Bacterial vaginosis (BV) is a common cause of abnormal vaginal discharge that is characterized by a depletion of optimal vaginal lactobacilli and increased abundance of facultative and anaerobic bacteria. BV has been linked to increased risk to human immunodeficiency virus infection (HIV) and other reproductive sequelae, possibly via alteration of the mucosal immune milieu. The pathogenesis of BV remains incompletely understood which has resulted in limited interventions that suffer high recurrence rates. Gardnerella has been proposed as a causative agent of BV, however this taxon has also been isolated from healthy individuals, challenging its etiological role. Relevant to this, genomic investigations have resolved four Gardnerella subgroups which exhibit differences in virulence potential in-vitro and may therefore play different roles in the pathogenesis of BV and associated sequelae. To better understand the significance of Gardnerella heterogeneity, cpn60 microbial profiling was used to examine the contributions of cervicovaginal microbiome dominance by different Gardnerella subgroups to microbiome-mucosal immune response associations and BV in a longitudinal cohort of reproductive age Kenyan women. This analysis showed non-Lactobacillus dominant microbiomes were generally associated with an increase in pro-inflammatory cytokines. Additionally, microbiomes dominated by different Gardnerella subgroups exhibited divergent associations with the chemokine IP-10 relative to optimal microbiomes. Those microbiomes associated with reduced IP-10 levels (polymicrobial and Gardnerella subgroup A dominant) were more common in those with BV. Given these findings and the relevance of Gardnerella dominant biofilms to BV, follow up in-vitro experiments were performed using isolates from Gardnerella subgroups A, B, and C to examine differences in biofilm forming capabilities and proteomic determinants of these. This analysis revealed superior in-vitro biofilm formation in the G. leopoldii (subgroup A) and G. piotii (subgroup B) isolates relative to the G. vaginalis (subgroup C) isolate used. Comparative proteomic analysis of these biofilms revealed significant differences in functional pathways as well as in many proteins including those associated with metabolic processes and bacterial virulence. In conclusion, this thesis highlights the importance of considering Gardnerella heterogeneity in studies of BV and the vaginal microbiome and sheds light on potential drivers of biofilm formation in different Gardnerella species.