RcsB plays a central role in H-NS-dependent regulation of motility and acid stress resistance in Escherichia coli

In Escherichia coli, hns mutants lack flagellar motility and display an increase in acid stress resistance. Spontaneous phenotypic revertants showed reversion of both H-NS-controlled phenotypes. In the present study, suppressor mutations were identified in the rcsB gene. In addition to RcsA, our experiments establish that H-NS indirectly controlled the RcsB regulator via repression of RcsD. We also show that RcsBD56E, mimicking phosphorylated RcsB, interacts with GadE to form a RcsB-P/GadE complex, a general direct regulator of glutamate-, arginine- and lysine-dependent acid resistance pathways. In addition, we showed that H-NS positively affects motility via the flhDC master operon repression by RcsB. This substantiates the central role of RcsB in H-NS-mediated control of motility and acid stress resistance.