Two novel, obligately anaerobic, Gram-stain-negative, rod or coccoid-shaped bacteria, designated strains 4NBBH2T and 6FBBBH3T, were isolated from faecal samples of a healthy Japanese woman and man. The 16S rRNA gene sequence analysis showed that these strains represent a distinct lineage within the family Sutterellaceae. Strain 4NBBH2T formed a monophyletic branch between the genera Parasutterella and Sutterella, with sequence similarity to Sutterella stercoricanis CCUG 47620T (92.6 %), followed by Sutterella wadsworthensis WAL 7877 (92.4 %), Sutterella parvirubra YIT 11816T (92.1 %) and Parasutterella secunda YIT 12071T (91.8 %). Strain 6FBBBH3T was affiliated to the genus Sutterella, with highest similarity to S. stercoricanis CCUG 47620T (97.1 %), followed by S. parvirubra YIT 11816T (96.6 %) and S. wadsworthensis WAL 7877 (95.2 %). Strains 4NBBH2T and 6FBBBH3T were asaccharolytic. Analysis of fatty acids revealed that strain 4NBBH2T could be differentiated from Sutterella species (including strain 6FBBBH3T) by the presence of a low concentration of C16 : 1ω7c. The major respiratory quinones of strain 4NBBH2T were menaquinone (MK)-6 and methylmenaquinone (MMK)-6, whereas those of strain 6FBBBH3T were MK-5 and MMK-5. The G+C content of the genomic DNA of strains 4NBBH2T and 6FBBBH3T were 56.9 and 62.8 mol%, respectively. On the basis of the collected data, strain 4NBBH2T represents a novel species in a novel genus of the family Sutterellaceae, for which the name Mesosutterella multiformis gen. nov., sp. nov. is proposed. The type strain is 4NBBH2T (=JCM 32464T=DSM 106860T). We also propose a novel Sutterella species, Sutterellamegalosphaeroides sp. nov., for strain 6FBBBH3T (=JCM 32470T=DSM 106861T).
Keywords: Sutterellaceae; asaccharolytic; hsp60; human faeces; quinone.