Genotypic and phenotypic differences among phase-variable colony variants conserved acrossGardnerellaspp

Abstract

AbstractTheGardnerellagenus, now made up of more than 13 species, is associated with the polymicrobial disorder bacterial vaginosis (BV). However, the details of BV pathogenesis are poorly defined, and the contributions made by individual species are largely unknown. We report here that colony phenotypes characterized by size (large and small) and opacity (opaque and translucent) are phase variable and are conserved among all testedGardnerellastrains, representing at least ten different species. With the hypothesis that these different variants could be an important missing piece to the enigma of how BV develops in vivo, we characterized their differences. Beyond increased colony size, large colony variants (Lg) showed reduced vaginolysin secretion and faster growth rate relative to small colony variants (Sm). The ability to inhibit growth ofNeisseria gonorrhoeaeand commensal lactobacillus species varied by strain and in some instances differed between variants. Proteomics analyses indicate that 127-173 proteins are differentially expressed between variants. Further, whole genome sequencing analyses revealed an abundance of genes associated with variable poly-guanine tracts, implicating slipped strand mispairing inGardnerellaphase variation, and illuminating the potential for previously unrecognized variability within clonal populations. Collectively, these results suggest that colony variants may be primed to serve different roles in BV pathogenesis.