During an ongoing female urinary microbiome research study, strains c17Ua_112T and c31Ua_26T isolated from urine samples of a patient diagnosed with overactive bladder and a healthy postmenopausal woman, respectively, could not be allocated to any Gardnerella species with valid names. In this work, we aimed to characterize these strains. The 16S rRNA gene sequences confirmed that these strains are members of the genus Gardnerella. Phylogenetic analysis based on cpn60 strongly supported two clades, one encompassing c17Ua_112T and nine other strains from the public database, and the other including c31Ua_26T and three other strains, which were distinct from currently recognized species of the genus Gardnerella. Likewise, the phylogenomic tree also showed that strains c17Ua_112T and c31Ua_26T formed independent and robust clusters. Average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between c17Ua_112T and c31Ua_26T were 79.27 and 27.4 %, respectively. Strain c17Ua_112T showed the highest ANI (94.8 %) and dDDH values (59.8 %) with Gardnerella piotii UGent 18.01T, and strain c31Ua_26T revealed highest ANI (84.2 %) and dDDH (29.1 %) values with Gardnerella swidsinskii GS 9838-1T. Based on the data presented here, the two strains c17Ua_112T and c31Ua_26T represent two novel species of the genus Gardnerella, for which the names Gardnerella pickettii (c17Ua_112T=DSM 113414T=CCP 71T) and Gardnerella greenwoodii (c31Ua_26T=DSM 113415T=CCP 72T) are proposed.
Keywords: Gardnerella greenwoodii sp. nov; Gardnerella pickettii sp. nov.; Gardnerella vaginalis; whole genome sequencing.