Showing papers on "Methanogen published in 1991"
TL;DR: The results indicate that both aerobes and anaerobes demethylate mercury in sediments, but that either group may dominate in a particular sediment type.
Abstract: Demethylation of monomethylmercury in freshwater and estuarine sediments and in bacterial cultures was investigated with 14CH3HgI. Under anaerobiosis, results with inhibitors indicated partial involvement of both sulfate reducers and methanogens, the former dominating estuarine sediments, while both were active in freshwaters. Aerobes were the most significant demethylators in estuarine sediments, but were unimportant in freshwater sediments. Products of anaerobic demethylation were mainly 14CO2 as well as lesser amounts of 14CH4. Acetogenic activity resulted in fixation of some 14CO2 produced from 14CH3HgI into acetate. Aerobic demethylation in estuarine sediments produced only 14CH4, while aerobic demethylation in freshwater sediments produced small amounts of both 14CH4 and 14CO2. Two species of Desulfovibrio produced only traces of 14CH4 from 14CH3HgI, while a culture of a methylotrophic methanogen formed traces of 14CO2 and 14CH4 when grown on trimethylamine in the presence of the 14CH3HgI. These results indicate that both aerobes and anaerobes demethylate mercury in sediments, but that either group may dominate in a particular sediment type. Aerobic demethylation in the estuarine sediments appeared to proceed by the previously characterized organomercurial-lyase pathway, because methane was the sole product. However, aerobic demethylation in freshwater sediments as well as anaerobic demethylation in all sediments studied produced primarily carbon dioxide. This indicates the presence of an oxidative pathway, possibly one in which methylmercury serves as an analog of one-carbon substrates.
297 citations
TL;DR: It was found that the sensitivity of the pure cultures was similar to that of the methanogens in the sludge, and the numbers of methanogenic bacteria were affected by the presence of propionate even at concentrations as low as 20 or 30 mM.
Abstract: The effect of propionate toxicity at different pH values (6.5, 7.0, and 8.0) on methanogen-enriched sludge. Methanobrevibacter smithii, and Methanospirillum hungatii was studied. Organisms were grown in Balch medium 3 in Hungate tubes, and toxicity was characterized by a decrease in production of methane and in bacterial numbers. Propionate inhibited bacterial growth and cumulative methane production at concentrations as low as 20 mM. In the absence of propionate, the methanogen-enriched sludge and M. smithii showed better cumulative methane production at pH 6.5 and 7.0 than at pH 8.0. However, in the presence of propionate, these organisms showed better cumulative methane production at pH 8.0. M. hungatii differed in its behavior; the best values of cumulative methane production for this organism occurred at pH 7.0. Bacterial numbers reflected the microbial response to the presence of propionate. The highest counts of methanogenic bacteria were observed at pH 6.5 and 8.0. The numbers of methanogens were affected by the presence of propionate even at concentrations as low as 20 or 30 mM; at propionate concentrations above 80 mM, the methanogen count was affected by at least 2 orders of magnitude. Upon comparison of the responses of the pure cultures and the methanogen-enriched sludge to increasing propionate concentrations, it was found that the sensitivity of the pure cultures was similar to that of the methanogens in the sludge.
137 citations
TL;DR: It is unlikely that the maintenance of a low pH2 within the cells due to H2-consumption by the bacteria is important to the ciliates, and the energetic advantage conferred by endosymbiont methanogens in Plagiopyla and in Metopus contortus probably is due to excretion of organic material from the bacteria at the expense of bacterial reproduction.
Abstract: Endosymbiotic methanogenic bacteria of three species of anaerobic ciliates (Plagiopyla frontata, Metopus conforms, and M. palaeformis) were inactivated with the specific methanogen inhibitor 2-bromoethanesulfonic acid. the absence of endosymbiont methanogens reduced growth rate and growth yield by about 30% in P. frontata and M. contortus, while no significant change in fitness was observed in M. palaeformis. In Plagiopyla the growth rate constant is not affected by an artificially increased pH2 neither in normal nor in methanogen-free ciliates. the energetic advantage conferred by endosymbiont methanogens in Plagiopyla and in Metopus contortus probably is due to excretion of organic material from the bacteria at the expense of bacterial reproduction. It is unlikely that the maintenance of a low pH2 within the cells due to H2-consumption by the bacteria is important to the ciliates.
73 citations
TL;DR: Reactor design did not appear to be as important as the wastewater composition in causing changes to the microbial communities and statistical analysis showed no significant difference between the numbers in each reactor and with respect to time after start-up.
70 citations
TL;DR: Examination of the anaerobic ciliates living in the hypolimnion of a 14 m deep sulphide-rich solution lake in Spain indicates that it is significant and that it may amount to 4 × 10(-5) g cm(-2)d(-1).
62 citations
TL;DR: It is established that anaerobic protozoa do live in municipal landfill material although they probably spend much of the time encysted, especially in the drier (< 40% water) site, and Dispersal of methanogen-bearing protozoan cysts through oxygenated environments is a potential mechanism of transfer between landfill sites and other an aerobic environments.
Abstract: We have established that anaerobic protozoa do live in municipal landfill material although they probably spend much of the time encysted, especially in the drier (< 40% water) site. At least eight species were observed; they were readily isolated by adding anoxic water to dry landfill samples. The ciliate Metopus palaeformis was frequently i isolated; it appears to be ubiquitous in anaerobic landfills. It has a polymorphic life cycle, it is positive for hydrogenase, each ciliate contains about 500 bromoethanesulfonate-sensitive methanogen symbionts (probably Methanobacterium formicicum), and maximum cell densities in culture exceed 3000 per ml. The methanogens are not attached to the hydrogenosomes, neither do they undergo morphological transformation; the ciliate receives no measurable energetic advantage from its symbionts. The ciliate encysts in response to a shortage of food or water, and the methanogens remain viable within the cysts. When the protozoon excysts, the methanogens resume growth and cell division within the trophic form of the ciliate. Unlike free-living methanogens, the M. palaeformis-methanogen consortium is not particularly sensitive to oxygen; the symbiotic methanogens remain viable following exposure of the consortium to atmospheric oxygen for several days. Dispersal of methanogen-bearing protozoan cysts through oxygenated environments is a potential mechanism of transfer between landfill sites and other anaerobic environments. Anaerobic protozoan consortia are theoretically capable of making a significant contribution to methane generation from wet landfill sites.
61 citations
TL;DR: M. methylutens, a methylotrophic methanogen isolated from submarine sediments, is suggested to be a new strain ofMethanococcoides methylutENS, an anaerobic methanogenic bacterium isolated from oxygenated coastal waters.
Abstract: Enrichment cultures containing marine plankton from oxygenated coastal waters (50–108% saturated) with supersaturated levels of methane (>700% saturated) yielded a strictly anaerobic methanogenic bacterium. Nonmotile, non-spore-forming, regular to slightly irregular cocci (0.5–0.8µm) were evident by phase contrast, epifluorescence, and scanning electron microscopies. The unpurified isolate required NaCl for growth, with maximal methanogenesis at 240 mM NaCl at 22°C. The optimal temperature range for growth was 22–31°C, and the optimal range for methanogenesis was 26–35°C. Mono-, di-, and trimethylated amines or methanol were substrates for methanogenesis; sodium acetate and H2:CO2 were not. The DNA base composition was 42 ±1% guanine plus cytosine. Serology suggested the isolate may be a new strain ofMethanococcoides methylutens. Morphology, growth physiology, DNA base content, and serology are all consistent with the type description ofM. methylutens, a methylotrophic methanogen isolated from submarine sediments.
47 citations
Patent•
24 May 1991
TL;DR: In this article, the authors proposed methods of improving anaerobic digestion by enhancing the microorganism population through the creation of a nutrient environment more favorable for microbial growth and through the addition of microbes and, more particularly, by the adding of chelating agents and methanogens.
Abstract: Methods of improving anaerobic digestion by enhancing the microorganism population through the creation of a nutrient environment more favorable for microbial growth and through the addition of microbes and, more particularly, by the addition of chelating agents, chelating agents and nutrients, and methanogens. Methods for the improved production of said methanogens by the provision of controlled amount of methanol and H 2 and CO 2 . Methods for the improved preservation of said methanogen by ultra-freezing and freeze-drying.
43 citations
TL;DR: The diffusion model demonstrated that for the particular system studied, the rates of hydrogen diffusion could account for the overall rate of methane production.
Abstract: The ability of hydrogen diffusion to account for the rates of methane production in microbial aggregates was studied in a defined coculture consisting of a sulfate reducer grown as a syntrophic hydrogen producer in the absence of sulfate and a methanogen. The hydrogen uptake kinetics of the methanogen were determined using the infinite dilution technique. The maximum hydrogen uptake velocity was 7.1 nmol/min/μg protein and the half saturation constant for hydrogen uptake was 386 nmol/liter. A threshold of 28 nmol/liter below which no further hydrogen consumption occurred was observed. The reconstituted co-culture was shown to produce methane at rates similar to mixed culture enrichments grown on lactate. The diffusion model demonstrated that for the particular system studied, the rates of hydrogen diffusion could account for the overall rate of methane production.
24 citations
TL;DR: In this article, the interrelationships between an obligate hydrogen-producing and two different hydrogen-scavenging populations grown as synthrophic members of a 3-chlorobenzoate degrading methanogenic consortium were studied.
Abstract: The interrelationships between an obligate hydrogen-producing and two different hydrogen-scavenging populations grown as synthrophic members of a 3-chlorobenzoate degrading methanogenic consortium were studied. The hydrogen producer was a benzoate degrader (strain BZ-2), and the hydrogen consumers were a 3-chlorobenzoate dechlorinating bacterium (Desulfomonile tiedjei) and a hydrogenotropic methanogen (Methanospirillum strain PM-1). When a mixture of 3-chlorobenzoate plus benzoate was added to this consortium, the rate of benzoate degradation was 50% higher, at slightly lower H2 concentrations, than when benzoate alone was added. The enhanced benzoate degradation rate was apparantly triggered by the lower H2 concentration, as the rate of benzoate degradation was shown to be a function of the H2 concentration. By offering a hydrogen sink, in addition to methanogenesis, the dechlorinating hydrogen-scavenging population stimulated the rate of benzoate degradation. The lowering of the H2 concentration was very small, which was in agreement with the observation that the rate of methanogenesis was hardly affected by this lower hydrogen concentration. Thus there was no significant competition for H2 between the two hydrogen-scavenging populations in the consortium, as they practically complemented each other's hydrogen-scavenging potential at in situ hydrogen concentrations during the degradation of 3-chlorobenzoate. The H2 concentrations at which hydrogen driven methanogenesis by Methanospirillum occurred in the consortium were well below the threshold concentration extrapolated for this methanogen after growth at high H2 concentrations.
22 citations
TL;DR: A co-culture of Clostridium formicoaceticum and Methanosarcina mazei converted lactate to methane and carbon dioxide at mesophilic temperatures and pH values near 7.0 and may be useful together with the homolactic bacterium Stretococcus lactis to convert lactose to methane.
Abstract: A co-culture of Clostridium formicoaceticum and Methanosarcina mazei converted lactate to methane and carbon dioxide at mesophilic temperatures and pH values near 7.0. Lactate was first converted to acetate by the homoacetogen, and then to CH4 and CO2 by the methanogen, with the second reaction as the rate-limiting step. The methane yield was about 1.45 mol/mol lactate. These two organisms formed a mutualistic association and may be useful together with the homolactic bacterium Stretococcus lactis to convert lactose to methane.
TL;DR: A new mesophilic, irregular coccoid methanogen isolated from a river sediment that had the polar lipid pattern and the polyamine content were similar to that found in several Methanoculleus species.
Abstract: A new mesophilic, irregular coccoid methanogen isolated from a river sediment is described. Hydrogen plus carbon dioxide or formate served as substrates for methanogenesis in a mineral salt medium. For growth acetate is strictly required. Elevated levels of sodium chloride were not required and were inhibitory at concentrations above 1.5% (w/v). The optimal growth temperature was at 45°C. The DNA base ratio was 48.6±1 mol% G+C. The polar lipid pattern and the polyamine content were similar to that found in several Methanoculleus species. The new isolate CB-1 was assigned as Methanoculleus oldenburgensis (DSM 6216).
TL;DR: Three metabolic types of obligately anaerobic, halophilic bacteria were isolated from oil reservoir brines and characterized to better understand the ecology of an oil reservoir.
Abstract: Three metabolic types of obligately anaerobic, halophilic bacteria were isolated from oil reservoir brines and characterized to better understand the ecology of an oil reservoir. These included a methanogenic bacterium, a sulfate-reducing bacterium, and a fermentative bacterium. All species were isolated by plating from enrichment cultures containing substrates specific for each metabolic type. The methanogenic bacterium was isolated by enrichment with trimethylamine. Methane production occurred only with trimethylamine compounds or methanol as substrates. Sodium, magnesium, and potassium were all required for growth. This organism appears to be a member of the genus Methanohalophilus , based on substrate utilization and general growth characteristics. The sulfate-reducing bacterium was isolated by enrichment with a lactate-sulfate medium containing 3% NaCl. This isolate utilized lactate as an electron donor for sulfate reduction and, in addition, contained desulfovirdin, typical of the genus Desulfovibrio. In contrast to the methanogen, only sodium was required for growth. Finally, the sheathed bacterium was isolated by enrichment with glucose. Sodium was also required by this isolate for growth. This organism is a fermentative bacterium surrounded by a sheath, and is capable of reducing elemental sulfur to hydrogen sulfide. These are all characteristics of the genus Thermotoga.
TL;DR: Increased diether lipid synthesis by methanogens was observed with oxygen addition, and methanogen lipid synthesis continued at a low level in the absence of detectable methanogenesis with chloroform addition, which may be due to previously unknown adaptations to toxic compounds by meethanogens.
Abstract: The effects of oxygen and chloroform addition on microbial metabolic activities were measured on a unique thermophilic high-solids high-productivity methanogenic reactor using a combination of radiotracer, lipid analysis, and microcosm techniques. Methane production and the incorporation of 14C-2-acetate into methane were decreased by both oxygen and chloroform treatment. Oxygen increased and chloroform decreased total CO2 production and CO2 production from labeled acetate. Introduction of oxygen decreased methanogenesis by facultative anaerobes competing for reducing equivalents. Chloroform was directly toxic to methanogens at the low application level, and inhibited all metabolic activities at the high application level. Increased diether lipid synthesis by methanogens was observed with oxygen addition, and methanogen lipid synthesis continued at a low level in the absence of detectable methanogenesis with chloroform addition. These responses may be due to previously unknown adaptations to toxic compounds by methanogens.
TL;DR: An overwhelmingly predominant methanogenic subpopulation was observed which, after 2.5 years of operation, represented nearly 90% of all methanogens detectable immunologically, reaching 97% 1 year later.
Abstract: Antibody probes and immunotechnology were used in qualitative and quantitative studies of the methanogenic flora of two mesophilic continuously stirred tank reactors in which wood or sorghum served as substrates. This represents the first immunological study of a wood-fermenting bioreactor. An overwhelmingly predominant methanogenic subpopulation was observed which, after 2.5 years of operation represented nearly 90% of all methanogens detectable immunologically, reaching 97% 1 year later. This subpopulation was weakly related antigenically to Methanomicrobium mobile BP and morphologically was indistinguishable from it. Such predominance of a single methanogen subpopulation and its relatedness to M. mobile BP has not been observed previously in bioreactors, and may be a distinctive trait of wood-fermenting bioreactors. The majority of other methanogens detected immunologically were not of the same immunotype as reference strains, suggesting that important methanogens remain to be isolated from these systems.