Comparison between microarray and primer extension results. a) Results from primer extension analyses of selected genes are presented. RNA samples were isolated at exponential or early stationary phase (exp. or stat., respectively). In b) quantitative evaluation (ratio of relative transcripts from ssrS-/ssrS+ from two to four independent experiments) of the primer extension results for selected genes and the corresponding results from the microarray analysis for the early stationary phase are shown. * hisL, the leader region of the his operon, has not been found differentially expressed by the microarrays but is 6S RNA sensitive according to primer extension.