Proposal of Roseburia faecis sp. nov., Roseburia hominis sp. nov. and Roseburia inulinivorans sp. nov., based on isolates from human faeces

Abstract

Seven recently cultured bacterial isolates, although similar in their 16S rRNA gene sequences to Roseburia intestinalis L1-82T (DSM 14610T), were not sufficiently related for inclusion within existing species, forming three separate clusters in a 16S rRNA gene phylogenetic tree. The isolates, which were obtained from human stools, were Gram-variable or Gram-negative, strictly anaerobic, slightly curved rods; cells from all strains measured approximately 0.5×1.5–5.0 μm and were motile. Two strains belonging to one cluster (A2-181 and A2-183T) were the only strains that were able to grow on glycerol and that failed to grow on any of the complex substrates tested (inulin, xylan and amylopectin). Strains belonging to a second cluster (represented by M6/1 and M72/1T) differed from the other isolates in their ability to grow on sorbitol. Isolates belonging to a third cluster (L1-83 and A2-194T) were the only strains that failed to grow on xylose and that gave good growth on inulin (strains M6/1 and M72/1T gave weak growth). All strains were net acetate utilizers. The DNA G+C contents of representative Roseburia strains A2-183T, A2-194T, M72/1T and R. intestinalis L1-82T were 47.4, 41.4, 42.0 and 42.6 mol%, respectively. Based on 16S rRNA gene sequence similarity, three novel Roseburia species are proposed, with the names Roseburia hominis sp. nov. (type strain A2-183T=DSM 16839T=NCIMB 14029T), Roseburia inulinivorans sp. nov. (type strain A2-194T=DSM 16841T=NCIMB 14030T) and Roseburia faecis sp. nov. (type strain M72/1T=DSM 16840T=NCIMB 14031T).