The release of bacterial membrane vesicles (BMVs) is a conserved mechanism common to all bacteria, which contributes to the dissemination of bacterial components including proteins, DNA, and RNA. Recently, BMVs have been described as a novel mechanism of horizontal gene transfer (HGT), as DNA-containing BMVs can transfer antimicrobial resistance genes (ARGs) to recipient bacteria, however this has only been described for a limited number of bacterial species. In this study, we examined BMVs produced by the mucosal opportunistic pathogen, P. aeruginosa, and by a mixed gut microbiota culture, to determine if they contain DNA encoding for ARGs which can be transferred to other bacteria.
We found that P. aeruginosa grown using planktonic conditions released BMVs containing plasmid-encoded ARGs. These BMVs could mediate HGT, resulting in antibiotic-resistant transformants at a significantly higher rate than plasmid DNA alone. As biofilms have been shown to enhance HGT, we next investigated the ability of BMVs produced by P. aeruginosa grown as a biofilm to facilitate HGT. BMVs produced by P. aeruginosa biofilms contained an increased level of plasmid ARGs compared to planktonic-derived BMVs, and we are currently comparing their HGT efficiencies in the transfer of DNA to planktonic and biofilm P. aeruginosa.
We next wanted to examine the ability of BMVs to contribute to HGT in a mixed microbial setting. As the human gut microbiome is considered a reservoir for ARGs, we purified BMVs produced by a mixed culture containing 95 microbiota bacteria to determine if they contain ARGs. Currently, we are sequencing the DNA contained within microbiota-derived BMVs to identify ARGs contained within them and whether they can facilitate HGT.
Collectively, these studies will advance our limited knowledge regarding the contribution of BMVs to the transfer of ARGs during physiological settings, such as within biofilms and the human gut microbiota.