A long-standing interest in the group has been the evolution of base composition. Initially our focus was on the evolution of GC content in mammals (Eyre-Walker and Hurst 2001) but recently we have become interested in the evolution of GC content in bacteria. Bacteria show an amazing diversity of genomic GC contents, ranging from species with GC below 20% to those with GC contents in excess of 70%. What causes this variation has been the subject of considerable debate. It has been suggested that the variation might be a consequence of mutation bias, selection or biased gene conversion. We recently showed that the variation in GC could not be due to mutation bias alone and that either selection or biased gene conversion (BGC) must be involved (Hildebrand, et al. 2010). We also provided some evidence against BGC. Current work is considering whether either selection or BGC alone can explain the pattern, or whether we have to invoke variation in both mutation bias and selection/BGC to explain the evolution of genomic GC in bacteria.

Eyre-Walker A, Hurst LD 2001. The evolution of isochores. Nature Rev. Genet. 2: 549-555.

Hildebrand F, Meyer A, Eyre-Walker A 2010. Evidence of selection upon genomic GC-content in bacteria. PLoS Genet 6: e1001107.