question: Are genes symmetrically distributed between leading and lagging DNA strand in bacteria?
answer: In most bacteria, genes are preferentially encoded on the leading strand than on the lagging strand. This avoids the potentially detrimental head-on collisions that occur between the replication and transcription machineries when genes are encoded on the lagging strand. Head-on collisions are more deleterious than codirectional collisions, and may lead to replication fork arrest and genomic instability. Genes of some functional categories such as ribosome have higher preferences to be on the leading strands, while genes of other functional categories such as transcription factor have higher preferences on the lagging strands. Strand-biased gene distribution correlates with replication-associated purine asymmetry and the presence or absence of polC. Especially essential and highly transcribed genes and genes whose expression is important for fitness are more preferentially situated at the leading strand in bacteria.