Is there a role for replication fork asymmetry in the distribution of genes in bacterial genomes?

Replication generates bacterial chromosomes with strands that differ in the number of genes and base composition. It has been suggested that in bacteria such as Bacillus subtilis, PoIC is responsible for the synthesis of the leading strand and DnaE for the lagging strand, whereas in many other bacteria DnaE is responsible for the synthesis of both strands. Here, I show that the possession of PoIC correlates with leading strands that contain an average of 78% of genes compared with 58% for genomes that do not contain PoIC. This suggests that asymmetrical replication forks could have a major role in defining and constraining the structure of the bacterial chromosome. The presence of PoIC is not correlated with compositional strand bias, suggesting that the two biases result from different types of structural asymmetry.