Comparative Genomics of Gardnerella vaginalis Strains Reveals Substantial Differences in Metabolic and Virulence Potential

Abstract

Background Gardnerella vaginalis is described as a common vaginal bacterial species whose presence correlates strongly with bacterial vaginosis (BV). Here we report the genome sequencing and comparative analyses of three strains of G. vaginalis. Strains 317 (ATCC 14019) and 594 (ATCC 14018) were isolated from the vaginal tracts of women with symptomatic BV, while Strain 409-05 was isolated from a healthy, asymptomatic individual with a Nugent score of 9.Principal FindingsSubstantial genomic rearrangement and heterogeneity were observed that appeared to have resulted from both mobile elements and substantial lateral gene transfer. These genomic differences translated to differences in metabolic potential. All strains are equipped with significant virulence potential, including genes encoding the previously described vaginolysin, pili for cytoadhesion, EPS biosynthetic genes for biofilm formation, and antimicrobial resistance systems, We also observed systems promoting multi-drug and lantibiotic extrusion. All G. vaginalis strains possess a large number of genes that may enhance their ability to compete with and exclude other vaginal colonists. These include up to six toxin-antitoxin systems and up to nine additional antitoxins lacking cognate toxins, several of which are clustered within each genome. All strains encode bacteriocidal toxins, including two lysozyme-like toxins produced uniquely by strain 409-05. Interestingly, the BV isolates encode numerous proteins not found in strain 409-05 that likely increase their pathogenic potential. These include enzymes enabling mucin degradation, a trait previously described to strongly correlate with BV, although commonly attributed to non-G. vaginalis species.ConclusionsCollectively, our results indicate that all three strains are able to thrive in vaginal environments, and therein the BV isolates are capable of occupying a niche that is unique from 409-05. Each strain has significant virulence potential, although genomic and metabolic differences, such as the ability to degrade mucin, indicate that the detection of G. vaginalis in the vaginal tract provides only partial information on the physiological potential of the organism.

Vaginolysin Drives Epithelial Ultrastructural Responses to Gardnerella vaginalis

“…vaginalis is an enigmatic bacterial species with a strong link to reproductive health in humans (9,(40)(41)(42). Mechanistic studies of specific gene products in G. vaginalis pathogenesis have been limited by the lack of strategies for genetic manipulation of this organism.…”

The primate vaginal microbiome: Comparative context and implications for human health and disease

“…Even phylogenetically similar bacterial species may exhibit different ecological and virulence properties (Jaspers and Overmann, 2004). New direct DNA analyses show functional diversity in Lactobacillus and many other taxa Verstraelen et al, 2004;Zhou et al, 2004;Hyman et al, 2005;Kim et al, 2009;Yeoman et al, 2010Yeoman et al, , 2013. In addition, bacterial communities composed of different species may still occupy similar ecological niches and exhibit similar metabolic functions (Langenheder et al, 2005).…”

Towards an Evolutionary Model of Animal-Associated Microbiomes

“…More recently it has been shown to affect more than a third (~34%) of all gene families [57]. Species within microbiomes do not escape this trend, with several studies providing evidence that HGT is pervasive within at least the GI [58] and vaginal [59] microbial ecosystems. Intraspecifically, HGT can lead to rapid evolution of novel functionality [60] and drive important ecological events such as speciation [61] and modularity [62].…”