Description of Propionispira arcuata sp. nov., isolated from a methanogenic reactor of cattle waste, reclassification of Zymophilus raffinosivorans and Zymophilus paucivorans as Propionispira raffinosivorans comb. nov. and Propionispira paucivorans comb. nov. and emended description of the genus Propionispira.

A strictly anaerobic bacterial strain, WK011T, was isolated from a methanogenic reactor treating waste from cattle farms. The cells stained Gram-negative and were curved rods with a polar or subpolar flagellum. Spore formation was not observed. The optimum temperature for growth was 35 °C and the optimum pH was 6.7. Tests for oxidase, catalase and nitrate-reduction activities were negative. Hydrogen sulfide was produced. The strain fermented carbohydrates and produced acetate and propionate as major fermentation products. The genomic DNA G+C content was 41.7 mol%. The major cellular fatty acids were C15 : 0, C16 : 1ω9c and C18 : 1 dimethylacetal. The diagnostic diamino acid of the cell-wall peptidoglycan was meso-diaminopimelic acid. The most closely related species to strain WK011T on the basis of 16S rRNA gene sequences were Propionispira arboris and Zymophilus raffinosivorans (95.6 % sequence similarity to the type strains of both species). It was shown by phylogenetic and phenotypic examination of the type strains of related species, including the second species of the genus Zymophilus , Zymophilus paucivorans , that the two genera should be combined and that the two species of the genus Zymophilus should be transferred to the genus Propionispira, as Propionispira raffinosivorans comb. nov. (type strain SH2T = ATCC 49691T = DSM 20765T) and Propionispira paucivorans comb. nov. (type strain AA1T = ATCC 49689T = DSM 20756T), with an emended description of the genus Propionispira . Based on differences in the phylogenetic and phenotypic characteristics of strain WK011T from those of closely related species, the novel species Propionispira arcuata sp. nov. is proposed to accommodate the strain. The type strain is WK011T ( = JCM 16475T = DSM 22929T).