Falcatimonas natans gen. nov., sp nov., a strictly anaerobic, amino-acid-decomposing bacterium isolated from a methanogenic reactor of cattle waste

A strictly anaerobic bacterial strain (WN011(T)) was isolated from a methanogenic reactor treating waste from cattle farms. Cells of the strain were Gram-stain-negative curved rods with a polar flagellum. Spores were not produced. The optimum temperature for growth was 35-37 degrees C and the optimum pH was 6.7. The strain did not utilize carbohydrates as growth substrates. The strain grew in PY medium and produced acetate, butyrate, isovalerate and H-2 as well as propionate and isobutyrate as minor products. Amino acids (L-isoleucine, L-leucine, L-lysine, L-serine, L-threonine and L-valine) added to PY medium enhanced growth of the strain and increased the amounts of fermentation products. Oxidase, catalase and nitrate-reducing activities were negative. Hydrogen sulfide was produced. The genomic DNA G+C content was 38.8 mol %. Compounds related to iso-C-15 : 0 (fatty acid, dimethylacetal and aldehyde) were detected as predominant components by the cellular fatty acids analysis. The diagnostic diamino acid of the cell-wall peptidoglycan was meso-diaminopimelic acid. On the basis of 16S rRNA gene sequences, three clones from wastewater were very closely related to strain WN011(T) (up to 99.9% sequence similarity). The most closely related described species were those in cluster XIVa of the class Clostridia such as Ruminococcus gauvreauii (93.8% 16S rRNA gene sequence similarity), Clostridium fimetarium (93.5 %) and Clostridium bolteae(93.5 %). Based on the distinct differences in phylogenetic and phenotypic characteristics of strain WN011(T) from those of related species, it is concluded that strain WN011(T) represents a novel species of a new genus in the family Lachnospiraceae, for which the name Falcatimonas natans gen. nov., sp. nov. is proposed. The type strain of the type species is WN011(T) (= JCM 16476(T) = DSM 22923(T)).