Ecological dynamics of plasmid transfer and persistence in microbial communities

Abstract

Plasmids are a major driver of horizontal gene transfer in prokaryotes, allowing the sharing of ecologically important accessory traits between distantly related bacterial taxa. Within microbial communities, interspecies transfer of conjugative plasmids can rapidly drive the generation genomic innovation and diversification. Recent studies are starting to shed light on how the microbial community context, that is, the bacterial diversity together with interspecies interactions that occur within a community, can alter the dynamics of conjugative plasmid transfer and persistence. Here, I summarise the latest research exploring how community ecology can both facilitate and impose barriers to the spread of conjugative plasmids within complex microbial communities. Ultimately, the fate of plasmids within communities is unlikely to be determined by any one individual host, rather it will depend on the interacting factors imposed by the community in which it is embedded.

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.