Faecalibacterium taiwanense sp. nov., isolated from human faeces

Two Gram-stain-negative, straight rods, non-motile, asporogenous, catalase-negative and obligately anaerobic butyrate-producing strains, HLW78 T and CYL33, were isolated from faecal samples of two healthy Taiwanese adults. Phylogenetic analyses of 16S rRNA and DNA mismatch repair protein MutL ( mutL ) gene sequences revealed that these two novel strains belonged to the genus Faecalibacterium . On the basis of 16S rRNA and mutL gene sequence similarities, the type strains Faecalibacterium butyricigenerans AF52-21 T (98.3–98.1 % and 79.0–79.5 % similarity), Faecalibacterium duncaniae A2-165 T (97.8–97.9 % and 70.9–80.1 %), Faecalibacterium hattorii APC922/41-1 T (97.1–97.3 % and 80.3–80.5 %), Faecalibacterium longum CM04-06 T (97.8–98.0% and 78.3 %) and Faecalibacterium prausnitzii ATCC 27768 T (97.3–97.4 % and 82.7–82.9 %) were the closest neighbours to the novel strains HLW78 T and CYL33. Strains HLW78 T and CYL33 had 99.4 % both the 16S rRNA and mutL gene sequence similarities, 97.9 % average nucleotide identity (ANI), 96.3 % average amino acid identity (AAI), and 80.5 % digital DNA–DNA hybridization (dDDH) values, indicating that these two strains are members of the same species. Phylogenomic tree analysis indicated that strains HLW78 T and CYL33 formed an independent robust cluster together with F. prausnitzii ATCC 27768 T . The ANI, AAI and dDDH values between strain HLW78 T and its closest neighbours were below the species delineation thresholds of 77.6–85.1 %, 71.4–85.2 % and 28.3–30.9 %, respectively. The two novel strains could be differentiated from the type strains of their closest Faecalibacterium species based on their cellular fatty acid compositions, which contained C 18 : 1 ω 7 c and lacked C 15 : 0 and C 17 : 1 ω 6 c , respectively. Phenotypic, chemotaxonomic and genotypic test results demonstrated that the two novel strains HLW78 T and CYL33 represented a single, novel species within the genus Faecalibacterium , for which the name Faecalibacterium taiwanense sp. nov. is proposed. The type strain is HLW78 T (=BCRC 81397 T =NBRC 116372 T ).