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  • 1
    ISSN: 1432-072X
    Keywords: Methanococcus jannaschii ; Thermophilic methanogenic bacteria ; Methanococcus ; Hydrothermal vent methanogen ; Deep sea methanogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A new extremely thermophilic methane-producing bacterium was isolated from a submarine hydrothermal vent sample collected by a research team from the Woods Hole Oceanographic Institution using the manned submersible ALVIN. The sample was obtained from the base of a “white smoker” chimney on the East Pacific Rise at 20° 50′ N latitude and 109° 06′ W longitude at a depth of 2600 m. The isolate was a motile irregular coccus with an osmotically fragile cell wall and a complex flagellar system. In defined medium with 80% H2 and 20% CO2, the isolate had a doubling time of 26 min at 85° C. The pH range for growth was 5.2 to 7.0 with an optimum near 6.0. NaCl was required for growth with an optimum of 2 to 3% (w/v). The mol % G+C was 31%. In cell-free extracts, methane formation from methylcoenzyme M was temperature-dependent, and H2 or formate served as electron donors. Methane formation from H2 and CO2 occurred at a much lower rate. Oligonucleotide cataloging of the 16S ribosomal RNA established the isolate as a new species of the genus Methanococcus and the name Methanococcus jannaschii is proposed. The isolation of M. jannaschii from a submarine hydrothermal vent provides additional evidence for biogenic production of CH4 from these deep-sea environments.
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  • 2
    ISSN: 1432-072X
    Keywords: Methanogenic bacteria ; Alcohols ; Ketones ; Aldehydes ; Alcohol dehydrogenase ; Enzyme expression ; Methanogenium thermophilum ; Factor F420
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In four species of methanogens able to grow with secondary alcohols as hydrogen donors the expression and properties of secondary alcohol dehydrogenase (sec-ADH) were investigated. Cells grown with 2-propanol and CO2 immediately started to oxidize secondary alcohols to ketones if transferred to new media. In the presence of H2, such cells reduced ketones or aldehydes to alcohols. In the absence of H2, aldehydes were dismutated (without growth) to primary alcohols and fatty acids. None of these reactions was catalyzed by cells grown with only H2 and CO2 at non-limiting concentration. This indicated an induction or derepression of sec-ADH by its substrate. Apparently, sec-ADH in all strains enabled not only the reduction of ketones or aldehydes, but also the dismutation of the latter. Sec-ADH was also expressed if strains were grown on H2 and CO2 in the presence of non-oxidizable, tertiary alcohols. Methanogenium thermophilum expressed sec-ADH even without added alcohol when H2 became limiting. From this species, an F420-specific sec-ADH was purified; the final gel filtration chromatography yielded a single protein peak that coincided with the activity. The enrichment was 12-fold, the activity recovery 26%. SDS polyacrylamide gel electrophoresis indicated that the enzyme was a homodimer with an apparent M r of 79,000. At the pH optimum around 4.2, the specific activity for oxidation of 2-propanol (130 mM) and reduction of acetone (20 mM) was 176 and 110 μmol/ min·mg, respectively (40°C). The apparent K m for 2-propanol and acetone (with 15 μM F420) was 2.5 and 0.25 mM, respectively. Aldehydes also were reduced.
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  • 3
    ISSN: 1432-072X
    Keywords: Methanogenic bacteria ; Taxonomy ; Phylogeny ; Methylreductase subunits ; Electrophoresis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A rapid procedure for measurement of the apparent molecular weight of the three subunits of component C, the methylreductase, has been developed. The procedure requires as little as 200mg of wet cells and uses a quick purification step on phenyl-Sepharose prior to sodium dodecyl slfate polyacrylamide gel electrophoresis. Eighteen species of methanogenic bacteria have been surveyed. The groups of organisms discerned by this procedure correspond to the phylogenic ones defined by 16S rRNA cataloging and sequencing data. The molecular weight of the smaller subunit of the methyl-reductase unequivocally differentiates the orders of the Methanobacteriales and Methanococcales (35,000–43,000) from the Methanomicrobiales (29,000–32,000). Within the order Methanomicrobiales, this method differentiates between the two families Methanomicrobiaceae and Methanosarcinaceae. A new isolate may quickly be assigned to its family. For example, on the basis of its subunit pattern, we propose that the new isolate Methanococcus frisius should be relocated in the genus Methanosarcina.
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  • 4
    ISSN: 1432-072X
    Keywords: Methanogenic bacteria ; Alcohols ; Trace elements ; Methylreductase ; Taxonomy ; Methanogenium thermophilum ; Methanogenium, organophilum ; Methanospirillum hungatei
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A thermophilic coccoid methanogenic bacterium, strain TCI, that grew optimally around 55° C was isolated with 2-propanol as hydrogen donor for methanogenesis from CO2. H2, formate or 2-butanol were used in addition. Each secondary alcohol was oxidized to its ketone. Growth occurred in defined freshwater as well as salt (2% NaCl, w/v) medium. Acetate was required as carbon source, and 4-aminobenzoate and biotin as growth factors. A need for molybdate or alternatively tungstate was shown. Strain TCI was further characterized together with two formerly isolated mesophilic secondary alcohol-utilizing methanogens, the coccoid strain CV and the spirilloid strain SK. The guanine plus cytosine content of the DNA of the three strains was 55,47, and 39 mol%, respectively. Determination of the molecular weights of the methylreductase subunits and sequencing of ribosomal 16S RNA of strains TCI and CV revealed close relationships to the genus Methanogenium. The new isolate TCI is classified as a strain of the existing species, Methanogenium thermophilum (thermophilicum). For strain CV, that uses ethanol or 1-propanol in addition, a classification as new species, Methanogenium organophilum, is proposed. Strain SK is affiliated with the existing species, Methanospirillum hungatei. The ability to use secondary alcohols was also tested with described species of methanogens. Growth with secondary alcohols was observed with Methanogenium marisnigri, Methanospirillum hungatei strain GP1 and Methanobacterium bryantii, but not with Methanospirillum strains JF1 and M1h, Methanosarcina barkeri, Methanococcus species or thermophilic strains or species other than the new isolate TCI.
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  • 5
    ISSN: 1432-072X
    Keywords: Anaerobic ; Benzoate ; Consortium ; Degradation ; Food chain ; Methane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A stabilized consortium of microbes which anaerobically degraded benzoate and produced CH4 was established by inoculation of a benzoate-mineral salts medium with sewage sludge; the consortium was routinely subcultured anaerobically in this medium for 3 years. Acetate, formate, H2 and CO2 were identified as intermediates in the overall conversion of benzoate to CH4 by the culture. Radioactivity was equally divided between the CH4 and CO2 from the degradation of uniformly ring-labeled [14C]benzoate. The methyl group of acetate was stoichiometrically converted to CH4. Acetate, cyclohexanecarboxylate, 2-hydroxycyclohexanecarboxylate, o-hydroxybenzoic acid and pimelic acid were converted to CH4 without a lag suggesting that benzoate was degraded by a reductive pathway. Addition of o-chlorobenzoate inhibited benzoate degradation but not acetate degradation or methane formation. Two methanogenic organisms were isolated from the mixed culture, neither organism was able to degrade benzoate, showing that the methanogenic bacteria served as terminal organisms of a metabolic food chain composed of several organisms. Removal of intermediates by the methanogenic bacteria provided thermodynamically favorable conditions for benzoate degradation.
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  • 6
    ISSN: 1432-072X
    Keywords: Methanobacterium ; Serine transhydroxymethylase ; Methanogen ; Tetrahydromethanopterin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Serine transhydroxymethylase of Methanobacterium thermoautotrophicum has been purified to within 95% of homogeneity. Activity was strictly dependent on tetrahydromethanopterin, tetrahydrofolate being unable to serve as the acceptor C1 units from l-serine. The native protein has a molecular weight of about 102,000 daltons. The enzyme shows maximal activity at 60°C, has a pH optimum of 8.1, and required pyridoxal-5′-phosphate and Mg2+ for optimal activity.
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  • 7
    ISSN: 1432-072X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Two bacterial species were isolated from cultures of Methanobacillus omelianskii grown on media, containing ethanol as oxidizable substrate. One of these, the S organism, is a gram negative, motile, anaerobic rod which ferments ethanol with production of H2 and acetate but is inhibited by inclusion of 0.5 atm of H2 in the gas phase of the medium. The other organism is a gram variable, nonmotile, anaerobic rod which utilizes H2 but not ethanol for growth and methane formation. The results indicate that M. omelianskii maintained in ethanol media is actually a symbiotic association of the two species.
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  • 8
    ISSN: 1432-072X
    Keywords: Methanogenium cariaci ; Methanogenium marisnigri ; Marine methanogenic bacteria ; Ultrastructure ; TaxonomyMethanogenium gen. nov.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A new genus of marine methanogenic bacteria and two species within this genus are described.Methanogenium is the proposed genus andMethanogenium cariaci the type species. Cells of the type species are Gram-negative, peritrichously flagellated, irregular cocci with a periodic wall surface pattern. Colonies formed by these bacteria are yellow, circular and umbonate with entire edges. The DNA base composition is 52 mol% guanine plus cytosine. Formate or hydrogen and carbon dioxide serve as substrates for growth. Cells ofMethanogenium marisnigri are of similar shape but smaller diameter thanM. cariaci. The colonies ofM. marisnigri are convex, and the DNA base composition is 61 mol % G+C. Formate or hydrogen and carbon dioxide are growth substrates. Sodium chloride is required for growth of both methanogens.
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  • 9
    ISSN: 1432-072X
    Keywords: Acetogenium kivui ; Thermophilic acetogenic bacteria ; Hydrogen oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Hydrogen-oxidizing acetogenic bacteria in pure culture are presently represented by the two mesophilic species, Acetobacterium woodii and Clostridium aceticum. From Lake Kivu we have isolated a Gram negative, chemolithotrophic, thermophilic anaerobe (LKT-1) that oxidizes hydrogen and reduces carbon dioxide to acetic acid. It is a non-motile, non-sporeforming rod, about 0.7μm in width and 2–7.5μm in length, often occuring in pairs or chains. The cell wall has a banded appearance; the surface layer contains a regular array of particles with six-fold rotational symmetry. No outer membrane is present. The temperature optimum for growth is 66°C, and the pH optimum is 6.4. Organic growth substrates include glucose, mannose, fructose, pyruvate, and formate; acetate is the principal product. The doubling time for growth on hydrogen and carbon dioxide is about 2h. Vitamins are neither required nor stimulatory. Yeast extract and Trypticase enhance the final yield but do not affect the growth rate. Cysteine or sulfide are required and cannot be replaced by thioglycolate or dithiothreitol. LKT-1 was mass cultured on hydrogen and carbon dioxide in a 24.1 fermentor with a yield of 34g (wet weight) of cells. The DNA base composition as determined by buoyant density is 38 mol % guanine plus cytosine. LKT-1 appears only distantly related to physiologically similar bacteria. A new genus Acetogenium is proposed, and the species is Acetogenium kivui.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 38 (1982), S. 198-201 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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