Table 1. Classification systems of Gardnerella isolates.

Group	Clade	Gardnerella genomospecies	Gardnerella species
C	C1	GS01	G. vaginalis (Gsp01) & Gsp02
B	C2	GS02	G. piotii & Gsp03
D	C3	GS05	Gsp08,Gsp09, & Gsp10
		GS04	Gsp07
A	C4	GS03	G. swidsinskii & G. leopoldii
B		GS06	Gsp11
		GS07	Gsp12
		GS08	Gsp13
		GS09

Classifications across lines in the table encompass approximately the same isolates. Groups A-D were assigned based on the phylogenetic relationships of a subsequence of the cpn60 gene [31]. Clades were assigned based on the qPCR detection of 4 genes, each specific for 4 major branches of Gardnerella isolates [37], designated as genovars by genome sequencing of 17 isolates [34]. Genomospecies (GS) were defined by integrating 4 methods of sequence comparisons of 103 genomic sequences [28]. Gardnerella species, labelled with names or numbers, were defined by analysis of 81 genome sequences by digital DNA-DNA hybridization, average nucleotide identity (ANI) and by MALDI-MS protein signatures [35]. Detailed placements of reference isolates are found in S1 Fig and S1 Table.