A novel propionate producing bacterium, strain JV5T, was isolated from the rumen fibrous content of a Holstein Friesian dairy cow. Cells of strain JV5T were Gram-stain-positive, non-motile and aerotolerant. Growth occurred between 35 and 45 °C, with an optimum at 39 °C. The pH range for growth was 6.5-8, with an optimum at pH 7. The 16S rRNA gene sequence of strain JV5T was 98.4 and 96.5 % identical to those of Propionibacterium australiense DSM 15818T and Propionibacterium acidifaciens DSM 21887T, respectively. Genome wide average nucleotide identity and digital DNA-DNA hybridization values were 88.3 and 35.5 %, respectively, against P. australiense DSM 15818T. The G+C content of strain JV5T was 68.9 mol%. Strain JV5T did not produce urease and was able to metabolize glutamate, but not aspartate and glycine. Strain JV5T was able to ferment a range of substrates including certain simple and complex carbohydrates, sugar alcohols and amino acids. Chemotaxonomic analysis of strain JV5T revealed the presence of meso-diamino pimelic acid isomers similar those found in P. australiense, but different from P. acidifaciens. The observed major (>10 %) cellular fatty acids in strain JV5T (C18 : 1 ω9c, anteiso-C15 : 1, C16 : 0, C17 : 0 and C16 : 0 alcohol) were also different from those observed in P. australiense and P. acidifaciens. Based on these findings, a novel species is proposed within the genus Propionibacterium, Propionibacterium ruminifibrarum sp. nov. (type strain JV5T=DSM 106771T=TISTR 2629T).
Keywords: 16S rRNA; Propionibacterium; dairy cow; methylcellulose; rumen fibres.