Transcription of sig genes in sigma mutants. sigABCDE genes were quantified in the wild type and the four sigma mutants (sigB, sigC, sigD and sigE). The gene quantified is indicated below each set of measurements. Within each set, the phenotype is indicated below each bar of the graph. All measurements were carried out under identical culture conditions for the wt and mutants strains. Values were normalized to the rpoA transcript. The expression of each gene in the wt strain was set equal to 10 (in arbitrary units). The reported values represent the average of 6 measurements obtained from two separate RNA preparations.