Fig. 2.

Orthologous genes known to be essential in E. coli are depleted for transposon insertions in Shigella. A region of the Shigella chromosome is shown, with genes whose orthologues are known to be essential for growth in E. coli (coloured in white) [1, 29], or non-essential (coloured in grey). The unique locations of transposon insertions are plotted as vertical black segments. In the genome region shown here, none of the genes essential in E. coli have orthologues that are interrupted in Shigella