Caproicibacter fermentans gen. nov., sp. nov., a new caproate-producing bacterium and emended description of the genus Caproiciproducens

A strictly anaerobic bacterial strain designated EA1 T was isolated from an enrichment culture inoculated with biogas reactor content. Cells of strain EA1 T are spore-forming rods (1–3×0.4–0.8 µm) and stain Gram-negative, albeit they possess a Gram-positive type of cell-wall ultrastructure. Growth of strain EA1 T was observed at 30 and 37 °C and within a pH range of pH 5–9. The major components recovered in the fatty acid fraction were C 14:0 , C 16:0 , C 16:0 DMA (dimethyl acetal) and C 16:1 ω 7 c . Strain EA1 T fermented several mono- and disaccharides. Metabolic end products from fructose were acetate, butyrate, caproate and lactate. Furthermore, ethanol, CO 2 and H 2 were identified as products. The genome consists of a chromosome (3.9 Mbp) with 3797 predicted protein-encoding genes and a G+C content of 51.25 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain EA1 T represents a novel taxon within the family Oscillospiraceae . The most closely related type strains of EA1 T , based on 16S rRNA gene sequence identity, are Caproiciproducens galactitolivorans BS-1 T (94.9 %), [ Clostridium ] leptum DSM 753 T (93.8 %), [ Clostridium ] sporosphaeroides DSM 1294 T (91.7 %) and Ruminococcus bromii ATCC 27255 T (91.0 %). Further phenotypic characteristics of strain EA1 T differentiate it from related, validly described bacterial species. Strain EA1 T represents a novel genus and novel species within the family Oscillospiraceae . The proposed name is Caproicibacter fermentans gen. nov., sp. nov. The type strain is EA1 T (DSM 107079 T =JCM 33110 T ).