Different evolutionary trends form the twilight zone of the bacterial pan-genome.
Horesh, Gal;
Taylor-Brown, Alyce;
McGimpsey, Stephanie;
Lassalle, Florent;
Corander, Jukka;
Heinz, Eva;
Thomson, Nicholas R;
(2021)
Different evolutionary trends form the twilight zone of the bacterial pan-genome.
Microbial genomics, 7 (9).
ISSN 2057-5858
DOI: https://doi.org/10.1099/mgen.0.000670
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The pan-genome is defined as the combined set of all genes in the gene pool of a species. Pan-genome analyses have been very useful in helping to understand different evolutionary dynamics of bacterial species: an open pan-genome often indicates a free-living lifestyle with metabolic versatility, while closed pan-genomes are linked to host-restricted, ecologically specialized bacteria. A detailed understanding of the species pan-genome has also been instrumental in tracking the phylodynamics of emerging drug resistance mechanisms and drug-resistant pathogens. However, current approaches to analyse a species' pan-genome do not take the species population structure into account, nor do they account for the uneven sampling of different lineages, as is commonplace due to over-sampling of clinically relevant representatives. Here we present the application of a population structure-aware approach for classifying genes in a pan-genome based on within-species distribution. We demonstrate our approach on a collection of 7500 Escherichia coli genomes, one of the most-studied bacterial species and used as a model for an open pan-genome. We reveal clearly distinct groups of genes, clustered by different underlying evolutionary dynamics, and provide a more biologically informed and accurate description of the species' pan-genome.