction by strain RCH2 under either aerobic or denitrifying conditions is primarily cometabolic in the sense that the physiological electron acceptor (oxygen or nitrate) appears to be required. Under both aerobic and denitrifying conditions, the gene(s) associated with chromate reduction are not inducible by Cr. Continuous culture (chemostat) studies showed strong correlations (r(2) values >0.93) between nitrate reduction rate and the transcript copy number of either nirS (cytochrome cd(1) nitrite reductase) or narG (nitrate reductase ? subunit). As our studies indicate that anaerobic Cr(VI) reduction by this pseudomonad requires active denitrification and that denitrification and chromate reduction rates are highly correlated (r(2) > 0.99), monitoring expression of such denitrification genes in biostimulated aquifers could provide valuable proxy information for in situ chromate reduction by similar bacteria even if the specific genes involved in chromate reduction have not been identified. We also report incomplete removal of reduced Cr from solution and on artifacts in the widely used diphenylcarbazide assay for Cr(VI), most notably, its complete inactivation in the presence of millimolar nitrite. PMID:20822129

Han, Ruyang; Geller, Jil T; Yang, Li; Brodie, Eoin L; Chakraborty, Romy; Larsen, Joern T; Beller, Harry R

2010-10-01

152

Effects of Temperature on Denitrifying Growth and Nitrate Reduction End Products of Comamonas testosteroni Isolated from Estuarine Sediment  

Directory of Open Access Journals (Sweden)

Full Text Available Predictions of seasonal changes in N2O emission that occur in natural estuaries are important to anticipate the future implications of global warming. This study showed the effect of temperature on denitrifying growth and nitrate reduction end product of Comamonas testoteroni isolated from estuarine sediment using both batch and continuous cultures. The ?max values of Comamonas testosteroni grown in anaerobic batch culture were increased with increasing temperature, and the highest ?max was found at 26 °C. Concentrations of nitrate reduced (mg-1 dried weight cells were higher at low temperature. Concentrations of N2 produced were higher at low temperature and the production of N2 was higher than both NO2- and N2O productions

IMAN RUSMANA

2007-01-01

153

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

154

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

155

Pandoraea oxalativorans sp. nov., Pandoraea faecigallinarum sp. nov. and Pandoraea vervacti sp. nov., isolated from oxalate-enriched culture.  

Science.gov (United States)

Five isolates, designated TA2, TA4, TA25(T), KOx(T) and NS15(T) were isolated in previous studies by enrichment in mineral medium with potassium oxalate as the sole carbon source and were characterized using a polyphasic approach. The isolates were Gram-reaction-negative, aerobic, non-spore-forming rods. Phylogenetic analyses based on 16S rRNA and DNA gyrase B subunit (gyrB) gene sequences confirmed that the isolates belonged to the genus Pandoraea and were most closely related to Pandoraea sputorum and Pandoraea pnomenusa (97.2-99.7?% 16S rRNA gene sequence similarity). The isolates could be differentiated from their closest relatives on the basis of several phenotypic characteristics. The major cellular fatty acid profiles of the isolates comprised C??:?, C??:??7c, C??:? cyclo and summed feature 3 (C??:??7c and/or iso-C??:? 2-OH). On the basis of DNA-DNA hybridization studies and phylogenetic analyses, the isolates represent three novel species within the genus Pandoraea, for which the names Pandoraea oxalativorans sp. nov. (TA25(T) ?=?NBRC 106091(T) ?=?CCM 7677(T) ?=?DSM 23570(T)), Pandoraea faecigallinarum sp. nov. (KOx(T) ?=?NBRC 106092(T) ?=?CCM 2766(T) ?=?DSM 23572(T)) and Pandoraea vervacti sp. nov. (NS15(T) ?=?NBRC 106088(T) ?=?CCM 7667(T) ?=?DSM 23571(T)) are proposed. PMID:20952546

Sahin, Nurettin; Tani, Akio; Kotan, Recep; Sedlácek, Ivo; Kimbara, Kazuhide; Tamer, Abdurrahman U

2011-09-01

156

Short communication: Viability of culture organisms in honey-enriched acidophilus-bifidus-thermophilus (ABT)-type fermented camel milk.  

Science.gov (United States)

The aim of this research was to monitor the survival during refrigerated storage of Lactobacillus acidophilus LA-5 (A), Bifidobacterium animalis ssp. lactis BB-12 (B), and Streptococcus thermophilus CHCC 742/2130 (T) in cultured dairy foods made from camel and, for comparison, cow milks supplemented with black locust (Robinia pseudoacacia L.) honey and fermented by an acidophilus-bifidus-thermophilus (ABT)-type culture. Two liters of dromedary camel milk and 2 L of cow milk were heated to 90 °C and held for 10 min, then cooled to 40 °C. One half of both types of milk was fortified with black locust honey at the rate of 5.0% (wt/vol), whereas the other half was devoid of honey and served as a control. The camel and cow milks with and without honey were subsequently inoculated with ABT-5 culture and were fermented at 37 °C until a pH value of 4.6 was reached. Thereafter, the probiotic fermented milks were cooled to 15 °C in ice water and were each separated into 18 fractions that were transferred in sterile, tightly capped centrifuge tubes. After 24 h of cooling at 8 °C (d 0), the samples were stored at refrigeration temperature (4 °C). Three tubes of all 4 products (i.e., fermented camel and cow milks with and without honey) were taken at each sampling time (i.e., following 0, 7, 14, 21, 28, and 35 d of storage), and the counts of characteristic microorganisms and those of certain spoilage microbes (yeasts, molds, coliforms, Escherichia coli) were enumerated. The entire experimental program was repeated twice. The results showed that addition of black locust honey at 5% to heat-treated camel and cow milks did not influence the growth and survival of starter streptococci during production and subsequent refrigerated storage of fermented ABT milks. In contrast, honey improved retention of viability of B. animalis ssp. lactis BB-12 in the camel milk-based product during storage at 4 °C up to 5 wk. No spoilage organisms were detected in any of the samples tested in this study. In conclusion, supplementation of cultured dairy foods, especially those made from camel milk, with honey is recommended because honey is a healthy natural sweetener with a variety of beneficial microbiological, nutritional, and sensory properties. PMID:25151879

Varga, L; Süle, J; Nagy, P

2014-11-01

157

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

158

A system to enrich for primitive streak-derivatives, definitive endoderm and mesoderm, from pluripotent cells in culture.  

Science.gov (United States)

Two lineages of endoderm develop during mammalian embryogenesis, the primitive endoderm in the pre-implantation blastocyst and the definitive endoderm at gastrulation. This complexity of endoderm cell populations is mirrored during pluripotent cell differentiation in vitro and has hindered the identification and purification of the definitive endoderm for use as a substrate for further differentiation. The aggregation and differentiation of early primitive ectoderm-like (EPL) cells, resulting in the formation of EPL-cell derived embryoid bodies (EPLEBs), is a model of gastrulation that progresses through the sequential formation of primitive streak-like intermediates to nascent mesoderm and more differentiated mesoderm populations. EPL cell-derived EBs have been further analysed for the formation of definitive endoderm by detailed morphological studies, gene expression and a protein uptake assay. In comparison to embryoid bodies derived from ES cells, which form primitive and definitive endoderm, the endoderm compartment of embryoid bodies formed from EPL cells was comprised almost exclusively of definitive endoderm. Definitive endoderm was defined as a population of squamous cells that expressed Sox17, CXCR4 and Trh, which formed without the prior formation of primitive endoderm and was unable to endocytose horseradish peroxidase from the medium. Definitive endoderm formed in EPLEBs provides a substrate for further differentiation into specific endoderm lineages; these lineages can be used as research tools for understanding the mechanisms controlling lineage establishment and the nature of the transient intermediates formed. The similarity between mouse EPL cells and human ES cells suggests EPLEBs can be used as a model system for the development of technologies to enrich for the formation of human ES cell-derived definitive endoderm in the future. PMID:22701686

Vassilieva, Svetlana; Goh, Hwee Ngee; Lau, Kevin X; Hughes, James N; Familari, Mary; Rathjen, Peter D; Rathjen, Joy

2012-01-01

159

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

160

Isolation and characterization of a mesophilic heavy-metals-tolerant sulfate-reducing bacterium Desulfomicrobium sp. from an enrichment culture using phosphogypsum as a sulfate source.  

Science.gov (United States)

A sulfate-reducing bacterium, was isolated from a 6 month trained enrichment culture in an anaerobic media containing phosphogypsum as a sulfate source, and, designated strain SA2. Cells of strain SA2 were rod-shaped, did not form spores and stained Gram-negative. Phylogenetic analysis of the 16S rRNA gene sequence of the isolate revealed that it was related to members of the genus Desulfomicrobium (average sequence similarity of 98%) with Desulfomicrobium baculatum being the most closely related (sequence similarity of 99%). Strain SA2 used thiosulfate, sulfate, sulfite and elemental sulfur as electron acceptors and produced sulfide. Strain SA2 reduced sulfate contained in 1-20g/L phosphogypsum to sulfide with reduction of sulfate contained in 2g/L phosphogypsum being the optimum concentration. Strain SA2 grew with metalloid, halogenated and non-metal ions present in phosphogypsum and with added high concentrations of heavy metals (125ppm Zn and 100ppm Ni, W, Li and Al). The relative order for the inhibitory metal concentrations, based on the IC(50) values, was Cu, Te>Cd>Fe, Co, Mn>F, Se>Ni, Al, Li>Zn. PMID:16979290

Azabou, Samia; Mechichi, Tahar; Patel, Bharat K C; Sayadi, Sami

2007-02-01

 
 
 
 
161

Isolation and characterization of a mesophilic heavy-metals-tolerant sulfate-reducing bacterium Desulfomicrobium sp. from an enrichment culture using phosphogypsum as a sulfate source  

International Nuclear Information System (INIS)

A sulfate-reducing bacterium, was isolated from a 6 month trained enrichment culture in an anaerobic media containing phosphogypsum as a sulfate source, and, designated strain SA2. Cells of strain SA2 were rod-shaped, did not form spores and stained Gram-negative. Phylogenetic analysis of the 16S rRNA gene sequence of the isolate revealed that it was related to members of the genus Desulfomicrobium (average sequence similarity of 98%) with Desulfomicrobium baculatum being the most closely related (sequence similarity of 99%). Strain SA2 used thiosulfate, sulfate, sulfite and elemental sulfur as electron acceptors and produced sulfide. Strain SA2 reduced sulfate contained in 1-20 g/L phosphogypsum to sulfide with reduction of sulfate contained in 2 g/L phosphogypsum being the optimum concentration. Strain SA2 grew with metalloid, halogenated and non-metal ions present in phosphogypsum and with added high concentrations of heavy metals (125 ppm Zn and 100 ppm Ni, W, Li and Al). The relative order for the inhibitory metal concentrations, based on the IC50 values, was Cu, Te > Cd > Fe, Co, Mn > F, Se > Ni, Al, Li > Zn

162

[Screening, denitrification characteristics, and anaerobic ammonium oxidation ability of denitrifying bacterium aHD7].  

Science.gov (United States)

A highly efficient denitrifying bacterium aHD7 was screened from activated sludge. After static culture at 30 degrees C for 3 days, the denitrification rate of the aHD7 reached 91.7%, and during denitrification, nitrite had lower accumulation, with its concentration basically maintained at 1.8 mg x L(-1). The microscopy observation demonstrated that the aHD7 was a gram-negative bacillus, with an average size of 0.5 microm x (1.5-2.5) microm. Based on its biochemical/morphological characteristics and homologic analysis of 16S rDNA sequence, the aHD7 was identified as Pseudomonas mendocina. The investigation on the factors affecting the denitrification capacity of aHD7 showed that at the initial concentration of nitrate nitrogen being less than 276.95 mg x L(-1), the denitrification rate was almost 100%, and when the initial concentration of nitrate nitrogen was as high as 553.59 mg x L(-1), the denitrification rate could reach 66.8%, with little nitrite accumulated. Ethanol was the most suitable carbon source. C/N ratio 6-8 and pH value 6-9 benefited the denitrification. The aHD7 had a good ability of anaerobic ammonium oxidation, and its average ammonium utilization rate reached 4.56 mg x L(-1) x d(-1). PMID:23431796

Chu, Shu-Yi; Jiang, Hui-Xia; Xiao, Ji-Bo; Shan, Sheng-Dao

2012-11-01

163

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

164

Assessing the Impact of Denitrifier-Produced Nitric Oxide on Other Bacteria  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A series of experiments was undertaken to learn more about the impact on other bacteria of nitric oxide (NO) produced during denitrification. The denitrifier Rhodobacter sphaeroides 2.4.3 was chosen as a denitrifier for these experiments. To learn more about NO production by this bacterium, NO levels during denitrification were measured by using differential mass spectrometry. This revealed that NO levels produced during nitrate respiration by this bacterium were in the low ?M range. This co...

Choi, Peter S.; Naal, Zeki; Moore, Charles; Casado-rivera, Emerilis; Abrun?a, Hector D.; Helmann, John D.; Shapleigh, James P.

2006-01-01

165

Nitric Oxide Reductase-Targeted Real-Time PCR Quantification of Denitrifier Populations in Soil?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The quantification of denitrifying bacteria is a component in the further understanding of denitrification processes in the environment. Real-time PCR primers were designed to target two segments of the denitrifier population (cnorBP [Pseudomonas mandelii and closely related strains] and cnorBB [Bosea, Bradyrhizobium, and Ensifer spp.]) in agricultural soils based on functional cnorB (nitric oxide reductase) gene sequences. Total population numbers were measured using 16S rRNA gene real-time ...

Dandie, C. E.; Miller, M. N.; Burton, D. L.; Zebarth, B. J.; Trevors, J. T.; Goyer, C.

2007-01-01

166

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

167

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

168

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

169

Uranium enrichment  

International Nuclear Information System (INIS)

This report looks at the following issues: How much Soviet uranium ore and enriched uranium are imported into the United States and what is the extent to which utilities flag swap to disguise these purchases? What are the U.S.S.R.'s enriched uranium trading practices? To what extent are utilities required to return used fuel to the Soviet Union as part of the enriched uranium sales agreement? Why have U.S. utilities ended their contracts to buy enrichment services from DOE?

170

Metaproteogenomic analysis of a sulfate-reducing enrichment culture reveals genomic organization of key enzymes in the m-xylene degradation pathway and metabolic activity of proteobacteria.  

Science.gov (United States)

This study aimed to ascertain the functional and phylogenetic relationships within an m-xylene degrading sulfate-reducing enrichment culture, which had been maintained for several years in the laboratory with m-xylene as the sole source of carbon and energy. Previous studies indicated that a phylotype affiliated to the Desulfobacteraceae was the main m-xylene assimilating organism. In the present study, genes and gene products were identified by a metaproteogenomic approach using LC-MS/MS analysis of the microbial community, and 2426 peptides were identified from 576 proteins. In the metagenome of the community, gene clusters encoding enzymes involved in fumarate addition to a methyl moiety of m-xylene (nms, bss), as well as gene clusters coding for enzymes involved in modified beta-oxidation to (3-methyl)benzoyl-CoA (bns), were identified in two separate contigs. Additionally, gene clusters containing homologues to bam genes encoding benzoyl-CoA reductase (Bcr) class II, catalyzing the dearomatization of (3-methyl)benzoyl-CoA, were identified. Time-resolved protein stable isotope probing (protein-SIP) experiments using (13)C-labeled m-xylene showed that the respective gene products were highly (13)C-labeled. The present data suggested the identification of gene products that were similar to those involved in methylnaphthalene degradation even though the consortium was not capable of growing in the presence of naphthalene, methylnaphthalene or toluene as substrates. Thus, a novel branch of enzymes was found that was probably specific for anaerobic m-xylene degradation. PMID:25156802

Bozinovski, Dragana; Taubert, Martin; Kleinsteuber, Sabine; Richnow, Hans-Hermann; von Bergen, Martin; Vogt, Carsten; Seifert, Jana

2014-10-01

171

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

172

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 demonstratemes 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.

173

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

174

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

175

Enriched weakness  

CERN Document Server

The basic notions of category theory, such as limit, adjunction, and orthogonality, all involve assertions of the existence and uniqueness of certain arrows. Weak notions arise when one drops the uniqueness requirement and asks only for existence. The enriched versions of the usual notions involve certain morphisms between hom-objects being invertible; here we introduce enriched versions of the weak notions by asking that the morphisms between hom-objects belong to a chosen class of "surjections". We study in particular injectivity (weak orthogonality) in the enriched context, and illustrate how it can be used to describe homotopy coherent structures.

Lack, Stephen

2010-01-01

176

Phosphorus removal and N2O production in anaerobic/anoxic denitrifying phosphorus removal process: Long-term impact of influent phosphorus concentration.  

Science.gov (United States)

This study was conducted to investigate the long-term impact of influent phosphorus concentration on denitrifying phosphorus removal and N2O production during denitrifying phosphorous removal process. The results showed that, denitrifying phosphate accumulating organisms (DPAOs) could become dominant populations quickly in anaerobic/anoxic SBR by providing optimum cultivating conditions, and the reactor performed well for denitrifying phosphorus removal. The influent phosphorus concentration significantly affected anaerobic poly-?-hydroxyalkanoates (PHA) synthesis, denitrifying phosphorus removal, and N2O production during the denitrifying phosphorus removal process. As the influent phosphorus concentration was more than 20mgL(-1), the activity of DPAOs began to be inhibited due to the transformation of the available carbon source type. Meanwhile, N2O production was inhibited with the mitigation of anoxic NO2(-)-N accumulation. Adoption of a modified feeding could enhance denitrifying phosphorus removal and inhibit N2O production during denitrifying phosphorous removal processes. PMID:25541320

Wang, Zhen; Meng, Yuan; Fan, Ting; Du, Yuneng; Tang, Jie; Fan, Shisuo

2015-03-01

177

Genetic diversity and relative activity of denitrifying bacteria in stream bed sediments  

Science.gov (United States)

In order to understand the controls on sediment denitrification rates, the vertical distribution and potential activity of denitrifiers were evaluated on sediment cores collected from two streams in an agricultural watershed, where nitrogen loads are elevated. Denitrifiers were detected by PCR and the community structure was evaluated by T-RFLP analysis of the nitrite reductase gene nirS, the enzyme which catalyzes the first committed step in the denitrification pathway. A comparative analysis of nirS profiles down core and between sites demonstrated a relationship between abundance and genetic diversity of nirS and geochemical and physical properties of the streambed environment. Denitrifiers tended to be more abundant, diverse and active in surface sediments (upper 3cm) and in sediments with a low C/N. Fine grain sediments or sediments with high C/N exhibited poorly developed and less active denitrifying communities. This study revealed the influence of environmental gradients on denitrifier abundance and diversity and may explain differences in denitrification rates under varying environmental conditions.

Voytek, M. A.; Kirshtein, J.; Harvey, J.

2002-12-01

178

Differential Isotopic Fractionation during Cr(VI) Reduction by an Aquifer-Derived Bacterium under Aerobic versus Denitrifying Conditions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Han, Ruyang; Qin, Liping; Brown, Shaun T.; Christensen, John N.; Beller, Harry R.

2012-01-01

179

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

180

[Identification and denitrification characteristics of a psychrotolerant facultative basophilic aerobic denitrifier].  

Science.gov (United States)

An aerobic denitrifier was isolated from the activated sludge of landfill leachate through traditional microbiological methods. Based on its morphological feature, physiological and biochemical properties, and 16S rDNA sequence analysis, this strain was identified as Pseudomonas sp., named as GL19 with an accession number of KC710974 in GenBank. Its aerobic denitrification characteristics and nitrification function were studied to show that the factors including carbon source, C/N, pH and cultivation temperature were important for denitrification. The optimized condition for aerobic denitrification was as follows: sodium citrate as the carbon resource, C/N no less than 15, pH of 6-10, DO of 4.8-7.7 mg x L(-1), culture temperature of 15-34 degrees C and the initial nitrate nitrogen of 140 mg x L(-1). Combining these conditions, the removal rate of nitrate nitrogen and average removal rate of TN reached 100% and 96.5%, respectively, without the accumulation of nitrite nitrogen. The strain had the capability to utilize nitrite nitrogen or ammonia nitrogen to achieve high nitrogen removal efficiency: the nitrite nitrogen removal rate reached 100% in 20 hours with an initial nitrite nitrogen of 140 mg x L(-1); the ammonia nitrogen was efficiently removed from 280 mg x L(-1) to 3.11 mg x L(-1) in 28 hours with the removal rate of up to 98.9%. These results suggested that strain GL19 with the function of cold resistance and highly effective aerobic denitrification could achieve simultaneous nitrification and denitrification. Hence, GL19 could have high potential in practical wastewater treatment in winter of south area. PMID:25158516

Wang, Zhao-Yang; Chen, Guo-Yao; Jiang, Ke; Xu, Pei-Ya

2014-06-01

 
 
 
 
181

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

182

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

183

Effect of pyrene on denitrification activity and abundance and composition of denitrifying community in an agricultural soil  

International Nuclear Information System (INIS)

Toxicity of pyrene on the denitrifiers was studied by spiking an agricultural soil with pyrene to a series of concentrations (0-500 mg kg-1) followed by dose-response and dynamic incubation experiments. Results showed a positive correlation between potential denitrification activity and copy numbers of denitrifying functional genes (nirK, nirS and nosZ), and were both negatively correlated with pyrene concentrations. Based on the comparison of EC50 values, denitrifiers harboring nirK, nirS or nosZ gene were more sensitive than denitrification activity, and denitrifiers harboring nirS gene were more sensitive than that harboring nirK or nosZ genes. Seven days after spiking with EC50 concentration of pyrene, denitrifiers diversity decreased and community composition changed in comparison with the control. Phylogenetic analyses of three genes showed that the addition of pyrene increased the proportion of Bradyrhizobiaceae, Rhodospirillales, Burkholderiales and Pseudomonadales. Some species belonging to these groups were reported to be able to degrade PAHs. - Highlights: ? Toxicity of pyrene on the denitrifiers was studied by spiking an agricultural soil with pyrene. ? PDA was positively correlated with the abundance of denitrifiers harboring nirK, nirS or nosZ gene. ? Both PDA and the abundance of denitrifiers were negatively correlated with pyrene concentrations. ? Denitrifiers harboring nirk, nirS or nosZ gene are more sensitiverS or nosZ gene are more sensitive to pyrene than PDA in soils. - Denitrifiers harboring nirK, nirS or nosZ gene are more sensitive to pyrene contamination than potential denitrification activity in soils.

184

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...

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

2006-01-01

185

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

186

ANAEROBIC BIODEGRADATION OF O-, M- AND P-CRESOL BY SULFATE-REDUCING BACTERIAL ENRICHMENT CULTURES OBTAINED FROM A SHALLOW ANOXIC AQUIFER  

Science.gov (United States)

Sulfate-reducing bacterial enrichments were obtained from a shallow anoxic aquifer for their ability to metabolize either o-, or p-cresol. C/MS and simultaneous adaptation experiments suggested that the anaerobic decomposition of p-cresol proceeds by the initial oxidation of the ...

187

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

188

Uranium enrichment  

International Nuclear Information System (INIS)

This paper reports that in 1990 the Department of Energy began a two-year project to illustrate the technical and economic feasibility of a new uranium enrichment technology-the atomic vapor laser isotope separation (AVLIS) process. GAO believes that completing the AVLIS demonstration project will provide valuable information about the technical viability and cost of building an AVLIS plant and will keep future plant construction options open. However, Congress should be aware that DOE still needs to adequately demonstrate AVLIS with full-scale equipment and develop convincing cost projects. Program activities, such as the plant-licensing process, that must be completed before a plant is built, could take many years. Further, an updated and expanded uranium enrichment analysis will be needed before any decision is made about building an AVLIS plant. GAO, which has long supported legislation that would restructure DOE's uranium enrichment program as a government corporation, encourages DOE's goal of transferring AVLIS to the corporation. This could reduce the government's financial risk and help ensure that the decision to build an AVLIS plant is based on commercial concerns. DOE, however, has no alternative plans should the government corporation not be formed. Further, by curtailing a planned public access program, which would have given private firms an opportunity to learn about the technology during the demonstration project, DOE may limit its ability to transfer ct, DOE may limit its ability to transfer AVLIS to the private sector

189

Nitric oxide reductase-targeted real-time PCR quantification of denitrifier populations in soil.  

Science.gov (United States)

The quantification of denitrifying bacteria is a component in the further understanding of denitrification processes in the environment. Real-time PCR primers were designed to target two segments of the denitrifier population (cnorB(P) [Pseudomonas mandelii and closely related strains] and cnorB(B) [Bosea, Bradyrhizobium, and Ensifer spp.]) in agricultural soils based on functional cnorB (nitric oxide reductase) gene sequences. Total population numbers were measured using 16S rRNA gene real-time PCR. Two soil microcosm experiments were conducted. Experiment 1 examined the response of the indigenous soil microbial population to the addition of 500 mg/kg glucose-C daily over 7 days in soil microcosms. Changes in the total population were correlated (r = 0.83) between 16S rRNA gene copy numbers and microbial biomass carbon estimates. Members of the cnorB(P) population of denitrifiers showed typical r-strategy by being able to increase their proportion in the total population from starting levels of <0.1% to around 2.4% after a daily addition of 500 mg/kg glucose-C. The cnorB(B) guild was not able to increase its relative percentage of the total population in response to the addition of glucose-C, instead increasing copy numbers only in proportion with the total population measured by 16S rRNA genes. Experiment 2 measured population dynamics in soil after the addition of various amounts of glucose-C (0 to 500 mg/kg) and incubation under denitrifying conditions. cnorB(P) populations increased proportionally with the amount of glucose-C added (from 0 to 500 mg/kg). In soil microcosms, denitrification rates, respiration, and cnorB(P) population densities increased significantly with increasing rates of glucose addition. cnorB(B) guild densities did not increase significantly under denitrifying conditions in response to increasing C additions. PMID:17449686

Dandie, C E; Miller, M N; Burton, D L; Zebarth, B J; Trevors, J T; Goyer, C

2007-07-01

190

Nitric Oxide Reductase-Targeted Real-Time PCR Quantification of Denitrifier Populations in Soil?  

Science.gov (United States)

The quantification of denitrifying bacteria is a component in the further understanding of denitrification processes in the environment. Real-time PCR primers were designed to target two segments of the denitrifier population (cnorBP [Pseudomonas mandelii and closely related strains] and cnorBB [Bosea, Bradyrhizobium, and Ensifer spp.]) in agricultural soils based on functional cnorB (nitric oxide reductase) gene sequences. Total population numbers were measured using 16S rRNA gene real-time PCR. Two soil microcosm experiments were conducted. Experiment 1 examined the response of the indigenous soil microbial population to the addition of 500 mg/kg glucose-C daily over 7 days in soil microcosms. Changes in the total population were correlated (r = 0.83) between 16S rRNA gene copy numbers and microbial biomass carbon estimates. Members of the cnorBP population of denitrifiers showed typical r-strategy by being able to increase their proportion in the total population from starting levels of <0.1% to around 2.4% after a daily addition of 500 mg/kg glucose-C. The cnorBB guild was not able to increase its relative percentage of the total population in response to the addition of glucose-C, instead increasing copy numbers only in proportion with the total population measured by 16S rRNA genes. Experiment 2 measured population dynamics in soil after the addition of various amounts of glucose-C (0 to 500 mg/kg) and incubation under denitrifying conditions. cnorBP populations increased proportionally with the amount of glucose-C added (from 0 to 500 mg/kg). In soil microcosms, denitrification rates, respiration, and cnorBP population densities increased significantly with increasing rates of glucose addition. cnorBB guild densities did not increase significantly under denitrifying conditions in response to increasing C additions. PMID:17449686

Dandie, C. E.; Miller, M. N.; Burton, D. L.; Zebarth, B. J.; Trevors, J. T.; Goyer, C.

2007-01-01

191

Isolation of Burkholderia cepacia by enrichment.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Burkholderia cepacia is a recognised cause of respiratory failure in patients with cystic fibrosis. The value of routine use of selective enrichment broth to increase the yield of B cepacia from cystic fibrosis sputa was investigated. Two hundred sputa from 86 adult and paediatric patients were cultured onto B cepacia selective agar and also in enrichment broth. The enrichment broths were subcultured after incubation onto B cepacia selective agar. Fourteen sputa from eight patients yielded B ...

Flanagan, P. G.; Paull, A.

1998-01-01

192

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

193

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

International Nuclear Information System (INIS)

Graphical abstract: Model evaluation applied to case study 1: (A-G) S2?, NO3?-N, NO2?-N, and Ac?-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?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 (S2?), nitrate (NO3?) and acetate (Ac?) 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 S2? concentration, S2?/NO3?-N ratio and Ac?-C/NO3?-N ratio. Simulation supported that the heterotrophic denitratation step (NO3? reduction to NO2?) was inhibited by S2? compared with the denitritation step (NO2? reduction to N2). Also, the S2? oxidation by autotrophic denitrifiers was shown two times lower in rate with NO2? as electron acceptor than that with NO3? as electron acceptor. NO3? reduction by autotrophic denitrifiers occurs 3–10 times slower when S0 participates as final electron donor compared to the S2?-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 S2? 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

194

Impacts of vegetation, tidal process, and depth on the activities, abundances, and community compositions of denitrifiers in mangrove sediment.  

Science.gov (United States)

Coastal mangrove wetland is well known to be intense in nitrogen cycling. The tidal process and plants are key factors in controlling the microbial processes in wetlands. However, mechanisms on how these factors and their interactions affect the microorganisms involved in denitrification remain poorly understood. In this study, the impacts of vegetation (bulk, Kandelia obovata, and Spartina alterniflora) and tidal process (falling tide and rising tide) on denitrification activities, abundances, and community compositions of denitrifiers in the sediments from different depths (0-5 and 5-10 cm) were investigated in a microcosm experiment. A significant enhancement of denitrification activities and gene abundances (nirS, nirK, and nosZ) in the vegetated sediments was observed. Activities and abundances were significantly higher in the 0-5-cm sediments when compared with the 5-10-cm counterparts. The effect of interaction between vegetation and tide or depth was also significant. Terminal restriction fragment length polymorphism (T-RFLP) analysis revealed that not only vegetation but also plant species had a significant impact on the community compositions of nirK denitrifiers, while the tidal process affected the community compositions of nirS and nosZ denitrifiers but not nirK denitrifiers. However, depth only significantly shaped the nirS denitrifier communities. These findings demonstrate the effects of these factors and their interactions in shaping the denitrifiers in sediments. PMID:25149447

Wang, Hai-Tao; Su, Jian-Qiang; Zheng, Tian-Ling; Yang, Xiao-Ru

2014-11-01

195

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

196

A technique for measuring nitrogen isotopic composition of nitrate using the denitrifier method  

International Nuclear Information System (INIS)

A measurement technique of the denitrifier method, which was developed for seawater isotopic analysis, was established for analyzing nitrogen isotopic composition of nitrate in groundwater and the vadose zone sediments. Experiments were conducted using international isotopic standards of IAEA-N3 and USGS34 and field samples. ?15N analyses of the two isotopic standards showed good reproducibility, with an average precision of 0.25 per thousand (ranging from 0.1 per thousand to 0.5 per thousand). Groundwater and sediment extracts were accurately reproduced, with precisions of better 0.5 per thousand. The results showed that the measurement technique of the denitrifier method could be used for analyzing nitrogen isotopic composition of nitrate in groundwater and sediments. A case study using the technique showed that a thick vadose zone sediment profile had no increase trend of ?15N values in depths below the vadose zone, indicating little denitrification occurrence. (authors)

197

Denitrifier Community Composition along a Nitrate and Salinity Gradient in a Coastal Aquifer  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Nitrogen flux into the coastal environment via submarine groundwater discharge may be modulated by microbial processes such as denitrification, but the spatial scales at which microbial communities act and vary are not well understood. In this study, we examined the denitrifying community within the beach aquifer at Huntington Beach, California, where high-nitrate groundwater is a persistent feature. Nitrite reductase-encoding gene fragments (nirK and nirS), responsible for the key step in th...

Santoro, Alyson E.; Boehm, Alexandria B.; Francis, Christopher A.

2006-01-01

198

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

199

Interactions between nitrifying and denitrifying bacteria in gnotobiotic microcosms planted with the emergent macrophyte Glyceria maxima  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The population dynamics of the chemolithoautotrophic nitrifiers Nitrosomonas europaea and Nitrobacter winogradskyi were studied in gnotobiotic microcosms fed with ammonium in response to the presence or absence of the emergent macrophyte Glyceria maxima and the heterotrophic denitrifying bacterium Pseudomonas chlororaphis. By subjecting the plants to different day lengths, the effect of possibly limiting factors (i.e. oxygen and ammonium) on the interactions between the nitrifiers an...

Bodelier, P. L. E.; Duyts, H.; Blom, C. W. P. M.; Laanbroek, H. J.

1998-01-01

200

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

 
 
 
 
201

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 denit...

Yu, Zheng; Yang, Jun; Liu, Lemian

2014-01-01

202

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

203

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

204

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

205

Aerobic and Anaerobic Toluene Degradation by a Newly Isolated Denitrifying Bacterium, Thauera sp. Strain DNT-1  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A newly isolated denitrifying bacterium, Thauera sp. strain DNT-1, grew on toluene as the sole carbon and energy source under both aerobic and anaerobic conditions. When this strain was cultivated under oxygen-limiting conditions with nitrate, first toluene was degraded as oxygen was consumed, while later toluene was degraded as nitrate was reduced. Biochemical observations indicated that initial degradation of toluene occurred through a dioxygenase-mediated pathway and the benzylsuccinate pa...

Shinoda, Yoshifumi; Sakai, Yasuyoshi; Uenishi, Hiroshi; Uchihashi, Yasumitsu; Hiraishi, Akira; Yukawa, Hideaki; Yurimoto, Hiroya; Kato, Nobuo

2004-01-01

206

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

207

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

Abdolmotaleb Seid-mohammadi; Hossein Movahedian Attar; Mahnaz Nikaeen

2013-01-01

208

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 ofut rather by the inherent recalcitrance of WDF

209

A comparative study of the bacterial community in denitrifying and traditional enhanced biological phosphorus removal processes.  

Science.gov (United States)

Denitrifying phosphorus removal is an attractive wastewater treatment process due to its reduced carbon source demand and sludge minimization potential. Two lab-scale sequencing batch reactors (SBRs) were operated in alternating anaerobic-anoxic (A-A) or anaerobic-oxic (A-O) conditions to achieve denitrifying enhanced biological phosphate removal (EBPR) and traditional EBPR. No significant differences were observed in phosphorus removal efficiencies between A-A SBR and A-O SBR, with phosphorus removal rates being 87.9% and 89.0% respectively. The community structures in denitrifying and traditional EBPR processes were evaluated by high-throughput sequencing of the PCR-amplified partial 16S rRNA genes from each sludge. The results obtained showed that the bacterial community was more diverse in A-O sludge than in A-A sludge. Taxonomy and ?-diversity analyses indicated that a significant shift occurred in the dominant microbial community in A-A sludge compared with the seed sludge during the whole acclimation phase, while a slight fluctuation was observed in the abundance of the major taxonomies in A-O sludge. One Dechloromonas-related OTU outside the 4 known Candidatus "Accumulibacter" clades was detected as the main OTU in A-A sludge at the stationary operation, while Candidatus "Accumulibacter" dominated in A-O sludge. PMID:24964811

Lv, Xiao-Mei; Shao, Ming-Fei; Li, Chao-Lin; Li, Ji; Gao, Xin-Lei; Sun, Fei-Yun

2014-09-17

210

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

211

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

212

Human Stem Cell Cultures from Cleft Lip/Palate Patients Show Enrichment of Transcripts Involved in Extracellular Matrix Modeling By Comparison to Controls  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Nonsyndromic cleft lip and palate (NSCL/P) is a complex disease resulting from failure of fusion of facial primordia, a complex developmental process that includes the epithelial-mesenchymal transition (EMT). Detection of differential gene transcription between NSCL/P patients and control individuals offers an interesting alternative for investigating pathways involved in disease manifestation. Here we compared the transcriptome of 6 dental pulp stem cell (DPSC) cultures from NSCL/P patients ...

Bueno, Daniela Franco; Sunaga, Daniele Yumi; Kobayashi, Gerson Shigeru; Aguena, Meire; Raposo-amaral, Cassio Eduardo; Masotti, Cibele; Cruz, Lucas Alvizi; Pearson, Peter Lees; Passos-bueno, Maria Rita

2011-01-01

213

Development of a Cell Culture Method To Isolate and Enrich Salmonella enterica Serotype Enteritidis from Shell Eggs for Subsequent Detection by Real-Time PCR?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Salmonella enterica serotype Enteritidis is a major cause of nontyphoidal salmonellosis from ingestion of contaminated raw or undercooked shell eggs. Current techniques used to identify Salmonella serotype Enteritidis in eggs are extremely laborious and time-consuming. In this study, a novel eukaryotic cell culture system was combined with real-time PCR analysis to rapidly identify Salmonella serotype Enteritidis in raw shell eggs. The system was compared to the standard microbiological metho...

Day, J. B.; Basavanna, U.; Sharma, S. K.

2009-01-01

214

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

215

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

216

Effects of elevated CO2 on communities of denitrifying bacteria and methanogens in a temperate marsh microcosm.  

Science.gov (United States)

The effects of elevated CO(2) on soil bacterial community with upland vegetation have been widely studied, but limited information is available regarding responses of denitrifier and methanogen communities to elevated CO(2) in wetland ecosystems. Using restriction fragment length polymorphism (RFLP), terminal RFLP analysis, and real-time quantitative PCR, we compared communities of denitrifiers and methanogens in a laboratory-scale wetland system planted with one of three macrophytes, Typha latifolia, Scirpus lacustris, or Juncus effusus, after 110 days of incubation. Our study showed that elevated CO(2) could affect community structures of both denitrifiers and methanogens, each of which had a unique response pattern. In particular, elevated CO(2) shifted nirS-containing community with a unique structure irrespective of vegetation type. mcrA-containing community appeared to shift to community with unique types of hydrogenotrophs under elevated CO(2) conditions. The change of dissolved organic carbon driven by elevated CO(2) appeared to be related with the shift of both denitrifiers and methanogens. Overall, this study indicates that elevated CO(2) could change the community structure of denitrifiers and methanogens temporarily. These results also suggest a presence of stable dominant populations that were not substantially affected by changes in CO(2) concentration. PMID:22441572

Lee, Seung-Hoon; Kim, Seon-Young; Kang, Hojeong

2012-08-01

217

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

218

Relating phylogenetic and functional diversity among denitrifiers and quantifying their capacity to predict community functioning  

Directory of Open Access Journals (Sweden)

Full Text Available Genetic diversity of phylogenetic or functional markers is widely used as a proxy of microbial diversity. However, it remains unclear at what extent functional diversity, gene sequence diversity and community functioning are linked. We analysed, for a range of denitrifying bacteria, the relationships between (i the similarity of functional traits evaluated from metabolic profiles (BIOLOG plates or from N2O accumulation patterns on different C sources, and (ii the similarity of phylogenetic (16S rRNA gene or functional (nir gene markers. We also calculated different proxies for the diversity of denitrifier community based on taxa richness, phylogenetic or functional similarities, and evaluated their performance in inferring the functioning of assembled denitrifying communities. For individual strains, the variation in the 16S rRNA gene sequence explained only 10% of the variation in metabolic patterns and were not related to N2O accumulation. The latter was correlated with the similarity of nitrite reductase residues. When nir genes were analysed separately, the similarity in amino acids coded by the nirS genes accounted for 48% of the variance of the observed pattern of N2O accumulation, whereas nirK amino acid residues were unrelated to N2O accumulation. For bacterial assemblages, phylogenetic diversity and mean community dissimilarity, calculated using 16S rRNA gene sequences, and functional diversity measures associated with BIOLOG, predicted poorly the variation in the functioning of assembled communities (below 15%. In contrast, the proxies of functional diversity based on N2O accumulation patterns performed better and explained from 23 to 42% of the variation in community functioning. Amongst those, community niche was the best metric, indicating the importance of complementarity for carbon resources among taxa in the context of denitrification.

JoanaFalcão Salles

2012-06-01

219

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

220

Genetic diversity of benzoyl coenzyme A reductase genes detected in denitrifying isolates and estuarine sediment communities.  

Science.gov (United States)

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 from the known benzoyl-CoA reductase genes from Thauera aromatica, Rhodopseudomonas palustris, and Azoarcus evansii. PCR amplification detected benzoyl-CoA reductase genes in the denitrifying isolates belonging to alpha-, beta-, or gamma-Proteobacteria as well as in the sediment samples. Phylogenetic analysis, sequence similarity comparison, and conserved indel determination grouped the new sequences into either the bcr type (found in T. aromatica and R. palustris) or the bzd type (found in A. evansii). All the Thauera strains and the isolates from the genera Acidovorax, Bradyrhizobium, Paracoccus, Ensifer, and Pseudomonas had bcr-type benzoyl-CoA reductases with amino acid sequence similarities of more than 97%. The genes detected from Azarocus strains were assigned to the bzd type. A total of 50 environmental clones were detected from denitrifying consortium and sediment samples, and 28 clones were assigned to either the bcr or the bzd type of benzoyl-CoA reductase genes. Thus, we could determine the genetic capabilities for anaerobic degradation of aromatic compounds in sediment communities of the Chesapeake Bay and the Arthur Kill on the basis of the detection of two types of benzoyl-CoA reductase genes. The detected genes have future applications as genetic markers to monitor aromatic compound degradation in natural and engineered ecosystems. PMID:15812036

Song, Bongkeun; Ward, Bess B

2005-04-01

 
 
 
 
221

Cultivation and irradiation of human fibroblasts in a medium enriched with platelet lysate for obtaining feeder layer in epidermal cell culture; Cultivo e irradiacao de fibroblastos humanos em meio enriquecido com lisado de plaquetas para obtencao de camada de sustentacao em culturas de celulas da epiderme  

Energy Technology Data Exchange (ETDEWEB)

For over 30 years, the use of culture medium, enriched with bovine serum, and murines fibroblasts, with the rate of proliferation controlled by irradiation or by share anticarcinogenic drugs, has been playing successfully its role in assisting in the development of keratinocytes in culture, for clinical purposes. However, currently there is a growing concern about the possibility of transmitting prions and animals viruses to transplanted patients. Taking into account this concern, the present work aims to cultivate human fibroblasts in a medium enriched with human platelets lysate and determine the irradiation dose of these cells, for obtaining feeder layer in epidermal cell culture. For carrying out the proposed objective, platelets lysis has standardized, this lysate was used for human fibroblasts cultivation and the irradiation dose enough to inhibit its duplication was evaluated. Human keratinocytes were cultivated in these feeder layers, in culture medium enriched with the lysate. With these results we conclude that the 10% platelets lysate promoted a better adhesion and proliferation of human fibroblasts and in all dose levels tested (60 to 300 Gy), these had their mitotic activity inactivated by ionizing irradiation, being that the feeder layers obtained with doses from 70 to 150 Gy were those that provided the best development of keratinocytes in medium containing 2.5% of human platelet lysate. Therefore, it was possible to standardize both the cultivation of human fibroblasts as its inactivation for use as feeder layer in culture of keratinocytes, so as to eliminate xenobiotics components. (author)

Yoshito, Daniele

2011-07-01

222

Autotrophic, Hydrogen-Oxidizing, Denitrifying Bacteria in Groundwater, Potential Agents for Bioremediation of Nitrate Contamination  

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Addition of hydrogen or formate significantly enhanced the rate of consumption of nitrate in slurried core samples obtained from an active zone of denitrification in a nitrate-contaminated sand and gravel aquifer (Cape Cod, Mass.). Hydrogen uptake by the core material was immediate and rapid, with an apparent Km of 0.45 to 0.60 ?M and a Vmax of 18.7 nmol cm-3 h-1 at 30°C. Nine strains of hydrogen-oxidizing denitrifying bacteria were subsequently isolated from the aquifer. Eight of the strai...

Smith, Richard L.; Ceazan, Marnie L.; Brooks, Myron H.

1994-01-01

223

Enzymes involved in anaerobic degradation of acetone by a denitrifying bacterium  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The pathway of anaerobic acetone degradation by the denitrifying bacterial strain BunN was studied by enzyme measurements in extracts of anaerobic acetone-grown cells. An ADP- and MgC12-dependent decarboxylation of acetoacetate was detected which could not be found in cell-free extracts of acetate-grown cells. It is concluded that free acetoacetate is formed by ATP-dependent arboxylation of acetone. Acetoacetate was converted into its coenzyme A ester by succinyl-CoA: acetoacetate CoA transf...

Platen, Harald; Schink, Bernhard

1990-01-01

224

A Cultural Classroom Library  

Science.gov (United States)

Native American and other cultural stories provide students with a broader perspective on the world. In addition, cultural stories connect science content and knowledge about the world to cultural interpretations and people's life ways. By implementing the ideas suggested in this article, you can select books that both enrich your science library and help students begin to appreciate the science contributions and connections from various cultures while enhancing cultural literacy among students.

Lawrence, Maria

2007-11-01

225

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

226

Community size and composition of ammonia oxidizers and denitrifiers in an alluvial intertidal wetland ecosystem  

Directory of Open Access Journals (Sweden)

Full Text Available Global nitrogen cycling is mainly mediated by the activity of microorganisms. Nitrogen cycle processes are mediated by functional groups of microorganisms that are affected by constantly changing environmental conditions and substrate availability. In this study, we investigated the temporal and spatial patterns of nitrifier and denitrifier communities in an intertidal wetland. Soil samples were collected over four distinct seasons from three locations with different vegetative cover. Multiple environmental factors and process rates were measured and analyzed together with the community size and composition profiles. We observed that the community size and composition of the nitrifiers and denitrifiers are affected significantly by seasonal factors, while vegetative cover affected the community composition. The seasonal impacts on the community size of ammonia oxidizing archaea (AOA are much higher than that of ammonia oxidizing bacteria (AOB. The seasonal change was a more important indicator for AOA community composition patterns, while vegetation was more important for the AOB community patterns. The microbial process rates were correlated with both the community size and composition.

Zhe-XueQuan

2014-07-01

227

Effect of organic toxicants on the activity of denitrifying granular sludge.  

Science.gov (United States)

Denitrification plays a key role in the biological nitrogen removal from the wastewater using granular sludge as the integral part of a high-rate denitrification technology. It is helpful to evaluate the effect of typical organic toxicants on the activity of denitrifying granular sludge for the application of denitrification technology. In this study, four typical organic toxicants, namely, penicillin, chloramphenicol, 2,4-dinitrophenol and polymyxin B sulphate were used to assess the effect of organic toxicants on the activity of denitrifying granular sludge. The results of individual toxicity indicated that penicillin, chloramphenicol and 2,4-dinitrophenol had significant inhibition, whose half-inhibitory concentrations were 0.534, 0.162 and 0.474?g/L with respective inhibitory magnitudes of 90.79%/(g/L), 282.5%/(g/L) and 138.83%/(g/L). Polymyxin B sulphate showed no significant inhibition. The results of combined toxicity indicated that the binary mixture of penicillin and chloramphenicol had an antagonistic effect, both the binary mixture of penicillin and 2,4-dinitrophenol and the binary mixture of chloramphenicol and 2,4-dinitrophenol had additive effects. The ternary mixture of penicillin, chloramphenicol and 2,4-dinitrophenol had a partial additive effect. PMID:25220622

Zhang, Zonghe; Zheng, Ping; Li, Wei; Wang, Ru; Ghulam, Abbas

2014-09-25

228

Genome Sequence of the Deep-Sea Denitrifier Pseudomonas sp. Strain MT-1, Isolated from the Mariana Trench  

Science.gov (United States)

Pseudomonas sp. strain MT-1 was the first deep-sea denitrifier isolated and characterized from mud recovered from a depth of 11,000 m in the Mariana Trench. We report here the genome sequence of this bacterium, which contributes to our understanding of denitrification and bioenergetics in the deep sea. PMID:25523772

Fujinami, Shun; Oikawa, Yuji; Araki, Takuma; Shinmura, Yui; Midorikawa, Ryota; Ishizaka, Hikari; Kato, Chiaki; Horikoshi, Koki; Ito, Masahiro

2014-01-01

229

Uranium enrichment plans  

International Nuclear Information System (INIS)

The following topics are covered: the status of the Government's existing uranium enrichment services contracts, natural uranium requirements based on the latest contract information, uncertainty in predicting natural uranium requirements based on uranium enrichment contracts, and domestic and foreign demand assumed in enrichment planning

230

Bryocella elongata gen. nov., sp. nov., a member of subdivision 1 of the Acidobacteria isolated from a methanotrophic enrichment culture, and emended description of Edaphobacter aggregans Koch et al. 2008.  

Science.gov (United States)

An aerobic, pink-pigmented, chemo-organotrophic bacterium, designated strain SN10(T), was isolated from a methanotrophic enrichment culture obtained from an acidic Sphagnum peat. This isolate was represented by Gram-negative, non-motile rods that multiply by normal cell division and form rosettes. Strain SN10(T) is an obligately acidophilic, mesophilic bacterium capable of growth at pH 3.2-6.6 (with an optimum at pH 4.7-5.2) and at 6-32 °C (with an optimum at 20-24 °C). The preferred growth substrates are sugars and several heteropolysaccharides of plant and microbial origin, such as pectin, lichenan, fucoidan and gellan gum. While not being capable of growth on C(1) compounds, strain SN10(T) can develop in co-culture with exopolysaccharide-producing methanotrophs by utilization of their capsular material. The major fatty acids determined in strain SN10(T) using the conventional lipid extraction procedure are iso-C(15:0) and C(16:1)?7c. Upon hydrolysis of total cell material, substantial amounts of the uncommon membrane-spanning lipid 13,16-dimethyl octacosanedioic acid (isodiabolic acid) were also detected. The polar lipids are two phosphohexoses, phosphatidylethanolamine, phosphatidylglycerol and several phospholipids of unknown structure. The major quinone is MK-8. Pigments are carotenoids. The G+C content of the DNA is 60.7 mol%. Strain SN10(T) forms a separate lineage within subdivision 1 of the phylum Acidobacteria and displays 94.0-95.4% 16S rRNA gene sequence similarity to members of the genera Edaphobacter and Granulicella, 93.0-93.7% similarity to members of the genus Terriglobus and 92.2-92.3?% similarity to the type strains of Telmatobacter bradus and Acidobacterium capsulatum. Therefore, strain SN10(T) is classified within a novel genus and species, for which the name Bryocella elongata gen. nov., sp. nov. is proposed. Strain SN10(T) (=LMG 25276(T) =DSM 22489(T)) is the type strain of Bryocella elongata. An emended description of Edaphobacter aggregans Koch et al. 2008 is also given. PMID:21551329

Dedysh, Svetlana N; Kulichevskaya, Irina S; Serkebaeva, Yulia M; Mityaeva, Maria A; Sorokin, Vladimir V; Suzina, Natalia E; Rijpstra, W Irene C; Damsté, Jaap S Sinninghe

2012-03-01

231

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

232

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

233

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

234

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

235

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

236

Habitat partitioning of denitrifying bacterial communities carrying nirS or nirK genes in the stratified water column of Lake Kinneret, Israel  

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The community composition of denitrifying bacteria was studied in the stratified water column of Lake Kinneret. The nitrite reductase genes nirS and nirK were amplified by PCR from water samples taken at 1, 14, 19 and 22 m depth, which represent the epi-, meta- and hypolimnion of the lake. The PCR products were analyzed with terminal restriction fragment length polymorphism (T-RFLP) and clone libraries. The highest diversity of nirS denitrifying communities was observed a...

Junier, Pilar; Kim, Ok-sun; Witzel, Karl-paul; Imhoff, Johannes F.; Hadas, Ora

2014-01-01

237

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)

238

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

239

Alternative isotope enrichment processes  

International Nuclear Information System (INIS)

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

240

Uranium enrichment: an overview  

International Nuclear Information System (INIS)

This paper is a general presentation of uranium enrichment processes and assessments of the prevailing commercial and industrial situations. It gives first some theoretical aspects of enrichment in general and explains the differences between statistical and selective processes in particular. Then a review of the different processes is made with a comparison between them. Finally, some general remarks concerning applications are given and the risks of proliferation related to enrichment are mentioned. (J.S.). 4 refs., 5 figs., 8 tabs

 
 
 
 
241

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)

242

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

243

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

244

The Bacterivorous Soil Flagellate Heteromita globosa Reduces Bacterial Clogging under Denitrifying Conditions in Sand-Filled Aquifer Columns  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An exopolymer (slime)-producing soil bacterium Pseudomonas sp. (strain PS+) rapidly clogged sand-filled columns supplied with air-saturated artificial groundwater containing glucose (500 mg liter?1) as a sole carbon source and nitrate (300 mg liter?1) as an alternative electron acceptor. After 80 days of operation under denitrifying conditions, the effective porosity and saturated hydraulic conductivity (permeability) of sand in these columns had fallen by 2.5- and 26-fold, respectively. ...

Mattison, Richard G.; Taki, Hironori; Harayama, Shigeaki

2002-01-01

245

Transitions in nirS-type denitrifier diversity, community composition, and biogeochemical activity along the Chesapeake Bay estuary  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Chesapeake Bay, the largest estuary in North America, can be characterized as having steep and opposing gradients in salinity and dissolved inorganic nitrogen along the main axis of the Bay. In this study, the diversity of nirS gene fragments (encoding cytochrome cd1-type nitrite reductase), physical/chemical parameters, and benthic N2-fluxes were analyzed in order to determine how denitrifier communities and biogeochemical activity vary along the estuary salinity gradient. The nirS gene fra...

ChristopherAFrancis; GregoryDO'Mullan; JeffreyCCornwell

2013-01-01

246

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

247

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

248

Nitrogen and phosphorus removal in a denitrifying phosphorus removal process in a sequencing batch reactor with a forced anoxic phase.  

Science.gov (United States)

The objective of this study was to establish such operating conditions in a sequencing batch reactor (SBR) that will enable the achievement of the highest possible share of denitrifying P removal in nutrient elimination. Two different operating strategies for SBRs were analysed. Both of these strategies used a forced anoxic phase in the SBR treatment cycle. The first one was based on an intermittent aeration, which led to periodic occurrence of anoxic conditions when the uptake of P-PO4(3-) could occur. The second strategy was based on mimicking the A2O process and forcing an anoxic phase straight after an anaerobic phase. The experiments were performed in a laboratory reactor operating at a maximum fill of 26.8-27.7 litres and a constant temperature of 18 degrees C. It was found that a SBR configuration with intermittent aeration did not allow the achievement of significant denitrifying P removal, despite the DPAO/PAO ratio being equal to 50.5%. Almost the entire load of orthophosphates was being removed in aerobic conditions right after the anaerobic phase, even though this aerobic period lasted only 20 minutes. However, a SBR with a forced anoxic phase occurring after an anaerobic phase and created by an introduction of NO(x) rich stream of wastewater guaranteed the highest DPAO/PAO ratio of 82.8% and the highest share of denitrifying P removal (above 80%) in the total removal of phosphorus. PMID:22519108

Podedworna, J; Zubrowska-Sudo?, M

2012-01-01

249

Commercial developments in enrichment  

International Nuclear Information System (INIS)

The significance of the dollars spent by government and industry so far on enrichment programs is enhanced by the number of engineering and component design and supply firms who have become involved in the public and private development and design projects. The knowhow gained from this experience provides the nucleus of the industrial manufacturing base for the unique enrichment technology necessary to build the future U.S. enrichment plants. The $1.5 billion CIP/CUP programs now under way and the $4.4 billion Portsmouth Add-On Plant are bringing the U.S. enrichment capacity to the capability to supply the contracted 323 GW of reactors, while conserving uranium by allowing operation at a lower, more nearly optimum tails assay. The government enrichment contract books have remained closed to new orders since July of 1975. Inevitably, new foreign enrichment projects are actively pursuing customers. Until the government or private U.S. enrichment ventures resume contracting activity, the foreign plants have no U.S. competition. The technology exists within ERDA and industry to maintain U.S. leadership in the world enrichment market if the institutional questions can be answered

250

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.)

251

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

252

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

253

Sustainable nitrogen removal by denitrifying anammox applied for anaerobic pre-treated potato wastewater.  

Science.gov (United States)

The feasibility of sustainable nitrogen removal was investigated in a two stage biofilm configuration consisting of a MBBR (Moving Bed Biofilm Reactor) and a Deamox reactor (Biobed-EGSB). The MBBR is used for nitrification and the denitrifying ammonium oxidation (Deamox) is aimed at a nitrogen removal process in which part of the required nitrite for the typical anammox reaction originated from nitrate. Anaerobic pre-treated potato wastewater was supplied to a MBBR and Deamox reactor operated in series with a bypass flow of 30%. The MBBR showed stable nitrite production at ammonium-loading rates of 0.9-1.0 kg NH?-N/m³ d with ammonium conversion rates of 0.80-0.85 kg NH?-N/m³ d. The nitrogen-loading rate and conversion rate of the Deamox reactor were 1.6-1.8 and 1.6 kg N/m³ d. The maximum ammonium removal capacity in the Deamox reactor was 0.6 kg NH?-N/m³ d. The removal efficiency of soluble total nitrogen reached 90%. The Deamox process performance was found to be negatively affected during decline of the operating temperature from 33 to 22 °C and by organic loading rates with a chemical oxygen demand (COD)/NO?-N ratio >1. PMID:23109579

Mulder, A; Versprille, A I; van Braak, D

2012-01-01

254

Microbial community analysis of an aerobic nitrifying-denitrifying MBR treating ABS resin wastewater.  

Science.gov (United States)

A two-stage aerobic membrane bioreactor (MBR) system for treating acrylonitrile butadiene styrene (ABS) resin wastewater was carried out in this study to evaluate the system performance on nitrification. The results showed that nitrification of the aerobic MBR system was significant and the highest TKN removal of approximately 90% was obtained at hydraulic retention time (HRT) 18 h. In addition, the result of nitrogen mass balance revealed that the percentage of TN removal due to denitrification was in the range of 8.7-19.8%. Microbial community analysis based on 16s rDNA molecular approach indicated that the dominant ammonia oxidizing bacteria (AOB) group in the system was a ?-class ammonia oxidizer which was identified as uncultured sludge bacterium (AF234732). A heterotrophic aerobic denitrifier identified as Thauera mechernichensis was found in the system. The results indicated that a sole aerobic MBR system for simultaneous removals of carbon and nitrogen can be designed and operated for neglect with an anaerobic unit. PMID:21236663

Chang, Chia-Yuan; Tanong, Kulchaya; Xu, Jia; Shon, Hokyong

2011-05-01

255

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 (nitrite reductase. Results showed a range of nirK quantities from 103 to 107 gene-copy-number gsed-1. A nonparametric statistical test showed no significant difference in nirK quantities among stream reaches, but revealed that samples with a high denitrification potential had significantly higher nirK quantities. Denitrification activity was positively correlated with nirK quantities with scatter in the data that can be attributed to varying environmental conditions along stream reaches. Dimensional analysis was used to evaluate denitrification activities according to environmental variables that describe fluid-flow properties, nitrate and organic material quantities, and 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

256

Halomonas cerina sp. nov., a moderately halophilic, denitrifying, exopolysaccharide-producing bacterium.  

Science.gov (United States)

Three bacterial strains were isolated from different saline soils in Spain. The novel strains were moderately halophilic, exopolysaccharide-producing, Gram-negative, non-motile rods. The strains required NaCl and grew best with 7.5-10 % (w/v) NaCl in the medium. They formed wax-coloured colonies, were oxidase-positive and showed respiratory metabolism, using oxygen, nitrate and nitrite as terminal electron acceptors. The novel strains were able to denitrify and did not produce acid from sugars. The DNA G+C contents varied between 62.7 and 66.2 mol%. Phylogenetic analyses based on 16S rRNA gene sequences and sequence signatures of this gene showed that all three novel isolates belonged to the genus Halomonas in the class Gammaproteobacteria and formed an independent phylogenetic line. The most phylogenetically related species were Halomonas alimentaria, Halomonas campaniensis, Halomonas gudaonensis and Halomonas ventosae, with which the novel strains showed 16S rRNA gene sequence similarity values of between 96.3 and 95.2 %. The principal fatty acids of the novel strains were 16 : 0, 18 : 1 omega 7c, 16 : 1 omega 7c and 19 : 0 cyclo omega 8c. The predominant respiratory lipoquinone was ubiquinone with nine isoprene units (Q-9). The name Halomonas cerina sp. nov. is proposed for these isolates. The type strain is SP4T (=CECT 7282T=LMG 24145T). PMID:18398173

González-Domenech, Carmen M; Martínez-Checa, Fernando; Quesada, Emilia; Béjar, Victoria

2008-04-01

257

Biodegradation of p-cresol and sulfide removal by a marine-denitrifying consortium.  

Science.gov (United States)

The simultaneous removal of sulfide and p-cresol was carried out by using a marine-denitrifying consortium collected in the coastal zone of Sonora, Mexico. Different experimental conditions were used to evaluate the capacity of the consortium to simultaneously eliminate nitrate, sulfide, and p-cresol. For instance, the first set of assays was conducted at different sulfide concentrations (20, 50, and 100?mg S(2-) L(-1) ), with a fixed concentration of p-cresol (45?mg C L(-1) ). The second set of assays was developed at different concentrations of p-cresol (45, 75, and 100?mg C L(-1) ), in the presence of 20?mg S(2-) L(-1) . In all cases, the concentration of nitrate was stoichiometrically added for the complete oxidization of the substrates. The results showed removal efficiencies up to 92% for p-cresol and nitrate at 20 and 50?mg S(2-) L(-1) ; whereas at 100?mg S(2-) L(-1) removal efficiencies were 77% and 59% for p-cresol and nitrate, respectively. On the other hand, sulfide (20?mg?L(-1) ) was completely removed under different concentrations of p-cresol tested, with a partial accumulation of nitrite according to the increment of p-cresol concentration. The results obtained indicate that the marine consortium was able to simultaneously remove the pollutants studied. PMID:25418931

Meza-Escalante, Edna R; Alvarez, Luis H; Serrano, Denisse; Mendoza, Erika; Bonola, Ramsés

2014-11-24

258

Mitigation of nitrous oxide (N2O) emissions from denitrifying fluidized bed bioreactors (DFBBRs) using calcium.  

Science.gov (United States)

Nitrous oxide (N2O) is a significant anthropogenic greenhouse gases (AnGHGs) emitted from biological nutrient removal (BNR) processes. In this study, N2O production from denitrifying fluidized bed bioreactors (DFBBR) was reduced using calcium (Ca(2+)) dosage. The DFBBRs were operated on a synthetic municipal wastewater at four different calcium concentrations ranging from the typical municipal wastewater Ca(2+) concentration (60mg Ca(2+)/L) to 240mg Ca(2+)/L at two different COD/N ratios. N2O emission rates, extracellular polymeric substances (EPS), water quality parameters, and microscopic images were monitored regularly in both phases. Calcium concentrations played a significant role in biofilm morphology with the detachment rates for R120Ca, R180Ca, and R240Ca 75% lower than for R60Ca, respectively. The N2O conversion rate at the typical municipal wastewater Ca(2+) concentration (R60Ca) was about 0.53% of the influent nitrogen loading as compared with 0.34%, 0.42%, and 0.41% for R120Ca, R180Ca, and R240Ca, respectively corresponding to 21-36% reduction. PMID:25310863

Eldyasti, Ahmed; Nakhla, George; Zhu, Jesse

2014-12-01

259

Pseudomonas xiamenensis sp. nov., a denitrifying bacterium isolated from activated sludge.  

Science.gov (United States)

A taxonomic study was carried out on strain C10-2T, a moderately halophilic denitrifier isolated from activated sludge samples collected in China. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain C10-2T belonged to the genus Pseudomonas, with highest sequence similarity of 98.1 and 97.7 % to 'Pseudomonas denitrificans' IAM 12023 and Pseudomonas pertucinogena JCM 11590T, respectively. The gyrB, rpoD and rpoB gene sequence similarity between strain C10-2T and P. pertucinogena JCM 11590T was respectively 84.1, 79.0 and 88.2 %. Phylogenetic trees based on these housekeeping genes showed that strain C10-2T and P. pertucinogena JCM 11590T form a clade at the periphery of the genus Pseudomonas. The DNA-DNA hybridization value between strain C10-2T and P. pertucinogena JCM 11590T was 30-32 %. The G+C content of the chromosomal DNA was 61.2 mol%. The combined genotypic and phenotypic data show that strain C10-2T represents a novel species of the genus Pseudomonas, for which the name Pseudomonas xiamenensis sp. nov. is proposed, with the type strain C10-2T (=CGMCC 1.6446 =JCM 13530T =MCCC 1A00089T). PMID:18676479

Lai, Qiliang; Shao, Zongze

2008-08-01

260

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.

2014-04-01

 
 
 
 
261

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)

262

Metal enrichment processes  

CERN Document Server

There are many processes that can transport gas from the galaxies to their environment and enrich the environment in this way with metals. These metal enrichment processes have a large influence on the evolution of both the galaxies and their environment. Various processes can contribute to the gas transfer: ram-pressure stripping, galactic winds, AGN outflows, galaxy-galaxy interactions and others. We review their observational evidence, corresponding simulations, their efficiencies, and their time scales as far as they are known to date. It seems that all processes can contribute to the enrichment. There is not a single process that always dominates the enrichment, because the efficiencies of the processes vary strongly with galaxy and environmental properties.

Schindler, S

2008-01-01

263

Uranium isotopic enrichment  

International Nuclear Information System (INIS)

After having recalled, with the help of tables the offer and demand for enrichment services in the world, the various techniques, namely: gas diffusion, ultracentrifugation, aerodynamic processes, chemical exchange and laser separation are compared from the technical, economic and proliferation angles. The producers of enriched uranium are: DOE (USA), Technabexport (USSR), Eurodif, Urenco and PNC (Japan). The article concludes with the techniques under development or projected

264

Urenco's enrichment experience  

International Nuclear Information System (INIS)

Although enrichment capacity will exceed the demand from nuclear power plants until the nineties, new enrichment capacity is being constructed in the USA and Europe. In both cases centrifuge technology is being employed. In the USA industrial-scale plants are replacing diffusion capacity on a step-wise basis. Urenco began construction of the first industrial centrifuge plants some 10 years ago and today possesses a capacity of about 1 200 t separative work per year

265

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

266

Different response of nitrifiers and denitrifiers to re-wetting shape the NO release from soils in laboratory incubation experiments  

Science.gov (United States)

Laboratory incubation studies incubating soils at a wide range of soil moistures, soil temperatures and mixing ratios of NO in the headspace and inorganic nutrient contents (NH4+,NO3-, NO2-) showed that release rates of NO follow an exponential function with increasing soil temperature and an optimum function for soil moisture. This approach assumes that environmental factors play the dominant role in shaping an ecosystem and thereby microbial communities and control the NO release from soil. We determined the NO release rate for a dryland farming soil under flooding irrigation in Xinjiang, China, a mid-latitude agricultural soil (Mainz, Germany), and a rice paddy (Ambai, India) upon wetting and subsequent drying out of soils. Only the release rate for the mid-latitude agricultural soil followed an optimum function for soil moisture. Release rates for the dryland farming soil and rice paddy, however, followed a two maxima function with distinct maxima at higher and lower soil moisture. Acknowledgement of two distinct maxima is critical for more accurately assessing regional biogenic NO emissions of soils under field conditions. To analyse the response of nitrifiers and denitrifiers involved in NO turnover in more detail we linked molecular analysis of functional gene expression (nirK and nirS, bacterial and archaeal amoA) and microbial community composition to NO release rates. We could show that the maximal transcriptional activity of denitrifiers and ammonia oxidizers differs with soil moisture and that higher transcriptional activity of nirS-type denitrifiers at higher soil moisture and of archaeal ammonia oxidizers at lower soil moisture may explain the two maxima for NO release.

Behrendt, Thomas; Wu, Dianming; Song, Guozheng; Pommerenke, Bianca; Braker, Gesche

2014-05-01

267

Abundance, Composition and Activity of Ammonia Oxidizer and Denitrifier Communities in Metal Polluted Rice Paddies from South China  

Science.gov (United States)

While microbial nitrogen transformations in soils had been known to be affected by heavy metal pollution, changes in abundance and community structure of the mediating microbial populations had been not yet well characterized in polluted rice soils. Here, by using the prevailing molecular fingerprinting and enzyme activity assays and comparisons to adjacent non-polluted soils, we examined changes in the abundance and activity of ammonia oxidizing and denitrifying communities of rice paddies in two sites with different metal accumulation situation under long-term pollution from metal mining and smelter activities. Potential nitrifying activity was significantly reduced in polluted paddies in both sites while potential denitrifying activity reduced only in the soils with high Cu accumulation up to 1300 mg kg?1. Copy numbers of amoA (AOA and AOB genes) were lower in both polluted paddies, following the trend with the enzyme assays, whereas that of nirK was not significantly affected. Analysis of the DGGE profiles revealed a shift in the community structure of AOA, and to a lesser extent, differences in the community structure of AOB and denitrifier between soils from the two sites with different pollution intensity and metal composition. All of the retrieved AOB sequences belonged to the genus Nitrosospira, among which species Cluster 4 appeared more sensitive to metal pollution. In contrast, nirK genes were widely distributed among different bacterial genera that were represented differentially between the polluted and unpolluted paddies. This could suggest either a possible non-specific target of the primers conventionally used in soil study or complex interactions between soil properties and metal contents on the observed community and activity changes, and thus on the N transformation in the polluted rice soils. PMID:25058658

Liu, Yuan; Liu, Yongzhuo; Ding, Yuanjun; Zheng, Jinwei; Zhou, Tong; Pan, Genxing; Crowley, David; Li, Lianqing; Zheng, Jufeng; Zhang, Xuhui; Yu, Xinyan; Wang, Jiafang

2014-01-01

268

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

269

Abundance, composition and activity of ammonia oxidizer and denitrifier communities in metal polluted rice paddies from South China.  

Science.gov (United States)

While microbial nitrogen transformations in soils had been known to be affected by heavy metal pollution, changes in abundance and community structure of the mediating microbial populations had been not yet well characterized in polluted rice soils. Here, by using the prevailing molecular fingerprinting and enzyme activity assays and comparisons to adjacent non-polluted soils, we examined changes in the abundance and activity of ammonia oxidizing and denitrifying communities of rice paddies in two sites with different metal accumulation situation under long-term pollution from metal mining and smelter activities. Potential nitrifying activity was significantly reduced in polluted paddies in both sites while potential denitrifying activity reduced only in the soils with high Cu accumulation up to 1300 mg kg-1. Copy numbers of amoA (AOA and AOB genes) were lower in both polluted paddies, following the trend with the enzyme assays, whereas that of nirK was not significantly affected. Analysis of the DGGE profiles revealed a shift in the community structure of AOA, and to a lesser extent, differences in the community structure of AOB and denitrifier between soils from the two sites with different pollution intensity and metal composition. All of the retrieved AOB sequences belonged to the genus Nitrosospira, among which species Cluster 4 appeared more sensitive to metal pollution. In contrast, nirK genes were widely distributed among different bacterial genera that were represented differentially between the polluted and unpolluted paddies. This could suggest either a possible non-specific target of the primers conventionally used in soil study or complex interactions between soil properties and metal contents on the observed community and activity changes, and thus on the N transformation in the polluted rice soils. PMID:25058658

Liu, Yuan; Liu, Yongzhuo; Ding, Yuanjun; Zheng, Jinwei; Zhou, Tong; Pan, Genxing; Crowley, David; Li, Lianqing; Zheng, Jufeng; Zhang, Xuhui; Yu, Xinyan; Wang, Jiafang

2014-01-01

270

Laser and gas centrifuge enrichment  

International Nuclear Information System (INIS)

Principles of uranium isotope enrichment using various laser and gas centrifuge techniques are briefly discussed. Examples on production of high enriched uranium are given. Concerns regarding the possibility of using low end technologies to produce weapons grade uranium are explained. Based on current assessments commercial enrichment services are able to cover the global needs of enriched uranium in the foreseeable future

271

Laser and gas centrifuge enrichment  

Energy Technology Data Exchange (ETDEWEB)

Principles of uranium isotope enrichment using various laser and gas centrifuge techniques are briefly discussed. Examples on production of high enriched uranium are given. Concerns regarding the possibility of using low end technologies to produce weapons grade uranium are explained. Based on current assessments commercial enrichment services are able to cover the global needs of enriched uranium in the foreseeable future.

Heinonen, Olli [Senior Fellow, Belfer Center for Science and International Affairs, Harvard Kennedy School, Cambridge, Massachusetts (United States)

2014-05-09

272

Laser and gas centrifuge enrichment  

Science.gov (United States)

Principles of uranium isotope enrichment using various laser and gas centrifuge techniques are briefly discussed. Examples on production of high enriched uranium are given. Concerns regarding the possibility of using low end technologies to produce weapons grade uranium are explained. Based on current assessments commercial enrichment services are able to cover the global needs of enriched uranium in the foreseeable future.

Heinonen, Olli

2014-05-01

273

Differential responses of nirK- and nirS-carrying bacteria to denitrifying conditions in the anoxic rice field soil.  

Science.gov (United States)

Denitrification occurs actively in rice field soils. In the present study, the responses of nirK and nirS denitrifier communities to nitrate addition in the anoxic rice soil were determined through molecular analyses of nitrite reductase genes nirK and nirS and 16S rRNA genes. Denitrification occurred rapidly when nitrate was added at the beginning of anoxic incubation (experiment I). The structure of nirK-type denitrifiers did not change; but their abundance as determined by quantitative (real-time) PCR increased in nitrate treatments compared with control. Both the structure and abundance of nirS denitrifiers remained unaffected in experiment I. The rate of denitrification was slowed down when nitrate was added 20 days after the onset of anoxic incubation (experiment II). The structure and abundance of nirK-type denitrifier community did not respond to nitrate addition; but the nirS community changed substantially in this experiment. The copy number of nirS genes increased by an order of magnitude in the treatments of 5?mM and 10?mM nitrate compared with control. The terminal restriction fragment length polymorphism (T-RFLP) analysis of nirS genes revealed that the 100?bp T-RF substantially increased in the nitrate treatments. Cloning and sequence analysis indicated that this T-RF had similarity of up to 90% with Herbaspirillum sp. T-RFLP profiles of the bacterial 16S rRNA genes also showed that Herbaspirillum sp. increased after nitrate amendments. Collectively, the nirK-type denitrifiers were probably active at the beginning of anaerobic incubation, while the nirS denitrifiers, especially those related with Herbaspirillum sp. probably were more active when anaerobic condition was fully developed. PMID:23757237

Yuan, Quan; Liu, Pengfei; Lu, Yahai

2012-02-01

274

[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

275

Decaying Cyanobacteria decrease N2O emissions related to diversity of intestinal denitrifiers of Chironomus plumosus  

Directory of Open Access Journals (Sweden)

Full Text Available Nitrous oxide (N2O emission of fresh invertebrates has too long been neglected in eutrophic lakes, although the sediments these animals inhabit are presumably hot spots of N2O emission. Thus, the experiment in this research was designed to gain insight into the influence of cyanobacterial degradation on the N2O emission by fresh water invertebrates (Chironomus plumosus. The presence of decaying cyanobacteria in Lake Taihu decreased the N2O emission rate of Chironomus plumosus larvae from the larvae body by almost 400% for the larvae as a whole. The N2O emission rate decreased by 350% based on readings from studies of their gut, which was mostly due to stimulation of intestinal complete denitrification. The quantitative PCR results showed that intestinal gene abundance of nirK, nosZ (encoding the copper nitrite reductase and N2O reductase, respectively were significantly increased with the presence of decaying cyanobacteria. In contrast nirS (encoding the cytochrome cd1 heme nitrite reductase and the total bacteria decreased. In the gut of Chironomus plumosus, the diversity and richness of nosZ and nirK were lower with the cyanobacteria. Phylogenetic analysis of the intestinal function genes (nosZ and nirK showed that the nosZ- and nirK-type denitrifying bacterial sequences were related to different phylotypes. Hence, additional cyanobacteria increased the abundance, but decreased the richness and diversity of intestinal nitrate-reducing bacteria, probably by providing more carbon source in the gut. The data obtained in this study elucidates that the decaying cyanobacteria decreased the emissions of N2O by the aquatic invertebrates in freshwater sediment and could serve as a valuable resource for nitrogen removal affecting greenhouse gas emissions.

Xu Sun

2014-02-01

276

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

277

Evaluation of droplet digital PCR for characterizing plasmid reference material used for quantifying ammonia oxidizers and denitrifiers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

DNA reference materials of certified value have a critical function in many analytical processes of DNA measurement. Quantification of amoA genes in ammonia oxidizing bacteria (AOB) and archaea (AOA), and of nirS and nosZ genes in the denitrifiers is very important for determining their distribution and abundance in the natural environment. A plasmid reference material containing nirS, nosZ, amoA-AOB, and amoA-AOA is developed to provide a DNA standard with copy number concentration for ensur...

Dong, Lianhua; Meng, Ying; Wang, Jing; Liu, Yingying

2014-01-01

278

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.)

279

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

280

Advanced uranium enrichment processes  

International Nuclear Information System (INIS)

Three advanced Uranium enrichment processes are dealt with in the report: AVLIS (Atomic Vapour LASER Isotope Separation), MLIS (Molecular LASER Isotope Separation) and PSP (Plasma Separation Process). The description of the physical and technical features of the processes constitutes a major part of the report. If further presents comparisons with existing industrially used enrichment technologies, gives information on actual development programmes and budgets and ends with a chapter on perspectives and conclusions. An extensive bibliography of the relevant open literature is added to the different subjects discussed. The report was drawn up by the nuclear research Centre (CEA) Saclay on behalf of the Commission of the European Communities

 
 
 
 
281

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.

282

Isotope shifts - target: enrichment  

International Nuclear Information System (INIS)

The Photochemistry Section at the National Research Council is working on laser-isotope separation using infra-red excitation from a carbon dioxide laser. The researchers hope that their technique might be applicable to heavy water enrichment and possibly the separation of heavier elements such as uranium. (R.A.)

283

Everyone Vegetarian, World Enriching  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This essay advocates global vegetarian diet. Firstly, seven personal health benefits and four global benefits of vegetarian dinners are specified to enrich the entire globe, and then, secondly, I explore concretely how to overcome internal hurdle and external hurdle, so as to effectively propagate vegetarian dinners throughout the world. Everyone wins, including animals!

Wu, John Y.

2014-01-01

284

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

285

Integration of denitrifying phosphorus removal via nitrite pathway, simultaneous nitritation-denitritation and anammox treating carbon-limited municipal sewage.  

Science.gov (United States)

High nutrients removal above 90% from carbon-limited municipal sewage was obtained without adding external carbon source. Achieving nitritation was a prerequisite to improve nutrients removal. Denitrifying phosphorus (P) removal using nitrite as electron acceptor was the key pathway in anoxic zone, where nitrogen removal reached above 60% and average denitrifying P removal was 88%. Simultaneous nitritation/denitritation and anaerobic ammonia oxidation (anammox) possibly contributed to nitrogen removal of 26-36% in aerobic zone. Quantitative PCR assays presented that the abundance of anammox bacteria under nitritation was more than that under complete nitrification. The largest amount of anammox bacteria was 1.32×10(6)copies/gVSS, about 5.6 times increase over a period of 255days. Nitrite concentration of 17mg/L in aerobic zone inhibited anammox bacteria. Quantitative results suggested possible occurrence of anammox. Based on performance of nitritation, combining heterotrophic denitrification with autotrophic nitrogen removal is an effective strategy to improve nutrients removal from carbon-limited wastewater. PMID:25280043

Zeng, Wei; Li, Boxiao; Wang, Xiangdong; Bai, Xinlong; Peng, Yongzhen

2014-11-01

286

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

287

Structure and function of denitrifying and nitrifying bacterial communities in relation to the plant species in a constructed wetland.  

Science.gov (United States)

The community structure and potential activities of nitrifying and denitrifying bacteria were studied in the rhizosphere of Typha latifolia and Phragmites australis present in a free water system constructed wetland (CW). Potential nitrate reduction and nitrification activities were shown to be significantly higher in the rhizosphere when compared with the nonvegetated sediment. Higher rates were generally obtained for P. australis. The community structure of denitrifying bacteria in the rhizosphere differed from that found at the bulk sediment, as revealed by PCR-denaturing gradient gel electrophoresis (DGGE) of the nitrous oxide reductase encoding gene nosZ. Results also show a greater nosZ genotype diversification and suggest a plant species effect in rhizosphere samples obtained during events of low hydraulic retention times. Ammonia-oxidizing communities were less complex on the basis of PCR-DGGE analysis of the 16S rRNA gene. Retrieved sequences were all related to Nitrosomonas marina and Nitrosomonas ureae, being both present in rhizosphere and bulk sediment regardless of environmental changes. The results demonstrate the effect of vegetation on the functioning and structure of bacterial communities involved in the removal of nitrogen in the treatment cells of a CW and point to the use of vegetation coverage to promote nitrification or denitrification in particular areas. PMID:19049502

Ruiz-Rueda, Olaya; Hallin, Sara; Bañeras, Lluis

2009-02-01

288

Effect of carbon dioxide and bicarbonate as inorganic carbon sources on growth and adaptation of autohydrogenotrophic denitrifying bacteria  

International Nuclear Information System (INIS)

Acclimation of autohydrogenotrophic denitrifying bacteria using inorganic carbon source (CO2 and bicarbonate) and hydrogen gas as electron donor was performed in this study. In this regard, activated sludge was used as the seed source and sequencing batch reactor (SBR) technique was applied for accomplishing the acclimatization. Three distinct strategies in feeding of carbon sources were applied: (I) continuous sparging of CO2, (II) bicarbonate plus continuous sparging of CO2, and (III) only bicarbonate. The pH-reducing nature of CO2 showed an unfavorable impact on denitrification rate; however bicarbonate resulted in a buffered environment in the mixed liquor and provided a suitable mean to maintain the pH in the desirable range of 7-8.2. As a result, bicarbonate as the only carbon source showed a faster adaptation, while carbon dioxide as the only carbon source as well as a complementary carbon source added to bicarbonate resulted in longer acclimation period. Adapted hydrogenotrophic denitrifying bacteria, using bicarbonate and hydrogen gas in the aforementioned pH range, caused denitrification at a rate of 13.33 mg NO3--N/g MLVSS/h for degrading 20 and 30 mg NO3--N/L and 9.09 mg NO3--N/g MLVSS/h for degrading 50 mg NO3--N/L

289

Shifts in the microbial community, nitrifiers and denitrifiers in the biofilm in a full-scale rotating biological contactor.  

Science.gov (United States)

The objective of this study was to investigate the microbial community shifts, especially nitrifiers and denitrifiers, in the biofilm of two rotating biological contactor (RBC) trains with different running times along the plug flowpath. The microbial consortia were profiled using multiple approaches, including 454 high-throughput sequencing of the V3-V4 region of 16S rRNA gene, clone libraries, and quantitative polymerase chain reaction (qPCR). The results demonstrated that (1) the overall microbial community at different locations had distinct patterns, that is, there were similar microbial communities at the beginnings of the two RBC trains and completely different populations at the ends of the two RBC trains; (2) nitrifiers, including ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB, Nitrosomonas) and nitrite-oxidizing bacteria (NOB, Nitrospira), increased in relative abundance in the biofilm along the flowpath, whereas denitrifiers (Rhodanobacter, Paracoccus, Thauera, and Azoarcus) markedly decreased; (3) the AOA were subdominant to the AOB in all sampled sections; and (4) strong ecological associations were shown among different bacteria. Overall, the results of this study provided more comprehensive information regarding the biofilm community composition and assemblies in full-scale RBCs. PMID:24936907

Peng, Xingxing; Guo, Feng; Ju, Feng; Zhang, Tong

2014-07-15

290

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.

2014-06-01

291

Motif enrichment tool.  

Science.gov (United States)

The Motif Enrichment Tool (MET) provides an online interface that enables users to find major transcriptional regulators of their gene sets of interest. MET searches the appropriate regulatory region around each gene and identifies which transcription factor DNA-binding specificities (motifs) are statistically overrepresented. Motif enrichment analysis is currently available for many metazoan species including human, mouse, fruit fly, planaria and flowering plants. MET also leverages high-throughput experimental data such as ChIP-seq and DNase-seq from ENCODE and ModENCODE to identify the regulatory targets of a transcription factor with greater precision. The results from MET are produced in real time and are linked to a genome browser for easy follow-up analysis. Use of the web tool is free and open to all, and there is no login requirement. ADDRESS: http://veda.cs.uiuc.edu/MET/. PMID:24860165

Blatti, Charles; Sinha, Saurabh

2014-07-01

292

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.)

293

South Australia, uranium enrichment  

International Nuclear Information System (INIS)

The Report sets out the salient data relating to the establishment of a uranium processing centre at Redcliff in South Australia. It is conceived as a major development project for the Commonwealth, the South Australian Government and Australian Industry comprising the refining and enrichment of uranium produced from Australian mines. Using the data currently available in respect of markets, demand, technology and possible financial return from overseas sales, the project could be initiated immediately with hexafluoride production, followed rapidly in stages by enrichment production using the centrifuge process. A conceptual development plan is presented, involving a growth pattern that would be closely synchronised with the mining and production of yellowcake. The proposed development is presented in the form of an eight-and-half-year programme. Costs in this Report are based on 1975 values, unless otherwise stated. (Author)

294

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

295

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

296

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

297

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

298

Insights into the effect of soil pH on N(2)O and N(2) emissions and denitrifier community size and activity.  

Science.gov (United States)

The objective of this study was to investigate how changes in soil pH affect the N(2)O and N(2) emissions, denitrification activity, and size of a denitrifier community. We established a field experiment, situated in a grassland area, which consisted of three treatments which were repeatedly amended with a KOH solution (alkaline soil), an H(2)SO(4) solution (acidic soil), or water (natural pH soil) over 10 months. At the site, we determined field N(2)O and N(2) emissions using the (15)N gas flux method and collected soil samples for the measurement of potential denitrification activity and quantification of the size of the denitrifying community by quantitative PCR of the narG, napA, nirS, nirK, and nosZ denitrification genes. Overall, our results indicate that soil pH is of importance in determining the nature of denitrification end products. Thus, we found that the N(2)O/(N(2)O + N(2)) ratio increased with decreasing pH due to changes in the total denitrification activity, while no changes in N(2)O production were observed. Denitrification activity and N(2)O emissions measured under laboratory conditions were correlated with N fluxes in situ and therefore reflected treatment differences in the field. The size of the denitrifying community was uncoupled from in situ N fluxes, but potential denitrification was correlated with the count of NirS denitrifiers. Significant relationships were observed between nirS, napA, and narG gene copy numbers and the N(2)O/(N(2)O + N(2)) ratio, which are difficult to explain. However, this highlights the need for further studies combining analysis of denitrifier ecology and quantification of denitrification end products for a comprehensive understanding of the regulation of N fluxes by denitrification. PMID:20118356

Cuhel, Jirí; Simek, Miloslav; Laughlin, Ronnie J; Bru, David; Chèneby, Dominique; Watson, Catherine J; Philippot, Laurent

2010-03-01

299

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)

300

Diversity of Nitrate-Reducing and Denitrifying Bacteria in a Marine Aquaculture Biofilter and their Response to Sulfide  

DEFF Research Database (Denmark)

DIVERSITY OF NITRATE-REDUCING AND DENITRIFYING BACTERIA IN A MARINE AQUACULTURE BIOFILTER AND THEIR RESPONSE TO SULFIDE B.U. Krieger 1,5, C. Schwermer 2, N. Rezakhani 5, M.A. Horn 1, A. Gieseke 2, E. Cytryn 3, D. Minz 3, J. van Rijn 4, H.L. Drake 1, A. Schramm 5 1 Dept. of Ecological Microbiology, University of Bayreuth, Bayreuth, Germany; 2 Max Planck Institute for Marine Microbiology, Bremen, Germany; 3 Institute for Soil, Water and Environmental Sciences, ARO, The Volcani Center, Bet Dagan, Israel; 4 Faculty of Agricultural, Food And Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot, Israel; 5 Dept of Biological Sciences, Microbiology, University of Aarhus, Denmark Conventional aquaculture systems release nitrogen compounds and organic matter into marine environments. As an environmentally-friendly alternative, a zero-discharge mariculture system recently was developed containing a 3-stage biofilter for nitrification, denitrification/anaerobic sludge digestion, and sulfide oxidation. Sulfate reduction in the anaerobic part of the system leads to sulfide concentrations exceeding 5 mM, which may affect nitrate reduction and denitrification. Sulfide can inhibit nitrous oxide reductase, trigger a shift from denitrification to dissimilatory nitrate reduction to ammonium (DNRA), or be used as electron donor for nitrate reduction. The goal of this study was to identify and isolate nitrate-reducing and denitrifying bacteria from the biofilter and to investigate their response to sulfide concentrations relevant for the system. Almost 500 nitrate-consuming isolates were screened by 16S rRNA gene-RFLP; for each RFLP pattern representatives were sequenced. In total, 40 different strains were identified, some of them novel species, mostly affiliating with Alphaproteobacteria but also including Beta- and Gammaproteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria. The diversity of the isolates was compared to the cultivation-independent diversity of nitrate-reducing and denitrifying bacteria based on narG and nosZ as functional marker genes. Growth experiments revealed great differences in sulfide-tolerance among isolates, ranging from < 50 µM to 5 mM; some strains were also able to oxidize sulfide. Increasing sulfide concentrations generally resulted in increased nitrous oxide production. Batch incubations of anaerobic sludge with 15N-nitrate confirmed the in situ relevance of these results and indicated a sulfide-induced shift from denitrification to DNRA.

Krieger, Bärbel; Schwermer, Carsten U.

2006-01-01

 
 
 
 
301

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

302

Rectoanal Mucosal Swab Culture Is More Sensitive Than Fecal Culture and Distinguishes Escherichia coli O157:H7-Colonized Cattle and Those Transiently Shedding the Same Organism  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Enrichment and direct (nonenrichment) rectoanal mucosal swab (RAMS) culture techniques were developed and compared to traditional fecal culture for the detection of Escherichia coli O157:H7 in experimentally infected and naturally infected cattle. Holstein steers (n = 16) orally dosed with E. coli O157:H7 were sampled after bacterial colonization starting 15 days postinoculation. Enrichment RAMS cultures (70.31% positive) were more sensitive than enrichment fecal cultures with 10 g of feces (...

Rice, Daniel H.; Sheng, Haiqing Q.; Wynia, Stacey A.; Hovde, Carolyn J.

2003-01-01

303

Whole-Genome Transcriptional Analysis of Chemolithoautotrophic Thiosulfate Oxidation by Thiobacillus denitrificans Under Aerobic vs. Denitrifying Conditions  

Energy Technology Data Exchange (ETDEWEB)

Thiobacillus denitrificans is one of the few known obligate chemolithoautotrophic bacteria capable of energetically coupling thiosulfate oxidation to denitrification as well as aerobic respiration. As very little is known about the differential expression of genes associated with ke chemolithoautotrophic functions (such as sulfur-compound oxidation and CO2 fixation) under aerobic versus denitrifying conditions, we conducted whole-genome, cDNA microarray studies to explore this topic systematically. The microarrays identified 277 genes (approximately ten percent of the genome) as differentially expressed using Robust Multi-array Average statistical analysis and a 2-fold cutoff. Genes upregulated (ca. 6- to 150-fold) under aerobic conditions included a cluster of genes associated with iron acquisition (e.g., siderophore-related genes), a cluster of cytochrome cbb3 oxidase genes, cbbL and cbbS (encoding the large and small subunits of form I ribulose 1,5-bisphosphate carboxylase/oxygenase, or RubisCO), and multiple molecular chaperone genes. Genes upregulated (ca. 4- to 95-fold) under denitrifying conditions included nar, nir, and nor genes (associated respectively with nitrate reductase, nitrite reductase, and nitric oxide reductase, which catalyze successive steps of denitrification), cbbM (encoding form II RubisCO), and genes involved with sulfur-compound oxidation (including two physically separated but highly similar copies of sulfide:quinone oxidoreductase and of dsrC, associated with dissimilatory sulfite reductase). Among genes associated with denitrification, relative expression levels (i.e., degree of upregulation with nitrate) tended to decrease in the order nar > nir > nor > nos. Reverse transcription, quantitative PCR analysis was used to validate these trends.

Beller, H R; Letain, T E; Chakicherla, A; Kane, S R; Legler, T C; Coleman, M A

2006-04-22

304

Denitrification of groundwater using a sulfur-oxidizing autotrophic denitrifying anaerobic fluidized-bed MBR: performance and bacterial community structure.  

Science.gov (United States)

This paper investigates a novel sulfur-oxidizing autotrophic denitrifying anaerobic fluidized bed membrane bioreactor (AnFB-MBR) that has the potential to overcome the limitations of conventional sulfur-oxidizing autotrophic denitrification systems. The AnFB-MBR produced consistent high-quality product water when fed by a synthetic groundwater with NO3 (-)-N ranging 25-80 mg/L and operated at hydraulic retention times of 0.5-5.0 h. A nitrate removal rate of up to 4.0 g NO3 (-)-N/Lreactord was attained by the bioreactor, which exceeded any reported removal capacity. The flux of AnFB-MBR was maintained in the range of 1.5-15 L m(-2) h(-1). Successful membrane cleaning was practiced with cleaning cycles of 35-81 days, which had no obvious effect on the AnFB-MBR performance. The (15)?N-tracer analyses elucidated that nitrogen was converted into (15)?N2-N and (15)?N-biomass accounting for 88.1-93.1 % and 6.4-11.6 % of the total nitrogen produced, respectively. Only 0.3-0.5 % of removed nitrogen was in form of (15)N2O-N in sulfur-oxidizing autotrophic denitrification process, reducing potential risks of a significant amount of N2O emissions. The sulfur-oxidizing autotrophic denitrifying bacterial consortium was composed mainly of bacteria from Proteobacteria, Chlorobi, and Chloroflexi phyla, with genera Thiobacillus, Sulfurimonas, and Ignavibacteriales dominating the consortium. The pyrosequencing assays also suggested that the stable microbial communities corresponded to the elevated performance of the AnFB-MBR. Overall, this research described relatively high nitrate removal, acceptable flux, indicating future potential for the technology in practice. PMID:25343972

Zhang, Lili; Zhang, Chao; Hu, Chengzhi; Liu, Huijuan; Qu, Jiuhui

2014-10-26

305

Spatiotemporal relationships between the abundance, distribution, and potential activities of ammonia-oxidizing and denitrifying microorganisms in intertidal sediments.  

Science.gov (United States)

The primary objective of this study was to gain an understanding of how key microbial communities involved in nitrogen cycling in estuarine sediments vary over a 12-month period. Furthermore, we sought to determine whether changes in the size of these communities are related to, or indicative of, seasonal patterns in fixed nitrogen dynamics in Elkhorn Slough-a small, agriculturally impacted estuary with a direct connection to Monterey Bay. We assessed sediment and pore water characteristics, abundance of functional genes for nitrification (bacterial and archaeal amoA, encoding ammonia monooxygenase subunit A) and denitrification (nirS and nirK, encoding nitrite reductase), and measurements of potential nitrification and denitrification activities at six sites. No seasonality in the abundance of denitrifier or ammonia oxidizer genes was observed. A strong association between potential nitrification activity and the size of ammonia-oxidizing bacterial communities was observed across the estuary. In contrast, ammonia-oxidizing archaeal abundances remained relatively constant in space and time. Unlike many other estuaries, salinity does not appear to regulate the distribution of ammonia-oxidizing communities in Elkhorn Slough. Instead, their distributions appear to be governed over two different time scales. Long-term niche characteristics selected for the gross size of archaeal and bacterial ammonia-oxidizing communities, yet covariation in their abundances between monthly samples suggests that they respond in a similar manner to short-term changes in their environment. Abundances of denitrifier and ammonia oxidizer genes also covaried, but site-specific differences in this relationship suggest differing levels of interaction (or coupling) between nitrification and denitrification. PMID:25038845

Smith, Jason M; Mosier, Annika C; Francis, Christopher A

2015-01-01

306

Community structures and activity of denitrifying microbes in a forested catchment in central Japan: survey using nitrite reductase genes  

Science.gov (United States)

To elucidate the mechanisms of denitrification processes in the forested catchment, microbial ecological approaches have been applied in an experimental watershed that has previously investigated its hydrological processes. The study catchment is located in the Chiba prefecture in central Japan under the temperate Asian monsoon climate. Potential activities of denitrification of soil samples were measured by incubation experiments under anoxic condition associated with Na15NO3 addition. Existence and variety of microbes having nitrite reductase genes were investigated by PCR amplification, cloning and sequencings of nirK and nirS fragments after DNA extraction. Contrary to our early expectation that the potential denitrification activity was higher at deeper soil horizon with consistent groundwater residence than that in the surface soil, denitrification potential was higher in shallower soil horizons than deeper soils. This suggested that the deficiency of NO3- as a respiratory substrate for denitrifier occurred in deeper soils especially in the summer. However, high denitrification activity and presence of microbes having nirK and nirS in surface soils usually under aerobic condition was explainable by the fact that the majority of denitrifying bacteria have been recognized as a facultative anaerobic bacterium. This also suggests the possibility of that denitrification occurs even in the surface soils if the wet condition is provided by rainwater during and after a storm event. Community structures of microbes having nirK were different between near surface and deeper soil horizons, and ones having nirS was different between saturated zone (under groundwater table) and unsaturated soil horizons. These imply that microbial communities with nisK are sensitive to the concentration of soil organic matters and ones with nirS is sensitive to soil moisture contents.

Ohte, N.; Aoki, M.; Katsuyama, C.; Suwa, Y.; Tange, T.

2012-12-01

307

Transitions in nirS-type Denitrifier Diversity, Community Composition, and Biogeochemical Activity along the Chesapeake Bay Estuary  

Directory of Open Access Journals (Sweden)

Full Text Available Chesapeake Bay, the largest estuary in North America, can be characterized as having steep and opposing gradients in salinity and dissolved inorganic nitrogen along the main axis of the Bay. In this study, the diversity of nirS gene fragments (encoding cytochrome cd1-type nitrite reductase, physical/chemical parameters, and benthic N2-fluxes were analyzed in order to determine how denitrifier communities and biogeochemical activity vary along the estuary salinity gradient. The nirS gene fragments were PCR-amplified, cloned, and sequenced from sediment cores collected at five stations. Sequence analysis of 96 to 123 nirS clones from each station revealed extensive overall diversity in this estuary, as well as distinct spatial structure in the nirS sequence distributions. Both nirS-based richness and community composition varied among stations, with the most dramatic shifts occurring between low-salinity (oligohaline and moderate-salinity (mesohaline sites. For four samples collected in April, the nirS-based richness, nitrate concentrations, and N2-fluxes all decreased in parallel along the salinity gradient from the oligohaline northernmost station to the highest salinity (polyhaline station near the mouth of the Bay. The vast majority of the 550 nirS sequences were distinct from cultivated denitrifiers, although many were closely related to environmental clones from other coastal and estuarine systems. Interestingly, 8 of the 172 OTUs identified accounted for 42% of the total nirS clones, implying the presence of a few dominant and many rare genotypes, which were distributed in a non-random manner along the salinity gradient of Chesapeake Bay. These data, comprising the largest dataset to investigate nirS clone sequence diversity from an estuarine environment, also provided information that was required for the development of nirS microarrays to investigate the interaction of microbial diversity, environmental gradients, and biogeochemical activity.

ChristopherAFrancis

2013-08-01

308

The world enrichment market  

International Nuclear Information System (INIS)

The enrichment market can be divided into two periods: the near-term market (1991 to 1995) and the long-term market (1995 and beyond). The near-term market is characterized by limited unfilled requirements of 4% per year, to be supplied by national stockpiles and excess inventories. This low-cost material will be drawn down by about 1993, causing a subsequent price rise. As the price rises, primary supplier activity is expected to increase. In the near-term, two contracting activities are apparent: spot; and intermediate-term. The current spot market is expected to last until available low cost inventories are drawn down. Recently, in attempts to gain market share, suppliers have offered attractively priced intermediate-term (3 year) contracts for 1996 to 1998. While a small spot market will continue after 1995, it is anticipated that utilities will prefer a mix of medium- and long-term (5 to 10 year) contracts from primary suppliers for most of their enrichment requirements. As national stockpiles and utility inventories are consumed, low-cost supply available to the spot market is expected to diminish. Consequently, with little low-cost supply available, the only apparent source of material will be from primary suppliers, and the resulting competition over market share is expected to be intense. (author)

309

Culturally Responsive Teaching for American Indian Learners.  

Science.gov (United States)

Teachers in a multicultural society need to respect cultural differences, know the cultural resources their students bring to class, and be skilled at tapping into learners' cultural resources in the teaching-learning process. They must believe that all students are capable of learning, and they must implement an enriched curriculum for all…

Pewewardy, Cornel D.

310

Successful enrichment of the ubiquitous freshwater acI Actinobacteria.  

Science.gov (United States)

Actinobacteria of the acI lineage are often the numerically dominant bacterial phylum in surface freshwaters, where they can account for > 50% of total bacteria. Despite their abundance, there are no described isolates. In an effort to obtain enrichment of these ubiquitous freshwater Actinobacteria, diluted freshwater samples from Lake Grosse Fuchskuhle, Germany, were incubated in 96-well culture plates. With this method, a successful enrichment containing high abundances of a member of the lineage acI was established. Phylogenetic classification showed that the acI Actinobacteria of the enrichment belonged to the acI-B2 tribe, which seems to prefer acidic lakes. This enrichment grows to low cell densities and thus the oligotrophic nature of acI-B2 was confirmed. PMID:24596259

Garcia, Sarahi L; McMahon, Katherine D; Grossart, Hans-Peter; Warnecke, Falk

2014-02-01

311

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

312

Thermal breeder fuel enrichment zoning  

International Nuclear Information System (INIS)

A method and apparatus for improving the performance of a thermal breeder reactor having regions of higher than average moderator concentration are disclosed. The fuel modules of the reactor core contain at least two different types of fuel elements, a high enrichment fuel element and a low enrichment fuel element. The two types of fuel elements are arranged in the fuel module with the low enrichment fuel elements located between the high moderator regions and the high enrichment fuel elements. Preferably, shim rods made of a fertile material are provided in selective regions for controlling the reactivity of the reactor by movement of the shim rods into and out of the reactor core. The moderation of neutrons adjacent the high enrichment fuel elements is preferably minimized as by reducing the spacing of the high enrichment fuel elements and/or using a moderator having a reduced moderating effect. 1 figure

313

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)

314

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

315

Ferrioxamine E-supplemented pre-enrichment and enrichment media improve various isolation methods for Salmonella.  

Science.gov (United States)

Supplementation of pre-enrichment broth and enrichment broth media with ferrioxamine E (1 microgram/ml) significantly improved the recovery of Salmonella from artificially or naturally contaminated foods. Based on the selectivity of ferrioxamine E, Salmonella enteritidis and S. typhimurium could be isolated also from various mixed cultures (one Salmonella cell in 10(3)-10(4)-fold concentration of cells of competitors) by shaking for 6 h in supplemented buffered peptone water followed by cultivation on XLD- or XLT-4 agars. Isolation of Salmonella from these pre-enrichment cultures by use of Dynabeads-Anti-Salmonella was highly effective. 27 S. typhimurium strains were isolated from 762 naturally infected chicken giblets by use of unsupplemented Tetrathionate broth. However, 33 S. typhimurium isolates were obtained with ferrioxamine E-supplemented Tetrathionate broth from the same samples. Three Salmonella isolates out of 50 evenly divided meat meal samples were obtained by use of ferrioxamine E-supplemented buffered peptone water followed by direct streaking onto XLD- and Rambach agars, no Salmonella isolates could be detected by the conventional method. PMID:8722189

Reissbrodt, R; Vielitz, E; Kormann, E; Rabsch, W; Kühn, H

1996-02-01

316

Effects of Heavy Metal Contamination upon Soil Microbes: Lead-induced Changes in General and Denitrifying Microbial Communities as Evidenced by Molecular Markers  

Directory of Open Access Journals (Sweden)

Full Text Available Lead (Pb is a common environmental contaminant found in soils. Unlike other metals, Pb has no biological role, and is potentially toxic to microorganisms. Effects of low (1 ppm and high (500-2000 levels of lead (Pb upon the soil microbial community was investigated by the PCR/DGGE analysis of the 16S and nirK gene markers, indicative of general microbial community and denitrifying community, respectively. Community analysis by use of those markers had shown that Pb has detectable effects upon the community diversity even at the lowest concentration tested. Analysis of sample diversity and similarity between the samples suggested that there are several thresholds crossed as metal concentration increase, each causing a substantial change in microbial diversity. Preliminary data obtained in this study suggest that the denitrifying microbial community adapts to elevated levels of Pb by selecting for metal-resistant forms of nitrite reductases.

Maria Begonia

2008-12-01

317

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

318

New generation enrichment monitoring technology for gas centrifuge enrichment plants  

Energy Technology Data Exchange (ETDEWEB)

The continuous enrichment monitor, developed and fielded in the 1990s by the International Atomic Energy Agency, provided a go-no-go capability to distinguish between UF{sub 6} containing low enriched (approximately 4% {sup 235}U) and highly enriched (above 20% {sup 235}U) uranium. This instrument used the 22-keV line from a {sup 109}Cd source as a transmission source to achieve a high sensitivity to the UF{sub 6} gas absorption. The 1.27-yr half-life required that the source be periodically replaced and the instrument recalibrated. The instrument's functionality and accuracy were limited by the fact that measured gas density and gas pressure were treated as confidential facility information. The modern safeguarding of a gas centrifuge enrichment plant producing low-enriched UF{sub 6} product aims toward a more quantitative flow and enrichment monitoring concept that sets new standards for accuracy stability, and confidence. An instrument must be accurate enough to detect the diversion of a significant quantity of material, have virtually zero false alarms, and protect the operator's proprietary process information. We discuss a new concept for advanced gas enrichment assay measurement technology. This design concept eliminates the need for the periodic replacement of a radioactive source as well as the need for maintenance by experts. Some initial experimental results will be presented.

Ianakiev, Kiril D [Los Alamos National Laboratory; Alexandrov, Boian, S. [Los Alamos National Laboratory; Boyer, Brian, D. [Los Alamos National Laboratory; Hill, Thomas, R. [Los Alamos National Laboratory; Macarthur, Duncan, W. [Los Alamos National Laboratory; Marks, Thomas [Los Alamos National Laboratory; Moss, Calvin, E. [Los Alamos National Laboratory; Sheppard, Gregory, A. [Los Alamos National Laboratory; Swinhoe, Martyn, T. [Los Alamos National Laboratory

2008-01-01

319

City model enrichment  

Science.gov (United States)

The combination of mobile communication technology with location and orientation aware digital cameras has introduced increasing interest in the exploitation of 3D city models for applications such as augmented reality and automated image captioning. The effectiveness of such applications is, at present, severely limited by the often poor quality of semantic annotation of the 3D models. In this paper, we show how freely available sources of georeferenced Web 2.0 information can be used for automated enrichment of 3D city models. Point referenced names of prominent buildings and landmarks mined from Wikipedia articles and from the OpenStreetMaps digital map and Geonames gazetteer have been matched to the 2D ground plan geometry of a 3D city model. In order to address the ambiguities that arise in the associations between these sources and the city model, we present procedures to merge potentially related buildings and implement fuzzy matching between reference points and building polygons. An experimental evaluation demonstrates the effectiveness of the presented methods.

Smart, Philip D.; Quinn, Jonathan A.; Jones, Christopher B.

320

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)

 
 
 
 
321

Enrichment and terminal differentiation of striated muscle progenitors in vitro  

International Nuclear Information System (INIS)

Enrichment and terminal differentiation of mammalian striated muscle cells is severely hampered by fibroblast overgrowth, de-differentiation and/or lack of functional differentiation. Herein we report a new, reproducible and simple method to enrich and terminally differentiate muscle stem cells and progenitors from mice and humans. We show that a single gamma irradiation of muscle cells induces their massive differentiation into structurally and functionally intact myotubes and cardiomyocytes and that these cells can be kept in culture for many weeks. Similar results are also obtained when treating skeletal muscle-derived stem cells and progenitors with Mitomycin C.

322

Enrichment and terminal differentiation of striated muscle progenitors in vitro  

Energy Technology Data Exchange (ETDEWEB)

Enrichment and terminal differentiation of mammalian striated muscle cells is severely hampered by fibroblast overgrowth, de-differentiation and/or lack of functional differentiation. Herein we report a new, reproducible and simple method to enrich and terminally differentiate muscle stem cells and progenitors from mice and humans. We show that a single gamma irradiation of muscle cells induces their massive differentiation into structurally and functionally intact myotubes and cardiomyocytes and that these cells can be kept in culture for many weeks. Similar results are also obtained when treating skeletal muscle-derived stem cells and progenitors with Mitomycin C.

Becher, Ulrich M.; Breitbach, Martin; Sasse, Philipp [Institute of Physiology I, Life and Brain Center, University of Bonn, Bonn (Germany); Garbe, Stephan [Department of Radiology, University of Bonn, Bonn (Germany); Ven, Peter F.M. van der [Institute for Cell Biology, University of Bonn, Bonn (Germany); Fuerst, Dieter O., E-mail: dfuerst@uni-bonn.de [Institute for Cell Biology, University of Bonn, Bonn (Germany); Fleischmann, Bernd K., E-mail: bernd.fleischmann@uni-bonn.de [Institute of Physiology I, Life and Brain Center, University of Bonn, Bonn (Germany)

2009-10-01

323

High enrichment to low enrichment core's conversion. Technical securities  

International Nuclear Information System (INIS)

This work presents the fulfillment of the technical securities subscribed by INVAP S.E. for the conversion of a high enriched uranium core. The reactor (of 5 thermal Mw), built in the 50's and 60's, is of the 'swimming pool' type, with light water and fuel elements of the curve plates MTR type, enriched at 93.15 %. These are neutronic and thermohydraulic securities. (Author)

324

Factorizable enriched categories and applications  

CERN Document Server

We define the twisted tensor product of two enriched categories, which generalizes various sorts of `products' of algebraic structures, including the bicrossed product of groups, the twisted tensor product of (co)algebras and the double cross product of bialgebras. The key ingredient in the definition is the notion of simple twisting systems between two enriched categories. To give examples of simple twisted tensor products we introduce matched pairs of enriched categories. Several other examples related to ordinary categories, posets and groupoids are also discussed.

Bârde?, Aura

2011-01-01

325

Physiological roles of two dissimilatory nitrate reductases in the deep-sea denitrifier Pseudomonas sp. strain MT-1.  

Science.gov (United States)

The deep-sea denitrifier Pseudomonas sp. strain MT-1 has two distinct gene clusters encoding dissimilatory nitrate reductases, periplasmic nitrate reductase (Nap) and membrane-bound nitrate reductase (Nar). In order to investigate the physiological roles of these enzymes, we determined the nitrate reductase activity of the soluble and membrane fractions from MT-1 and the type strain of Pseudomonas stutzeri (closely related with MT-1) grown under various conditions. In MT-1, the activities of both fractions were highest when the cells were grown anaerobically in the presence of nitrate under atmospheric pressure. However, the activity of the soluble fraction decreased when the cells were grown under high pressure, whereas that of membrane fraction remained constant. Further, the activity of the soluble fraction decreased when the enzyme reaction was performed at low temperature, although that of membrane fraction was not similarly affected. Additionally, the results of RT-PCR showed that expression of the nar genes was strongly induced under high pressure. In contrast, P. stutzeri(T) showed no such response following a shift in growth pressure. These results suggest that MT-1 possesses a special mechanism for adaptation to the low-temperature and high-pressure environments of the deep sea, and that Nar is the main dissimilatory nitrate reductase in MT-1 in such environments. PMID:19352028

Ikeda, Eriko; Andou, Satomi; Iwama, Ubu; Kato, Chiaki; Horikoshi, Koki; Tamegai, Hideyuki

2009-04-23

326

[Characteristics of soil denitrifying enzyme activity in riparian zones with different land use types in Chongming Island, Shanghai of China].  

Science.gov (United States)

By using acetylene inhibition method, this paper studied the soil denitrifying enzyme activity (DEA) and its affecting factors in the riparian zone with different land use types (cropland riparian, forested riparian, and grassy riparian zones) in Chongming Island, Shanghai of China. The riparian soil DEA was (0.69 +/- 0.11)--(134.93 +/- 33.72) microg N x kg(-1) x h(-1), which differed obviously among different land types, with a decreasing trend of forested riparian zone > cropland riparian zone > grassy riparian zone. The soil DEA was significantly (P < 0.05) higher in 0-10 cm in 10-30, 30-50, and 50-70 cm layers. There were significant positive relationships between soil DEA and soil TOC, TN, and NO(3-)-N (P < 0.01). Land use change mainly altered the soil natural structure and soil physical and chemical properties, decreased the accumulation of soil organic carbon, and affected the soil nitrogen transformation, and thus, inhibited the occurrence of riparian soil denitrification. PMID:24483089

Chen, Gang-Liang; Li, Jian-Hua; Yang, Chang-Ming

2013-10-01

327

The effect of poly-?-hydroxyalkanoates degradation rate on nitrous oxide production in a denitrifying phosphorus removal system.  

Science.gov (United States)

Poly-?-hydroxyalkanoates (PHAs) and free nitrous acid (FNA) have been revealed as significant factors causing nitrous oxide (N2O) production in denitrifying phosphorus removal systems. In this study, the effect of PHA degradation rate on N2O production was studied at low FNA levels. N2O production always maintained at approximately 40% of the amount of nitrite reduced independent of the PHA degradation rate. The electrons distributed to nitrite reduction were 1.6 times that to N2O reduction. This indicated that electron competition between these two steps was not affected by the PHA degradation rate. Continuous feed of nitrate was proposed, and demonstrated to reduce N2O accumulation by 75%. While being kept low, a possible compounding effect of a low-level FNA could not be ruled out. The sludge used likely contained both polyphosphate- and glycogen-accumulating organisms, and the results could not be simply attributed to either group of organisms. PMID:25129233

Wei, Yan; Wang, Shuying; Ma, Bin; Li, Xiyao; Yuan, Zhiguo; He, Yuelan; Peng, Yongzhen

2014-10-01

328

Atomic resolution structure of pseudoazurin from the methylotrophic denitrifying bacterium Hyphomicrobium denitrificans: structural insights into its spectroscopic properties.  

Science.gov (United States)

The crystal structure of native pseudoazurin (HdPAz) from the methylotrophic denitrifying bacterium Hyphomicrobium denitrificans has been determined at a resolution of 1.18 A. After refinement with SHELX employing anisotropic displacement parameters and riding H atoms, R(work) and R(free) were 0.135 and 0.169, respectively. Visualization of the anisotropic displacement parameters as thermal ellipsoids provided insight into the atomic motion within the perturbed type 1 Cu site. The asymmetric unit includes three HdPAz molecules which are tightly packed by head-to-head cupredoxin dimer formation. The shape of the Cu-atom ellipsoid implies significant vibrational motion diagonal to the equatorial xy plane defined by the three ligands (two His and one Cys). The geometric parameters of the type 1 Cu site in the HdPAz structure differ unambiguously from those of other pseudoazurins. It is demonstrated that their structural aspects are consistent with the unique visible absorption spectrum. PMID:19153470

Hira, Daisuke; Nojiri, Masaki; Suzuki, Shinnichiro

2009-01-01

329

31 CFR 540.316 - Uranium enrichment.  

Science.gov (United States)

...2010-07-01 false Uranium enrichment. 540.316 Section 540...Definitions § 540.316 Uranium enrichment. The term uranium enrichment means the process of increasing the concentration of the isotope U235 relative to that of...

2010-07-01

330

Uranium enrichment and nuclear weapon proliferation  

International Nuclear Information System (INIS)

The subject is covered in chapters, entitled: (Part 1) fundamentals of uranium enrichment; enrichment and proliferation; options for control; conclusions and recommendations; (Part 2) general principles of uranium enrichment; enrichment processes (gaseous diffusion; gas centrifuge; aerodynamic methods; chemical-exchange methods; laser isotope separation; electromagnetic and plasma processes; miscellaneous methods); (Part 3) history of non-proliferation efforts; world enrichment picture. Appendices cover: nuclear power growth 1980-1990; demand for and supply of enrichment services. (U.K.)

331

Tritium enrichment by gas chromatography  

International Nuclear Information System (INIS)

Hydrogen gas was used in the enrichment. Molecular sieve 4A was found to be the most suitable adsorbent. The chosen adsorption temperature is approximately 630K. The column is cooled down and filled with helium to operating pressure (approximately 150 mm Hg). The system should be capable to give 100-fold enrichment, starting from some 100 litres of hydrogen (5 to 10 moles) within 3 hours and a tritium recovery near unity

332

Enrichment techniques employed in phosphoproteomics  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Rapid changes of protein phosphorylation play a crucial role in the regulation of many cellular processes. Being post-translationally modified, phosphoproteins are often present in quite low abundance and tend to co-exist with their unphosphorylated isoform within the cell. To make their identification more practicable, the use of enrichment protocols is often required. The enrichment strategies can be performed either at the level of phosphoproteins or at the level of phosphopeptides. Both a...

Fi?la, Jan; Honys, David

2012-01-01

333

Uranium enrichment by displacement chromatography  

International Nuclear Information System (INIS)

Natural Uranium contains 0.72% of fissile isotope 235U. Need for 235U enriched uranium for light water moderated reactors and other uses are well known. Uranium enrichment is a highly complex and tedious process owing to extremely small separation factor. Several processes have been tried; however, gaseous diffusion and centrifugation techniques based on mass dependent isotope effect are being exploited for producing enriched uranium. In the recent past, Isotope fractionation based on mass independent isotope effect such as LASER technique, ion exchange displacement chromatography etc. have drawn the attention of separation scientist and efforts are being made for development and industrial deployment of these technologies. Indian Nuclear Power Programme is based on use of natural uranium (PHWRs) and slightly enriched uranium (BWRs, PWRs) with emphasis on use of vast resources of thorium. Spent fuel from PHWRs, which is depleted in 235U (0.2 to 0.3%), appears to be a promising source of slightly enriched uranium (1 to 3% 235U). Harnessing this source for 235U enrichment would augment fuel supply for PHWR and light water reactors. Ion exchange displacement chromatography is a proliferation resistant novel technique for 235U enrichment. It is based on nuclear field shift - an isotope shift in orbital electrons resulting from the isotopic difference in nuclear size and shape. Due to this effect lighter isotope (235U) exhibits a stronger tendency for a higher valence i.e. UO22+ as compared to heavier isotope (238U). Preliminary laboratory study is being carried out at HWP, Manuguru for exploring feasibility of using ion exchange displacement chromatography for enriching 235U using 4-vinyl pyridine based anion exchange resin

334

Isotopomeric characterization of nitrous oxide produced by reaction of enzymes extracted from nitrifying and denitrifying bacteria  

Directory of Open Access Journals (Sweden)

Full Text Available Nitrous oxide (N2O is a potent greenhouse gas and produced in denitrification and nitrification in environmental nitrogen cycle by various microorganism. Site preference (SP of 15N in N2O, which is defined as the difference in the natural abundance of isotopomers 14N15NO and 15N14NO relative to 14N14NO, has been reported to be a useful tool to quantitatively distinguish N2O production pathway. To determine representative SP value for each microbial process, we firstly measured SP of N2O produced in the enzyme reaction of hydroxylamine oxidoreductase (HAO purified from two species of ammonia oxidizing bacteria (AOB, Nitrosomonas europaea and Nitrosococcus oceani, and that of nitric oxide reductase (NOR from Paracoccus denitrificans, respectively. The SP value for NOR reaction (?5.9 ± 2.1‰ showed nearly the same value as that reported for N2O produced by P. denitrificans in pure culture. In contrast, SP value for HAO reaction (36.3 ± 2.3‰ was a little higher than the values reported for N2O produced by AOB in aerobic pure culture. Using the SP values obtained by HAO and NOR reactions, we calculated relative contribution of the nitrite (NO2– reduction (which is followed by NO reduction to N2O production by N. oceani incubated under different O2 availability. Our calculations revealed that previous in vivo studies might have underestimated the SP value for NH2OH oxidation pathway possibly due to a small contribution of NO2– reduction pathway. Further evaluation of isotopomer signatures of N2O using common enzymes of other processes related to N2O would improve the isotopomer analysis of N2O in various environments.

T. Yamazaki

2013-10-01

335

Isotopomeric characterization of nitrous oxide produced by reaction of enzymes extracted from nitrifying and denitrifying bacteria  

Science.gov (United States)

Nitrous oxide (N2O) is a potent greenhouse gas and produced in denitrification and nitrification by various microorganisms. Site preference (SP) of 15N in N2O, which is defined as the difference in the natural abundance of isotopomers 14N15NO and 15N14NO relative to 14N14NO, has been reported to be a useful tool to quantitatively distinguish N2O production pathways. To determine representative SP values for each microbial process, we firstly measured SP of N2O produced in the enzyme reaction of hydroxylamine oxidoreductase (HAO) purified from two species of ammonia oxidizing bacteria (AOB), Nitrosomonas europaea and Nitrosococcus oceani, and that of nitric oxide reductase (NOR) from Paracoccus denitrificans. The SP value for NOR reaction (-5.9 ± 2.1‰) showed nearly the same value as that reported for N2O produced by P. denitrificans in pure culture. In contrast, SP value for HAO reaction (36.3 ± 2.3‰) was a little higher than the values reported for N2O produced by AOB in aerobic pure culture. Using the SP values obtained by HAO and NOR reactions, we calculated relative contribution of the nitrite (NO2-) reduction (which is followed by NO reduction) to N2O production by N. oceani incubated under different O2 availability. Our calculations revealed that previous in vivo studies might have underestimated the SP value for the NH2OH oxidation pathway possibly due to a small contribution of NO2- reduction pathway. Further evaluation of isotopomer signatures of N2O using common enzymes of other processes related to N2O would improve the isotopomer analysis of N2O in various environments.

Yamazaki, T.; Hozuki, T.; Arai, K.; Toyoda, S.; Koba, K.; Fujiwara, T.; Yoshida, N.

2014-05-01

336

Comparison of enrichment measurement techniques for gas centrifuge enrichment plants  

International Nuclear Information System (INIS)

A comparison of enrichment techniques has been carried out using a small bank of gas centrifuge enrichment units to simulate conditions in a commercial plant. The detectors compared included an in-line version of the gas phase enrichment monitor and a prototype Go-NoGo monitor. In these comparisons it was found that the gas phase enrichment monitor had an ultimate precision of about 0.5% for all measurements of enrichment between natural and 20%. The Go-NoGo instrument developed in the present programme was based on previous studies, and took advantage of the experience gained in other support programmes. Two different methods of correcting for wall deposits were investigated. On the basis of these studies a versatile Go-NoGo instrument has been designed for usage on pipes varying in diameter from 30 to 120 mm. Further development of this instrument will be carried out using a UF6 test loop facility which is currently under construction. (author)

337

Advances in uranium enrichment processes  

International Nuclear Information System (INIS)

Advances in gas centrifuges and development of the atomic vapour laser isotope separation process promise substantial reductions in the cost of enriched uranium. The resulting reduction in LWR fuel costs could seriously erode the economic advantage of CANDU, and in combination with LWR design improvement, shortened construction times and increased operational reliability could allow the LWR to overtake CANDU. CANDU's traditional advantages of neutron economy and high reliability may no longer be sufficient - this is the challenge. The responses include: combining neutron economy and dollar economy by optimizing CANDU for slightly enriched uranium fuel; developing cost-reducing improvements in design, manufacture and construction; and reducing the cost of heavy water. Technology is a renewable resource which must be continually applied to a product for it to remain competitive in the decades to come. Such innovation is a prerequisite to Canada increasing her share of the international market for nuclear power stations. The higher burn-up achievable with enriched fuel in CANDU can reduce the fuel cycle costs by 20 to 40 percent for a likely range of costs for yellowcake and separative work. Alternatively, some of the benefits of a higher fissile content can take the form of a cheaper reactor core containing fewer fuel channels and less heavy water, and needing only a single fuelling machine. An opportunity that is linked to this need to introduce an enriched uranium fue need to introduce an enriched uranium fuel cycle into CANDU is to build an enrichment business in Canada. This could offer greater value added to our uranium exports, security of supply for enriched CANDUs, technological growth in Canada and new employment opportunities. AECL has a study in progress to define this opportunity

338

Superheavy isotope enrichment using a carbon isotope enrichment plant  

International Nuclear Information System (INIS)

A13C isotope distillation separation plant was used to search for naturally-occurring superheavy isotopes. Superheavy (X-) isotopes of carbon in CO would be only slightly less volatile than the normal 12C16O. Over 100,000 mol CO were passed through the distillation columns without product withdrawal during the experiment. Following cessation of flows, 201 gas samples were collected from the bottom of the high enrichment column. An argon impurity in the CO provided a wedge to enrich X- isotopes at the CO/Ar interface in the column. Carbon isotopic compositions were used to calculate which samples might contain the superheavy isotopes. Enrichments of X- isotope concentrations of ?105 were obtained in several 0.1 mol samples, which were analyzed for the existence of X- isotopes at another laboratory. A limited amount of extremely pure 13CO was produced as a side benefit

339

Quantitative molecular biology and gas flux measurements demonstrate soil treatment and depth affects on the distribution and activity of denitrifiers  

Science.gov (United States)

The growing industrialisation of agriculture has led to a dramatic increase in organic and inorganic nitrogen (N) fertiliser inputs to agro-ecosystems. This increase has had negative effects on the quality of water ecosystems and greenhouse gas emissions.The study objective was to quantify denitrification and denitrifying microorganisms, using real-time PCR assays of the nitrite reductase(nir) and nitrous oxide reductase(nos) functional gene copy concentrations (GCC g[soil]-1) in Irish agricultural surface and subsoils. Soil cores from 3 soil horizons (A:0-10 cm; B:45-55 cm; C:120-130cm) were amended with 3 alternate N- and C-source amendments (NO3-; NO3-+glucose-C; NO3-+Dissolved Organic Carbon (DOC). Real-time production of N2O and N2 was recorded by gas chromatography in a specialized He/O2 environment. N2O and Total Denitrification (TDN) (N2O+N2) production was generally greater in surface soil (2.052 mg/kg/d TDN) than in subsoils (0.120 mg/kg/d TDN). The abundance of denitrifying nirS, nirK (nir) and nos genes was higher in the surface soil, decreasing with soil depth, except in incubations amended with NO3- and DOC, where the carbon source directly positively affected gene copy numbers and fluxes of N2O and N2 production. C addition increased soil denitrification rates, and resulted in higher N2O/(N2O+N2) ratios in surface soil (0.39) than subsoils (0.005), indicating that the subsoil had higher potential for complete reduction of N2O to N2. In the subsoils, complete reduction of NO3- due to glucose-C and DOC addition was observed. Interestingly, at all 3 soil depths, lower nirK abundance (2.78 105 GCC) was recorded, compared to nirS (1.45 107 GCC), but the overall abundance of nir (S+K) i.e. (1.54 107GCC), corresponded with N2O emission fluxes (3.34 mg/kg/d) Statistical analysis indicates negative correlation between nirK GCC and N2O production, but a strong positive correlation was observed between nirS GCC and N2O. We therefore hypothesize that the potential for complete nitrate reduction can be inferred using the relationship - ([nirS + nirK] - nosZ): (nosZ). Specifically, at 45-55 cm depth ([nirS + nirK] - nosZ): (nosZ) ratios were lower (2.13) compared to 120-130cm (94.4), overall the ([nirS + nirK] - nosZ): (nosZ) ratios for horizons A, B and C, was 27.9, 40.3, 69.4, respectively, thus decreasing potential for full microbial denitrification with decreasing depth. Mean Bac:nir and Bac:nosZ gene copy ratios g[soil]-1 increased from horizon A(Bac:nir - 3.91) (Bac:nosZ - 111.24) to horizon B (Bac:nir - 8.89) (Bac:nosZ -295.0 ), and decreased again in horizon C (Bac:nir - 0.723) (Bac:nosZ - 46.2) . Overall, denitrification in subsoils occurs at a lower rate than surface soils, but the microbial populations favored more complete reduction thus reducing emissions of NO3- to water and N2O to the atmosphere. The gene copy ratio suggests that the soil microbial community containing nirs and nosZ genes act as the driving force, and in the partitioning of N2O and N2 emissions from soil.

Barrett, M. M.; Jahangir, M.; Cardenas, L.; Khalil, M.; Richards, K. R.; O'Flaherty, V.

2010-12-01

340

Diagnosis and quantification of glycerol assimilating denitrifying bacteria in an integrated fixed-film activated sludge reactor via 13C DNA stable-isotope probing.  

Science.gov (United States)

Glycerol, a byproduct of biodiesel and oleo-chemical manufacturing operations, represents an attractive alternate to methanol as a carbon and electron donor for enhanced denitrification. However, unlike methanol, little is known about the diversity and activity of glycerol assimilating bacteria in activated sludge. In this study, the microbial ecology of glycerol assimilating denitrifying bacteria in a sequencing batch integrated fixed film activated sludge (SB-IFAS) reactor was investigated using (13)C-DNA stable isotope probing (SIP). During steady state SB-IFAS reactor operation, near complete nitrate removal (92.7 ± 5.8%) was achieved. Based on (13)C DNA clone libraries obtained after 360 days of SB-IFAS reactor operation, bacteria related to Comamonas spp. and Diaphorobacter spp. dominated in the suspended phase communities. (13)C assimilating members in the biofilm community were phylogenetically more diverse and were related to Comamonas spp., Bradyrhizobium spp., and Tessaracoccus spp. Possibly owing to greater substrate availability in the suspended phase, the glycerol-assimilating denitrifying populations (quantified by real-time PCR) were more abundant therein than in the biofilm phase. The biomass in the suspended phase also had a higher specific denitrification rate than the biofilm phase (p = 4.33e-4), and contributed to 69.7 ± 4.5% of the overall N-removal on a mass basis. The kinetics of glycerol based denitrification by suspended phase biomass were approximately 3 times higher than with methanol. Previously identified methanol assimilating denitrifying bacteria were not associated with glycerol assimilation, thereby suggesting limited cross-utilization of these two substrates for denitrification in the system tested. PMID:21053955

Lu, Huijie; Chandran, Kartik

2010-12-01

 
 
 
 
341

Effect of land use on the density of nitrifying and denitrifying bacteria in the Colombian Coffee Region  

Directory of Open Access Journals (Sweden)

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Soil microbial communities involved in the cycling of nitrogen (N are essential to maintaining and improving soil fertility, productivity and functionality of natural and agricultural ecosystems. However, some compounds generated during the metabolic processes performed by nitrifying (NB and denitrifying (DB bacteria are associated with the production of greenhouse gases, groundwater pollution and acidification. Therefore, the study of these bacteria is essential for economic and environmental sustainability. This study evaluated the effect of different land uses in two river basins (La Vieja and Otun on NB and DB densities. Two sampling events (SE were conducted by selecting the most representative land uses. Physicochemical (T °, pH, moisture and nitrate and microbiological properties (NB and DB densities were evaluated. In both SEs, significantly higher densities of NB and DB were observed in the land uses: pasture, guadua (DB only and unshaded coffee (La Vieja and onion (Otun. These land uses, excluding guadua, are dependent on nitrogen fertilizers, which together with the activities of grazing livestock on pastures may lead to greater availability of substrates for the NB. The use of agricultural machinery and overgrazing in pasture and onion uses generate compacted soil and other physical disturbances, encouraging the growth of DB. Forests had the lowest densities of NB and DB possibly due to a reduced availability of N and the releasing of allelopathic compounds from certain plants. Finally, the densities of ammonium-oxidizing bacteria had the greatest differences between the land uses evaluated, demonstrating its high sensitivity to agricultural management practices and livestock. We suggest that changes in the abundance of this community could serve as a relevant and cost-effective bioindicator for soil monitoring.

Vallejo Quintero Victoria Eugenia

2011-12-01

342

Do freshwater macrophytes influence the community structure of ammonia-oxidizing and denitrifying bacteria in the rhizospere?  

DEFF Research Database (Denmark)

DO FRESHWATER MACROPHYTES INFLUENCE THE COMMUNITY STRUCTURE OF AMMONIA-OXIDIZING AND DENITRIFYING BACTERIA IN THE RHIZOSPHERE? M. Herrmann, A. Schramm Department of Biological Sciences, Microbiology, University of Aarhus, Aarhus, Denmark Aquatic macrophytes such as Littorella uniflora and Lobelia dortmanna have been shown to release oxygen from their roots and to stimulate nitrification and coupled nitrification-denitrification in the rhizosphere. Together with the excretion of root exudates, this effect leads to strongly modified microenvironments at the root surface and in the rhizosphere compared to unvegetated sediment, especially with respect to the availability of oxygen, organic carbon, and inorganic nitrogen. We hypothesize that macrophyte species create specific niches for ammonia oxidizing and nitrate-reducing bacteria in their rhizosphere, leading to plant-dependant differences in abundance, activity and composition of these microbial communities between root surface (rhizoplane), rhizosphere and unvegetated sediment. Comparative investigations are carried out focussing on the macrophyte species Littorella uniflora, Juncus bulbosus and Myriophyllum spicatum. Microsensor measurements confirmed the photosynthesis-dependant, species-specific release of oxygen into the rhizosphere; batch incubations indicated a higher nitrification potential in the rhizosphere of Littorella uniflora compared to unvegetated sediment, and will be complemented with the determination of rates of coupled nitrification-denitrification using the 15N isotope pairing technique. Ammonia-oxidizing and nitrate-reducing populations are analyzed based on the ammonia monooxygenase gene (amoA) and the nitrate reductase gene (narG) as functional markers. Preliminary data indicate that there in fact exist differences in the community composition of ammonia oxidizing bacteria between the root surface, the rhizosphere and unvegetated sediment and between plant species, however, differences in the community composition among sampling sites also suggest a strong impact of the chemical properties of the sediment.

Herrmann, Martina; Schramm, Andreas

2006-01-01

343

Evaluation of droplet digital PCR for characterizing plasmid reference material used for quantifying ammonia oxidizers and denitrifiers.  

Science.gov (United States)

DNA reference materials of certified value have a critical function in many analytical processes of DNA measurement. Quantification of amoA genes in ammonia oxidizing bacteria (AOB) and archaea (AOA), and of nirS and nosZ genes in the denitrifiers is very important for determining their distribution and abundance in the natural environment. A plasmid reference material containing nirS, nosZ, amoA-AOB, and amoA-AOA is developed to provide a DNA standard with copy number concentration for ensuring comparability and reliability of quantification of these genes. Droplet digital PCR (ddPCR) was evaluated for characterization of the plasmid reference material. The result revealed that restriction endonuclease digestion of plasmids can improve amplification efficiency and minimize the measurement bias of ddPCR. Compared with the conformation of the plasmid, the size of the DNA fragment containing the target sequence and the location of the restriction site relative to the target sequence are not significant factors affecting plasmid quantification by ddPCR. Liquid chromatography-isotope dilution mass spectrometry (LC-IDMS) was used to provide independent data for quantifying the plasmid reference material. The copy number concentration of the digested plasmid determined by ddPCR agreed well with that determined by LC-IDMS, improving both the accuracy and reliability of the plasmid reference material. The reference value, with its expanded uncertainty (k?=?2), of the plasmid reference material was determined to be (5.19?±?0.41)?×?10(9) copies ?L(-1) by averaging the results of two independent measurements. Consideration of the factors revealed in this study can improve the reliability and accuracy of ddPCR; thus, this method has the potential to accurately quantify DNA reference materials. PMID:24493332

Dong, Lianhua; Meng, Ying; Wang, Jing; Liu, Yingying

2014-02-01

344

Gaseous diffusion -- the enrichment workhorse  

International Nuclear Information System (INIS)

Construction of the first large-scale gaseous diffusion facility was started as part of the Manhattan Project in Oak Ridge, Tennessee, in 1943. This facility, code named ''K-25,'' began operation in January 1945 and was fully on stream by September 1945. Four additional process buildings were later added in Oak Ridge as the demand for enriched uranium escalated. New gaseous diffusion plants were constructed at Paducah, Kentucky, and Portsmouth, Ohio, during this period. The three gaseous diffusion plants were the ''workhorses'' which provided the entire enriched uranium demand for the United States during the 1950s and 1960s. As the demand for enriched uranium for military purposes decreased during the early 1960s, power to the diffusion plants was curtailed to reduce production. During the 1960s, as plans for the nuclear power industry were formulated, the role of the diffusion plants gradually changed from providing highly-enriched uranium for the military to providing low-enriched uranium for power reactors

345

Why is Brazil enriching uranium?  

Energy Technology Data Exchange (ETDEWEB)

In Brazil construction began in 1971 on Angra 1, a 626 MW Westinghouse pressurized water reactor (PWR). It was completed in 1984. Later, Angra 2 (a Kraftwerk Union PWR) achieved commercial operation in 2000. Brazil is considering the construction of seven nuclear power plants over the next 15 years. In preparation for this nuclear industry expansion, Brazil is building a uranium enrichment facility to provide nuclear fuel for Angra 1 and 2 starting in 2010 at Resende in the state of Rio de Janeiro, and collated with nuclear fuel fabrication facilities. This paper investigates whether the Resende Enrichment Facility will be able to provide uranium enrichment services at a cost lower than the international market price. We find that while Brazil is unlikely to be internationally competitive in the enrichment market, the Resende Enrichment Facility completes the front end of Brazil's nuclear fuel cycle. This assures uninterrupted nuclear fuel to its currently operating light water reactors, while providing the option of expanding capacity, lowering cost, and competing in the international nuclear fuel market after 2020. (author)

Cabrera-Palmer, Belkis [Center for International Security and Cooperation (CISAC), Stanford University, Stanford, CA 94305-6165 (United States); Rothwell, Geoffrey [Department of Economics, Stanford University, Stanford, CA 94305-6072 (United States)

2008-07-15

346

Uranium enrichment: technology, economics, capacity  

International Nuclear Information System (INIS)

Large-scale enrichment of uranium has now been carried out for 40 years. While the gaseous diffusion process was the original choice of several countries and continues today to provide the major component of the world production of separative work, the last two decades have witnessed the development of a number of alternative processes for enrichment. These processes, which are being studied and deployed around the world, offer a wide range of technical and economic characteristics which will be useful in assuring adequate capacity to meet projected reactor fuel market needs through the rest of this century at competitive prices. With present uncertainties in future enriched uranium needs, it is apparent that flexibility in the deployment and operation of any enrichment process will be one of the prime considerations for the future. More economical production of separative work not only can have a beneficial impact on reactor fuel costs, but also tends to conserve natural uranium resources. This paper reviews the world scene in the enrichment component of the fuel cycle, including existing or planned commercial-scale facilities and announced R and D efforts on various processes

347

Why is Brazil enriching uranium?  

International Nuclear Information System (INIS)

In Brazil construction began in 1971 on Angra 1, a 626 MW Westinghouse pressurized water reactor (PWR). It was completed in 1984. Later, Angra 2 (a Kraftwerk Union PWR) achieved commercial operation in 2000. Brazil is considering the construction of seven nuclear power plants over the next 15 years. In preparation for this nuclear industry expansion, Brazil is building a uranium enrichment facility to provide nuclear fuel for Angra 1 and 2 starting in 2010 at Resende in the state of Rio de Janeiro, and collated with nuclear fuel fabrication facilities. This paper investigates whether the Resende Enrichment Facility will be able to provide uranium enrichment services at a cost lower than the international market price. We find that while Brazil is unlikely to be internationally competitive in the enrichment market, the Resende Enrichment Facility completes the front end of Brazil's nuclear fuel cycle. This assures uninterrupted nuclear fuel to its currently operating light water reactors, while providing the option of expanding capacity, lowering cost, and competing in the international nuclear fuel market after 2020

348

Insights into the Effect of Soil pH on N2O and N2 Emissions and Denitrifier Community Size and Activity ?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The objective of this study was to investigate how changes in soil pH affect the N2O and N2 emissions, denitrification activity, and size of a denitrifier community. We established a field experiment, situated in a grassland area, which consisted of three treatments which were repeatedly amended with a KOH solution (alkaline soil), an H2SO4 solution (acidic soil), or water (natural pH soil) over 10 months. At the site, we determined field N2O and N2 emissions using the 15N gas flux method and...

C?uhel, Jir?i?; S?imek, Miloslav; Laughlin, Ronnie J.; Bru, David; Che?neby, Dominique; Watson, Catherine J.; Philippot, Laurent

2010-01-01

349

Effects of Heavy Metal Contamination upon Soil Microbes: Lead-induced Changes in General and Denitrifying Microbial Communities as Evidenced by Molecular Markers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Lead (Pb) is a common environmental contaminant found in soils. Unlike other metals, Pb has no biological role, and is potentially toxic to microorganisms. Effects of low (1 ppm) and high (500-2000) levels of lead (Pb) upon the soil microbial community was investigated by the PCR/DGGE analysis of the 16S and nirK gene markers, indicative of general microbial community and denitrifying community, respectively. Community analysis by use of those markers had shown that Pb has detectable effects ...

Maria Begonia; Dmitri Sobolev

2008-01-01

350

Molecular Diversity of Denitrifying Genes in Continental Margin Sediments within the Oxygen-Deficient Zone off the Pacific Coast of Mexico  

Digital Repository Infrastructure Vision for European Research (DRIVER)

To understand the composition and structure of denitrifying communities in the oxygen-deficient zone off the Pacific coast of Mexico, the molecular diversity of nir genes from sediments obtained at four stations was examined by using a PCR-based cloning approach. A total of 50 operational taxonomic units (OTUs) for nirK and 82 OTUs for nirS were obtained from all samples. Forty-four of the nirS clones and 31 of the nirK clones were sequenced; the levels of similarity of the nirS clones were 5...

Liu, Xueduan; Tiquia, Sonia M.; Holguin, Gina; Wu, Liyou; Nold, Stephen C.; Devol, Allan H.; Luo, Kuan; Palumbo, Anthony V.; Tiedje, James M.; Zhou, Jizhong

2003-01-01

351

Biotransformation of 2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12-Hexaazaisowurtzitane (CL-20) by Denitrifying Pseudomonas sp. Strain FA1  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The microbial and enzymatic degradation of a new energetic compound, 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), is not well understood. Fundamental knowledge about the mechanism of microbial degradation of CL-20 is essential to allow the prediction of its fate in the environment. In the present study, a CL-20-degrading denitrifying strain capable of utilizing CL-20 as the sole nitrogen source, Pseudomonas sp. strain FA1, was isolated from a garden soil. Studies with i...

Bhushan, Bharat; Paquet, Louise; Spain, Jim C.; Hawari, Jalal

2003-01-01

352

Two-Stage Mineralization of Phenanthrene by Estuarine Enrichment Cultures  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 U...

Guerin, William F.; Jones, Galen E.

1988-01-01

353

21 CFR 866.2330 - Enriched culture medium.  

Science.gov (United States)

21 Food and Drugs 8 2010-04-01 2010-04-01... 866.2330 Section 866.2330 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT... MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Microbiology Devices §...

2010-04-01

354

Selective Enrichment of a Methanol-Utilizing Consortium Using Pulp and Paper Mill Waste Streams  

Science.gov (United States)

Efficient utilization of carbon inputs is critical to the economic viability of the current forest products sector. Input carbon losses occur in various locations within a pulp mill, including losses as volatile organics and wastewater. Opportunities exist to capture this carbon in the form of value-added products such as biodegradable polymers. Wasteactivated sludge from a pulp mill wastewater facility was enriched for 80 days for a methanol-utilizing consortium with the goal of using this consortium to produce biopolymers from methanol-rich pulp mill waste streams. Five enrichment conditions were utilized: three high-methanol streams from the kraft mill foul condensate system, one methanol-amended stream from the mill wastewater plant, and one methanol-only enrichment. Enrichment reactors were operated aerobically in sequencing batch mode at neutral pH and 25°C with a hydraulic residence time and a solids retention time of 4 days. Non-enriched waste activated sludge did not consume methanol or reduce chemical oxygen demand. With enrichment, however, the chemical oxygen demand reduction over 24-h feed/ decant cycles ranged from 79 to 89%, and methanol concentrations dropped below method detection limits. Neither the non-enriched waste-activated sludge nor any of the enrichment cultures accumulated polyhydroxyalkanoates (PHAs) under conditions of nitrogen sufficiency. Similarly, the non-enriched waste activated sludge did not accumulate PHAs under nitrogen-limited conditions. By contrast, enriched cultures accumulated PHAs to nearly 14% on a dry weight basis under nitrogen-limited conditions. This indicates that selectively enriched pulp mill waste activated sludge can serve as an inoculum for PHA production from methanol-rich pulp mill effluents.

Mockos, Gregory R.; Smith, William A.; Loge, Frank J.; Thompson, David N.

355

Selective enrichment of a methanol-utilizing consortium using pulp & paper mill waste streams  

Energy Technology Data Exchange (ETDEWEB)

Efficient utilization of carbon inputs is critical to the economic viability of the current forest products sector. Input carbon losses occur in various locations within a pulp mill, including losses as volatile organics and wastewater . Opportunities exist to capture this carbon in the form of value-added products such as biodegradable polymers. Waste activated sludge from a pulp mill wastewater facility was enriched for 80 days for a methanol-utilizing consortium with the goal of using this consortium to produce biopolymers from methanol-rich pulp mill waste streams. Five enrichment conditions were utilized: three high-methanol streams from the kraft mill foul condensate system, one methanol-amended stream from the mill wastewater plant, and one methanol-only enrichment. Enrichment reactors were operated aerobically in sequencing batch mode at neutral pH and 25°C with a hydraulic residence time and a solids retention time of four days. Non-enriched waste activated sludge did not consume methanol or reduce chemical oxygen demand. With enrichment, however, the chemical oxygen demand reduction over 24 hour feed/decant cycles ranged from 79 to 89 %, and methanol concentrations dropped below method detection limits. Neither the non-enriched waste activated sludge nor any of the enrichment cultures accumulated polyhydroxyalkanoates (PHAs) under conditions of nitrogen sufficiency. Similarly, the non-enriched waste activated sludge did not accumulate PHAs under nitrogen limited conditions. By contrast, enriched cultures accumulated PHAs to nearly 14% on a dry weight basis under nitrogen limited conditions. This indicates that selectively-enriched pulp mill waste activated sludge can serve as an inoculum for PHA production from methanol-rich pulp mill effluents.

Gregory R. Mockos; William A. Smith; Frank J. Loge; David N. Thompson

2007-04-01

356

Enrichment of light hydrocarbon mixture  

Science.gov (United States)

Light hydrocarbon enrichment is accomplished using a vertically oriented distillation column having a plurality of vertically oriented, nonselective micro/mesoporous hollow fibers. Vapor having, for example, both propylene and propane is sent upward through the distillation column in between the hollow fibers. Vapor exits neat the top of the column and is condensed to form a liquid phase that is directed back downward through the lumen of the hollow fibers. As vapor continues to ascend and liquid continues to countercurrently descend, the liquid at the bottom of the column becomes enriched in a higher boiling point, light hydrocarbon (propane, for example) and the vapor at the top becomes enriched in a lower boiling point light hydrocarbon (propylene, for example). The hollow fiber becomes wetted with liquid during the process.

Yang, Dali (Los Alamos, NM); Devlin, David (Santa Fe, NM); Barbero, Robert S. (Santa Cruz, NM); Carrera, Martin E. (Naperville, IL); Colling, Craig W. (Warrenville, IL)

2011-11-29

357

The uranium enrichment services market  

International Nuclear Information System (INIS)

There are two main processes for the enrichment of uranium, to give uranium with a higher U235 content than occurs naturally (usually 2 to 4% of the total). One is gaseous diffusion, the other is the gas centrifuge process. These and other less common methods (which are not used commercially), are described. The role of Urenco in the supply of enriched uranium is explained. Financed by the UK, Netherlands and Federal Republic of Germany, it has uranium enrichment plants at Capenhurst in England, Urenco Nederland at Almelo and Urenco Deutschland at Gronau. Other suppliers are also mentioned. Demand fluctuations are discussed. Price developments and the total demand and contracts signed by the supplier up to the year 2000 are illustrated. (UK)

358

Advances in uranium enrichment processes  

International Nuclear Information System (INIS)

Advances in gas centrifuges and development of the atomic vapour laser isotope separation process promise substantial reductions in the cost of enriched uranium. The resulting reduction in LWR fuel costs could seriously erode the economic advantage of CANDU, and in combination with LWR design improvements, shortened construction times and increased operational reliability could allow the LWR to overtake CANDU. CANDU's traditional advantages of neutron economy and high reliability may no longer be sufficient - this is the challenge. The responses include: combining neutron economy and dollar economy by optimizing CANDU for slightly enriched uranium fuel; developing cost-reducing improvements in design, manufacture and construction; and reducing the cost of heavy water. Technology is a renewable resource which must be continually applied to a product for it to remain competitive in the decades to come. Such innovation is a prerequisite to Canada increasing her share of the international market for nuclear power stations. The higher burn-up achievable with enriched fuel in CANDU can reduce the fuel cycle costs by 20 to 40 percent for a likely range of costs for yellowcake and separative work. Alternatively, some of the benefits of a higher fissile content can take the form of a cheaper reactor core containing fewer fuel channels and less heavy water, and needing only a single fuelling machine. An opportunity that is linked to this need to introduce an enriched uranium fuel cycle into CANDU is to build an enrichment business in Canada. This could offer greater value added to our uranium exports, security of supply for enriched CANDUs, technological growth in Canada and new employment opportunities. AECL has a study in progress to define this opportunity

359

Uranium enriched granites in Sweden  

International Nuclear Information System (INIS)

Granites with uranium contents higher than normal occur in a variety of geological settings in the Swedish Precambrian, and represent a variety of granite types and ages. They may have been generated by (1) the anatexis of continental crust (2) processes occurring at a much greater depth. They commonly show enrichement in F, Sn, W and/or Mo. Only in one case is an important uranium mineralization thought to be directly related to a uranium-enriched granite, while the majority of epigenetic uranium mineralizations with economic potential are related to hydrothermal processes in areas where the bedrock is regionally uranium-enhanced. (Authors)

360

Uranium enrichment. 1980 annual report  

International Nuclear Information System (INIS)

This report contains data and related information on the production of enriched uranium at the gaseous diffusion plants and an update on the construction and project control center for the gas centrifuge plant. Power usage at the gaseous diffusion plants is illustrated. The report contains several glossy color pictures of the plants and processes described. In addition to gaseous diffusion and the centrifuge process, three advanced isotope separation process are now being developed. The business operation of the enrichment plants is described; charts on revenue, balance sheets, and income statements are included

 
 
 
 
361

AVLIS enrichment of medical isotopes  

International Nuclear Information System (INIS)

Under the Sponsorship of the United states Enrichment Corporation (USEC), we are currently investigating the large scale separation of several isotopes of medical interest using atomic vapor isotope separation (AVLIS). This work includes analysis and experiments in the enrichment of thallium 203 as a precursor to the production of thallium 201 used in cardiac imaging following heart attacks, on the stripping of strontium 84 from natural strontium as precursor to the production of strontium 89, and on the stripping of lead 210 from lead used in integrated circuits to reduce the number of alpha particle induced logic errors

362

Business History : A Cultural and Narrative Approach  

DEFF Research Database (Denmark)

This article argues that a cultural and narrative perspective can enrich the business history field, encourage new and different questions and answers, and provide new ways of thinking about methods and empirical material. It discusses what culture is and how it relates to narratives. Taking a cultural and narrative approach may affect questions, sources, and methodologies, as well as the status of our results. Finally, a narrative approach may contribute to our historical understanding of entrepreneurship and globalization.

Hansen, Per H.

2012-01-01

363

Enriched Fell Bundles and Spaceoids  

CERN Document Server

We propose a definition of involutive categorical bundle (Fell bundle) enriched in an involutive monoidal category and we argue that such a structure is a possible suitable environment for the formalization of different equivalent versions of spectral data for commutative C*-categories.

Bertozzini, Paolo; Lewkeeratiyutkul, Wicharn

2011-01-01

364

Environmental Development Plan: uranium enrichment  

International Nuclear Information System (INIS)

This Environmental Development Plan identifies and examines the environmental, health, safety, and socioeconomic concerns and corresponding requirements associated with the DOE research, development, demonstration, and operation of the Uranium Enrichment program, including the gaseous diffusion process, the centrifuge process, centrifuge rotor fabrication, and related research and development activities

365

Enriched uranium recovery flowsheet improvements  

International Nuclear Information System (INIS)

Savannah River uses 7.5% TBP to recover and purify enriched uranium. Adequate decontamination from fission products is necessary to reduce personnel exposure and to ensure that the enriched uranium product meets specifications. Initial decontamination of the enriched uranium from the fission products is carried out in the 1A bank, 16 stages of mixer-settlers. Separation of the enriched uranium from the fission product, 95Zr, has been adequate, but excessive solvent degradation caused by the long phase contact times in the mixer-settlers has limited the 95Zr decontamination factor (DF). An experimental program is investigating the replacement of the current 1A bank with either centrifugal contactors or a combination of centrifugal contactors and mixer-settlers. Experimental work completed has compared laboratory-scale centrifugal contactors and mixer-settlers for 95Zr removal efficiencies. Feed solutions spiked with actual plant solutions were used. The 95Zr DF was significantly better in the mixer-settlers than in the centrifugal contactors. As a result of this experimental study, a hybrid equipment flowsheet has been proposed for plant use. The hybrid equipment flowsheet combines the advantages of both types of solvent extraction equipment. Centrifugal contactors would be utilized in the extraction and initial scrub sections, followed by additional scrub stages of mixer-settlers

366

Enrichment and characterization of sulfate reducing, naphthalene degrading microorganisms  

Science.gov (United States)

Polycyclic aromatic hydrocarbons (PAH) are pollutants of great concern due to their potential toxicity, mutagenicity and carcinogenicity. PAH are widely distributed in the environment by accidental discharges during the transport, use and disposal of petroleum products, and during forest and grass fires. Caused by their hydrophobic nature, PAH basically accumulate in sediments from where they are slowly released into the groundwater. Although generally limited by the low water solubility of PAH, microbial degradation is one of the major mechanisms leading to the complete clean-up of PAH-contaminated sites. Whereas organisms and biochemical pathways responsible for the aerobic breakdown of PAH are well known, anaerobic PAH biodegradation is less understood; only a few anaerobic PAH degrading cultures have been described. We studied the anaerobic PAH degradation in a microcosm approach to enrich anaerobic PAH degraders. Anoxic groundwater and sediment samples were used as inoculum. Groundwater samples were purchased from the erstwhile gas works facility and a former wood impregnation site. In contrast, sources of sediment samples were a former coal refining area and an old fuel depot. Samples were incubated in anoxic mineral salt medium with naphthalene as sole carbon source and sulfate as terminal electron acceptor. Grown cultures were characterized by feeding with 13C-labeled naphthalene, 16S rRNA gene sequencing using an Illumina® approach, and functional proteome analyses. Finally, six enrichment cultures able to degrade naphthalene under anoxic conditions were established. First results point to a dominance of identified sequences affiliated to the freshwater sulfate-reducing strain N47, which is a known anaerobic naphthalene degrader, in four out of the six enrichments. In those enrichments, peptides related to the pathway of anoxic naphthalene degradation in N47 were abundant. Overall the data underlines the importance of Desulfobacteria for natural attenuation of environmental contaminants. Understanding of diversity and physiology of anaerobic PAH degradation will contribute to remediation efforts of low-oxygen environments such as aquifers or river sediments.

Steffen, Kümmel; Florian-Alexander, Herbst; Márcia, Duarte; Dietmar, Pieper; Jana, Seifert; Bergen Martin, von; Hans-Hermann, Richnow; Carsten, Vogt

2014-05-01

367

[Optimization and stability of denitrifying-phosphorus removal in a two-sludge system for treating wastewater with low carbon source].  

Science.gov (United States)

Poly-beta-hydroxybutyrate (PHB) could be efficiently accumulated under optimized conditions in a sequencing batch moving bed biological reactor (SBMBBR), and a high performance of denitrifying phosphorus removal in the reactor could be achieved by coupling with a two-sludge system. Denitrifying phosphorus removal achieved the highest efficiency under influent COD of 200 mg/L, neutral pH and stirring speed of 80 r/min. The removal rates of phosphorus, NO3(-)-N and NO2(-)-N reached 83.7%, 81.4% and above 100%, respectively. High biomass in the SBMBBR is one of keys to improve the performance in removal of nitrogen and phosphorus. When the SBMBBR was conducted under a two-sludge system, stable and high performance was obtained. Removal rates of phosphorus and TN reached 89.2% and 84.5% under the influent COD of 140-170 mg/L and TN of 34-42 mg/L, respectively. In the process, phosphorus content in excess sludge approached to that in the feeding, and other path of phosphorus removal was not found. PMID:21717742

Zhang, Yao-Bin; Xing, Ya-Bin; Qin, Si-Fei; Quan, Xie; Chen, Shuo

2011-04-01

368

Spatial distribution and viability of nitrifying, denitrifying and ANAMMOX bacteria in biofilms of sponge media retrieved from a full-scale biological nutrient removal plant.  

Science.gov (United States)

The spatial distribution and activities of nitrifying and denitrifying bacteria in sponge media were investigated using diverse tools, because understanding of in situ microbial condition of sponge phase is critical for the successful design and operation of sponge media process. The bacterial consortia within the media was composed of diverse groups including a 14.5% Nitrosomonas spp.-like ammonia oxidizing bacteria (AOB), 12.5% Nitrobacter spp.-like nitrite oxidizing bacteria (NOB), 2.0% anaerobic ammonium-oxidizing (ANAMMOX) bacteria and 71.0% other bacteria. The biofilm appeared to be most dense in the relatively outer region of the media and gradually decreased with depth, but bacterial viabilities showed space-independent feature. The fluorescent in situ hybridization results revealed that AOB and NOB co-existed in similar quantities on the side fragments of the media, which was reasonably supported by the microelectrode measurements showing the concomitant oxidation of NH(4) (+) and production of NO(3) (-) in this zone. However, a significantly higher fraction of AOB was observed in the center than side fragment. As with the overall biofilm density profile, the denitrifying bacteria were also more abundant on the side than in the center fragments. ANAMMOX bacteria detected throughout the entire depth offer another advantage for the removal of nitrogen by simultaneously converting NH(4) (+) and NO(2) (-) to nitrogen gas. PMID:22367527

Chae, Kyu-Jung; Kim, Sung-Min; Oh, Sang-Eun; Ren, Xianghao; Lee, Jinwook; Kim, In S

2012-09-01

369

Safeguards Culture  

Energy Technology Data Exchange (ETDEWEB)

The concepts of nuclear safety and security culture are well established; however, a common understanding of safeguards culture is not internationally recognized. Supported by the National Nuclear Security Administration, the authors prepared this report, an analysis of the concept of safeguards culture, and gauged its value to the safeguards community. The authors explored distinctions between safeguards culture, safeguards compliance, and safeguards performance, and evaluated synergies and differences between safeguards culture and safety/security culture. The report concludes with suggested next steps.

Frazar, Sarah L.; Mladineo, Stephen V.

2012-07-01

370

Anaerobic degradation of benzene by enriched consortia with humic acids as terminal electron acceptors  

International Nuclear Information System (INIS)

Highlights: ? Enriched consortia were able to couple the anaerobic degradation of benzene to the reduction of humic acids. ? Electron-equivalents derived from anaerobic benzene oxidation were highly recovered as reduced humic acids. ? Several species from classes ?-, ?- and ?-Proteobacteria were enriched during the anaerobic degradation of benzene. - Abstract: The anaerobic degradation of benzene coupled to the reduction of humic acids (HA) was demonstrated in two enriched consortia. Both inocula were able to oxidize benzene under strict anaerobic conditions when the humic model compound, anthraquinone-2,6-disulfonate (AQDS), was supplied as terminal electron acceptor. An enrichment culture originated from a contaminated soil was also able to oxidize benzene linked to the reduction of highly purified soil humic acids (HPSHA). In HPSHA-amended cultures, 9.3 ?M of benzene were degraded, which corresponds to 279 ± 27 micro-electron equivalents (?Eq) L-1, linked to the reduction of 619 ± 81 ?Eq L-1 of HPSHA. Neither anaerobic benzene oxidation nor reduction of HPSHA occurred in sterilized controls. Anaerobic benzene oxidation did not occur in soil incubations lacking HPSHA. Furthermore, negligible reduction of HPSHA occurred in the absence of benzene. The enrichment culture derived from this soil was dominated by two ?-Proteobacteria phylotypes. A benzene-degrading AQDS-reducing enrichment originated from a sediment sample showed the pediment sample showed the prevalence of different species from classes ?-, ?- and ?-Proteobacteria. The present study provides clear quantitative demonstration of anaerobic degradation of benzene coupled to the reduction of HA.

371

Relationship between N2O Fluxes from an Almond Soil and Denitrifying Bacterial Populations Estimated by Quantitative PCR  

Science.gov (United States)

Cultivated soils emit substantial quantities of nitrous oxide (N2O), a greenhouse gas with almost 300 times the radiative forcing potential of CO2. Agriculture-related activities generate from 6 to 35 Tg N2O-N per year, or about 60 to 70% of global production. The microbial processes of nitrification, denitrification and nitrifier denitrification are major biogenic sources of N2O to the atmosphere from soils. Denitrification is considered the major source of N2O especially when soils are wet. The microbial N transformations that produce N2O depend primarily on nitrogen (N) fertilizer, with water content, available carbon and soil temperature being secondary controllers. Despite the fact that microbial processes are responsible for N2O emissions, very little is known about the numbers or types of populations involved. The objective of this study was to relate changes in denitrifying population densities, using quantitative PCR (qPCR) of functional genes, to N2O emissions in a fertilized almond orchard. Quantitative PCR targeted three specific genes involved in denitrification: nirS, nirK and nosZ. Copy numbers of the genes were related back to population densities and the portion of organisms likely to produce nitrous oxide. The study site, a 21.7 acre almond orchard fitted with micro-sprinklers, was fertigated (irrigated and fertilized simultaneously) with 50 lbs/acre sodium nitrate in late March 2008, then irrigated weekly. Immediately after the initial fertigation, fluxes of N2O and CO2, moisture content, inorganic N and denitrification gene copy numbers were measured 6 times over 24 days. Despite the fact that N2O emissions increased following fertigation, there was no consistent increase in any of the targeted genes. The genes nirK and nirS ranged from 0.4-1.4 × 107 and 0.4-1.4 × 108, whereas nosZ ranged from 2-8 × 106 copy numbers per g soil, respectively. Considerable variation, compounded by the small sample sizes used for DNA analysis, made it difficult to discern trends over time. High spatial variability was also observed with one of the field replicates have a substantially higher flux of N2O. This replicate also had the highest water filled pore space (WFPS) and water content, factors that likely favored denitrification. Water saturation of soil air space, optimal at >60% for denitrification to occur, was relatively low in the other field replicates. Thus, the low N2O flux measurements and gene copy numbers agreed in supporting the hypothesis denitrification was relatively low under the environmental conditions of these particular almond soils.

Matiasek, M.; Suddick, E. C.; Smart, D. R.; Scow, K. M.

2008-12-01

372

Trace elements affect methanogenic activity and diversity in enrichments from subsurface coal bed produced water  

Directory of Open Access Journals (Sweden)

Full Text Available Microbial methane from coal beds accounts for a significant and growing percentage of natural gas worldwide. Our knowledge of physical and geochemical factors regulating methanogenesis is still in its infancy. We hypothesized that in these closed systems, trace elements (as micronutrients are a limiting factor for methanogenic growth and activity. Trace elements are essential components of enzymes or cofactors of metabolic pathways associated with methanogenesis. This study examined the effects of eight trace elements (iron, nickel, cobalt, molybdenum, zinc, manganese, boron, and copper on methane production, on mcrA transcript levels, and on methanogenic community structure in enrichment cultures obtained from coal bed methane well produced water samples from the Powder River Basin, Wyoming. Methane production was shown to be limited both by a lack of additional trace elements as well as by the addition of an overly concentrated trace element mixture. Addition of trace elements at concentrations optimized for standard media enhanced methane production by 37%. After seven days of incubation, the levels of mcrA transcripts in enrichment cultures with trace element amendment were much higher than in cultures without amendment. Transcript levels of mcrA correlated positively with elevated rates of methane production in supplemented enrichments (R2=0.95. Metabolically-active methanogens, identified by clone sequences of mcrA mRNA retrieved from enrichment cultures, were closely related to Methanobacterium subterraneum and Methanobacterium formicicum. Enrichment cultures were dominated by M. subterraneum and had slightly higher predicted methanogenic richness, but less diversity than enrichment cultures without amendments. These results suggest that varying concentrations of trace elements in produced water from different subsurface coal wells may cause changing levels of coal bed methane production and alter the composition of the active methanogenic community.

KlausNüsslein

2012-05-01

373

Nitrous oxide nitrification and denitrification 15N enrichment factors from Amazon forest soils.  

Science.gov (United States)

The isotopic signatures of 15N and 18O in N2O emitted from tropical soils vary both spatially and temporally, leading to large uncertainty in the overall tropical source signature and thereby limiting the utility of isotopes in constraining the global N2O budget. Determining the reasons for spatial and temporal variations in isotope signatures requires that we know the isotope enrichment factors for nitrification and denitrification, the two processes that produce N2O in soils. We have devised a method for measuring these enrichment factors using soil incubation experiments and report results from this method for three rain forest soils collected in the Brazilian Amazon: soil with differing sand and clay content from the Tapajos National Forest (TNF) near Santarém, Pará, and Nova Vida Farm, Rondônia. The 15N enrichment factors for nitrification and denitrification differ with soil texture and site: -111 per thousand +/- 12 per thousand and -31 per thousand +/- 11 per thousand for a clay-rich Oxisol (TNF), -102 per thousand +/- 5 per thousand and -45 per thousand +/- 5 per thousand for a sandier Ultisol (TNF), and -10.4 per thousand +/- 3.5 per thousand (enrichment factor for denitrification) for another Ultisol (Nova Vida) soil, respectively. We also show that the isotopomer site preference (delta15Nalpha - delta15Nbeta, where alpha indicates the central nitrogen atom and beta the terminal nitrogen atom in N2O) may allow differentiation between processes of production and consumption of N2O and can potentially be used to determine the contributions of nitrification and denitrification. The site preferences for nitrification and denitrification from the TNF-Ultisol incubated soils are: 4.2 per thousand +/- 8.4 per thousand and 31.6 per thousand +/- 8.1 per thousand, respectively. Thus, nitrifying and denitrifying bacteria populations under the conditions of our study exhibit significantly different 15N site preference fingerprints. Our data set strongly suggests that N2O isotopomers can be used in concert with traditional N2O stable isotope measurements as constraints to differentiate microbial N2O processes in soil and will contribute to interpretations of the isotopic site preference N2O values found in the free troposphere. PMID:17205894

Pérez, Tibisay; Garcia-Montiel, Diana; Trumbore, Susan; Tyler, Stanley; de Camargo, Plínio; Moreira, Marcelo; Piccolo, Marisa; Cerri, Carlos

2006-12-01

374

Culture matters.  

Science.gov (United States)

Zebaa Arif reflects on changes during her career as a mental health nurse in relation to cultural care issues: Cultural awareness is becoming embedded in patient care. All aspects of care are influenced by cultural beliefs and should form part of assessment. Leadership is essential in influencing cultural care, as is organisational commitment. PMID:16262169

Arif, Zeba

375

Tritium electrolytic enrichment using metal cells  

International Nuclear Information System (INIS)

Results of reproducibility of enrichment parameter for cells are reported and experience with a new set of 24 cells is described with the initial volume of water of 500 ml used in the electrolytic enrichment of tritium in water samples

376

Uranium enrichment (a strategy analysis overview)  

International Nuclear Information System (INIS)

An analysis of available information on enrichment technology, separative work supply and demand, and SWU cost is presented. Estimates of present and future enrichment costs are provided for use in strategy analyses of alternate nuclear fuel cycles and systems. (auth)

377

Enrichment demand boosts SWU prices  

International Nuclear Information System (INIS)

The enrichment market is picking up significantly on very brisk demand. US utilities, which normally purchase material nine months to a year ahead of time, are already hitting the market to fill their 1996 requirements. In June, two non-US utilities, one European entity and a US utility bought SWUs, the entity in an off-market deal. But that doesn't tell the whole story. Three other US utilities entered the market during the month. Meanwhile, we count 13 more utilities getting ready to hit the market for more than 4 million SWUs. Why the surge in demand? Utilities, uncertain of the role to be played by the new US Enrichment Corp. and seeking to take advantage of low interest rates, are implementing buy and hold strategies. As a result, the upper end of NUKEM's SWU price range inched up to $78. The lower end dipped to $67 based on the European deal

378

Uranium enrichment plans and policies  

International Nuclear Information System (INIS)

Significant progress has been made in US efforts to expand its enrichment capacity. The Cascade Improvement Program (CIP) and Cascade Upgrading Program (CUP) are now complete at Oak Ridge and Paducah and almost complete at Portsmouth. Considerable progress has also been made in constructing the Gas Centrifuge Enrichment Plant (GCEP), and physical construction of the first process building is well under way. Current plans are to have two process buildings on-line by 1989 with the remaining six buildings to be added sequentially as needed to meet demand. The status of DOE enrichment services contracts is essentially unchanged from that reported at last year's seminar. The OUEA latest forecast of nuclear power growth, however, is considerably lower than reported last year, although a leveling trend is becoming apparent. The Variable Tails Assay Option (VTAO) of the AFC contract was made available for the third time for FY 1983. The DOE inventories of natural uranium still remain high. The Department of Energy will dispose of this material by using it for Government programs and for enrichment plant operations. It appears that Government inventories of uranium are adequate through at least the mid-1990s. It remains DOE policy not to dispose of its natural uranium stocks through direct sales in the marketplace, except for very small quantities or if an emergency situation would exist and all reasonable attempts had been made, without success, to obtain natural uranium fromut success, to obtain natural uranium from commercial sources. Finally, with regard to DOE plans on future transaction tails assays, it still appears likely that the current 0.20 percent uranium-235 reference tails assay will be maintained until well into the 1990s, at which time it might be increased up to 0.25 percent uranium-235

379

Boron Enrichment in Martian Clay  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We have detected a concentration of boron in martian clay far in excess of that in any previously reported extra-terrestrial object. This enrichment indicates that the chemistry necessary for the formation of ribose, a key component of RNA, could have existed on Mars since the formation of early clay deposits, contemporary to the emergence of life on Earth. Given the greater similarity of Earth and Mars early in their geological history, and the extensive disruption of Earth's earliest minera...

Stephenson, James D.; Hallis, Lydia J.; Nagashima, Kazuhide; Freeland, Stephen J.

2013-01-01

380

Network-based functional enrichment  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Background Many methods have been developed to infer and reason about molecular interaction networks. These approaches often yield networks with hundreds or thousands of nodes and up to an order of magnitude more edges. It is often desirable to summarize the biological information in such networks. A very common approach is to use gene function enrichment analysis for this task. A major drawback of this method is that it ignores information about the edges in the net...

Poirel Christopher L; Owens Clifford C; Murali T M

2011-01-01

 
 
 
 
381

Austenite stabilization through manganese enrichment  

International Nuclear Information System (INIS)

A model is proposed to predict austenite stabilization through manganese partitioning between ferrite and austenite. The model predicts retained austenite fractions as a function of intercritical annealing temperature based on equilibrium phase fractions and solute contents. Thermodynamic data are used to calculate the Ms temperature of the enriched austenite in order to predict fresh martensite formation upon cooling to room temperature. An intercritical annealing temperature resulting in the greatest retained austenite fraction is predicted which correlates to some experimental observations.

382

The prospect of enriched boron products  

International Nuclear Information System (INIS)

A mass production technique for producing enriched boron was developed jointly by Kobe Steel and Stella Chemifa Co. in the 1990s. Enriched boron commercial production started in 2001 and since then, as a result of boron market research, several new enriched boron materials such as boron aluminum, boron acid, and boron carbide have been added to our production schedule. The demand for enriched boron is expected to increase rapidly if the material can be steadily supplied at a reasonable price. (author)

383

Environmental signatures of enrichment facilities  

International Nuclear Information System (INIS)

Environmental sampling is a potentially useful tool that could be used for the detection of undeclared enrichment facilities. However, this would be likely to require the use of sophisticated and expensive analytical techniques to evaluate 235U/238U ratios. It would be, therefore, unlikely to be an inexpensive approach to detect proliferation. The probability of detecting an enrichment operation will depend on the type of facility. A gaseous diffusion operation will be relatively difficult to detect in relation to an EMIS facility and a gaseous centrifuge plant will be more difficult still. Releases from an enrichment operation are likely to be restricted to atmospheric discharges. Aquatic discharges would be relatively easy to contain and it would be unwise to devise a sampling strategy based on the measurement of these. The detection of atmospheric discharges is likely to be dependent on meteorological conditions, in particular stability. Stable atmospheric conditions are the most favourable for detecting releases at significant distances from the plant. Given stable conditions, detection of an EMIS facility might be possible at a distance of several 10s of km

384

Enriching Music and Language Arts Experiences  

Science.gov (United States)

The article focuses on enriching music and language arts experiences of students. Music can enrich literature and language arts, poetry, theater arts, transitions, science, and math, as well as help meet special learner needs. A well-understood example of enrichment is the alphabet song. A music or classroom teacher using the alphabet song helps…

Flohr, John W.

2006-01-01

385

Urenco's contribution to the enrichment market  

International Nuclear Information System (INIS)

The paper deals with the Present status of Urenco Enrichment Plants and Order Book, Urenco's future development, The Western World enrichment supply situation, Urenco's Policy on the reliability of enrichment supplies, and its contribution to a reliable, stable and competitive world enrichment market. Urenco's current plant capacity and forward committed expansion plans up to 1990 and its present position in the western world enrichment market are described. The application of Urenco's centrifuge technology to the enrichment of recycles uranium and the relevance of laser enrichment development to Urenco are discussed. The paper next discusses the structure and main characteristics of the major sectional markets of the western world enrichment market, i.e. particularly in the United States, Western Europe and Asia (Japan, Korea and Taiwan). Urenco's contractual approach regarding the reliability of enrichment supplies is discussed, it is shown that Urenco's development of the centrifuge process to the point of economic maturity, Urenco's establishment of a multi-national commercial enrichment organization, Urenco's achievement in the world enrichment market by a commercial and competitive approach, Urenco's preparedness to negotiate suitable supply arrangements including the establishment of plants in other market areas have vastly contributed to a stabilisation of the world enrichment market. (J.P.N.)

386

How Did the IGM Become Enriched?  

CERN Document Server

The enrichment of the intergalactic medium with heavy elements is a process that lies at the nexus of poorly-understood aspects of physical cosmology. We review current understanding of the processes that may remove metals from galaxies, the basic predictions of these models, the key observational constraints on enrichment, and how intergalactic enrichment may be used to test cosmological simulations.

Aguirre, A; Aguirre, Anthony; Schaye, Joop

2006-01-01

387

Decoding cultural landscapes: guiding principles for the management of interpretation in cultural world heritage sites  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Conserving the cultural significance of heritage sites - as the guardians of social unity, place identity, and national pride - plays an essential role in maintaining sustainable social development, as well as preserving the variations identifying cultural groups and enriching the interaction between them. Consequently, and considering the importance of the built environment in communicating, as well as documenting, cultural messages, this research project, started in 2007, develops a set of ...