Prevotella paludivivens sp. nov., a novel strictly anaerobic, Gram-negative, hemicellulose-decomposing bacterium isolated from plant residue and rice roots in irrigated rice-field soil

Abstract

Two strictly anaerobic bacterial strains, KB7T and A42, were isolated from rice plant residue and living rice roots, respectively, from irrigated rice-field soil in Japan. These two strains were closely related to each other with 16S rRNA gene sequence similarity of 99.8 %. Both strains showed almost the same physiological properties. Cells were Gram-negative, non-motile, non-spore-forming rods. Growth was remarkably stimulated by the addition of haemin to the medium. The strains utilized various saccharides including xylan, xylose, pectin and carboxymethylcellulose and produced acetate and succinate with small amounts of formate and malate. The strains grew at 10–40 °C; optimum growth was observed at 30 °C and pH 5.7–6.7. Oxidase, catalase and nitrate-reducing activities were not detected. Aesculin was hydrolysed. The major cellular fatty acids were anteiso-C15 : 0, iso-C15 : 0, C15 : 0 and iso-C17 : 0 3-OH. Menaquinones MK-11 and MK-11(H2) were the major respiratory quinones and the genomic DNA G+C content was 39.2 mol%. Phylogenetic analysis based on 16S rRNA gene sequences placed both strains in the phylum Bacteroidetes. 16S rRNA gene sequence analysis showed that the most related species to both strains was Prevotella oulorum (92.8–92.9 % similarity). Prevotella veroralis and Prevotella melaninogenica were the next most closely related known species with sequence similarities of 91.9–92.4 %. Based on differences in the phylogenetic, ecological, physiological and chemotaxonomic characteristics between the two isolates and related species, it is proposed that strains KB7T and A42 represent a novel species, Prevotella paludivivens sp. nov. This is the first described Prevotella species derived from a natural habitat; all other Prevotella species are from mammalian sources. The type strain of Prevotella paludivivens is KB7T (=JCM 13650T=DSM 17968T).