Further dissection of Gardnerella vaginalis: description of Gardnerella lacydonensis sp. nov. (formerly genomic species 2), Gardnerella bretellae sp. nov. (formerly genomic species 9), Gardnerella massiliensis sp. nov. (formerly genomic species 14) and Gardnerella phocaeensis sp. nov.

Four bacterial strains - Marseille-Q9181T, Marseille-QA0894T, Marseille-Q9179T and Marseille-Q2328T - were isolated, the first three from vaginal samples and the last from a blood sample. MALDI-TOF MS analysis failed to assign these isolates to any known species within the genus Gardnerella. Consequently, phenotypic and taxonogenomic characterizations were conducted. All four strains were Gram-negative, non-motile and non-spore-forming coccobacilli. Strains Marseille-Q9181T, Marseille-Q2328T and Marseille-Q9179T were facultative anaerobes with microaerophilic capabilities, whereas Marseille-QA0894T was strictly anaerobic and microaerophilic. The dominant fatty acids (>10%) identified in strains Marseille-Q9181T, Marseille-QA0894T and Marseille-Q2328T were C16 : 0, C18 : 1 ω9c and C18 : 0. In strain Marseille-Q9179T, C18 : 0 was also among the most abundant fatty acids, along with the aforementioned three. Digital DNA-DNA hybridization (dDDH) values for strains Marseille-Q9181T, Marseille-QA0894T and Marseille-Q2328T against Gardnerella vaginalis 1400E (genomic species 2), G. vaginalis 6119V5 (genomic species 9) and G. vaginalis NR010 (genomic species 14) were 72.1%, 72.4% and 75.5%, respectively. The corresponding OrthoANI values were 96.99%, 97.16% and 97.66%, all above the species demarcation threshold. In contrast, strain Marseille-Q9179T exhibited both dDDH and OrthoANI values below the accepted thresholds (70% and 95-96%, respectively), suggesting that it represents a novel genomic lineage. Based on comprehensive phenotypic and genomic analyses, we propose that these strains represent four new species within the genus Gardnerella, for which the following names are proposed: Gardnerella lacydonensis sp. nov. (type strain: Marseille-Q9181T=CSUR Q9181T=CECT 31121T), Gardnerella bretellae sp. nov. (type strain: Marseille-QA0894T=CSUR QA0894T=CECT 31122T), Gardnerella massiliensis sp. nov. (type strain: Marseille-Q2328T=CSUR Q2328T=CECT 30239T) and Gardnerella phocaeensis sp. nov. (type strain: Marseille-Q9179T=CSUR Q9179T=CECT 31120T).