Ecological drivers of intragenomic conflict resolution

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The classical view of evolution is as a process of gradual accumulation of small changes by mutations passed on to descendants. However, genome sequencing has revealed that in bacteria genes are frequently exchanged between cells and species by a process called horizontal gene transfer, allowing evolution to make big, fast jumps. Genes often pass from one bacterial cell to another on circular pieces of DNA called plasmids. However, acquiring a plasmid can be costly to a bacterial cell because plasmids use energy and introduce new genes that disrupt the normal working of the bacterium. In evolutionary theory these costs are called intragenomic conflicts because what is good for the plasmid is bad for the bacterial chromosome, and vice versa. We have recently shown that evolution can resolve these conflicts by a process of 'compensatory evolution', whereby either the bacterial chromosome or the plasmid gains mutations that lessen the cost of carrying the plasmid. By increasing plasmid survival, compensatory evolution is likely to increase the chance of new genes jumping onto plasmids from bacterial chromosomes, allowing these to be shared with other species in the community. In this proposal we will discover how the ecology of microbial communities and the environments they live in shape the processes of compensatory evolution, and whether compensatory evolution itself speeds up the sharing of genes between species.