| Abstract |
Two facultatively anaerobic bacterial strains, designated WR061(T) and WR054, were isolated from rice-straw residue in a methanogenic reactor treating waste from cattle farms in Japan. The two strains were phylogenetically positioned close to one another and had almost the same phenotypic properties. Cells were Gram-reaction-positive, non-motile, non-spore-forming, irregular rods. Cobalamin (vitamin B₁₂) was required for growth. The strains utilized various carbohydrates, including hexoses and disaccharides, and produced acetate and propionate from these carbohydrates. Pentoses and polysaccharides were not utilized. They grew at 20-37 °C (optimum 35 °C) and pH 5.3-8.0 (optimum pH 6.8-7.5). Catalase and nitrate-reducing activities were detected. Aesculin was hydrolysed. The major cellular fatty acids were anteiso-C₁₅:₀ and C₁₅:₀ DMA, the major respiratory quinone was menaquinone MK-9(H₄) and the genomic DNA G+C content was 69.3-69.5 mol%. The diagnostic diamino acid in the peptidoglycan was meso-diaminopimelic acid. Phylogenetic analysis based on 16S rRNA gene sequences placed the strains in the phylum Actinobacteria. Both strains were remotely related to the species in the family Propionibacteriaceae and Propionibacterium propionicum JCM 5830(T) was the most closely related type strain with a sequence similarity of 91.6 %. Based on phylogenetic, physiological and chemotaxonomic analyses, the two novel strains together represent a novel species of a new genus, for which the name Propioniciclava tarda gen. nov., sp. nov. is proposed. The type strain is WR061(T) ( = JCM 15804(T) = DSM 22130(T)).
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