Geometrical ordering of DNA in bacteria.

The bacterium Caulobacter crescentus shows a remarkable spatial ordering of its chromosome that leads to a strong linear correlation between the position of genes on the chromosomal map and their spatial position in the cellular volume. In a recent study we have shown that a robust and universal geometrical ordering mechanism can explain this correlation. We demonstrated that self-avoidance of DNA, specific positioning of one or few DNA loci (such as origin or terminus) together with the action of DNA compaction proteins (that organize the chromosome into topological domains) are sufficient to get a linear arrangement of the chromosome along the cell axis. This configuration, however, only represents the population average. Individual cells can have DNA arrangements that deviate significantly from the mean configuration and that break left-right symmetry. Symmetry breaking is stronger for longer chromosomes.