The human vagina is known to host a vast number of diverse, dynamic and complex bacterial communities, which include both commensal and pathogenic microorganisms. Despite the variation and diversification, it is now recognised that microbiota of healthy premenopausal women is represented by lactobacilli. A more diverse group is formed mostly by anaerobic microorganisms that cause bacterial vaginosis (BV). The co-existence of these microorganisms suggests that they might be engaged in some type of communication between themselves and most likely with the host using extracellular vesicles (EVs) as mediators. This research is focused on the evaluation and comparison of EVs produced by bacteria that represent normal and BV conditions - Lactobacillus gasseri ATCC 9857 and Gardnerella vaginalis ATCC 14018.
In this study, we compared two purification methods - density gradient centrifugation (DGC) and size exclusion chromatography (SEC). Molecules of interest (protein and nucleic acids) were quantified. We also compared the protein content of purified vesicles from two bacterial species.
We demonstrated that both bacteria released properly structured membrane EVs with an average diameter of 100 nm (shown by Transmission Electron Microscopy and Nanoparticle tracking analysis). Hight concentration of protein was detected in vesicles from L. gasseri and G. vaginalis. Although, RNA concentration was also high in these vesicles (as shown by Tape station), these nucleic acids were associated with EVs but not located inside them and protected by their membranes (shown by enzymatic treatment).
The ability of these bacteria to release EVs with distinct protein profiles, regardless of the composition of their cell wall, could indicate their active involvement in association with the host organism and other surrounding microorganisms.