Simple models for bacterial evolution with migration

In nature, evolution proceeds not only through mutation and selection of better adapted organisms within a uniform population, but also through migration of organisms between different environments. The role of migration in asexual microbes was long underestimated. However, recent experiments have suggested that many pathogenic bacteria which cause infections are not in their native environment but are actually colonisers from nearby environments where they are non-pathogenic. For example, a pathogenic strain of the bacterium E. coli which infect the urinary tract is thought to come from the human gut where it does not cause any harm. It is an open question how such pathogenic strains emerge from their non-pathogenic counterparts.

In my research, I investigate the role of migration in the evolution of genetic diversity in microbes. I have published (with R. Allen and M. Evans) a paper in which we show that moderate migration strongly increases genetic diversity, but too strong migration inhibits adaptation to the new environment. I am also working on how this scenario is modified in the presence of cooperation between different bacterial species, horizontal gene transder, and predation by phages (viruses that infect bacteria).

wp496c9eb4_06The bacterium E. coli which is a common cause of urinary tract infections is thought to live primarily in the large intestine.
In our model, bacteria migrate from a large, primary habitat to a smaller, secondary habitat where different genotypes have different growth rates compared to the “source” habitat.

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