Figure 5. The control of phoP by regulatory sRNAs is accompanied by a strong decrease in the steady-state level of phoPQ mRNA, but not always of PhoP protein.

(A) The level of phoPQ mRNA was monitored by Northern-Blot upon overproduction of MicA, GcvB and their derivatives. Strains used in this experiment are MG1516 and MG1517, where the wt phoPQ operon (MG1516) or the phoPQ operon interrupted by the insertion of a kanamycin resistance cassette within phoP (MG1517) were put respectively under control of the P_BAD promoter. (B) Western-Blot analysis of PhoP protein upon overproduction of MicA, GcvB and their derivatives. Strains are MG1173 (phoP⁺) or MG1446 (phoP⁻). The level of EF-Tu was monitored and used as a loading control.