Outer membrane vesicles (OMVs) are naturally produced by all Gram‑negative bacteria throughout their growth. Bacteria can produce OMVs by either releasing them as part of their normal growth, or as a result of explosive cell lysis mediated by the prophage endolysin Lys. Once produced, OMVs have a range of functions based on their cargo composition, such as lysing competing bacteria due to their lysin content. We have previously identified that bacterial growth stage regulates the cargo composition of OMVs, and we hypothesise that the mechanism of OMV biogenesis can also regulate their composition. In this study, we examined if the mechanism of OMV biogenesis regulates their cargo composition and their subsequent biological functions.
To do this, we have isolated OMVs from three Pseudomonas aeruginosa strains, PAO1 which produces OMVs naturally, PAO1∆lys that cannot produce OMVs by explosive cell lysis, and PAO1∆lys pJN105lys which has an inducible expression of OMV production by explosive cell lysis. We then tested the antimicrobial activity of OMVs produced by each P. aeruginosa strain. Our results show that OMVs generated from PAO1 and PAO1∆lys could not inhibit P. aeruginosa or Staphylococcus aureus growth. However, OMVs generated by PAO1∆lys pJN105lys explosive cell lysis inhibited the growth of both P. aeruginosa and S. aureus. We are currently attempting to induce OMV production by explosive cell lysis in PAO1 and determine the antimicrobial activity of these OMVs. Additionally, we are investigating if explosive cell lysis OMVs can inhibit the growth of other bacterial species.
Collectively, our data shows that OMVs produced by explosive cell lysis have a greater antimicrobial function than OMVs released during normal growth. This work will enable us to advance our understanding regarding how the mechanism of OMV biogenesis can determine their cargo composition and regulate their subsequent biological functions, including their antimicrobial activity.