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Taxonomic relationships between Lactobacillus casei , Lactobacillus paracasei and Lactobacillus zeae have long been debated. Results of previous analyses have shown that overall genome relatedness indices (such as average nucleotide identity and core nucleotide identity) between the type strains L. casei ATCC 393T and L. zeae ATCC 15820T were 94.6 and 95.3 %, respectively, which are borderline for species definition. However, the digital DNA‒DNA hybridization value was 57.3 %, which was clearly lower than the species delineation threshold of 70 %, and hence raised the possibility that L. casei could be reclassified into two species. To re-evaluate the taxonomic relationship of these taxa, multilocus sequence analysis (MLSA) based on the concatenated five housekeeping gene (dnaJ, dnaK, mutL, pheS and yycH) sequences, phylogenomic and core genome multilocus sequence typing analyses, gene presence and absence profiles using pan-genome analysis, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) profiling analysis, cellular fatty acid compositions, and phenotype analysis were carried out. The results of phenotypic characterization, MLSA, whole-genome sequence-based analyses and MALDI-TOF MS profiling justified an independent species designation for the L. zeae strains, and supported an emended the description of the name of Lactobacillus zeae (ex Kuznetsov 1956) Dicks et al. 1996, with ATCC 15820T (=DSM 20178T=BCRC 17942T) as the type strain.

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A strictly anaerobic predominant bacterium, designated as strain gm001T, was isolated from a freshly voided faecal sample collected from a healthy Taiwanese adult. Cells were Gram-stain-negative rods, non-motile and non-spore-forming. Strain gm001T was identified as a member of the genus Prevotella , and a comparison of 16S rRNA and hsp60 gene sequences revealed sequence similarities of 98.5 and 93.3 %, respectively, demonstrating that it was most closely related to the type strain of Prevotella copri . Phylogenomic tree analysis indicated that the gm001T cluster is an independent lineage of P. copri DSM 18205T. The average nucleotide identity, digital DNA‒DNA hybridization and average amino acid identity values between strain gm001T and P. copri DSM 18205T were 80.9, 28.6 and 83.8 %, respectively, which were clearly lower than the species delineation thresholds. The species-specific genes of this novel species were also identified on the basis of pan-genomic analysis. The predominant menaquinones were MK-11 and MK-12, and the predominant fatty acids were anteiso-C15 : 0, C15 : 0 and iso-C15 : 0. Acetate and succinate were produced from glucose as metabolic end products. Taken together, the results indicate that strain gm001T represents a novel species of the genus Prevotella , for which the name Prevotella hominis sp. nov. is proposed. The type strain is gm001T (=BCRC 81118T=JCM 33280T).