Showing papers on "Methanogen published in 2003"

Isolation of a methanogen from deep marine sediments that contain methane hydrates, and description of Methanoculleus submarinus sp. nov.

Abstract: We isolated a methanogen from deep in the sediments of the Nankai Trough off the eastern coast of Japan. At the sampling site, the water was 950 m deep and the sediment core was collected at 247 m below the sediment surface. The isolated methanogen was named Nankai-1. Cells of Nankai-1 were nonmotile and highly irregular coccoids (average diameter, 0.8 to 2 m) and grew with hydrogen or formate as a catabolic substrate. Cells required acetate as a carbon source. Yeast extract and peptones were not required but increased the growth rate. The cells were mesophilic, growing most rapidly at 45°C (no growth at 55°C). Cells grew with a maximum specific growth rate of 2.43 day 1 at 45°C. Cells grew at pH values between 5.0 and 8.7 but did not grow at pH 4.7 or 9.0. Strain Nankai-1 grew in a wide range of salinities, from 0.1 to 1.5 M Na. The described phenotypic characteristics of this novel isolate were consistent with the in situ environment of the Nankai Trough. This is the first report of a methanogenic isolate from methane hydrate-bearing sediments. Phylogenetic analysis of its 16S rRNA gene sequence indicated that it is most closely related to Methanoculleus marisnigri (99.1% sequence similarity), but DNA hybridization experiments indicated a DNA sequence similarity of only 49%. Strain Nankai-1 was also found to be phenotypically similar to M. marisnigri, but two major phenotypic differences were found: strain Nankai-1 does not require peptones, and it grows fastest at a much higher temperature. We propose a new species, Methanoculleus submarinus, with strain Nankai-1 as the type strain.

Microsite-dependent changes in methanogenic populations in a boreal oligotrophic fen.

Abstract: Summary Wetlands, including peatlands, are the main source of natural methane emission. Well-defined fen microsites have different methane emissions rates, but it is not known whether the methane-producing Archaea communities vary at these sites. Possible horizontal variations of communities, in a natural oligotrophic fen, were analysed by characterizing the methanogens from two well-defined microsites: Eriophorum lawn and Hummock. Community structures were studied at two different layers of the fen, showing, respectively, high and low methane production. The structure of methanogen populations was determined using molecular techniques targeting the 16SrRNA gene and combined denaturing gradient gel electrophoresis (DGGE) and restriction fragment length polymorphism (RFLP) analysis. Results subjected to non-metric multidimensional scaling (MDS), diversity indices calculation and phylogenetic analysis revealed that upper layer communities changed with site while deeper layer communities remained the same. Phylogenetic analyses revealed six different clusters of sequences grouping with only two known orders of methanogens. Upper layers of Hummock were dominated by sequences clustering with members of Methanomicrobiales and sequences dominating the upper part of the Eriophorum lawn were related to members of the order Methanosarcinales. Novel methanogenic sequences were found at both sites at both depths. Vegetation characterizing the microsites probably influences the microbial communities in the layers of the fen where methane is produced.

Methanogen population in a marine biofilm corrosive to mild steel.

Abstract: This study was conducted to analyze the methanogen population in a corrosive marine biofilm based on 16S rDNA analysis, using a PCR-cloning-sequencing approach. There were 80 methanogen clones developed from the PCR-amplified DNA extracted from the biofilm on the mild steel surface. All clones were categorized into one of five operational taxonomy units (OTUs). Two OTUs (comprising 57 clones) were affiliated with the acetotrophic Methanosaeta genus; the remaining three OTUs (23 clones) were affiliated with the hydrogenotrophic genera of Methanogenium, Methanoplanus and Methanocalculus. The hydrogenotrophic methanogens could directly cause metal corrosion through cathodic depolarization, whereas the acetotrophic methanogens grew syntrophically with corrosion-causing sulfate-reducing bacteria, as observed by fluorescent in situ hybridization, and thus contribute indirectly to metal corrosion.

Molecular analysis of methanogenic archaeal communities in managed and natural upland pasture soils

Abstract: Grassland management influences soil archaeal communities, which appear to be dominated by nonthermophilic crenarchaeotes. To determine whether methanogenic Archaea associated with the Euryarchaeota lineage are also present in grassland soils, anaerobic microcosms containing both managed (improved) and natural (unimproved) grassland rhizosphere soils were incubated for 28 days to encourage the growth of anaerobic Archaea. The contribution of potential methanogenic organisms to the archaeal community was assessed by the molecular analysis of RNA extracted from soil, using primers targeting all Archaea and Euryarchaeota. Archaeal RT-PCR products were obtained from all anaerobic microcosms. However, euryarchaeal RT-PCR products (of putative methanogen origin) were obtained only from anaerobic microcosms of improved soil, their presence coinciding with detectable methane production. Sequence analysis of excised denaturing gradient gel electrophoresis (DGGE) bands revealed the presence of euryarchaeal organisms that could not be detected before anaerobic enrichment. These data indicate that nonmethanogenic Crenarchaeota dominate archaeal communities in grassland soil and suggest that management practices encourage euryarchaeal methanogenic activity.

Sporotomaculum syntrophicum sp. nov., a novel anaerobic, syntrophic benzoate-degrading bacterium isolated from methanogenic sludge treating wastewater from terephthalate manufacturing

Abstract: An anaerobic, mesophilic, syntrophic benzoate-degrading bacterium, designated strain FBT, was isolated from methanogenic sludge which had been used to treat wastewater from the manufacture of terephthalic acid. Cells were non-motile gram-positive rods that formed spores. The optimum temperature for growth was 35–40 °C, and the optimum pH was 7.0–7.2. A co-culture with the hydrogenotrophic methanogen Methanospirillum hungatei converted benzoate to acetate, carbon dioxide, and methane. Butyrate transiently accumulated at a high concentration of 2.5 mM during degradation. Besides benzoate, no other compound tested supported growth of the co-culture. Crotonate supported growth of strain FBT in pure culture. Furthermore, the strain degraded benzoate in pure culture with crotonate as co-substrate to produce acetate and butyrate. The strain was not able to utilize sulfate, sulfite, thiosulfate, nitrate, fumarate, or Fe(III) as electron acceptor. The G+C content of the DNA was 46.8 mol%. Strain FBT contained MK-7 as the major quinone and C16:1 as the major fatty acid. 16S rDNA sequence analysis revealed that the strain was a member of the genus Sporotomaculum, even though it exhibited significant differences, such as the capacity for syntrophic growth, to the known member of the genus. Hence, we propose the name Sporotomaculum syntrophicum sp. nov. for strain FBT. The type strain is strain FBT (DSM 14795, JCM 11475).

Methanogenic activity in human periodontal pocket.

Abstract: Samples of subgingival dental tissues were examined for the presence of methanogenic activities. Using enrichment cultures, methanogenic activities were detected in 9 of 17 individuals. A mesophilic, Gram-positive, irregular coccoid methanogen, which showed close resemblance to a Methanosarcina sp., was isolated from one sample collected from a patient with type IV periodontal pocket (the periodontal pocket is a space bounded by the tooth on one side and by ulcerated epithelium lining the soft tissue wall on the other). The isolate used methanol, methylamine, acetate, and H(2)-CO(2) as the sole source of carbon. However, the isolate was unable to use formate and trimethylamine as growth substrates. The organism had an optimum pH of 6.5 and an optimum temperature of 37 degrees C. The isolate not only used ammonia, but also used nitrate as a nitrogen source. The niche of this methanogen in periodontal pockets may be to carry out terminal oxidation of simple organic compounds such as methanol and acetate produced by other obligate anaerobes present in periodontal pockets. This methanogen may also play a vital role in interspecies hydrogen transfer, as demonstrated by its use of H(2)-CO(2) as a substrate. The isolate produced significant amount of methane in vitro.

Effect of temperature on methane production and oxidation in soils

Abstract: The influence of temperature and its mechanism on methane production and oxidation in soils were reviewed in this paper. Temperature can alter the soil ability to produce methane through changing types of dominant methanogens in archaeal community. Dominant methanogen is Methanosarcinaceae at higher temperature which can utilize both H 2/CO 2 and acetate as the precursor to produce methane, while Methanosaetaceae at lower temperature which only use acetate as the precursor and produce far less methane than do Methanosarcinaceae. Increasing soil temperature apparently raises soil ability to produce methane, which is called temperature effectiveness and expressed as Q 10 with a range from 1.5 to 28 and an average of 4.1. There is an obviously positive correlation between temperature effectiveness (Q 10) on methane production and substrate content. As compared to methane production, effect of temperature on methane oxidation is lower, which may be related to the strong affinity of methanotrophs for methane.

Characteristics of an Anaerobic, Syntrophic, Butyrate-degrading Bacterium in Paddy Field Soil

Abstract: The number of syntrophic butyrate-degrading bacte- ria in a flooded paddy field soil was 1.7×103 MPN/g dry soil. Butyrate was degraded to acetate and methane when paddy soils were incubated anaerobically with the addition of butyrate. However, butyrate degradation was completely suppressed by the addition of the specific inhibitor of methanogenesis, 2-bromoethanesulfonate (BES) to the soil. A hydrogen-using methanogen, strain TM-8, was isolated from flooded paddy field soil. Strain TM-8 was identified as Methanobacterium formicicum based on its physiology and phylogeny. Syntrophic butyrate-degrading bacteria were enumerated and isolated using strain TM-8. A syntrophic butyrate-degrading bacterium, strain TB-6, was isolated in coculture with strain TM-8 from paddy soil. The strain was Gram-negative, had curved rods, and grew on crotonate. Sulfate was not used as an electron acceptor. Strain TB-6 was closely related to S. wolfei subsp. wolfei. The relation between strain TB-6 and the members of Syntrophomon...

Effect of physical irradiation and chemical mutagen treatment on methane production by methanogenic bacteria

Abstract: Biomethanation is one of the desirable options for obtaining clean fuel from abundant renewable biomass resources. Improvement of biomethane production may be achieved by using improved strains of microbes, particularly the terminal microbes – the methanogens. Attempts have been made to improve the efficiency of the methanogens isolated from local sources by subjecting the methanogens to mutagenic changes by physical (by γ irradiation, neutron bombardment) or chemical (by addition of chemicals like acridine orange, colchicine) means. The effects of the treated methanogens on biomethanation were studied. γ Irradiation or neutron bombardment mutagenesis was dose-dependent and time-dependent. High doses proved to be lethal but methanogens were found to be to some extent radiation resistant when subjected to irradiation at small doses for short duration (∼5–10 s). No or marginal improvement of methane production occurred for the two strains TDM and TRM. Improvement of methane production occurred from successive transfers of radiation treated strain SSM. Chemical mutagens invariably inhibited biomethanation and the inhibition was dose dependent.

Metabolic characteristics of an aerobe isolated from a methylotrophic methanogenic enrichment culture.

Abstract: An anaerobic methylotrophic methanogenic enrichment culture, with sustained metabolic characteristics, including that of methanation for over a decade, was the choice of the present study on interspecies interactions. Growth and methanation by the enrichment were suppressed in the presence of antibiotics, and no methanogen grown on methanol could be isolated using stringent techniques. The present study confirmed syntrophic metabolic interactions in this enrichment with the isolation of a strain ofPseudomonas sp. The organism had characteristic metabolic versatility in metabolizing a variety of substrates including alcohols, aliphatic acids, amino acids, and sugars. Anaerobic growth was favoured with nitrate in the growth medium. Cells grown anaerobically with methanol, revealed maximal nitrate reductase activity. Constitutive oxidative activity of the membrane system emerged from the high-specific oxygen uptake and nitrate reductase activities of the aerobically and anerobically grown cells respectively. Cells grown anaerobically on various alcohols effectively oxidized methanol in the presence of flavins, cofactor FAD and the methanogenic cofactor F420, suggesting a constitutive alcohol oxidizing capacity. In cells grown anaerobically on methanol, the rate of methanol oxidation with F420 was three times that of FAD. Efficient utilization of alcohols in the presence of F420 is a novel feature of the present study. The results suggest that utilization of methanol by the mixed culture would involve metabolic interactions between thePseudomonas sp. and the methanogen(s). Methylotrophic, methanogenic partnership involving an aerobe is a novel feature hitherto unreported among anaerobic syntrophic associations and is of ecological significance.

Microscopic observation of microorganisms involved in methane production and oxidation in paddy field soil

Abstract: Methane is major greenhouse gas, next to carbon dioxide, and about 20% of methane in the atmosphere is released from paddy fields (1). One of the characteristics of paddy field soil is that the supply of oxygen is limited under submersion, resulting in the lowering of redox potential. Therefore, organic matter in flooded paddy field soil is decomposed anaerobically into methane and carbon dioxide. Three microorganism groups are involved in the process by which organic matter is decomposed into methane and carbon dioxide. At the beginning, high molecular compounds such as cellulose and starch are hydrolyzed by fermentative bacteria and converted to alcohols such as ethanol and butanol and organic acids such as lactate and butyrate. Then, butyrate and ethanol are converted to acetate, hydrogen and carbon dioxide by the syntrophic association with a hydrogen―producing, acetate―producing bacterium and a hydrogen―utilizing methanogen. Acetate, hydrogen and carbon dioxide are converted to methane and carbon dioxide by methanogens in the last stage. With respect to anaerobes in paddy field soil, fermentative bacteria, sulfate―reducing bacteria and methanogens have been isolated from paddy field soil so far. However, until now, there have been few examinations of how fatty acids are degraded in a syntrophic association with hydrogen―utilizing methanogens, and how sulfate―reducing bacteria degrade lactate in syntrophic association with hydrogen― utilizing methanogens under the condition without sulfate. In paddy field soil, methane―oxidizing bacteria, which convert methane to carbon dioxide, live in paddy field soil. We describe here Type II methane― oxidizing bacteria that can grow without copper dominant over the Type I species in paddy field soil. This report shows that the cell morphology of anaerobes involved in methane production and intracytoplasmic membranes of methane―oxidizing bacteria were observed with a photo and an electron microscope.