The following major advances were made in the past two years: both acetate activating enzymes were characterized and the regulation of synthesis was studied; direct biochemical evidence for the proposed function of the CODH was obtained, and the CODH comp...

Our current understanding of the pathway of acetate conversion to methane in Methanosarcina thermophila is depicted. Our accomplishments this past year include phosphotransacetylase, the corrinoid/Fe-S protein component of the carbon monoxide dehydrogenas...

Anaerobic methane oxidation is a general process important in controlling fluxes of methane from anoxic marine sediments. The responsible organism has not been isolated, and little is known about the electron acceptors and substrates involved in the process. Laboratory evidence indicates that sulfate reducers and methanogens are able to oxidize small quantities of methane. ...

The competition between acetate utilizing methane-producing bacteria (MB) and sulfate-reducing bacteria (SRB) was studied in mesophilic (30 degrees C) upflow anaerobic sludge bed (UASB) reactors (upward velocity 1 m h-1; pH 8) treating volatile fatty acids and sulfate. The UASB reactors treated a VFA mixture (with ...

The competition between acetate utilizing methane-producing bacteria (MB) and sulfate-reducing bacteria (SRB) was studied in mesophilic (30 C) upflow anaerobic sludge bed (UASB) reactors treating volatile fatty acids and sulfate. The UASB reactors treated a VFA mixture (with an acetate:propionate:butyrate ratio of ...

Population development of key groups of bacteria involved in municipal refuse conversion to methane was measured from the time of initial incubation through the onset of methane production. Hemicellulolytic bacteria, cellulolytic bacteria, hydrogen-producing acetogens, and acetate-and H{sub 2}-plus-CO{sub 2}-utilizing ...

Acetate conversion to methane and C0{sub 2} by the methanogenic archaebacteria is a primary rate limiting step in anaerobic biodegradative processes in nature. However, the genetic study of these organisms has not been experimentally tractable due to the inability to grow and plate the organisms as single cells, and to extract high molecular weight DNA and RNA without ...

Acetate conversion to methane and C0{sub 2} by the methanogenic archaebacteria is a primary rate limiting step in anaerobic biodegradative processes in nature. However, the genetic study of these organisms has not been experimentally tractable due to the inability to grow and plate the organisms as single cells, and to extract high molecular weight DNA and RNA without ...

We studied syntrophic butyrate degradation in thermophilic mixed cultures containing a butyrate-degrading bacterium isolated in coculture with Methanobacterium thermoautotrophicum or in triculture with M. thermoautotrophicum and the TAM organism, a thermophilic acetate-utilizing methanogenic bacterium. Butyrate was ?-oxidized to acetate with protons as the ...

Major acetate-utilizing bacterial and archaeal populations in methanogenic anaerobic digester sludge were identified and quantified by radioisotope- and stable-isotope-based functional analyses, microautoradiography-fluorescence in situ hybridization (MAR-FISH) and stable-isotope probing of 16S rRNA (RNA-SIP) that can directly link 16S rRNA phylogeny with ...

Investigations into the biochemistry and physiology of the four major groups of microorganisms (primary, ancillary, secondary and methane bacteria) involved in the anaerobic conversion of cellulose to methane and carbon dioxide are presented. The investigations of the ancillary bacteria emphasize the isolation of new strains and increasing ethanol ...

Population development of key groups of bacteria involved in municipal refuse conversion to methane was measured from the time of initial incubation through the onset of methane production. Hemicellulolytic bacteria, cellulolytic bacteria, hydrogen-producing acetogens, and acetate- and H(2)-plus-CO(2)-utilizing ...

Population development of key groups of bacteria involved in municipal refuse conversion to methane was measured from the time of initial incubation through the onset of methane production. Hemicellulolytic bacteria, cellulolytic bacteria, hydrogen-producing acetogens, and acetate- and ...

Anaerobic degradation of protein-rich material results in the release of ammonium. An increase in levels of ammonium in biogas reactors usually results in less effective degradation and lower methane-formation rates for two reasons: Acetate-utilizing meth...

This paper describes the effect of the nutrients iron (Fe), nickel (Ni), zinc (Zn), cobalt (Co), and molybdenum (Mo) on biomass evolution in an upflow anaerobic sludge blanket (UASB) reactor metabolizing synthetic sulfate-laden organics at varying operating conditions during a period of 540 days. A bench-scale model of a UASB reactor was operated at a temperature of 35 degrees C for a chemical ...

The general features are known for the pathway by which most methane is produced in nature. All acetate-utilizing methanogenic microorganisms contain CODH which catalyzes the cleavage of acetyl-CoA; however, the pathway differs from all other acetate-utilizing anaerobes in that the methyl group is reduced to methane with electrons ...

The 16S ribosomal RNZs from two species of met methanogenic bacteria, the mesophile Methanobacterium

The C isotopic composition of CH4 emissions are strongly influenced by the pathway of CH4 formation. Contrary to data from other freshwater systems, soil gas and surface flux measurements made in the tropical rain forests of Puerto Rico strongly suggest that CH4 produced in these environments was derived from CO2 reduction, rather than from acetate consumption. This study explored the effects of ...

The organization and species composition of bacterial trophic groups associated with lactose biomethanation were investigated in a whey-processing chemostat by enumeration, isolation, and general characterization studies. The bacteria were spatially organized as free-living forms and as self-immobilized forms appearing in flocs. Three dominant bacterial trophic group ...

Methane fermentation has been widely used as a waste-water treatment system because of the low consumption of energy, low level of sludge production, and recovery of methane as a source of energy. In this system, acetate is the precursor for about 70% of the methane produced during the anaerobic digestion of organic compounds, and the decarboxylation of acetate is considered to be the ...

Methanogenic bacteria were isolated from mesophilic anaerobic digesters. The isolates were able to utilize H2 and CO2 acetate, formate and methanol, but were not able to metabolize propionate and butyrate. It was shown the propionate and butyrate are not substrates for methanogen...

... ENZYMATIC ANALYSIS TO MEASUREMENTS OF THE ACTIVITY OF METHANOGENIC BACTERIA, WHICH AFFECT BIOGAS PRODUCTION AND ...

Concurrent geochemical analyses of porewater and genetic analyses of wetland sediment over time in laboratory microcosm experiments are being used to define biodegradation pathways of 1,1,2,2-tetrachloroethane (PCA) and associated critical microorganisms in anaerobic wetland sediments. These experiments were conducted to better understand factors controlling in situ daughter product distribution ...

Fluoride is a common contaminant in a variety of industrial wastewaters. Available information on the potential toxicity of fluoride to microorganisms implicated in biological wastewater treatment is very limited. The objective of this study was to evaluate the inhibitory effect of fluoride towards the main microbial populations responsible for the removal of organic constituents and nutrients in ...

Methanogenic bacteria are anaerobic, oxygen-intolerant microorganisms, and it is only by studying the different habitats of such bacteria that fundamental information about their ecology becomes available. This research has evaluated methanogenic bacteria in apparently aerobic ecosystems, in ...

A mixed culture of human fecal bacteria was grown for 120 days in a three-stage continuous culture system. To reproduce some of the nutritional and pH characteristics of the large gut, each vessel had a different operating volume (0.3, 0.5, and 0.8 liter) and pH (6.0, 6.5, and 7.0). A mixture of polysaccharides and proteins was used as carbon and nitrogen sources. Measurements ...

Twelve vaginal samples were collected from separate patients, processed anaerobically, and added to methanogenic enrichment medium. Methanogenic activity was detected in two samples, both of which were from patients with bacterial vaginosis. None of the samples from healthy patients yielded positive methanogen cultures. One sample from ...

Twelve vaginal samples were collected from separate patients, processed anaerobically, and added to methanogenic enrichment medium. Methanogenic activity was detected in two samples, both of which were from patients with bacterial vaginosis. None of the samples from healthy patients yielded positive methanogen cultures. One sample from ...

Electron-microscopic studies using thin sections revealed that methane-producing bacteria were an ultrastructurally diverse group. Fine structure and morphological characteristics separated these bacteria into four discrete cell types. Methanogenic bacteria displayed a gram-positive cell wall that varied ...

Methanogenic bacteria were isolated from mesophilic anaerobic digesters. The isolates were able to utilize H2 and CO2 acetate, formate and methanol, but were not able to metabolize propionate and butyrate. It was shown the propionate and butyrate are not ...

Chemical and physical factors which may influence the formation of methane by methanogenic bacteria in landfills have been investigated. Laboratory-scale lysimeter studies of leachate composition and biogas formation have been conducted. The effect of lea...

Methanogenic bacteria, or methanogens, were studied systematically with immunologic techniques. A comprehensive bank of reference antisera was organized from which calibrated antibody probes were generated of high resolution power for rapid bacterial iden...

Ecological observations suggest that sulfate-reducing and methanogenic bacteria might metabolize nitroaromatic compounds under anaerobic conditions if appropriate electron donors and electron acceptors are present in the environment, but this ability had ...

The Geochemistry, Ecology and Taxonomy of Antarctic Methanogenic Bacteria Entry ID: ASAC_264. [ View Full Record ]. [ Update this Record ] ...

Dec 6, 2002 ... Today, methanogenic bacteria grow in anaerobic environments such as the intestines of ruminants and the waterlogged soils underlying rice ...

... halophilic, methylotrophic species of methanogenic bacteria, is described. ... A search for narrow band signals with SERENDIP II: a progress report ...

... sequences from mesophilic and less thermophilic methanogens ... Descriptors : *MOLECULAR BIOLOGY, *BACTERIA, CHEMICAL BONDS, CLONES ...

acetate, and "non-competitive" substratea by methanogenic bacteria ...... Inhibition experiments on anaerobic methane oxidation,. Appl. Environ. Microbiol ., ...

A search for narrow band signals with SERENDIP II: a progress report ... halophilic, methylotrophic species of methanogenic bacteria, is described. ...

Acetate is the precursor of approximately two-thirds of the methane produced by anaerobic bioreactors and many other methanogenic habitats. Besides their intrinsic interest, thermophilic acetotrophic methanogenic cultures usually grow at least twice as fast as their mesophilic counterparts, making them more amenable to study. In recent years, attention has ...

Acetate is a key intermediate in the anaerobic degradation of organic matter. In anoxic environments, available acetate is a competitive substrate for sulfate-reducing bacteria (SRB) and methane-producing archaea. Little is known about the fractionation of carbon isotopes by sulfate reducers. Therefore, we determined carbon isotope compositions in cultures of three ...

The 16S ribosomal RNAs from 10 species of methanogenic bacteria have been characterized in terms of the oligonucleotides produced by T/sub 1/ RNase digestion. Comparative analysis of these data reveals the methanogens to constitute a distinct phylogenetic group containing two major divisions. These organisms appear to be only distantly ...

Methanogenic activity in a thermophilic-dry anaerobic reactor was determined by comparing the amount of methane generated for each of the organic loading rates with the size of the total and specific methanogenic population, as determined by fluorescent in situ hybridization. A high correlation was evident between the total ...

Methanogenic activity in a thermophilic-dry anaerobic reactor was determined by comparing the amount of methane generated for each of the organic loading rates with the size of the total and specific methanogenic population, as determined by fluorescent in situ hybridization. A high correlation was evident between the total ...

Samples of human dental plaque were examined for the presence of methanogenic bacteria. Of 54 samples from 36 patients, 20 yielded H2/CO2-using methanogenic enrichment cultures. All methanogen-positive samples were from patients with some degree of periodontal disease. The predominant populations in the enrichments ...

Samples of human dental plaque were examined for the presence of methanogenic bacteria. Of 54 samples from 36 patients, 20 yielded H2/CO2-using methanogenic enrichment cultures. All methanogen-positive samples were from patients with some degree of periodontal disease. The predominant populations in the enrichments ...

Samples of anaerobic sediments were collected for inoculation of enrichment cultures. Although we have not yet obtained axenic isolates of methanogens from this batch of samples, culture attempts are in progress on enrichments containing organisms of unusual morphology or physiology. Epifluorescence of methanogenic bacteria was used to ...

Batch tests to measure maximum acetate utilization rates were used to determine the distribution of acetate utilizers in expanded-bed sand and expanded-bed granular activated carbon (GAC) reactors. The reactors were fed a mixture of acetate and 3-ethylphenol, and they contained the same predominant aceticlastic ...

Our current understanding of the pathway of acetate conversion to methane in Methanosarcina thermophila is depicted. Our accomplishments this past year include phosphotransacetylase, the corrinoid/Fe-S protein component of the carbon monoxide dehydrogenase, and ferredoxin were characterized in further detail; two methyl transferase activities were resolved; and putative positive clones containing ...

Several enzymes in the pathway of acetate conversion to methane and carbon dioxide have been purified from Methanosarcina thermophila. The mechanisms of these enzymes are under investigation utilizing biochemical, biophysical and molecular genetic approaches. Acetate kinase and phosphotransacetylase catalyzes the activation of acetate to acetyl-CoA. The primary structure of these enzymes will be ...

Several enzymes in the pathway of acetate conversion to methane and carbon dioxide have been purified from Methanosarcina thermophila. The mechanisms of these enzymes are under investigation utilizing biochemical, biophysical and molecular genetic approaches. Acetate kinase and phosphotransacetylase catalyzes the activation of acetate to acetyl-CoA. The primary structure of these enzymes will be ...

Using molecular techniques and microsensors for H{sub 2}S and CH{sub 4}, the authors studied the population structure of and the activity distribution in anaerobic aggregates. The aggregates originated from three different types of reactors: a methanogenic reactor, a methanogenic-sulfidogenic reactor, and a sulfidogenic reactor. Microsensor measurements in ...

The hydrophobicities and electrophoretic mobilities of isolates from methanogenic anaerobic granular sludge were measured and compared with those of strains from culture collections. All new isolates were highly hydrophobic, indicating that the upflow anaerobic sludge blanket reactor concept selects for hydrophobic bacteria. Methanothrix soehngenii, a ...

Methane-producing microorganisms (methanogens) catalyze the terminal reactions in the anaerobic digestion of biomass. This is a well-established biotechnological process used for both waste treatment and the production of the renewal energy source methane...

This project is aimed at determining the biochemical mechanisms of one-carbon reactions and the genetic-control mechanisms of methanogenesis, an important step in the conversion of biomass to methane. Two enzymes (acetate kinase and a ferredoxin) were purified from methanogenic bacteria. These results extend the understanding of how ...

Kinetics of substrate utilization for different groups of bacteria in an anaerobic system fed propionate (HPr) and sulfate (SO[sub 4]) were determined using batch experiments. Six major COD flow pathways were identified based on thermodynamics: incomplete oxidation of propionate by sulfate reducing bacteria (SRB), propionate fermentation to acetate (HAc) ...

When microorganisms eluted from upper Hudson River sediment were cultured without any substrate except polychlorobiphenyl (PCB)-free Hudson River sediment, methane formation was the terminal step of the anaerobic food chain. In sediments containing Aroclor 1242, addition of eubacterium-inhibiting antibiotics, which should have directly inhibited fermentative bacteria and ...

A dual approach consisting of cultivation and molecular retrieval of partial archaeal 16S rRNA genes was carried out to characterize the diversity and structure of the methanogenic community inhabiting the anoxic bulk soil of flooded rice microcosms. The molecular approach identified four groups of known methanogens. Three environmental sequences clustered ...

Cellulytic bacteria, cellobiose fermentors, sulfate-reducing bacteria and methanogenic bacteria have been isolated from established anaerobic mesophilic and thermophilic cellulose-methane fermentations and these isolates, plus known laboratory strains, ha...

Production of methane in the hindgut of the cockroach Periplaneta americana was found to vary, depending on the feeding regimen. Methane production was positively correlated with the numbers of the ciliate Nyctotherus ovalis living in the cockroach hindgut. Defaunation of the cockroaches by means of low concentrations of metronidazole (Flagyl) resulted in a quick drop of methane production. ...

Production of methane in the hindgut of the cockroach Periplaneta americana was found to vary, depending on the feeding regimen. Methane production was positively correlated with the numbers of the ciliate Nyctotherus ovalis living in the cockroach hindgut. Defaunation of the cockroaches by means of low concentrations of metronidazole (Flagyl) resulted in a quick drop of methane production. ...

Jun 16, 2011 ... (1991), Psychrotrophic, lactic acid-producing bacteria from anoxic waters in Ace Lake, Antarctica; Carnobacterium funditum sp. nov. and ...

The Geochemistry, Ecology and Taxonomy of Antarctic Methanogenic Bacteria Entry ID: ASAC_264. [ View Full Record ]. [ Update this Record ] ...

"Is it possible forming pyroglutamic acid from glutamic acid in free solution? ... The hyperthermophilic methanogen was isolated from a hydrothermal vent. .... pyrosequencing; diversity; bacteria; archaea; eukaryotes marine ecology ...

The objective of the project has been to quantitatively define the intermediate molecules preceding methane formation during sludge digestion. The assumption is made that if these intermediates are clearly defined the factors influencing their rates of me...

... are associated particularly with methylotrophic methanogens. ... The WXE isotope composition at GN suggests that these bacteria utilize photoautotrophy incorporating .... At the time of writing, sensor calibration is in progress. ...

perchlorate affects anaerobic digestion of sludge or the growth of methanogenic bacteria. REFERENCES. Daum, R. J., and E. Kilcreas: Mimeo. ms. on Probit ...

The lipids of nine different methanogenic bacterial strains are comprised of diphytanyl glycerol diethers, previously known only in extremely halophilic bacteria, as well as dibiphytanyl diglycerol tetraethers, known formerly only in the extremely thermoacidophilic bacteria Thermoplasma and Sulfolobus. Of the ...

The following subjects are discussed in this review: classification and characterization of methanogenic bacteria; cellulose hydrolysis and ethanol production; methanogenesis; acidogenesis;biodegradation and biotoxicity; process optimization; process application; and patents. (DAD)

... presence of sn-2 hydroxyarchaeol, a biomarker for methylotrophic methanogens . .... Abstract: This interim report describes progress on the development of ... AAP bacteria comprised 5% to 16% of total prokaryotes in the Atlantic but ...

Butyrate-degrading bacteria in four methanogenic sludges were studied by RNA-based stable isotope probing. Bacterial populations in the ¹³C-labeled rRNA fractions were distinct from unlabeled fractions, and Syntrophaceae species, Tepidanaerobacter sp., and Clostridium spp. dominated. These results suggest that diverse microbes were ...

To determine which methanogens occur in digestors, we performed a quantitative immunologic analysis of a variety of samples. A comprehensive panel of calibrated polyclonal antibody probes of predefined specificity spectra was used. This allowed precise identification of bacteria by antigenic fingerprinting. A considerable diversity of ...

Methanogenesis from the biomass in the anoxic biogas reactors is catalyzed by syntrophic cooperation between anaerobic bacteria, syntrophic acetogenic bacteria and methanogenic archaea. Understanding of microbial community composition within the biogas reactors may improve the methane production from biomass fermentation. In this ...

The degradation of amino acids in anaerobic digestion was examined in terms of the interactions between amino-acid-degrading bacteria and methanogenic bacteria. Certain amino acids were degraded oxidatively by dehydrogenation, with methanogenic bacteria acting as H/sub 2/ acceptors. The ...

The objectives of this study were to formulate a vaccine based upon the different species/strains of methanogens present in sheep intended to be immunized and to determine if a targeted vaccine could be used to decrease the methane output of the sheep. Two 16S rRNA gene libraries were used to survey the methanogenic archaea in sheep prior to vaccination, ...

This study determined the incidence and concentration of methane-producing bacteria in tap water enema samples of 130 individuals taken before sigmoidoscopy. The number of subjects classified in five major colonic groups were as follows: normal colon 36, diverticulosis 57, inflammatory bowel disease 11, colon polyps 34, and colon cancer 11. Some patients were placed in more ...

This study determined the incidence and concentration of methane-producing bacteria in tap water enema samples of 130 individuals taken before sigmoidoscopy. The number of subjects classified in five major colonic groups were as follows: normal colon 36, diverticulosis 57, inflammatory bowel disease 11, colon polyps 34, and colon cancer 11. Some patients were placed in more ...

Methanogens and sulphate reducing bacteria compete for H2 in the human colon, and, as a result, faeces usually contain high concentrations of just one of these two organisms. There is controversy over which of these organisms wins the competition for H2, although theoretical data suggest that sulphate reducing bacteria should ...

A bank of antisera to the majority of methanogenic bacteria is now available. Three antibody probes, R, S, and T, were derived from each antiserum in the bank and used for analysis of antigenic relatedness among methanogens by immunofluorescence. The T probe reacted only with the immunizing (or homologous) strain, the S probe gave ...

A bank of antisera to the majority of methanogenic bacteria is now available. Three antibody probes, R, S, and T, were derived from each antiserum in the bank and used for analysis of antigenic relatedness among methanogens by immunofluorescence. The T probe reacted only with the immunizing (or homologous) strain, the S probe gave ...

The aim of this work was to determine whether reductive acetogenesis can provide an alternative to methanogenesis in the rumen. Gnotobiotic lambs were inoculated with a functional rumen microbiota lacking methanogens and reared to maturity on a fibrous diet. Lambs with a methanogen-free rumen grew well, and the feed intake and ruminal volatile fatty acid ...

Specific antisera were raised in rabbits to 19 methanogenic bacteria representing the species available in pure culture at the present time. The antisera were characterized, labeled, and organized in a bank to serve as a source of material for preparation of antibody probes and thus provide standardized reagents for immunological analysis of ...

Hydrogen partial pressures were measured in a thermophilic coculture comprised of a eubacterial rod which oxidized acetate to H{sub 2} and CO{sub 2} and a hydrogenotrophic methanogen, Methanobacterium sp. strain THF. H{sub 2} partial pressures in the coculture were measured to be between 20 and 50 Pa (0.12 to 0.30 {mu}M) during acetate ...

The sulfate-reducing bacteria form competitive or syntrophic interactions with the methanogenic bacteria by virtue of their ability to consume or produce molecular hydrogen. The goal of the research has been to identify, through a combined biochemical - g...

Our project focussed on understanding of one and multicarbon metabolism in acetogenic and methanogenic bacteria. The studies with acetate catabolism pathway in Methanosarcina barkeri showed involvement of methyl reductase, methyl coenzyme M and carbon mon...

In anaerobic digestors and natural environments, the sulfate-reducing bacteria (SRB) play a pivotal role in methane generation, either providing hydrogen and acetate for methane formation or competing with the methanogens for those same substrates. The SR...

Peatlands, as fens and bods, make up a large percentage of northern latitude terrestrial environments. They are organic rich and support an active community of anaerobic bacteria, such as methanogenic and sulfate-reducing bacteria. The end products of the...

We elucidated the pathway for the anaerobic degradation of chlorophenols under methanogenic conditions and studied the microbial interactions of the community being directly or indirectly involved in this process. At least 6 different bacteria, --constitu...

The relationship of the total intracellular concentration of the coenzyme F/sub 420/ to the biomass and metabolic activity of methanogenic bacteria was investigated in static cultures of M.barkeri with methanol and of M.byantii with H/sub 2/ and CO/sub 2/...

The production of methane from organic wastes is seen as a major untapped source of energy. Methanogenic bacteria and their ecology are reviewed. Sources of methanogenic bacteria are also reviewed, such as ruminant and nonruminant intestinal tracts, freshwater and marine sediments, flooded soils and living trees. ...

Methanogens represented about 0.5% of the total bacteria in sediments from a Georgia salt marsh in which Spartina alterniflora is the predominant vegetation. The population of methanogens was composed of at least two groups of nearly equal size. One group was represented by cocci which were able to utilize trimethylamine and were ...

The methanogenic Archaea bring a broadened perspective to the field of nitrogen fixation. Biochemical and genetic studies show that nitrogen fixation in Archaea is evolutionarily related to nitrogen fixation in Bacteria and operates by the same fundamental mechanism. At least six nif genes present in Bacteria (nif H, D, K, E, N and X) ...

Three predominant ruminal cellulolytic organisms, Fibrobacter succinogenes S85, Ruminococcus albus 8, and R. flavefaciens FD-1, were cultured with a methanogen, Methanobrevibacter smithii. Growth rates, bacterial protein, organic acids, and methane production were measured. When grown in diculture with the methanogen, a fermentative advantage was observed ...

An examination of the methanofurans isolated from a wide range of methanogenic bacteria and from Archaeoglobus fulgidus has revealed at least five chromatographically distinct methanofurans. Bacteria from each major genus of methanogenic bacteria have been found to contain a chemically ...

Methanobacterium thermoautotrophicum has been reported to require nickel for growth and to contain high concentrations of a nickel tetrapyrrole designated factor F430. In this communication it is shown that all methanogenic bacteria investigated incorporated nickel during growth and also synthesized factor F430. This was also true for Methanobrevibacter ...

Hydrogen produced during colonic fermentation may be excreted, or removed by H2 consuming bacteria such as methanogenic and sulphate reducing bacteria. In vitro, sulphate reducing bacteria compete with methanogenic bacteria for hydrogen when sulphate is present. In this ...