Selenomonas bovis sp. nov., isolated from yak rumen contents

Two strictly anaerobic, crescent-shaped bacterial strains, designated WGT and Ycb08, were isolated from a cellulose-degrading mixed culture enriched from yak rumen contents. The strains were Gram-negative, non-spore-forming and motile, with four to six flagella situated at the centre of the concave side of the cell. The cells were 0.9-1.1x4-6 microm. Growth was observed at 27-46 degrees C (optimum 39 degrees C) and pH 4.2-8.3 (optimum pH 7.0-7.2). Arabinose, glucose, mannose, cellobiose, lactose, sucrose, trehalose, melibiose, raffinose, salicin and aesculin were fermented. The end products of glucose fermentation were acetate, propionate and CO2. The G+C contents of strains WGT and Ycb08 were respectively 63.9+/-0.2 and 62.5+/-0.2 mol% (Tm). Phylogenetic analysis based on 16S rRNA gene sequences revealed that the two strains were related to the genera Mitsuokella and Selenomonas at similarity levels below 97%; however, they differed from members of the genus Mitsuokella in their flagellar arrangement. On the basis of phenotypic, genotypic and physiological evidence, strains WGT and Ycb08 are identified as members of a novel species of the genus Selenomonas, for which the name Selenomonas bovis sp. nov. is proposed. The type strain is WGT (=CGMCC 1.5073T=JCM 15470T).