Sporacetigenium mesophilum gen. nov., sp. nov., isolated from an anaerobic digester treating municipal solid waste and sewage

Abstract

Two mesophilic, anaerobic bacterial strains (ZLJ115Tand L4-2) were isolated from the sludge of an anaerobic digester treating municipal solid waste and sewage in Fujian province, China. The strains were Gram-positive, spore-forming, motile rods (0·9–1·0×3·6–7·3 μm). Growth of the strains was observed at 20–42 °C and pH 6·0–9·5. Both strains fermented several mono- and disaccharides. The main fermentation products from glucose were acetate, ethanol, hydrogen and carbon dioxide. Optimal hydrogen production by the new isolates was observed at pH 8·8 and 39 °C, and 1·4 mol H2was detected from fermentation of 1 mol glucose. The DNA G+C contents of strains ZLJ115Tand L4-2 were 53·9 and 54·3 mol%, respectively. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the isolates represented a novel phyletic sublineage within cluster XI of the clostridia, clustering with four thermophilic species, with <93·8 % 16S rRNA gene sequence similarity to previously described species. Phenotypically, the new isolates were distinguished from their phylogenetic relatives by growing mesophilically and by fermenting a variety of pentoses, as well as their higher genome DNA G+C content. On the basis of polyphasic evidence from this study, a novel genus and species are proposed,Sporacetigenium mesophilumgen. nov., sp. nov.; strain ZLJ115T(=DSM 16796T=AS 1.5019T) is the type strain ofSporacetigenium mesophilum.