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

A strictly anaerobic bacterial strain designated EA1Twas isolated from an enrichment culture inoculated with biogas reactor content. Cells of strain EA1Tare 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 EA1Twas 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 C14:0, C16:0, C16:0DMA (dimethyl acetal) and C16:1ω7c. Strain EA1Tfermented several mono- and disaccharides. Metabolic end products from fructose were acetate, butyrate, caproate and lactate. Furthermore, ethanol, CO2and H2were 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 EA1Trepresents a novel taxon within the familyOscillospiraceae. The most closely related type strains of EA1T, based on 16S rRNA gene sequence identity, areCaproiciproducens galactitolivoransBS-1T(94.9 %), [Clostridium]leptumDSM 753T(93.8 %), [Clostridium]sporosphaeroidesDSM 1294T(91.7 %) andRuminococcus bromiiATCC 27255T(91.0 %). Further phenotypic characteristics of strain EA1Tdifferentiate it from related, validly described bacterial species. Strain EA1Trepresents a novel genus and novel species within the familyOscillospiraceae. The proposed name isCaproicibacter fermentansgen. nov., sp. nov. The type strain is EA1T(DSM 107079T=JCM 33110T).