Tepidanaerobacter syntrophicus gen. nov., sp. nov., an anaerobic, moderately thermophilic, syntrophic alcohol- and lactate-degrading bacterium isolated from thermophilic digested sludges

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Abstract
Three anaerobic, moderately thermophilic, syntrophic primary alcohol- and lactate-degrading microbes, designated strains JLT, JE and OL, were isolated from sludges of thermophilic (55 °C) digesters that decomposed either municipal solid wastes or sewage sludge. The strains were strictly anaerobic organisms. All three strains grew at 25–60 °C and pH 5.5–8.5 and optimum growth was observed at 45–50 °C and pH 6.0–7.0. The three organisms grew chemo-organotrophically on a number of carbohydrates in the presence of yeast extract. In co-culture with the hydrogenotrophic methanogenMethanothermobacter thermautotrophicus, all strains could utilize ethanol, glycerol and lactate syntrophically for growth, although these compounds were not metabolized in pure culture without additional external electron acceptors. All strains could reduce thiosulphate. Quinones were not detected. The DNA G+C contents of strains JLT, JE and OL were 38.0, 37.3 and 37.7 mol%, respectively. Major cellular fatty acids of the strains were iso-C15 : 0, C16 : 0and unsaturated species of C15 : 1. Phylogenetic analyses based on 16S rRNA gene sequences revealed that the strains belong to a deeply branched lineage of the phylumFirmicutes; the most closely related species wasThermovenabulum ferriorganovorum(16S rRNA gene sequence similarity of 88 %). The three strains were phylogenetically very closely related to each other (99–100 % 16S rRNA gene sequence similarity) and were physiologically and chemotaxonomically similar. These genetic and phenotypic properties suggest that the strains should be classified as representatives of a novel species and genus; the nameTepidanaerobacter syntrophicusgen. nov., sp. nov. is proposed. The type strain ofTepidanaerobacter syntrophicusis strain JLT(=JCM 12098T=NBRC 100060T=DSM 15584T).

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