Gene expression measurements for flagella biosynthesis. Gene expression measurements for the fli operon from Salmonella typhimurium. The genome is represented as two barplots, one for each strand. Each gene has three bars representing expression at 4 h, 8 h and 12 h post macrophage infection. Gene expression measurements (y-axis) are ratios of test RNA to control RNA on the log 2 scale. Distance between genes is relative and representative of intergenic distance. The fli operon is involved in flagella biosynthesis and this image clearly shows that the entire operon is strongly down-regulated during macrophage infection. Significantly differentially expressed genes are coloured red or green, whereas non-significant genes are coloured white. All but three of the 14 genes in the operon are significantly differentially expressed.