Host and Bacterial Functions in Bacterial Vaginosis Elucidated by Metaproteomics

Abstract

Bacterial vaginosis (BV) is a highly prevalent dysbiosis of the vaginal microbiota which causes a variety of unpleasant symptoms and places patients at higher risk of adverse sequelae. BV is a complex condition, and many of the host and bacterial functions which contribute to its development and recurrence are unknown. This dissertation describes an optimized metaproteomic analysis of cervicovaginal lavage samples from women with and without BV to identify host and bacterial proteins that may contribute to BV. Using this approach, we uncovered new potential synergistic interactions between BV-associated bacteria (BVAB) based on glutamate and identified a possible host response to increased concentrations of free heme in BV. We also demonstrated a novel syntrophic interaction between Dialister micraerophilus and Fannyhessea vaginae to increase putrescine biosynthesis, likely through cross-feeding of the arginine metabolite ornithine. Despite past reports that human amylase is primarily responsible for breaking down vaginal glycogen into fermentable carbohydrates, we identified glycogen-degrading enzymes from L. crispatus and G. vaginalis in samples from both BV- and BV+ study participants. This observation led to our discovery that a wide range of BVAB, but only L. crispatus and L. iners among the commensal Lactobacillus spp., can directly metabolize glycogen. Finally, we described the construction of an E. coli-Gardnerella shuttle vector that can be applied for genetic manipulation of this genus. This work contains novel insights into BV and opens new avenues to study the biology of vaginal bacteria, with implications for treatment and prevention of this condition.