Proteiniclasticum ruminis gen. nov., sp. nov., a strictly anaerobic proteolytic bacterium isolated from yak rumen

Abstract

Two strictly anaerobic, proteolytic bacterial strains, designated strain D3RC-2T and D3RC-3r, were isolated from a cellulose-degrading mixed culture enriched from yak rumen content. The strains were Gram-stain negative and non-spore-forming with cell sizes of 0.5–0.8×0.6–2.0 μm. The temperature range for growth was 24–46 °C (optimum 38–39 °C) and the pH range was between 5.6 and 8.7 (optimum 7.0–7.3). Both strains used soya peptone, tryptone, l-phenylalanine, l-leucine, l-methionine, l-serine, l-valine, l-threonine and l-histidine as carbon and nitrogen sources, but did not use any of the saccharides tested. The major fermentation products from PY medium were acetate, propionate and iso-butyrate. The DNA G+C contents of strains D3RC-2T and D3RC-3r were 41.0±0.1 mol% and 41.3±0.1 mol% (HPLC), respectively. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the two strains represented a new phyletic sublineage within the family Clostridiaceae, with <93.8 % 16S rRNA gene sequence similarity to recognized species. On the basis of the phenotypic, genotypic and physiological evidence, strains D3RC-2T and D3RC-3r are proposed as representing a novel species of a new genus, for which the name Proteiniclasticum ruminis gen. nov., sp. nov. is proposed. The type strain of the type species is D3RC-2T (=AS 1.5057T=JCM 14817T).