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

<p>(A) The level of <i>phoPQ</i> 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 <i>phoPQ</i> operon (MG1516) or the <i>phoPQ</i> operon interrupted by the insertion of a kanamycin resistance cassette within <i>phoP</i> (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 (<i>phoP⁺</i>) or MG1446 (<i>phoP⁻</i>). The level of EF-Tu was monitored and used as a loading control.