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All species exist within a complex network of biotic interactions. Evolutionary changes within one pairwise species interaction can cascade through interaction networks, altering the evolutionary trajectory of connected species.

 

The partnership between rhizobia (nitrogen fixing bacteria) and legumes is an intimate and globally important relationship. Rhizobia facilitate the flow of nitrogen from the atmosphere to the plant, while plants provide bacteria with nutrients and shelter in the form of root nodules. However, rhizobia also live as free-living bacteria in the soil where they face interactions with a diverse microbial community. Key members of these soil communities are the temperate phages – bacterial viruses which can play numerous roles in bacterial populations as viral predators, as agents of horizontal gene transfer and as weapons of bacterial warfare.

bacteria plasmid coevolution

evolution in Rhizobial communities

Collaborators: Peter Young (York), Ville Friman (York), Phil Poole (Oxford), Tim Daniell (Sheffield), Euan James (James Hutton Institute) , Pete Iannatta (James Hutton Institute)

Collaborators: Mike Brockhurst (Sheffield), Steve Paterson (Liverpool), Andrew Spiers (Abertay), Jamie Hall (Liverpool), Calvin Dytham (York)

Conjugative plasmids play a major role in bacterial evolution as vectors for horizontal gene transfer. However acquiring a new plasmid can be highly disruptive to the bacterial cell resulting in strong selective pressure to either loose the plasmid or ameliorate its cost.

 

In this work we have demonstrated that compensatory evolution to alleviate the cost of plasmid carriage is a major force underlying bacteria-plasmid relationships, helping to explain their ubiquity in the environment. These changes can have important consequences for the wider community, affecting coevolutionary interactions with other partners and the rate of gene transfer in other species. Current work is focused on understanding the mechanisms which underly these compensatory mutations and the impact of these evolutionary processes in more complex communities.

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