Ecological drivers of intragenomic conflict resolution

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.

Who will benefit from this research and how?

This is basic blue-skies research that will advance fundamental understanding of evolutionary processes and dynamics in bacterial communities. Nevertheless, bacterial evolution has a broad range of important impacts upon society, for example through the effects of rapid evolutionary change on the prognosis of clinical infections, the evolutionary emergence of antibiotic resistance, and evolutionary responses of microbial communities underpinning the functioning of ecosystems to environmental change. Despite the widespread and fundamental impact of rapid microbial evolution in general and horizontal gene transfer (HGT) in particular upon society, these evolutionary processes remain very poorly understood by the general public and policy-makers. The key benefits deriving from this research will therefore be increased knowledge and understanding of bacterial evolution among the following groups:

Secondary school age children: Teaching of evolution in Key Stages 2 and 3 of the National Curriculum is mainly theoretical and lacking in engaging practical classes. We will take experimental evolution into the school classroom allowing pupils to experience evolution in action themselves in real time, generating excitement about microbes and evolution and offering deeper experiential learning.

General public: Bacterial evolution is high on the news agenda due to the crisis in antimicrobial resistance (AMR), however few non-scientists realise that this societal problem is exacerbated by HGT-mediated evolution. Public engagement activities will enhance public understanding of HGT and put this into the context of AMR to show what we can all do to reduce the risks of AMR.

Policy makers in healthcare and agri-food sectors: HGT impacts the evolutionary emergence of AMR in the clinic and the spread of functional traits in soil bacterial communities. Designing policies and interventions that aim to e.g. limit the spread of AMR or conserve the functional diversity of soil bacterial communities, requires sharing knowledge and understanding of the dynamics of HGT and how these are shaped by the ecology of microbial communities and their environments arising from this research with stakeholders and policymakers in these sectors. We will engage with healthcare stakeholders via an established clinical network (PARC; PI Brockhurst is a member) and agri-food stakeholders via the N8 AgriFood Partnership facilitated by the N8 AgriFood Knowledge Exchange Fellows.