Interspecific competition can drive plasmid loss from a focal species in a microbial community

Abstract

Plasmids are key disseminators of antimicrobial resistance genes and virulence factors, and it is therefore critical to predict and reduce plasmid spread within microbial communities. The cost of plasmid carriage is a key metric that can be used to predict plasmids’ ecological fate, and it is unclear whether plasmid costs are affected by growth partners in a microbial community. We carried out competition experiments and tracked plasmid maintenance using a model system consisting of a synthetic and stable five-species community and a broad host-range plasmid, engineered to carry different payloads. We report that both the cost of plasmid carriage and its long-term maintenance in a focal strain depended on the presence of competitors, and that these interactions were species specific. Addition of growth partners increased the cost of a high-payload plasmid to a focal strain, and accordingly, plasmid loss from the focal species occurred over a shorter time frame. We propose that the destabilising effect of interspecific competition on plasmid maintenance may be leveraged in clinical and natural environments to cure plasmids from focal strains.

Environmental microbiome diversity and stability is a barrier to antimicrobial resistance gene accumulation

“…On the other hand, in more diverse communities it can be harder to encounter a permissive conjugation partner, which reduces transferability due to this dilution effect 62 . Further, competition with other community members might increase the costs of resistance 63 – 65 and could ultimately drive the loss of ARG hosting plasmids from the community 66 . This loss process would be expected to be elevated in more diverse communities with better competitors.…”