Prevotella herbatica sp. nov., a plant polysaccharide-decomposing anaerobic bacterium isolated from a methanogenic...

An obligately anaerobic bacterial strain (WR041^T) was isolated from a plant residue sample in a methanogenic reactor. Cells of the strain were Gram-stain-negative, non-motile, non-spore-forming rods. Prevotella paludivivens JCM 13650^T was the closest species of the strain based on 16S rRNA gene sequencing (98.9 % similarity). Genome analysis of strain WR041^T indicated that the genome size of the strain was 3.52 Mb and the genomic DNA G+C content was 37.5 mol%. Although the 16S rRNA gene sequence similarity of strain WR041^T with the closest species was higher than the threshold value of the recommended species delineation (98.7 %), the average nucleotide identity and the digital DNA-DNA hybridization value between them were 91-92 and 45.5 %, respectively, suggesting that strain WR041^T represents a novel species in the genus. Strain WR041^T essentially required haemin and CO₂/Na₂CO₃ for growth. The strain was saccharolytic and decomposed various polysaccharides (glucomannan, inulin, laminarin, pectin, starch and xylan) and produced acetate and succinate. The optimum growth conditions were 35 °C and pH 6.8. The major cellular fatty acids were branched-chain fatty acids such as anteiso-C_15 : 0 and iso-C_15 : 0. Menaquinones MK-11 and MK-12 were the major respiratory quinones. Many protein-coding genes which were not found in the genome of P. paludivivens as orthologous genes were detected in the genome of strain WR041^T. Based on the differences in the phylogenetic, genomic and physiological characteristics between strain WR041^T and related species, the name Prevotella herbatica sp. nov. is proposed to accommodate strain WR041^T (=NBRC 115134^T = DSM 112534^T).