Outer membrane vesicles (OMVs) are produced by all Gram‑negative bacteria and have a major role contributing to gene transfer, cell‑to‑cell communication and host‑pathogen interactions. Although numerous studies have examined the composition of OMVs, the impact of bacterial growth stage on regulating the size, composition and functions of OMVs has not been determined. This study aims to compare the quantity, size and composition of OMVs produced during various stages of bacterial growth.
In this study, we examined the production and composition of OMVs produced by Helicobacter pylori at early log, late log and stationary phase of growth (16, 48 and 72 hours of growth, respectively). We found that H. pylori produced approximately 1000 OMVs per bacterium during early log phase, which further increased 30-fold at 48 hrs and 32-fold at 72 hrs of bacterial growth. Furthermore, we demonstrated that OMV size decreased in heterogeneity as bacterial growth stage progressed. Specifically, OMVs from 16 hrs of growth displayed a broader range of OMV populations compared to OMVs from 48 or 72 hours of growth. Quantification of the content associated with OMVs purified from each growth stage was also determined. We found a large decrease in the amount of protein, DNA and RNA associated with OMVs as bacterial growth stage progressed from early log, to late log and stationary phase of bacterial growth. We are currently performing further analyses of OMVs to elucidate the effect of bacterial growth stage on OMV protein composition and immunogenicity.
Collectively, the findings from this study will provide detailed analysis of how bacterial growth stage affects OMV production, composition and functions. We aim to expand this study to determine if the bacterial growth stage of other Gram-negative pathogens regulates the production and content of their OMVs. Collectively, this knowledge will allow us to determine whether the regulation of OMV production and composition by bacterial growth stage is species specific or a conserved phenomenon used to increase bacterial virulence.