Coprococcus intestinalis sp. nov., Parabacteroides caecihominis sp. nov., and "Akkermansia massiliensis" B2-R-115 with High Probiotic Potential from the Human Gut Microbiome

초록

Three novel bacterial strains obtained from human fecal samples were characterized for their taxonomic classification and probiotic potential. The strains included one Gram-stain-positive (B2-R-112T) and two Gram-stain-negative (TA-V-105T and B2-R-115) strains; all were anaerobic and non-motile. Phylogenetic analysis based on 16S rRNA gene sequences placed them within the genera Coprococcus, Parabacteroides, and Akkermansia. Specifically, B2-R-112T showed 97.7% sequence similarity to Coprococcus catus L8T, TA-V-105T showed 97.8% to Parabacteroides goldsteinii DSM 19448T, and B2-R-115 exhibited 99.6% sequence similarity to "Akkermansia massiliensis" Marseille P6666T. The genome sizes were 3,311,086 bp, 7,396,255 bp, and 3,288,486 bp, with G + C contents of 43.9%, 43.2%, and 57.8%, respectively. All strains demonstrated strong survival at pH 2.0-3.0 and robust bile salt tolerance (0.3% w/v oxgall) after 4 h, maintaining high viability in simulated gastric (pH 2.5, 4 h) and intestinal (pH 8.0, 6 h) fluids. They also exhibited significant antioxidant, antidiabetic, and anti-inflammatory activities. In silico DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) analyses, using thresholds of >= 70% and >= 95%, respectively, supported the classification of strain B2-R-112T and strain TA-V-105T as novel species. Based on these phenotypic, genomic, and phylogenetic analyses, we propose the classification of these potential probiotic strains as novel species: Coprococcus intestinalis sp. nov. (type strain B2-R-112T = KCTC 25419T = CGMCC 1.17967T and Parabacteroides caecihominis) sp. nov. (type strain TA-V-105T = KCTC 25451T = CGMCC 1.17989T.

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