A different arrangement of a cluster of genes involved in division and cell-wall synthesis
separates bacilli from other bacteria in a phylogenetic analysis. We conclude that the
relationships between these genes are not random and might reflect significant events in the
evolution of the coupling between growth and division in bacteria.

The tree structure (Fig. 3) reveals a correlation of cell shape with the order of the genes and
not simply with their presence or absence. Most strikingly, this classification differs from the
standard relationships between bacterial species obtained when using traits such as the
comparison of small-subunit rRNAs6 or gene family composition of genomes7, 8. It also
varies significantly from the tree obtained when considering simply the pr esence or
absence of t he individual dcw genes; it is closer to the proposed phylogenies based on …