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

Abstract

An obligately anaerobic bacterial strain (WR041T) 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 13650T was the closest species of the strain based on 16S rRNA gene sequencing (98.9 % similarity). Genome analysis of strain WR041T 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 WR041T 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 WR041T represents a novel species in the genus. Strain WR041T 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-C15 : 0 and iso-C15 : 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 WR041T. Based on the differences in the phylogenetic, genomic and physiological characteristics between strain WR041T and related species, the name Prevotella herbatica sp. nov. is proposed to accommodate strain WR041T (=NBRC 115134T = DSM 112534T).