Mechanisms for co-ordinate control of motility and bioflim formation by the sensor-regulator MorA in pseudomonas spp

Abstract

C-di-GMP signalling affects developmental transitions of diverse bacteria. In <i>Pseudomonas </i>spp., we have previously reported that the sensor-regulator MorA controls motility by affecting the number and timing of flagellar development, and, biofilm formation. Unlike the enteric <i>Escherichia coli </i>model, less is known in <i>Pseudomonas</i> motility. Here, we describe <i>Pseudomonas </i>motility and show that unlike enteric bacteria, <i>Pseudomonas</i> flagellar motor rotates in the clockwise direction for significant periods, and that the flagellar rotations are interspersed with pauses. MorA affected flagellar motor function by reducing rotation speeds and increasing these pauses through its diguanylate cyclase (DGC) activity. DGC is the dominant activity of MorA, but a weak phosphodiesterase (PDE) activity is also present. Interestingly, two inter-domain interactions of the PDE domain on DGC activity were discovered - a constitutive requirement of the PDE domain for DGC activity, and, a c-di-GMP dose-dependent product inhibition involving leucine of the EAL motif. These inter-domain interactions corroborate with in vivo findings on motility and biofilm formation, where activities were pathway and developmental stage-specific.