Reclassification of Eubacterium rectale (Hauduroy et al. 1937) Prévot 1938 in a new genus Agathobacter gen. nov. as Agathobacter rectalis comb. nov., and description of Agathobacter ruminis sp. nov., isolated from the rumen contents of sheep and cows

Abstract

Three strains of a butyrate-producing bacterium were isolated from the rumen contents of grazing sheep and cows. The strains were anaerobic, with Gram-positive cell walls, straight-to-slightly-curved, rod-shaped, non-spore-forming and single flagellate. C_{14 : 1}, C_{14 : 0}, C_{16 : 0} and C_{16 : 1} were the predominant fatty acids. The cell-wall peptidoglycan type was A1<i>γ</i>. The DNA G+C content varied from 41.4 to 42.2 mol%. 16S rRNA gene sequence similarities between the isolates and <i>Eubacterium rectale</i>, <i>Roseburia hominis</i> and <i>Roseburia intestinalis</i> were found to be 96, 95 and 95 %, respectively. The phylogenetic tree showed that the strains constituted a different taxon, separate from other taxa with validly published names and forming a cluster with strains of <i>Eubacterium rectale.</i> On the basis of phenotypic, chemotaxonomic and phylogenetic results (16S RNA, <i>dnaK</i>, <i>groEL</i>, <i>atpA</i> genes), the isolates are considered to represent a novel species of a new genus of the family <i>Lachnospiraceae</i>, for which the name <i>Agathobacter ruminis</i> gen. nov., sp. nov. is proposed (type strain JK623^T = DSM 29029^T = LMG 28559^T). We also propose the transfer of <i>Eubacterium rectale</i> to the new genus <i>as Agathobacter rectalis</i> gen. nov., comb nov. This new genus represents saccharoclastic, chemo-organotrophic and obligatory anaerobic, non-spore-forming rods with Gram-positive membrane. The main fermentation products on peptone yeast glucose (PYG) medium were butyrate, acetate, hydrogen and lactate. The type species of the genus is <i>Agathobacter rectalis</i> gen. nov., comb nov. (Prévot, 1938) with type strain ATCC 33656^T ( = JCM 17463^T).