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1.
Int J Syst Evol Microbiol ; 64(Pt 8): 2792-2797, 2014 Aug.
Article in English | MEDLINE | ID: mdl-24860110

ABSTRACT

A novel anaerobic, mesophilic, hydrogen-producing bacterium, designated strain M2/40(T), was isolated from a mesophilic, two-phase, laboratory-scale biogas reactor fed continuously with maize silage supplemented with 5% wheat straw. 16S rRNA gene sequence comparison revealed an affiliation to the genus Clostridium sensu stricto (cluster I of the clostridia), with Clostridium cellulovorans as the closest characterized species, showing 93.8% sequence similarity to the type strain. Cells of strain M2/40(T) were rods to elongated filamentous rods that showed variable Gram staining. Optimal growth occurred at 35 °C and at pH 7. Grown on glucose, the main fermentation products were H2, CO2, formate, lactate and propionate. The DNA G+C content was 29.6 mol%. The major fatty acids (>10 %) were C(16 : 0), summed feature 10 (C(18 : 1)ω11c/ω9t/ω6t and/or unknown ECL 17.834) and C(18 : 1)ω11c dimethylacetal. Based on phenotypic, chemotaxonomic and phylogenetic differences, strain M2/40(T) represents a novel species within the genus Clostridium, for which we propose the name Clostridium bornimense sp. nov. The type strain is M2/40(T) ( = DSM 25664(T) = CECT 8097(T)).


Subject(s)
Biofuels , Bioreactors/microbiology , Clostridium/classification , Phylogeny , Silage/microbiology , Bacterial Typing Techniques , Base Composition , Clostridium/genetics , Clostridium/isolation & purification , DNA, Bacterial/genetics , Fatty Acids/chemistry , Fermentation , Molecular Sequence Data , RNA, Ribosomal, 16S/genetics , Sequence Analysis, DNA
2.
Proc Natl Acad Sci U S A ; 109(47): 19321-6, 2012 Nov 20.
Article in English | MEDLINE | ID: mdl-23129626

ABSTRACT

The methane-rich, hydrothermally heated sediments of the Guaymas Basin are inhabited by thermophilic microorganisms, including anaerobic methane-oxidizing archaea (mainly ANME-1) and sulfate-reducing bacteria (e.g., HotSeep-1 cluster). We studied the microbial carbon flow in ANME-1/ HotSeep-1 enrichments in stable-isotope-probing experiments with and without methane. The relative incorporation of (13)C from either dissolved inorganic carbon or methane into lipids revealed that methane-oxidizing archaea assimilated primarily inorganic carbon. This assimilation is strongly accelerated in the presence of methane. Experiments with simultaneous amendments of both (13)C-labeled dissolved inorganic carbon and deuterated water provided further insights into production rates of individual lipids derived from members of the methane-oxidizing community as well as their carbon sources used for lipid biosynthesis. In the presence of methane, all prominent lipids carried a dual isotopic signal indicative of their origin from primarily autotrophic microbes. In the absence of methane, archaeal lipid production ceased and bacterial lipid production dropped by 90%; the lipids produced by the residual fraction of the metabolically active bacterial community predominantly carried a heterotrophic signal. Collectively our results strongly suggest that the studied ANME-1 archaea oxidize methane but assimilate inorganic carbon and should thus be classified as methane-oxidizing chemoorganoautotrophs.


Subject(s)
Autotrophic Processes/physiology , Bacteria/metabolism , Biota , Carbon Cycle/physiology , Methane/metabolism , Anaerobiosis , Carbon/metabolism , Carbon Isotopes , Isotope Labeling , Lipid Metabolism , Mexico , Molecular Sequence Data , Oxidation-Reduction
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