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, PolC 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 PolC correlates with leading strands that contain an average of 78% of genes compared with 58% for genomes that do not contain PolC. This suggests that asymmetrical replication forks could have a major role in defining and constraining the structure of the bacterial chromosome. The presence of PolC is not correlated with compositional strand bias, suggesting that the two biases result from different types of structural asymmetry.