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  • 1
    Electronic Resource
    Electronic Resource
    Classification of secondary alcohol-utilizing methanogens including a new thermophilic isolate (1988)
    Springer
    Archives of microbiology 150 (1988), S. 477-481 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00422290
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Expression of secondary alcohol dehydrogenase in methanogenic bacteria and purification of the F420-specific enzyme from Methanogenium thermophilum strain TCI (1989)
    Springer
    Archives of microbiology 152 (1989), S. 322-328 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00425168
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    Paper (German National Licenses)
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