FIG. 1.

(A) Southern blot analysis of the rpoS region. Chromosomal DNA harvested from the indicated strains was digested with HindIII and hybridized with a probe specific for nlpD, which lies immediately upstream of the rpoS coding sequence. Lane C6709-1 shows the presence of the wild-type rpoS HindIII fragment, while lane DSM-V491 shows a smaller band due to an in-frame deletion of the rpoS coding sequence. Three and two independent isolates of reverted DSM-V506 and DSM-V491, respectively, are shown. In each case, the ΔrpoS band is absent and the wild-type rpoS band is regained. (B) Hydrogen peroxide sensitivity, shown as percent survival after 30 min of exposure to hydrogen peroxide as described in Materials and Methods. In each of the three data sets, a C6709-1 wild-type control is shown, as the three experiments were performed on different days.