Figure 1.

Summary of the discussed factors within multispecies communities that can act to limit (a–c) or facilitate (d–f) the persistence of plasmids. (a) Parasitism, for example, by bacteriophage, can drive selective sweeps for resistance mutations resulting in the loss of plasmids. (b) The presence of less permissive hosts in a community can dilute the transfer efficiency of conjugative plasmids reducing the stability of plasmids that rely on infectious transfer for their maintenance. (c) The proficiency of the original donor determines the ability of a plasmid to become established within a community, with less proficient donors being unable to disseminate plasmids to a wide diversity of novel hosts. (d) Protist predation can maintain populations in continuous growth phase which elevates conjugation rates and increases plasmid persistence. (e) Highly efficient donors can act as sources of plasmids, maintaining them in less proficient hosts due to high intraspecies conjugation rates. (f) Variation in plasmid fitness effects can stabilise plasmids within populations even when the net effect of harbouring a plasmid is costly.