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 species. In this study, we examined BMVs produced by the opportunistic pathogen
Pseudomonas aeruginosa, grown in planktonic or biofilm conditions, as well as BMVs from a mixed gut microbiota culture to determine if they packaged and protected DNA encoding for ARGs which can be transferred to other bacteria.
We found that P. aeruginosa grown in planktonic conditions released BMVs containing plasmid-encoded ARGs which were protected from DNase degradation. These BMVs could bind recipient P. aeruginosa in order to mediate HGT, resulting in antibiotic resistant transformants at a significantly higher rate than plasmid DNA transformation alone. As biofilms have been shown to enhance HGT, we next investigated BMVs produced by P. aeruginosa biofilms and their ability to facilitate HGT. P. aeruginosa biofilm BMVs contained an increased amount of ARGs compared to planktonic-derived BMVs, and we are currently comparing their HGT efficiencies.
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 from a mixed culture containing 95 microbiota bacteria to determine if they contain ARGs. We are currently sequencing the DNA contained within microbiota-derived BMVs to identify the genes associated with these BMVs, and whether they can facilitate HGT.
Collectively, these studies will advance our limited knowledge regarding the contribution of BMVs to HGT during physiological settings, such as within biofilms and the human gut microbiota.