Evidence of selection upon genomic GC-content in bacteria

Hildebrand, Falk, Meyer, Axel and Eyre-Walker, Adam (2010) Evidence of selection upon genomic GC-content in bacteria. PLoS Genetics, 6 (9). e1001107. ISSN 1553-7390

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The genomic GC-content of bacteria varies dramatically, from less than 20% to more than 70%. This variation is generally ascribed to differences in the pattern of mutation between bacteria. Here we test this hypothesis by examining patterns of synonymous polymorphism using datasets from 149 bacterial species. We find a large excess of synonymous GC->AT mutations over AT->GC mutations segregating in all but the most AT-rich bacteria, across a broad range of phylogenetically diverse species. We show that the excess of GC->AT mutations is inconsistent with mutation bias, since it would imply that most GC-rich bacteria are declining in GC-content; such a pattern would be unsustainable. We also show that the patterns are probably not due to translational selection or biased gene conversion, because optimal codons tend to be AT-rich, and the excess of GC->AT SNPs is observed in datasets with no evidence of recombination. We therefore conclude that there is selection to increase synonymous GC-content in many species. Since synonymous GC-content is highly correlated to genomic GC-content, we further conclude that there is selection on genomic base composition in many bacteria.

Item Type: Article
Schools and Departments: School of Life Sciences > Evolution, Behaviour and Environment
Subjects: Q Science
Depositing User: Adam Eyre-Walker
Date Deposited: 06 Feb 2012 20:31
Last Modified: 02 Jul 2019 22:19
URI: http://sro.sussex.ac.uk/id/eprint/26398

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