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1
Wang, James C., Joehassin Cordero, Yan Sun, Mayank Aranke, Randall Wolcott, Jane A. Colmer-Hamood, and Abdul N. Hamood. "Planktonic Growth ofPseudomonas aeruginosaaround a Dual-Species Biofilm Supports the Growth ofFusobacterium nucleatumwithin That Biofilm." International Journal of Otolaryngology 2017 (2017): 1–12. http://dx.doi.org/10.1155/2017/3037191.
Повний текст джерелаАнотація:
Purpose.The goal of this study was to understand the potential interaction betweenPseudomonas aeruginosaandFusobacterium nucleatumwithin the middle ear.Methods.We examined the microbiota of ear fluid and tympanostomy tubes (TTs) obtained from patients with posttympanostomy tube otorrhea. We also examined biofilms formed byP. aeruginosaandF. nucleatum, singly or together, under aerobic or anaerobic conditions.Results.While the facultative anaerobeP. aeruginosadominated the bacterial population within the ear fluid, strict anaerobes, includingF. nucleatum,dominated bacterial populations within the TTs.F. nucleatumwas able to grow under aerobic conditions only in the presence ofP. aeruginosa, whose growth reduced the level of dissolved oxygen within the broth to nearly anoxic condition within 4 h after inoculation. The presence ofP. aeruginosaallowedF. nucleatumto maintain its growth for 72 h within the dual-species biofilm but not within the planktonic growth. Visualization of the biofilms revealed coaggregation ofP. aeruginosaandF. nucleatum.Conclusion.Extrapolation of these results suggests that, within the middle ear fluid, the growth ofP. aeruginosaproduces the anaerobic conditions required for the growth ofF. nucleatum, both within effusion and within biofilms.
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Ye, Rick W., Wang Tao, Laura Bedzyk, Thomas Young, Mario Chen, and Liao Li. "Global Gene Expression Profiles of Bacillus subtilis Grown under Anaerobic Conditions." Journal of Bacteriology 182, no. 16 (August 15, 2000): 4458–65. http://dx.doi.org/10.1128/jb.182.16.4458-4465.2000.
Повний текст джерелаАнотація:
ABSTRACT Bacillus subtilis can grow under anaerobic conditions, either with nitrate or nitrite as the electron acceptor or by fermentation. A DNA microarray containing 4,020 genes from this organism was constructed to explore anaerobic gene expression patterns on a genomic scale. When mRNA levels of aerobic and anaerobic cultures during exponential growth were compared, several hundred genes were observed to be induced or repressed under anaerobic conditions. These genes are involved in a variety of cell functions, including carbon metabolism, electron transport, iron uptake, antibiotic production, and stress response. Among the highly induced genes are not only those responsible for nitrate respiration and fermentation but also those of unknown function. Certain groups of genes were specifically regulated during anaerobic growth on nitrite, while others were primarily affected during fermentative growth, indicating a complex regulatory circuitry of anaerobic metabolism.
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Janssen, Peter H. "Growth of Enterobacteria on Malonate Under Strictly Anaerobic Conditions." Systematic and Applied Microbiology 14, no. 1 (January 1991): 93–97. http://dx.doi.org/10.1016/s0723-2020(11)80367-x.
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Churchill, A. Coolidge. "Growth characteristics of Zostera marina seedlings under anaerobic conditions." Aquatic Botany 43, no. 4 (November 1992): 379–92. http://dx.doi.org/10.1016/0304-3770(92)90049-o.
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Kelly, W. J., R. V. Asmundson, and D. H. Hopcroft. "Growth ofLeuconostoc oenosunder Anaerobic Conditions." American Journal of Enology and Viticulture 40, no. 4 (1989): 277–82. http://dx.doi.org/10.5344/ajev.1989.40.4.277.
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Lee, Hoyul, Rena Ma, Michael C. Grimm, Stephen M. Riordan, Ruiting Lan, Ling Zhong, Mark Raftery, and Li Zhang. "Examination of the Anaerobic Growth ofCampylobacter concisusStrains." International Journal of Microbiology 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/476047.
Повний текст джерелаАнотація:
Campylobacter concisusis an oral bacterium that is associated with intestinal diseases.C. concisuswas previously described as a bacterium that requires H2-enriched microaerobic conditions for growth. The level of H2in the oral cavity is extremely low, suggesting thatC. concisusis unlikely to have a microaerobic growth there. In this study, the anaerobic growth ofC. concisuswas investigated. The growth of fifty-seven oralC. concisusstrains and six entericC. concisusstrains under various atmospheric conditions including anaerobic conditions with and without H2was examined. The atmospheric conditions were generated using commercially available gas-generation systems.C. concisusputative virulence proteins were identified using mass spectrometry analysis. Under anaerobic conditions, 92% of the oralC. concisusstrains (52/57) and all six enteric strains grew without the presence of H2and the presence of H2greatly increasedC. concisusgrowth. An oralC. concisusstrain was found to express a number of putative virulence proteins and the expression levels of these proteins were not affected by H2. The levels of H2appeared to affect the optimal growth ofC. concisus. This study provides useful information in understanding the natural colonization site and pathogenicity ofC. concisus.
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McCaughey, Gerard, Deirdre F. Gilpin, Thamarai Schneiders, Lucas R. Hoffman, Matt McKevitt, J. Stuart Elborn, and Michael M. Tunney. "Fosfomycin and Tobramycin in Combination Downregulate Nitrate Reductase GenesnarGandnarH, Resulting in Increased Activity against Pseudomonas aeruginosa under Anaerobic Conditions." Antimicrobial Agents and Chemotherapy 57, no. 11 (August 19, 2013): 5406–14. http://dx.doi.org/10.1128/aac.00750-13.
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ABSTRACTThe activity of aminoglycosides, which are used to treatPseudomonas aeruginosarespiratory infection in cystic fibrosis (CF) patients, is reduced under the anaerobic conditions that reflect the CF lungin vivo. In contrast, a 4:1 (wt/wt) combination of fosfomycin and tobramycin (F:T), which is under investigation for use in the treatment of CF lung infection, has increased activity againstP. aeruginosaunder anaerobic conditions. The aim of this study was to elucidate the mechanisms underlying the increased activity of F:T under anaerobic conditions. Microarray analysis was used to identify the transcriptional basis of increased F:T activity under anaerobic conditions, and key findings were confirmed by microbiological tests, including nitrate utilization assays, growth curves, and susceptibility testing. Notably, growth in subinhibitory concentrations of F:T, but not tobramycin or fosfomycin alone, significantly downregulated (P< 0.05) nitrate reductase genesnarGandnarH, which are essential for normal anaerobic growth ofP. aeruginosa. Under anaerobic conditions, F:T significantly decreased (P< 0.001) nitrate utilization inP. aeruginosastrains PAO1, PA14, and PA14lasR::Gm, a mutant known to exhibit increased nitrate utilization. A similar effect was observed with two clinicalP. aeruginosaisolates. Growth curves indicate that nitrate reductase transposon mutants had reduced growth under anaerobic conditions, with these mutants also having increased susceptibility to F:T compared to the wild type under similar conditions. The results of this study suggest that downregulation of nitrate reductase genes resulting in reduced nitrate utilization is the mechanism underlying the increased activity of F:T under anaerobic conditions.
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Liu, Zihe, Tobias Österlund, Jin Hou, Dina Petranovic та Jens Nielsen. "Anaerobic α-Amylase Production and Secretion with Fumarate as the Final Electron Acceptor in Saccharomyces cerevisiae". Applied and Environmental Microbiology 79, № 9 (22 лютого 2013): 2962–67. http://dx.doi.org/10.1128/aem.03207-12.
Повний текст джерелаАнотація:
ABSTRACTIn this study, we focus on production of heterologous α-amylase in the yeastSaccharomyces cerevisiaeunder anaerobic conditions. We compare the metabolic fluxes and transcriptional regulation under aerobic and anaerobic conditions, with the objective of identifying the final electron acceptor for protein folding under anaerobic conditions. We find that yeast produces more amylase under anaerobic conditions than under aerobic conditions, and we propose a model for electron transfer under anaerobic conditions. According to our model, during protein folding the electrons from the endoplasmic reticulum are transferred to fumarate as the final electron acceptor. This model is supported by findings that the addition of fumarate under anaerobic (but not aerobic) conditions improves cell growth, specifically in the α-amylase-producing strain, in which it is not used as a carbon source. Our results provide a model for the molecular mechanism of anaerobic protein secretion using fumarate as the final electron acceptor, which may allow for further engineering of yeast for improved protein secretion under anaerobic growth conditions.
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BELAY, NEGASH, and AVRAHAM RASOOLY. "Staphylococcus aureus Growth and Enterotoxin A Production in an Anaerobic Environment." Journal of Food Protection 65, no. 1 (January 1, 2002): 199–204. http://dx.doi.org/10.4315/0362-028x-65.1.199.
Повний текст джерелаАнотація:
The effects of strict anaerobic conditions on the growth of Staphylococcus aureus and the production of staphylococcal enterotoxin A (SEA) were studied. The growth of S. aureus, a facultative anaerobic bacterium, is slower anaerobically than aerobically. When grown on brain heart infusion broth at 37°C, the anaerobic generation time at mid-log phase was 80 min, compared with 35 min for the aerobic control. In contrast to previous studies demonstrating that staphylococcal cell density was 9- to 17-fold greater in aerobic than in anaerobic cultures, data for a staphylococcal strain implicated in food poisoning showed that the cell density was only two to three times as great in aerobic cultures. Production of SEA was monitored by Western immunoblotting and shown to be growth dependent. With slower anaerobic growth, relatively less toxin was produced than under aerobic conditions, but in both cases SEA was detected after 120 min of incubation. The combined effects of temperature and aeration on S. aureus were also studied. Growth and toxin production of aerobic and anaerobic cultures at temperatures ranging from 14 to 37°C were analyzed. Growth was still observed at low temperatures in both environments. A linear model for S. aureus aerobic or anaerobic growth as a function of incubation temperature was developed from these studies. The model was tested from 17 to 35.5°C, and the results suggest that the model can accurately predict the S. aureus growth rate in this temperature range. The data suggest that anaerobic conditions are not an effective barrier against S. aureus growth.
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Michel, Andrea, Abigail Koch-Koerfges, Karin Krumbach, Melanie Brocker, and Michael Bott. "Anaerobic Growth of Corynebacterium glutamicum via Mixed-Acid Fermentation." Applied and Environmental Microbiology 81, no. 21 (August 14, 2015): 7496–508. http://dx.doi.org/10.1128/aem.02413-15.
Повний текст джерелаАнотація:
ABSTRACTCorynebacterium glutamicum, a model organism in microbial biotechnology, is known to metabolize glucose under oxygen-deprived conditions tol-lactate, succinate, and acetate without significant growth. This property is exploited for efficient production of lactate and succinate. Our detailed analysis revealed that marginal growth takes place under anaerobic conditions with glucose, fructose, sucrose, or ribose as a carbon and energy source but not with gluconate, pyruvate, lactate, propionate, or acetate. Supplementation of glucose minimal medium with tryptone strongly enhanced growth up to a final optical density at 600 nm (OD600) of 12, whereas tryptone alone did not allow growth. Amino acids with a high ATP demand for biosynthesis and amino acids of the glutamate family were particularly important for growth stimulation, indicating ATP limitation and a restricted carbon flux into the oxidative tricarboxylic acid cycle toward 2-oxoglutarate. Anaerobic cultivation in a bioreactor with constant nitrogen flushing disclosed that CO2is required to achieve maximal growth and that the pH tolerance is reduced compared to that under aerobic conditions, reflecting a decreased capability for pH homeostasis. Continued growth under anaerobic conditions indicated the absence of an oxygen-requiring reaction that is essential for biomass formation. The results provide an improved understanding of the physiology ofC. glutamicumunder anaerobic conditions.
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Tang, Yinjie J., Adam L. Meadows, James Kirby, and Jay D. Keasling. "Anaerobic Central Metabolic Pathways in Shewanella oneidensis MR-1 Reinterpreted in the Light of Isotopic Metabolite Labeling." Journal of Bacteriology 189, no. 3 (November 17, 2006): 894–901. http://dx.doi.org/10.1128/jb.00926-06.
Повний текст джерелаАнотація:
ABSTRACT It has been proposed that during growth under anaerobic or oxygen-limited conditions, Shewanella oneidensis MR-1 uses the serine-isocitrate lyase pathway common to many methylotrophic anaerobes, in which formaldehyde produced from pyruvate is condensed with glycine to form serine. The serine is then transformed through hydroxypyruvate and glycerate to enter central metabolism at phosphoglycerate. To examine its use of the serine-isocitrate lyase pathway under anaerobic conditions, we grew S. oneidensis MR-1 on [1-13C]lactate as the sole carbon source, with either trimethylamine N-oxide (TMAO) or fumarate as an electron acceptor. Analysis of cellular metabolites indicated that a large percentage (>70%) of lactate was partially oxidized to either acetate or pyruvate. The 13C isotope distributions in amino acids and other key metabolites indicate that under anaerobic conditions, although glyoxylate synthesized from the isocitrate lyase reaction can be converted to glycine, a complete serine-isocitrate pathway is not present and serine/glycine is, in fact, oxidized via a highly reversible degradation pathway. The labeling data also suggest significant activity in the anapleurotic (malic enzyme and phosphoenolpyruvate carboxylase) reactions. Although the tricarboxylic acid (TCA) cycle is often observed to be incomplete in many other anaerobes (absence of 2-oxoglutarate dehydrogenase activity), isotopic labeling supports the existence of a complete TCA cycle in S. oneidensis MR-1 under certain anaerobic conditions, e.g., TMAO-reducing conditions.
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Starck, Joakim, Gunilla Källenius, Britt-Inger Marklund, Dan I. Andersson, and Thomas Åkerlund. "Comparative proteome analysis of Mycobacterium tuberculosis grown under aerobic and anaerobic conditions." Microbiology 150, no. 11 (November 1, 2004): 3821–29. http://dx.doi.org/10.1099/mic.0.27284-0.
Повний текст джерелаАнотація:
Data are presented from two-dimensional (2-D) PAGE analysis of Mycobacterium tuberculosis strain Harlingen grown during aerobic and anaerobic culture, according to a modified Wayne dormancy model. M. tuberculosis cultures were grown to the transition point between exponential growth and stationary phase in the presence of oxygen (7 days) and then part of the cultures was shifted to anaerobic conditions for 16 days. Growth declined similarly during aerobic and anaerobic conditions, whereas the ATP consumption rapidly decreased in the anaerobic cultures. 2-D PAGE revealed 50 protein spots that were either unique to, or more abundant during, anaerobic conditions and 16 of these were identified by MALDI-TOF. These proteins were the α-crystalline homologue (HspX), elongation factor Tu (Tuf), GroEL2, succinyl-CoA : 3-oxoacid-CoA transferase (ScoB), mycolic acid synthase (CmaA2), thioredoxin (TrxB2), β-ketoacyl-ACP synthase (KasB), l-alanine dehydrogenase (Ald), Rv2005c, Rv2629, Rv0560c, Rv2185c and Rv3866. Some protein spots were found to be proteolytic fragments, e.g. HspX and GroEL2. These data suggest that M. tuberculosis induces expression of about 1 % of its genes in response to dormancy.
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González-Hernández, Yusmel, Emilie Michiels, and Patrick Perré. "A Comprehensive Mechanistic Yeast Model Able to Switch Metabolism According to Growth Conditions." Fermentation 8, no. 12 (December 6, 2022): 710. http://dx.doi.org/10.3390/fermentation8120710.
Повний текст джерелаАнотація:
This paper proposes a general approach for building a mechanistic yeast model able to predict the shift of metabolic pathways. The mechanistic model accounts for the coexistence of several metabolic pathways (aerobic fermentation, glucose respiration, anaerobic fermentation and ethanol respiration) whose activation depends on growth conditions. This general approach is applied to a commercial strain of Saccharomyces cerevisiae. Stoichiometry and yeast kinetics were mostly determined from aerobic and completely anaerobic experiments. Known parameters were taken from the literature, and the remaining parameters were estimated by inverse analysis using the particle swarm optimization method. The optimized set of parameters allows the concentrations to be accurately determined over time, reporting global mean relative errors for all variables of less than 7 and 11% under completely anaerobic and aerobic conditions, respectively. Different affinities of yeast for glucose and ethanol tolerance under aerobic and anaerobic conditions were obtained. Finally, the model was successfully validated by simulating a different experiment, a batch fermentation process without gas injection, with an overall mean relative error of 7%. This model represents a useful tool for the control and optimization of yeast fermentation systems. More generally, the modeling framework proposed here is intended to be used as a building block of a digital twin of any bioproduction process.
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Nielsen, P. H., P. Roslev, T. E. Dueholm, and J. L. Nielsen. "Microthrix parvicella, a specialized lipid consumer in anaerobic–aerobic activated sludge plants." Water Science and Technology 46, no. 1-2 (July 1, 2002): 73–80. http://dx.doi.org/10.2166/wst.2002.0459.
Повний текст джерелаАнотація:
The in situ physiology of the filamentous bacterium Microthrix parvicella was investigated in anaerobic-aerobic dynamic phases in activated sludge with focus on the uptake of long chain fatty acids (LCFA) and growth. When 14C-labeled oleic acid was added to activated sludge with an excessive growth of M. parvicella, only little 14C-CO2 was produced under anaerobic conditions while a lot was produced under aerobic conditions. Microautoradiographic studies revealed that M. parvicella took up oleic acid under both anaerobic and aerobic conditions, while only a few floc formers were able to take it up under anaerobic conditions. Extraction and separation of the radioactive biomass into different lipid fractions showed that the oleic acid was stored mainly as neutral lipids under anaerobic conditions, whereas conversion to membrane phospholipids occurred almost exclusively under aerobic conditions, indicating growth. The surface properties of M. parvicella and other bacteria were characterized by hydrophobic fluorescent microspheres, which showed that M. parvicella was relatively hydrophobic. Furthermore, a surface-associated extracellular lipase activity was observed, indicating the ability of M. parvicella to degrade lipids near the filament surface. The results support the hypothesis that uptake and storage of LCFA as lipids under anaerobic conditions provide an effective competition strategy against bacteria that can only take up LCFA under aerobic conditions. Thus, M. parvicella seems to be a specialized lipid consumer with a physiological potential analogous to PAOs and GAOs being able to take up LCFA (but not short chain fatty acids or glucose) under anaerobic conditions and subsequently use the storage material for growth when nitrate or oxygen are available as electron acceptors.
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ter Linde, J. J. M., H. Liang, R. W. Davis, H. Y. Steensma, J. P. van Dijken, and J. T. Pronk. "Genome-Wide Transcriptional Analysis of Aerobic and Anaerobic Chemostat Cultures of Saccharomyces cerevisiae." Journal of Bacteriology 181, no. 24 (December 15, 1999): 7409–13. http://dx.doi.org/10.1128/jb.181.24.7409-7413.1999.
Повний текст джерелаАнотація:
ABSTRACT The yeast Saccharomyces cerevisiae is unique among eukaryotes in exhibiting fast growth in both the presence and the complete absence of oxygen. Genome-wide transcriptional adaptation to aerobiosis and anaerobiosis was studied in assays using DNA microarrays. This technique was combined with chemostat cultivation, which allows controlled variation of a single growth parameter under defined conditions and at a fixed specific growth rate. Of the 6,171 open reading frames investigated, 5,738 (93%) yielded detectable transcript levels under either aerobic or anaerobic conditions; 140 genes showed a >3-fold-higher transcription level under anaerobic conditions. Under aerobic conditions, transcript levels of 219 genes were >3-fold higher than under anaerobic conditions.
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Malik, Muhammad, Syed Hussain, and Karl Drlica. "Effect of Anaerobic Growth on Quinolone Lethality with Escherichia coli." Antimicrobial Agents and Chemotherapy 51, no. 1 (October 16, 2006): 28–34. http://dx.doi.org/10.1128/aac.00739-06.
Повний текст джерелаАнотація:
ABSTRACT Quinolone activity against Escherichia coli was examined during aerobic growth, aerobic treatment with chloramphenicol, and anaerobic growth. Nalidixic acid, norfloxacin, ciprofloxacin, and PD161144 were lethal for cultures growing aerobically, and the bacteriostatic activity of each quinolone was unaffected by anaerobic growth. However, lethal activity was distinct for each quinolone with cells treated aerobically with chloramphenicol or grown anaerobically. Nalidixic acid failed to kill cells under both conditions; norfloxacin killed cells when they were grown anaerobically but not when they were treated with chloramphenicol; ciprofloxacin killed cells under both conditions but required higher concentrations than those required with cells grown aerobically; and PD161144, a C-8-methoxy fluoroquinolone, was equally lethal under all conditions. Following pretreatment with nalidixic acid, a shift to anaerobic conditions or the addition of chloramphenicol rapidly blocked further cell death. Formation of quinolone-gyrase-DNA complexes, observed as a sodium dodecyl sulfate (SDS)-dependent drop in cell lysate viscosity, occurred during aerobic and anaerobic growth and in the presence and in the absence of chloramphenicol. However, lethal chromosome fragmentation, detected as a drop in viscosity in the absence of SDS, occurred with nalidixic acid treatment only under aerobic conditions in the absence of chloramphenicol. With PD161144, chromosome fragmentation was detected when the cells were grown aerobically and anaerobically and in the presence and in the absence of chloramphenicol. Thus, all quinolones tested appear to form reversible bacteriostatic complexes containing broken DNA during aerobic growth, during anaerobic growth, and when protein synthesis is blocked; however, the ability to fragment chromosomes and to rapidly kill cells under these conditions depends on quinolone structure.
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Finn, Thomas J., Sonal Shewaramani, Sinead C. Leahy, Peter H. Janssen, and Christina D. Moon. "Dynamics and genetic diversification ofEscherichia coliduring experimental adaptation to an anaerobic environment." PeerJ 5 (May 3, 2017): e3244. http://dx.doi.org/10.7717/peerj.3244.
Повний текст джерелаАнотація:
BackgroundMany bacteria are facultative anaerobes, and can proliferate in both anoxic and oxic environments. Under anaerobic conditions, fermentation is the primary means of energy generation in contrast to respiration. Furthermore, the rates and spectra of spontaneous mutations that arise during anaerobic growth differ to those under aerobic growth. A long-term selection experiment was undertaken to investigate the genetic changes that underpin how the facultative anaerobe,Escherichia coli, adapts to anaerobic environments.MethodsTwenty-one populations ofE. coliREL4536, an aerobically evolved 10,000th generation descendent of theE. coliB strain, REL606, were established from a clonal ancestral culture. These were serially sub-cultured for 2,000 generations in a defined minimal glucose medium in strict aerobic and strict anaerobic environments, as well as in a treatment that fluctuated between the two environments. The competitive fitness of the evolving lineages was assessed at approximately 0, 1,000 and 2,000 generations, in both the environment of selection and the alternative environment. Whole genome re-sequencing was performed on random colonies from all lineages after 2,000-generations. Mutations were identified relative to the ancestral genome, and based on the extent of parallelism, traits that were likely to have contributed towards adaptation were inferred.ResultsThere were increases in fitness relative to the ancestor among anaerobically evolved lineages when tested in the anaerobic environment, but no increases were found in the aerobic environment. For lineages that had evolved under the fluctuating regime, relative fitness increased significantly in the anaerobic environment, but did not increase in the aerobic environment. The aerobically-evolved lineages did not increase in fitness when tested in either the aerobic or anaerobic environments. The strictly anaerobic lineages adapted more rapidly to the anaerobic environment than did the fluctuating lineages. Two main strategies appeared to predominate during adaptation to the anaerobic environment: modification of energy generation pathways, and inactivation of non-essential functions. Fermentation pathways appeared to alter through selection for mutations in genes such asnadR, adhE, dcuS/R, andpflB. Mutations were frequently identified in genes for presumably dispensable functions such as toxin-antitoxin systems, prophages, virulence and amino acid transport. Adaptation of the fluctuating lineages to the anaerobic environments involved mutations affecting traits similar to those observed in the anaerobically evolved lineages.DiscussionThere appeared to be strong selective pressure for activities that conferred cell yield advantages during anaerobic growth, which include restoring activities that had previously been inactivated under long-term continuous aerobic evolution of the ancestor.
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Lee, Kang-Mu, Junhyeok Go, Mi Young Yoon, Yongjin Park, Sang Cheol Kim, Dong Eun Yong, and Sang Sun Yoon. "Vitamin B12-Mediated Restoration of Defective Anaerobic Growth Leads to Reduced Biofilm Formation in Pseudomonas aeruginosa." Infection and Immunity 80, no. 5 (February 27, 2012): 1639–49. http://dx.doi.org/10.1128/iai.06161-11.
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ABSTRACTPseudomonas aeruginosaundergoes cell elongation and forms robust biofilms during anaerobic respiratory growth using nitrate (NO3−) as an alternative electron acceptor. Understanding the mechanism of cell shape change induced upon anaerobiosis is crucial to the development of effective treatments againstP. aeruginosabiofilm infection. Here, we uncovered the molecular basis of anaerobiosis-triggered cell elongation and identified vitamin B12to be a molecule that can reinstate defective anaerobic growth ofP. aeruginosa. The ratio of total cellular DNA content to protein content was significantly decreased in the PAO1 strain grown under anaerobic conditions, indicating that DNA replication is impaired during anaerobic growth. Anaerobic growth of PAO1 reached a higher cell density in the presence of vitamin B12, an essential coenzyme of class II ribonucleotide reductase. In addition, cell morphology returned to a normal rod shape and transcription of stress-response genes was downregulated under the same anaerobic growth conditions. These results suggest that vitamin B12, the production of which was suppressed during anaerobic growth, can restore cellular machineries for DNA replication and therefore facilitate better anaerobic growth ofP. aeruginosawith normal cell division. Importantly, biofilm formation was substantially decreased when grown with vitamin B12, further demonstrating that anaerobiosis-induced cell elongation is responsible for robust biofilm formation. Taken together, our data reveal mechanistic details of a morphological change that naturally occurs during anaerobic growth ofP. aeruginosaand illustrates the ability of vitamin B12to modulate the biofilm-forming capacity ofP. aeruginosaunder such condition.
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Maklashina, Elena, Deborah A. Berthold, and Gary Cecchini. "Anaerobic Expression of Escherichia coli Succinate Dehydrogenase: Functional Replacement of Fumarate Reductase in the Respiratory Chain during Anaerobic Growth." Journal of Bacteriology 180, no. 22 (November 15, 1998): 5989–96. http://dx.doi.org/10.1128/jb.180.22.5989-5996.1998.
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ABSTRACT Succinate-ubiquinone oxidoreductase (SQR) from Escherichia coli is expressed maximally during aerobic growth, when it catalyzes the oxidation of succinate to fumarate in the tricarboxylic acid cycle and reduces ubiquinone in the membrane. The enzyme is similar in structure and function to fumarate reductase (menaquinol-fumarate oxidoreductase [QFR]), which participates in anaerobic respiration by E. coli. Fumarate reductase, which is proficient in succinate oxidation, is able to functionally replace SQR in aerobic respiration when conditions are used to allow the expression of the frdABCD operon aerobically. SQR has not previously been shown to be capable of supporting anaerobic growth ofE. coli because expression of the enzyme complex is largely repressed by anaerobic conditions. In order to obtain expression of SQR anaerobically, plasmids which utilize the PFRD promoter of the frdABCD operon fused to the sdhCDAB genes to drive expression were constructed. It was found that, under anaerobic growth conditions where fumarate is utilized as the terminal electron acceptor, SQR would function to support anaerobic growth ofE. coli. The levels of amplification of SQR and QFR were similar under anaerobic growth conditions. The catalytic properties of SQR isolated from anaerobically grown cells were measured and found to be identical to those of enzyme produced aerobically. The anaerobic expression of SQR gave a greater yield of enzyme complex than was found in the membrane from aerobically grown cells under the conditions tested. In addition, it was found that anaerobic expression of SQR could saturate the capacity of the membrane for incorporation of enzyme complex. As has been seen with the amplified QFR complex, E. coli accommodates the excess SQR produced by increasing the amount of membrane. The excess membrane was found in tubular structures that could be seen in thin-section electron micrographs.
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Thomsson, Elisabeth, Lena Gustafsson, and Christer Larsson. "Starvation Response of Saccharomyces cerevisiae Grown in Anaerobic Nitrogen- or Carbon-Limited Chemostat Cultures." Applied and Environmental Microbiology 71, no. 6 (June 2005): 3007–13. http://dx.doi.org/10.1128/aem.71.6.3007-3013.2005.
Повний текст джерелаАнотація:
ABSTRACT Anaerobic starvation conditions are frequent in industrial fermentation and can affect the performance of the cells. In this study, the anaerobic carbon or nitrogen starvation response of Saccharomyces cerevisiae was investigated for cells grown in anaerobic carbon or nitrogen-limited chemostat cultures at a dilution rate of 0.1 h−1 at pH 3.25 or 5. Lactic or benzoic acid was present in the growth medium at different concentrations, resulting in 16 different growth conditions. At steady state, cells were harvested and then starved for either carbon or nitrogen for 24 h under anaerobic conditions. We measured fermentative capacity, glucose uptake capacity, intracellular ATP content, and reserve carbohydrates and found that the carbon, but not the nitrogen, starvation response was dependent upon the previous growth conditions. All cells subjected to nitrogen starvation retained a large portion of their initial fermentative capacity, independently of previous growth conditions. However, nitrogen-limited cells that were starved for carbon lost almost all their fermentative capacity, while carbon-limited cells managed to preserve a larger portion of their fermentative capacity during carbon starvation. There was a positive correlation between the amount of glycogen before carbon starvation and the fermentative capacity and ATP content of the cells after carbon starvation. Fermentative capacity and glucose uptake capacity were not correlated under any of the conditions tested. Thus, the successful adaptation to sudden carbon starvation requires energy and, under anaerobic conditions, fermentable endogenous resources. In an industrial setting, carbon starvation in anaerobic fermentations should be avoided to maintain a productive yeast population.
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Santiago-Martínez, M. Geovanni, Elizabeth Lira-Silva, Rusely Encalada, Erika Pineda, Juan Carlos Gallardo-Pérez, Armando Zepeda-Rodriguez, Rafael Moreno-Sánchez, Emma Saavedra, and Ricardo Jasso-Chávez. "Cadmium removal by Euglena gracilis is enhanced under anaerobic growth conditions." Journal of Hazardous Materials 288 (May 2015): 104–12. http://dx.doi.org/10.1016/j.jhazmat.2015.02.027.
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Lee, Changsoo, Jaai Kim, Kwanghyun Hwang, and Seokhwan Hwang. "Fermentation and growth kinetic study of Aeromonas caviae under anaerobic conditions." Applied Microbiology and Biotechnology 83, no. 4 (June 2009): 767–73. http://dx.doi.org/10.1007/s00253-009-1983-y.
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Müller-Herbst, Stefanie, Stefanie Wüstner, Anna Mühlig, Daniela Eder, Thilo M. Fuchs, Claudia Held, Armin Ehrenreich, and Siegfried Scherer. "Identification of genes essential for anaerobic growth of Listeria monocytogenes." Microbiology 160, no. 4 (April 1, 2014): 752–65. http://dx.doi.org/10.1099/mic.0.075242-0.
Повний текст джерелаАнотація:
The facultative anaerobic bacterium Listeria monocytogenes encounters microaerophilic or anaerobic conditions in various environments, e.g. in soil, in decaying plant material, in food products and in the host gut. To elucidate the adaptation of Listeria monocytogenes to variations in oxygen tension, global transcription analyses using DNA microarrays were performed. In total, 139 genes were found to be transcribed differently during aerobic and anaerobic growth; 111 genes were downregulated and 28 genes were upregulated anaerobically. The oxygen-dependent transcription of central metabolic genes is in agreement with results from earlier physiological studies. Of those genes more strongly expressed under lower oxygen tension, 20 were knocked out individually. Growth analysis of these knock out mutants did not indicate an essential function for the respective genes during anaerobiosis. However, even if not essential, transcriptional induction of several genes might optimize the bacterial fitness of Listeria monocytogenes in anaerobic niches, e.g. during colonization of the gut. For example, expression of the anaerobically upregulated gene lmo0355, encoding a fumarate reductase α chain, supported growth on 10 mM fumarate under anaerobic but not under aerobic growth conditions. Genes essential for anaerobic growth were identified by screening a mutant library. Eleven out of 1360 investigated mutants were sensitive to anaerobiosis. All 11 mutants were interrupted in the atp locus. These results were further confirmed by phenotypic analysis of respective in-frame deletion and complementation mutants, suggesting that the generation of a proton motive force via F1F0-ATPase is essential for anaerobic proliferation of Listeria monocytogenes.
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Rosca, Aliona S., Joana Castro, and Nuno Cerca. "Evaluation of different culture media to support in vitro growth and biofilm formation of bacterial vaginosis-associated anaerobes." PeerJ 8 (September 10, 2020): e9917. http://dx.doi.org/10.7717/peerj.9917.
Повний текст джерелаАнотація:
Background Bacterial vaginosis (BV) is one of the most common vaginal infections worldwide. It is associated with the presence of a dense polymicrobial biofilm on the vaginal epithelium, formed mainly by Gardnerella species. The biofilm also contains other anaerobic species, but little is known about their role in BV development. Aim To evaluate the influence of different culture media on the planktonic and biofilm growth of six cultivable anaerobes frequently associated with BV, namely Gardnerella sp., Atopobium vaginae, Lactobacillus iners, Mobiluncus curtisii, Peptostreptococcus anaerobius and Prevotella bivia. Methods A total of nine different culture media compositions, including commercially available and chemically defined media simulating genital tract secretions, were tested in this study. Planktonic cultures and biofilms were grown under anaerobic conditions (10% carbon dioxide, 10% helium and 80% nitrogen). Planktonic growth was assessed by optical density measurements, and biofilm formation was quantified by crystal violet staining. Results Significant planktonic growth was observed for Gardnerella sp., A. vaginae and L. iners in New York City III broth, with or without ascorbic acid supplementation. Biofilm quantification showed high in vitro biofilm growth for Gardnerella sp., P. anaerobius and P. bivia in almost all culture media excluding Brucella broth. Contrary, only New York City III broth was able to promote biofilm formation for A. vaginae, L. iners and M. curtisii. Conclusions Our data demonstrate that New York City III broth relative to the other tested media is the most conducive for future studies addressing polymicrobial biofilms development as this culture medium allowed the formation of significant levels of single-species biofilms.
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Beranová, Jana, María C. Mansilla, Diego de Mendoza, Dana Elhottová, and Ivo Konopásek. "Differences in Cold Adaptation of Bacillus subtilis under Anaerobic and Aerobic Conditions." Journal of Bacteriology 192, no. 16 (June 25, 2010): 4164–71. http://dx.doi.org/10.1128/jb.00384-10.
Повний текст джерелаАнотація:
ABSTRACT Bacillus subtilis, which grows under aerobic conditions, employs fatty acid desaturase (Des) to fluidize its membrane when subjected to temperature downshift. Des requires molecular oxygen for its activity, and its expression is regulated by DesK-DesR, a two-component system. Transcription of des is induced by the temperature downshift and is decreased when membrane fluidity is restored. B. subtilis is also capable of anaerobic growth by nitrate or nitrite respiration. We studied the mechanism of cold adaptation in B. subtilis under anaerobic conditions that were predicted to inhibit Des activity. We found that in anaerobiosis, in contrast to aerobic growth, the induction of des expression after temperature downshift (from 37°C to 25°C) was not downregulated. However, the transfer from anaerobic to aerobic conditions rapidly restored the downregulation. Under both aerobic and anaerobic conditions, the induction of des expression was substantially reduced by the addition of external fluidizing oleic acid and was fully dependent on the DesK-DesR two-component regulatory system. Fatty acid analysis proved that there was no desaturation after des induction under anaerobic conditions despite the presence of high levels of the des protein product, which was shown by immunoblot analysis. The cold adaptation of B. subtilis in anaerobiosis is therefore mediated exclusively by the increased anteiso/iso ratio of branched-chain fatty acids and not by the temporarily increased level of unsaturated fatty acids that is typical under aerobic conditions. The degrees of membrane fluidization, as measured by diphenylhexatriene fluorescence anisotropy, were found to be similar under both aerobic and anaerobic conditions.
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Kurabayashi, Kumiko, Koichi Tanimoto, Shinobu Fueki, Haruyoshi Tomita, and Hidetada Hirakawa. "Elevated Expression of GlpT and UhpT via FNR Activation Contributes to Increased Fosfomycin Susceptibility in Escherichia coli under Anaerobic Conditions." Antimicrobial Agents and Chemotherapy 59, no. 10 (July 27, 2015): 6352–60. http://dx.doi.org/10.1128/aac.01176-15.
Повний текст джерелаАнотація:
ABSTRACTBecause a shortage of new antimicrobial agents is a critical issue at present, and with the spread of multidrug-resistant (MDR) pathogens, the use of fosfomycin to treat infections is being revisited as a “last-resort option.” This drug offers a particular benefit in that it is more effective against bacteria growing under oxygen-limited conditions, unlike other commonly used antimicrobials, such as fluoroquinolones and aminoglycosides. In this study, we showed thatEscherichia colistrains, including enterohemorrhagicE. coli(EHEC), were more susceptible to fosfomycin when grown anaerobically than when grown aerobically, and we investigated how the activity of this drug was enhanced during anaerobic growth ofE. coli. Our quantitative PCR analysis and a transport assay showed thatE. colicells grown under anaerobic conditions had higher levels of expression ofglpTanduhpT, encoding proteins that transport fosfomycin into cells with their native substrates, i.e., glycerol-3-phosphate and glucose-6-phosphate, and led to increased intracellular accumulation of the drug. Elevation of expression of these genes during anaerobic growth requires FNR, a global transcriptional regulator that is activated under anaerobic conditions. Purified FNR bound to DNA fragments from regions upstream ofglpTanduhpT, suggesting that it is an activator of expression ofglpTanduhpTduring anaerobic growth. We concluded that the increased antibacterial activity of fosfomycin towardE. coliunder anaerobic conditions can be attributed to elevated expression of GlpT and UhpT following activation of FNR, leading to increased uptake of the drug.
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Li, Jia-Yi, Lu Wang, Yi-Fan Liu, Lei Zhou, Hong-Ze Gang, Jin-Feng Liu, Shi-Zhong Yang, and Bo-Zhong Mu. "Microbial Lipopeptide-Producing Strains and Their Metabolic Roles under Anaerobic Conditions." Microorganisms 9, no. 10 (September 25, 2021): 2030. http://dx.doi.org/10.3390/microorganisms9102030.
Повний текст джерелаАнотація:
The lipopeptide produced by microorganisms is one of the representative biosurfactants and is characterized as a series of structural analogues of different families. Thirty-four families covering about 300 lipopeptide compounds have been reported in the last decades, and most of the reported lipopeptides produced by microorganisms were under aerobic conditions. The lipopeptide-producing strains under anaerobic conditions have attracted much attention from both the academic and industrial communities, due to the needs and the challenge of their applications in anaerobic environments, such as in oil reservoirs and in microbial enhanced oil recovery (MEOR). In this review, the fifty-eight reported bacterial strains, mostly isolated from oil reservoirs and dominated by the species Bacillus subtilis, producing lipopeptide biosurfactants, and the species Pseudomonas aeruginosa, producing glycolipid biosurfactants under anaerobic conditions were summarized. The metabolic pathway and the non-ribosomal peptide synthetases (NRPSs) of the strain Bacillus subtilis under anaerobic conditions were analyzed, which is expected to better understand the key mechanisms of the growth and production of lipopeptide biosurfactants of such kind of bacteria under anaerobic conditions, and to expand the industrial application of anaerobic biosurfactant-producing bacteria.
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Sonderegger, Marco, and Uwe Sauer. "Evolutionary Engineering of Saccharomyces cerevisiae for Anaerobic Growth on Xylose." Applied and Environmental Microbiology 69, no. 4 (April 2003): 1990–98. http://dx.doi.org/10.1128/aem.69.4.1990-1998.2003.
Повний текст джерелаАнотація:
ABSTRACT Xylose utilization is of commercial interest for efficient conversion of abundant plant material to ethanol. Perhaps the most important ethanol-producing organism, Saccharomyces cerevisiae, however, is incapable of xylose utilization. While S. cerevisiae strains have been metabolically engineered to utilize xylose, none of the recombinant strains or any other naturally occurring yeast has been able to grow anaerobically on xylose. Starting with the recombinant S. cerevisiae strain TMB3001 that overexpresses the xylose utilization pathway from Pichia stipitis, in this study we developed a selection procedure for the evolution of strains that are capable of anaerobic growth on xylose alone. Selection was successful only when organisms were first selected for efficient aerobic growth on xylose alone and then slowly adapted to microaerobic conditions and finally anaerobic conditions, which indicated that multiple mutations were necessary. After a total of 460 generations or 266 days of selection, the culture reproduced stably under anaerobic conditions on xylose and consisted primarily of two subpopulations with distinct phenotypes. Clones in the larger subpopulation grew anaerobically on xylose and utilized both xylose and glucose simultaneously in batch culture, but they exhibited impaired growth on glucose. Surprisingly, clones in the smaller subpopulation were incapable of anaerobic growth on xylose. However, as a consequence of their improved xylose catabolism, these clones produced up to 19% more ethanol than the parental TMB3001 strain produced under process-like conditions from a mixture of glucose and xylose.
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Sari, Tewfik. "Best Operating Conditions for Biogas Production in Some Simple Anaerobic Digestion Models." Processes 10, no. 2 (January 28, 2022): 258. http://dx.doi.org/10.3390/pr10020258.
Повний текст джерелаАнотація:
We consider one-step and two-step simple models of anaerobic digestion that are able to adequately capture the main dynamical behaviour of the full anaerobic digestion model ADM1. We do not consider specific growth functions. We only require them to satisfy certain qualitative assumptions. These assumptions are satisfied for concave growth functions, but they are also satisfied for a large class of growth functions found in many applications. We consider the maximisation of the biogas production with respect to the operating parameters of the model, which are the dilution rate and the substrate input concentration. We give the best operating conditions and we describe them as a subset of the set of operating parameters. Our models incorporate biomass decay terms, corresponding to maintenance. Numerical plots with specified growth functions and biological parameters illustrate the obtained results.
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Fjölnisdóttir, Birta Líf, Pálína Haraldsdóttir, Eva María Ingvadóttir, Sean M. Scully, and Jóhann Örlygsson. "Characterization of a 1,2-Propanediol Producing Escherichia Strain Isolated from a Geothermally Heated Intertidal Pool in Northern Iceland." Fine Focus 4, no. 1 (May 1, 2018): 19–39. http://dx.doi.org/10.33043/ff.4.1.19-39.
Повний текст джерелаАнотація:
The ability of a mesophilic isolate, strain CC5C, isolated from a temperate geothermally-heated intertidal pool in northern Iceland is described herein. Strain CC5C belongs to the family Enterobacteriaceae with greater than 99.1% similarity to Escherichia marmotae and Shigella dysenteriae based upon 16S rRNA gene analysis. Strain CC5C is a facultative anaerobe exhibiting growth between 5 and 50°C with an optimal growth at 40°C, initial pH values between 4.0 and 9.0 with an optimum at pH 7.5. Strain CC5C, unlike its nearest phylogenetic neighbors, degrades starch, dulcitol, and sucrose as well as potentially cellobiose which are uncommon features among these genera. Under aerobic conditions the catabolism of L-rhamnose and L-fucose revealed that the dominant product was 1,2-propanediol while under anaerobic conditions it was a mixture of acetate and 1,2-propanediol. The effect of increased initial substrate concentration was investigated for glucose, L-fucose, and L-rhamnose with inhibition apparent at concentrations above 20 mM under both anaerobic and aerobic conditions. Although, differences in end product formation were observed between aerobic and anaerobic conditions for L-rhamnose. Strain CC5C rapidly catabolizes rhamnose and produces 1,2-PD at a rate of 3.41 mmol/h on L-rhamnose and 2.37 mmol/h on a mixture of glucose and rhamnose with up to 96% of the theoretical yield on L-rhamnose.
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López-Marqués, Rosa L., José R. Pérez-Castiñeira, Manuel Losada, and Aurelio Serrano. "Differential Regulation of Soluble and Membrane-Bound Inorganic Pyrophosphatases in the Photosynthetic Bacterium Rhodospirillum rubrum Provides Insights into Pyrophosphate-Based Stress Bioenergetics." Journal of Bacteriology 186, no. 16 (August 15, 2004): 5418–26. http://dx.doi.org/10.1128/jb.186.16.5418-5426.2004.
Повний текст джерелаАнотація:
ABSTRACT Soluble and membrane-bound inorganic pyrophosphatases (sPPase and H+-PPase, respectively) of the purple nonsulfur bacterium Rhodospirillum rubrum are differentially regulated by environmental growth conditions. Both proteins and their transcripts were found in cells of anaerobic phototrophic batch cultures along all growth phases, although they displayed different time patterns. However, in aerobic cells that grow in the dark, which exhibited the highest growth rates, Northern and Western blot analyses as well as activity assays demonstrated high sPPase levels but no H+-PPase. It is noteworthy that H+-PPase is highly expressed in aerobic cells under acute salt stress (1 M NaCl). H+-PPase was also present in anaerobic cells growing at reduced rates in the dark under either fermentative or anaerobic respiratory conditions. Since H+-PPase was detected not only under all anaerobic growth conditions but also under salt stress in aerobiosis, the corresponding gene is not invariably repressed by oxygen. Primer extension analyses showed that, under all anaerobic conditions tested, the R. rubrum H+-PPase gene utilizes two activator-dependent tandem promoters, one with an FNR-like sequence motif and the other with a RegA motif, whereas in aerobiosis under salt stress, the H+-PPase gene is transcribed from two further tandem promoters involving other transcription factors. These results demonstrate a tight transcriptional regulation of the H+-PPase gene, which appears to be induced in response to a variety of environmental conditions, all of which constrain cell energetics.
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Liu, Wei, Shi Lei Dong, Fei Xu, Xue Qin Wang, T. Ryan Withers, Hongwei D. Yu, and Xin Wang. "Effect of Intracellular Expression of Antimicrobial Peptide LL-37 on Growth of Escherichia coli Strain TOP10 under Aerobic and Anaerobic Conditions." Antimicrobial Agents and Chemotherapy 57, no. 10 (July 15, 2013): 4707–16. http://dx.doi.org/10.1128/aac.00825-13.
Повний текст джерелаАнотація:
ABSTRACTAntimicrobial peptides (AMPs) can cause lysis of target bacteria by directly inserting themselves into the lipid bilayer. This killing mechanism confounds the identification of the intracellular targets of AMPs. To circumvent this, we used a shuttle vector containing the inducible expression of a human cathelicidin-related AMP, LL-37, to examine its effect onEscherichia coliTOP10 under aerobic and anaerobic growth conditions. Induction of LL-37 caused growth inhibition and alteration in cell morphology to a filamentous phenotype. Further examination of theE. colicell division protein FtsZ revealed that LL-37 did not interact with FtsZ. Moreover, intracellular expression of LL-37 results in the enhanced production of reactive oxygen species (ROS), causing lethal membrane depolarization under aerobic conditions. Additionally, the membrane permeability was increased after intracellular expression of LL37 under both aerobic and anaerobic conditions. Transcriptomic analysis revealed that intracellular LL-37 mainly affected the expression of genes related to energy production and carbohydrate metabolism. More specifically, genes related to oxidative phosphorylation under both aerobic and anaerobic growth conditions were affected. Collectively, our current study demonstrates that intracellular expression of LL-37 inE. colican inhibit growth under aerobic and anaerobic conditions. While we confirmed that the generation of ROS is a bactericidal mechanism for LL-37 under aerobic growth conditions, we also found that the intracellular accumulation of cationic LL-37 influences the redox and ion status of the cells under both growth conditions. These data suggest that there is a new AMP-mediated bacterial killing mechanism that targets energy metabolism.
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Hunt, Kristopher A., Jeffrey M. Flynn, Belén Naranjo, Indraneel D. Shikhare, and Jeffrey A. Gralnick. "Substrate-Level Phosphorylation Is the Primary Source of Energy Conservation during Anaerobic Respiration of Shewanella oneidensis Strain MR-1." Journal of Bacteriology 192, no. 13 (April 16, 2010): 3345–51. http://dx.doi.org/10.1128/jb.00090-10.
Повний текст джерелаАнотація:
ABSTRACT It is well established that respiratory organisms use proton motive force to produce ATP via F-type ATP synthase aerobically and that this process may reverse during anaerobiosis to produce proton motive force. Here, we show that Shewanella oneidensis strain MR-1, a nonfermentative, facultative anaerobe known to respire exogenous electron acceptors, generates ATP primarily from substrate-level phosphorylation under anaerobic conditions. Mutant strains lacking ackA (SO2915) and pta (SO2916), genes required for acetate production and a significant portion of substrate-level ATP produced anaerobically, were tested for growth. These mutant strains were unable to grow anaerobically with lactate and fumarate as the electron acceptor, consistent with substrate-level phosphorylation yielding a significant amount of ATP. Mutant strains lacking ackA and pta were also shown to grow slowly using N-acetylglucosamine as the carbon source and fumarate as the electron acceptor, consistent with some ATP generation deriving from the Entner-Doudoroff pathway with this substrate. A deletion strain lacking the sole F-type ATP synthase (SO4746 to SO4754) demonstrated enhanced growth on N-acetylglucosamine and a minor defect with lactate under anaerobic conditions. ATP synthase mutants grown anaerobically on lactate while expressing proteorhodopsin, a light-dependent proton pump, exhibited restored growth when exposed to light, consistent with a proton-pumping role for ATP synthase under anaerobic conditions. Although S. oneidensis requires external electron acceptors to balance redox reactions and is not fermentative, we find that substrate-level phosphorylation is its primary anaerobic energy conservation strategy. Phenotypic characterization of an ackA deletion in Shewanella sp. strain MR-4 and genomic analysis of other sequenced strains suggest that this strategy is a common feature of Shewanella.
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ZURERA-COSANO, G., A. M. CASTILLEJO-RODRÍGUEZ, R. M. GARCÍA-GIMENO, and F. RINCÓN-LEÓN. "Performance of Response Surface and Davey Model for Prediction of Staphylococcus aureus Growth Parameters under Different Experimental Conditions." Journal of Food Protection 67, no. 6 (June 1, 2004): 1138–45. http://dx.doi.org/10.4315/0362-028x-67.6.1138.
Повний текст джерелаАнотація:
The combined effect of different temperatures (7 to 19°C), pH levels (4.5 to 8.5), sodium chloride levels (0 to 8%), and sodium nitrite levels (0 to 200 ppm) on the predicted growth rate and lag time of Staphylococcus aureus under aerobic and anaerobic conditions was studied. The two predictive models developed, response surface (RS) and the Davey model, provided reliable estimates of the two kinetic parameters studied. The RS provided better predictions of maximum specific growth rate, with bias factors of 1.06 and 1.31 and accuracy factors of 1.17 and 1.37, respectively, in aerobic and anaerobic conditions. The Davey model performed more accurately for lag time, with a bias factor of 1.12 and an accuracy factor of 1.49, for both aerobic and anaerobic conditions. Predictive growth models are a valuable tool, enabling swift determination of Staphylococcus aureus growth rate and lag time. These data are essential for ensuring staphylococcus-relatedquality and safety of food products.
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Shearer, Neil, Andrew P. Hinsley, Rob J. M. Van Spanning, and Stephen Spiro. "Anaerobic Growth of Paracoccus denitrificans Requires Cobalamin: Characterization ofcobK and cobJ Genes." Journal of Bacteriology 181, no. 22 (November 15, 1999): 6907–13. http://dx.doi.org/10.1128/jb.181.22.6907-6913.1999.
Повний текст джерелаАнотація:
ABSTRACT A pleiotropic mutant of Paracoccus denitrificans, which has a severe defect that affects its anaerobic growth when either nitrate, nitrite, or nitrous oxide is used as the terminal electron acceptor and which is also unable to use ethanolamine as a carbon and energy source for aerobic growth, was isolated. This phenotype of the mutant is expressed only during growth on minimal media and can be reversed by addition of cobalamin (vitamin B12) or cobinamide to the media or by growth on rich media. Sequence analysis revealed the mutation causing this phenotype to be in a gene homologous to cobK of Pseudomonas denitrificans, which encodes precorrin-6x reductase of the cobalamin biosynthesis pathway. Convergently transcribed with cobK is a gene homologous tocobJ of Pseudomonas denitrificans, which encodes precorrin-3b methyltransferase. The inability of the cobalamin auxotroph to grow aerobically on ethanolamine implies that wild-typeP. denitrificans (which can grow on ethanolamine) expresses a cobalamin-dependent ethanolamine ammonia lyase and that this organism synthesizes cobalamin under both aerobic and anaerobic growth conditions. Comparison of the cobK and cobJgenes with their orthologues suggests that P. denitrificansuses the aerobic pathway for cobalamin synthesis. It is paradoxical that under anaerobic growth conditions, P. denitrificansappears to use the aerobic (oxygen-requiring) pathway for cobalamin synthesis. Anaerobic growth of the cobalamin auxotroph could be restored by the addition of deoxyribonucleosides to minimal media. These observations provide evidence that P. denitrificansexpresses a cobalamin-dependent ribonucleotide reductase, which is essential for growth only under anaerobic conditions.
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Atwal, A. S., R. M. Teather, S. N. Liss, and F. W. Collins. "Antimicrobial activity of 2-aminophenoxazin-3-one under anaerobic conditions." Canadian Journal of Microbiology 38, no. 10 (October 1, 1992): 1084–88. http://dx.doi.org/10.1139/m92-177.
Повний текст джерелаАнотація:
Potential toxicity of 2-aminophenoxazin-3-one to 20 bacterial species and two fungi and its inactivation under anaerobic conditions were investigated. Minimum inhibitory concentration for cellulolytic bacteria was in the range of 50–100 μg∙mL−1, but at 100 μg∙mL−1 of 2-aminophenoxazin-3-one, there was no effect on the growth of any of the noncellulolytic bacteria. Four noncellulolytic bacterial strains showed no inhibition of growth, even at 200 μg∙mL−1 of this compound. Under anaerobic conditions and in the presence of cysteine, the long wavelength absorption band of this compound slowly shifted from about 434 to 320 nm, and its inhibitory effect on RNA synthesis was relieved after one-half of a generation time in cultures of cellulolytic ruminai bacteria. A similar shift of absorption band was observed in rumen fluid filtered through a 0.22-μm Millipore filter. It was concluded that protonation of 2-aminophenoxazin-3-one under anaerobic conditions present in the rumen would considerably reduce its potential toxicity to cellulolytic bacteria. Key words: questomycin A, cellulolytic bacteria, cysteine, 2-aminophenoxazin-3-one, RNA synthesis.
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Escobar, Blanca, and Tomas Vargas. "Anaerobic Growth of Acidithiobacillus ferrooxidans on Pyrite." Advanced Materials Research 825 (October 2013): 96–99. http://dx.doi.org/10.4028/www.scientific.net/amr.825.96.
Повний текст джерелаАнотація:
In the bioleaching of mineral sulphides under the catalytic action ofAt. ferrooxidans,ferrous ion oxidation and sulfides/sulfur solubilization uses oxygen as the final electron acceptor. Also, under anaerobic conditions,At. ferrooxidanscan alternatively catalize the oxidation of sulfur or reduced inorganic sulfur compounds (RISC) using ferric iron as electron acceptor [1]. The formation of Fe (II) from pyrite and covellite in the ferric anaerobic bioleaching withA. ferrooxidans,has been studied and well documented [2,3]. The requirements of ferric iron as electron acceptor for the anaerobic growth ofAt. ferrooxidanson elemental sulfur has been demonstrated and a linear relationship was obtained between the concentration of ferrous iron accumulated in the cultures and the increase in cell density [4]. It has been suggested a possible role in the solubilization of metals from sulfide ores involving the participation of the enzyme sulfur (sulfide): Fe (III) oxidoreductase [5]. Bacterial growth ofAt. ferrooxidanshas also been reported in the oxidative anaerobic respiration using hydrogen as electron donor and ferric iron as electron acceptor [6]. Anaerobic reduction of ferric iron and ferrous iron production from pyrite byAt. ferrooxidanshas been demonstrated [2], however there are no reports about bacterial growth using this mineral. In this work, we studied the anaerobic bioleaching of pyrite with the aim to determine ifAt. ferrooxidansis capable to anaerobic growth on pyrite using ferric iron as electron acceptor.
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Smetanková, Jana, Zuzana Hladíková, František Valach, Michaela Zimanová, Zlatica Kohajdová, Gabriel Greif, and Mária Greifová. "Influence of aerobic and anaerobic conditions on the growth and metabolism of selected strains of Lactobacillus plantarum." Acta Chimica Slovaca 5, no. 2 (November 1, 2012): 204–10. http://dx.doi.org/10.2478/v10188-012-0031-1.
Повний текст джерелаАнотація:
Abstract Three wild strains of Lactobacillus plantarum were investigated for their growth and ability to produce lactic acid, acetic acid and ethanol under aerobic and anaerobic conditions. They were tested at three different temperatures (30 °C, 37 °C and 45 °C). The growth of lactobacilli was studied by measuring optical density (OD) at λ = 600 nm and pH value at the following times. With increasing temperature difference of cell yield was observed. The final cell yield under aerobic conditions was higher. Organic acids and ethanol were analysed using an HPLC RID method. Formation of lactic acid (as the major metabolite) was the slowest during cultivation at 30 °C, but the final amount of lactic acid showed the highest values. Concentrations of metabolites produced by lactobacilli after 48th hours of cultivation were: 9.18-11.48 g.dm-3 (lactic acid), 0.84-1.65 g.dm-3 (acetic acid) and 2.51-4.03 g.dm-3 (ethanol). No significant differences (p = 0.05) were found in production of lactic acid and ethanol by different bacterial strains under aerobic and anaerobic conditions. Statistically significant differences (p = 0.05) were observed in production of acetic acid by 2L2 under aerobic and anaerobic conditions and for production of ethanol under anaerobic conditions by strains 1L5 and 2L2.
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Härtig, Elisabeth, Anja Hartmann, Manuela Schätzle, Alessandra M. Albertini, and Dieter Jahn. "The Bacillus subtilis nrdEF Genes, Encoding a Class Ib Ribonucleotide Reductase, Are Essential for Aerobic and Anaerobic Growth." Applied and Environmental Microbiology 72, no. 8 (August 2006): 5260–65. http://dx.doi.org/10.1128/aem.00599-06.
Повний текст джерелаАнотація:
ABSTRACT Ribonucleotide reductases (RNRs) are essential for the biosynthesis of the deoxyribonucleoside triphosphates of DNA. Recently, it was proposed that externally supplied deoxyribonucleosides or DNA is required for the growth of Bacillus subtilis under strict anaerobic conditions (M. J. Folmsbee, M. J. McInerney, and D. P. Nagle, Appl. Environ. Microbiol. 70:5252-5257, 2004). Cultivation of B. subtilis on minimal medium in the presence of oxygen indicators in combination with oxygen electrode measurements and viable cell counting demonstrated that growth occurred under strict anaerobic conditions in the absence of externally supplied deoxyribonucleosides. The nrdEF genes encode the only obvious RNR in B. subtilis. A temperature-sensitive nrdE mutant failed to grow under aerobic and anaerobic conditions, indicating that this oxygen-dependent class I RNR has an essential role under both growth conditions. Aerobic growth and anaerobic growth of the nrdE mutant were rescued by addition of deoxynucleotides. The nrd locus consists of an nrdI-nrdE-nrdF-ymaB operon. The 5′ end of the corresponding mRNA revealed transcriptional start sites 45 and 48 bp upstream of the translational start of nrdI. Anaerobic transcription of the operon was found to be dependent on the presence of intact genes for the ResDE two-component redox regulatory system. Two potential ResD binding sites were identified approximately 62 bp (site A) and 50 bp (site B) upstream of the transcriptional start sites by a bioinformatic approach. Only mutation of site B eliminated nrd expression. Aerobic transcription was ResDE independent but required additional promoter elements localized between 88 and 275 bp upstream of the transcriptional start.
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Ali, Muhamad, Melinda Sanggu Artha, Muhamad Aidil Fadjar Suryadi, Djoko Kisworo, and Muhamad Amin. "The Growth and Bacteriocin Productions of Enterococcus Faecium Cultured in Aerobic and Anaerobic Conditions." IOP Conference Series: Earth and Environmental Science 1036, no. 1 (July 1, 2022): 012063. http://dx.doi.org/10.1088/1755-1315/1036/1/012063.
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Abstract Bacteriocins are antimicrobial compounds produced by diverse members of lactic acid bacteria (LAB). Bacteriocins can be used as food bio preservatives to increase the shelf life of food naturally by preventing or killing foodborne pathogens. One of the lactic acid bacteria that produce bacteriocin is Enterococcus faecium. Some LAB grown on semi-synthetic complex media such as MRS (de Mann Rogosa Sharpe) can make a high population of bacterial cells and relatively large bacteriocins. This study aimed to observe the growth of E. faecium on MRS and LB media under aerobic and anaerobic conditions. Cultures were performed for 4.5h, 5h, 5.5h, 6h, 6.5h, and 7h. The amount of bacteriocin produced was investigated by SDS-PAGE. Meanwhile, the inhibitory activity was measured against Listeria monocytogenes (LM). The results showed that E. faecium grew better in deMan Rogosa Sharp (MRS) medium under anaerobic conditions than in MRS medium under aerobic conditions as well as Luria Bertani (LB) media under aerobic and anaerobic conditions. The SDS-PAGE results showed a protein band measuring about 90 kDa, which was thought to be a bacteriocin. The inhibition test showed a clear zone in the LM culture, which indicated that the bacteria produced bacteriocins that could inhibit the growth of pathogenic bacteria.
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Vemuri, G. N., M. A. Eiteman, and E. Altman. "Effects of Growth Mode and Pyruvate Carboxylase on Succinic Acid Production by Metabolically Engineered Strains of Escherichia coli." Applied and Environmental Microbiology 68, no. 4 (April 2002): 1715–27. http://dx.doi.org/10.1128/aem.68.4.1715-1727.2002.
Повний текст джерелаАнотація:
ABSTRACT Escherichia coli NZN111, which lacks activities for pyruvate-formate lyase and lactate dehydrogenase, and AFP111, a derivative which contains an additional mutation in ptsG (a gene encoding an enzyme of the glucose phophotransferase system), accumulate significant levels of succinic acid (succinate) under anaerobic conditions. Plasmid pTrc99A-pyc, which expresses the Rhizobium etli pyruvate carboxylase enzyme, was introduced into both strains. We compared growth, substrate consumption, product formation, and activities of seven key enzymes (acetate kinase, fumarate reductase, glucokinase, isocitrate dehydrogenase, isocitrate lyase, phosphoenolpyruvate carboxylase, and pyruvate carboxylase) from glucose for NZN111, NZN111/pTrc99A-pyc, AFP111, and AFP111/pTrc99A-pyc under both exclusively anaerobic and dual-phase conditions (an aerobic growth phase followed by an anaerobic production phase). The highest succinate mass yield was attained with AFP111/pTrc99A-pyc under dual-phase conditions with low pyruvate carboxylase activity. Dual-phase conditions led to significant isocitrate lyase activity in both NZN111 and AFP111, while under exclusively anaerobic conditions, an absence of isocitrate lyase activity resulted in significant pyruvate accumulation. Enzyme assays indicated that under dual-phase conditions, carbon flows not only through the reductive arm of the tricarboxylic acid cycle for succinate generation but also through the glyoxylate shunt and thus provides the cells with metabolic flexibility in the formation of succinate. Significant glucokinase activity in AFP111 compared to NZN111 similarly permits increased metabolic flexibility of AFP111. The differences between the strains and the benefit of pyruvate carboxylase under both exclusively anaerobic and dual-phase conditions are discussed in light of the cellular constraint for a redox balance.
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Chovanec, Peter, Michal Kaliňák, Tibor Liptaj, Naďa Pronayová, Tibor Jakubík, Daniela Hudecová, and Ľudovít Varečka. "Study ofTrichoderma viridemetabolism under conditions of the restriction of oxidative processes." Canadian Journal of Microbiology 51, no. 10 (September 1, 2005): 853–62. http://dx.doi.org/10.1139/w05-075.
Повний текст джерелаАнотація:
Trichoderma viride was capable of growth and conidiation in the presence of high concentrations of the uncoupler 3,3′,4′,5-tetrachlorosalicylanilide (up to 100 µmol·L–1) and of the respiration inhibitor mucidin (up to 100 µmol·L–1) in both submerged and surface cultivation. When vegetative mycelia were cultivated on the solid Czapek-Dox medium with yeast autolysate under an anaerobic and CO2-containing atmosphere, the growth was observed only rarely but the microorganism survived as long as 3 months under these conditions. Major products of metabolism of both aerobic and anaerobic submerged mycelia were identified by means of1H-NMR measurements. Major products excreted to the medium under aerobic conditions were succinic and citric acids. Major metabolites present in the submerged mycelia were γ-aminobutyric (and glutamic) acid and alanine. Under anaerobic conditions, citric acid was not excreted into the medium but ethanol appeared. Its production could not be increased upon increasing the sugar concentration. The appearance of secondary metabolites was found to be modified by oxygen availability during the mycelial growth. Results suggest that the vegetative form of T. viride is capable of fermentative metabolism characterized by the production of ethanol and succinate and that the excretion of carboxylic acids is developmentally regulated and modified by oxygen availability.Key words: Trichoderma, mycelia, anaerobiosis, citrate, succinate, ethanol, GABA.
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Sigalevich, Pavel, and Yehuda Cohen. "Oxygen-Dependent Growth of the Sulfate-Reducing Bacterium Desulfovibrio oxyclinae in Coculture withMarinobacter sp. Strain MB in an Aerated Sulfate-Depleted Chemostat." Applied and Environmental Microbiology 66, no. 11 (November 1, 2000): 5019–23. http://dx.doi.org/10.1128/aem.66.11.5019-5023.2000.
Повний текст джерелаАнотація:
ABSTRACT A chemostat coculture of the sulfate-reducing bacteriumDesulfovibrio oxyclinae and the facultatively aerobic heterotroph Marinobacter sp. strain MB was grown for 1 week under anaerobic conditions at a dilution rate of 0.05 h−1. It was then exposed to an oxygen flux of 223 μmol min−1by gassing the growth vessel with 5% O2. Sulfate reduction persisted under these conditions, though the amount of sulfate reduced decreased by 45% compared to the amount reduced during the initial anaerobic mode. After 1 week of growth under these conditions, sulfate was excluded from the incoming medium. The sulfate concentration in the growth vessel decreased exponentially from 4.1 mM to 2.5 μM. The coculture consumed oxygen effectively, and no residual oxygen was detected during either growth mode in which oxygen was supplied. The proportion of D. oxyclinae cells in the coculture as determined by in situ hybridization decreased from 86% under anaerobic conditions to 70% in the microaerobic sulfate-reducing mode and 34% in the microaerobic sulfate-depleted mode. As determined by the most-probable-number (MPN) method, the numbers of viable D. oxyclinae cells during the two microaerobic growth modes decreased compared to the numbers during the anaerobic growth mode. However, there was no significant difference between the MPN values for the two modes when oxygen was supplied. The patterns of consumption of electron donors and acceptors suggested that when oxygen was supplied in the absence of sulfate and thiosulfate, D. oxyclinaeperformed incomplete aerobic oxidation of lactate to acetate. This is the first observation of oxygen-dependent growth of a sulfate-reducing bacterium in the absence of either sulfate or thiosulfate. Cells harvested during the microaerobic sulfate-depleted stage and exposed to sulfate and thiosulfate in a respiration chamber were capable of anaerobic sulfate and thiosulfate reduction.
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Kane, Aunica L., Evan D. Brutinel, Heena Joo, Rebecca Maysonet, Chelsey M. VanDrisse, Nicholas J. Kotloski, and Jeffrey A. Gralnick. "Formate Metabolism in Shewanella oneidensis Generates Proton Motive Force and Prevents Growth without an Electron Acceptor." Journal of Bacteriology 198, no. 8 (February 16, 2016): 1337–46. http://dx.doi.org/10.1128/jb.00927-15.
Повний текст джерелаАнотація:
ABSTRACTShewanella oneidensisstrain MR-1 is a facultative anaerobe that thrives in redox-stratified environments due to its ability to utilize a wide array of terminal electron acceptors. Conversely, the electron donors utilized byS. oneidensisare more limited and include products of primary fermentation such as lactate, pyruvate, formate, and hydrogen. Lactate, pyruvate, and hydrogen metabolisms inS. oneidensishave been described previously, but little is known about the role of formate oxidation in the ecophysiology of these bacteria. Formate is produced byS. oneidensisthrough pyruvate formate lyase during anaerobic growth on carbon sources that enter metabolism at or above the level of pyruvate, and the genome contains three gene clusters predicted to encode three complete formate dehydrogenase complexes. To determine the contribution of each complex to formate metabolism, strains lacking one, two, or all three annotated formate dehydrogenase gene clusters were generated and examined for growth rates and yields on a variety of carbon sources. Here, we report that formate oxidation contributes to both the growth rate and yield ofS. oneidensisthrough the generation of proton motive force. Exogenous formate also greatly accelerated growth onN-acetylglucosamine, a carbon source normally utilized very slowly byS. oneidensisunder anaerobic conditions. Surprisingly, deletion of all three formate dehydrogenase gene clusters enabled growth ofS. oneidensisusing pyruvate in the absence of a terminal electron acceptor, a mode of growth never before observed in these bacteria. Our results demonstrate that formate oxidation is a fundamental strategy under anaerobic conditions for energy conservation inS. oneidensis.IMPORTANCEShewanellaspecies have garnered interest in biotechnology applications for their ability to respire extracellular terminal electron acceptors, such as insoluble iron oxides and electrodes. While much effort has gone into studying the proteins for extracellular electron transport, how electrons generated through the oxidation of organic carbon sources enter this pathway remains understudied. Here, we quantify the role of formate oxidation in the anaerobic physiology ofShewanella oneidensis. Formate oxidation contributes to both the growth rate and yield on a variety of carbon sources through the generation of proton motive force. Advances in our understanding of the anaerobic metabolism ofS. oneidensisare important for our ability to utilize and engineer this organism for applications in bioenergy, biocatalysis, and bioremediation.
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Najafpour, Ghasem D., Marjan Khorrami, Habibollah Younesi, and Maryam N. Hosseinpour. "BIODEMINERALIZATION OF SHRIMP SHELL VIA AEROBIC AND ANAEROBIC CONDITIONS: GROWTH KINETIC STUDIES." Environmental Engineering and Management Journal 14, no. 4 (2015): 731–36. http://dx.doi.org/10.30638/eemj.2015.081.
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Avnimelech, Yoram, and Gill Zohar. "The effect of local anaerobic conditions on growth retardation in aquaculture systems." Aquaculture 58, no. 3-4 (November 1986): 167–74. http://dx.doi.org/10.1016/0044-8486(86)90082-7.
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Dou, Junfeng, Wei Qin, Jing Yuan, Aizhong Ding, En Xie, Yingying Wang, and Xiang Liu. "Growth Kinetics ofMicrobacterium lacticumand Nitrate-Dependent Degradation of Ethylbenzene under Anaerobic Conditions." Bioremediation Journal 18, no. 3 (July 3, 2014): 248–57. http://dx.doi.org/10.1080/10889868.2014.889074.
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Medina-Colorado, Audrie A., Kathleen L. Vincent, Aaron L. Miller, Carrie A. Maxwell, Lauren N. Dawson, Trevelyn Olive, Elena V. Kozlova, Marc M. Baum, and Richard B. Pyles. "Vaginal ecosystem modeling of growth patterns of anaerobic bacteria in microaerophilic conditions." Anaerobe 45 (June 2017): 10–18. http://dx.doi.org/10.1016/j.anaerobe.2017.04.014.
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Mijaylova-Nacheva, P., E. Ramírez-Camperos, and S. Cuevas-Velasco. "Treatment of organic synthesis wastewater using anaerobic packed bed and aerobic suspended growth bioreactors." Water Science and Technology 55, no. 7 (April 1, 2007): 235–43. http://dx.doi.org/10.2166/wst.2007.150.
Повний текст джерелаАнотація:
The performance of an anaerobic mesophilic packed bed reactor, with a mixture of GAC and tezontle, followed by an aerobic suspended growth system was studied for the treatment of organic chemical wastewater with a high COD concentration (22–29 g/L). The testing of the anaerobic–aerobic system was conducted in an experimental set-up for almost 2.5 years. Different operational conditions were evaluated. The anaerobic reactor showed performance stability and COD removals higher than 80% were obtained with loads up to 16.6 kg.m−3.d−1. The acclimation of the aerobic biomass to the substrate in the anaerobic effluent was very quick and COD removals higher than 94% were obtained even at high organic loads. The combined anaerobic–aerobic system allowed total COD removals higher than 99.5% and the accomplishment of the discharge requirements of 200 mgCOD/L when the anaerobic reactor was operated with loads of 8–11 kg.m−3.d−1 and the aerobic reactor with 0.33 kg.kg−1.d−1, being the total HRT of 4.4. The average TKN removal in the anaerobic–aerobic system was 97%, the average for the anaerobic reactor being 52% and that one for the aerobic system being 94%.
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Chudoba, P., J. J. Chevalier, J. Chang, and B. Capdeville. "Effect of Anaerobic Stabilization of Activated Sludge on its Production under Batch Conditions at Various So/Xo Ratios." Water Science and Technology 23, no. 4-6 (February 1, 1991): 917–26. http://dx.doi.org/10.2166/wst.1991.0543.
Повний текст джерелаАнотація:
The effect of anaerobic stabilization of returned activated sludge in a continuous system on biomass production under batch conditions at various So/Xo ratios was studied. A system without anaerobic sludge stabilization was also operated as a control unit. All experiments were carried out with Toulouse settled wastewater. Biomass growth, substrate removal, oxygen uptake and carbon dioxide production were measured using a quadrupole mass spectrometer (Inficon IQ 200) coupled to a 15-liter fermentor (Biolafitte). The results confirmed that one of the most important parameters in batch cultivation is the initial So/Xo ratio. It was found that anaerobic treatment of activated sludge changed its behaviour during batch cultivation. As a consequence, the observed biomass yield (Yobs) decreased with increasing So/Xo while it remained constant with the sludge from the control unit. In the anaerobic reactor, microorganisms are subject to a physiological shock due to lack of oxygen and food. Under the above conditions, they use ATP as a source of energy. After they are returned to aerobiosis and supplied with exogenous substrate, they rebuild energy reserves at the expense of growth.