Plasmid maintenance in multispecies bacterial communities

Horizontal Gene Transfer (HGT) is a common method among bacteria to share genes and is important for bacterial survival, for example, it can promote antibiotic resistance. Plasmid conjugation is a common method of HGT. Plasmids can be lost due to the fitness cost associated with plasmid maintenance, but this fitness cost can be offset by the rapid rate of plasmid transfer between cells. In multispecies communities of cells, there is the potential for variable rates of growth and conjugation as well as interspecies interactions. Experiments have shown that interspecies interactions may strongly influence plasmid maintenance within communities, although in general plasmid maintenance within communities is not well understood. Using experiments and theory, we aim to understand how the community members impact plasmid maintenance. We developed a dynamical model for plasmids conjugation that follows mass-action kinetics plus Lotka-Volterra dynamics. The model approximates serial passage experiments with a two species community and one conjugation plasmid. The simulations revealed how plasmid fitness cost and conjugation rates determined the percentage of cells containing the plasmid. These results demonstrated that a second species has the potential to expand the region of parameter space where the plasmid is maintained. Such insights into plasmids maintenance within multispecies communities will have implications on bacterial community ecology and evolution and biomedical applications.