Reclassification of eight Akkermansia muciniphila strains and description of Akkermansia massiliensis sp. nov. and Candidatus Akkermansia timonensis, isolated from human feces.

Akkermansia muciniphila is a human intestinal tract bacterium that plays an important role in the mucus layer renewal. Several studies have demonstrated that it is a modulator for gut homeostasis and a probiotic for human health. The Akkermansia genus contains two species with standing in nomenclature but their genomic diversity remains unclear. In this study, eight new Akkermansia sp. strains were isolated from the human gut. Using the digital DNA-DNA hybridization (dDDH), average nucleotide identity (ANI) and core genome-based phylogenetic analysis applied to 104 A. muciniphila whole genomes sequences, strains were reclassified into three clusters. Cluster I groups A. muciniphila strains (including strain ATCC BAA-835 as type strain), whereas clusters II and III represent two new species. A member of cluster II, strain Marseille-P6666 differed from A. muciniphila strain ATCC BAA-835 and from A. glycaniphila strain Pyt in its ability to grow in microaerophilic atmosphere up to 42 °C, to assimilate various carbon sources and to produce acids from a several compounds. The major fatty acids of strain Marseille-P6666 were 12-methyl-tetradecanoic and pentadecanoic acids. The DNA G + C content of strain Marseille-P6666 was 57.8%. On the basis of these properties, we propose the name A. massiliensis sp. nov. for members of cluster II, with strain Marseille-P6666 (= CSUR P6666 = CECT 30548) as type strain. We also propose the name "Candidatus Akkermansia timonensis" sp. nov. for the members of cluster III, which contains only uncultivated strains, strain Akk0196 being the type strain.