The distribution of recombination repair genes is linked to information content in bacteria

• The distribution of recombination repair genes is examined in 900 bacterial genomes.
• The presence of the genes in a genome is correlated with proteome size.
• The more widely distributed genes are absent from smaller genomes on average.
• The data provide support for the proteomic constraint theory.
• The theory proposes that proteome size exerts a selective pressure on DNA repair.

The concept of a ‘proteomic constraint’ proposes that the information content of the proteome exerts a selective pressure to reduce mutation rates, implying that larger proteomes produce a greater selective pressure to evolve or maintain DNA repair, resulting in a decrease in mutational load. Here, the distribution of 21 recombination repair genes was characterized across 900 bacterial genomes. Consistent with prediction, the presence of 17 genes correlated with proteome size. Intracellular bacteria were marked by a pervasive absence of recombination repair genes, consistent with their small proteome sizes, but also consistent with alternative explanations that reduced effective population size or lack of recombination may decrease selection pressure. However, when only non-intracellular bacteria were examined, the relationship between proteome size and gene presence was maintained. In addition, the more widely distributed (i.e. conserved) a gene, the smaller the average size of the proteomes from which it was absent. Together, these observations are consistent with the operation of a proteomic constraint on DNA repair. Lastly, a correlation between gene absence and genome AT content was shown, indicating a link between absence of DNA repair and elevated genome AT content.