Indexed on: 27 Apr '16Published on: 27 Apr '16Published in: Journal of bacteriology
The second messenger cyclic diguanylate (c-di-GMP) is an important regulator of motility in many bacterial species. In Pseudomonas aeruginosa, elevated levels of c-di-GMP promote biofilm formation and repress flagellum-driven swarming motility. The rotation of P. aeruginosa's polar flagellum is controlled by two distinct stator complexes: MotAB, which cannot support swarming motility, and MotCD, which promotes swarming motility. Here we show that when c-di-GMP levels are elevated, swarming motility is repressed by the PilZ domain-containing protein FlgZ and by Pel polysaccharide production. We demonstrate that FlgZ interacts specifically with the motility-promoting stator protein MotC in a c-di-GMP-dependent manner, and that a functional GFP-FlgZ fusion protein shows significantly reduced polar localization in a strain lacking the MotCD stator. Our results establish FlgZ as a c-di-GMP receptor affecting swarming motility by P. aeruginosa and support a model wherein c-di-GMP-bound FlgZ impedes motility via its interaction with the MotCD stator.The regulation of surface-associated motility plays an important role in bacterial surface colonization and biofilm formation. C-di-GMP signaling is a widespread means of controlling bacterial motility, yet the mechanism whereby this signal controls surface-associated motility remains poorly understood in P. aeruginosa Here we identify a PilZ domain-containing, c-di-GMP effector protein that contributes to c-di-GMP-mediated repression of swarming motility by P. aeruginosa We provide evidence that this effector FlgZ impacts swarming motility via its interactions with flagellar stator protein MotC. Thus, we propose a new mechanism for c-di-GMP-mediated regulation of motility for a bacterium with two flagellar stator sets, increasing our understanding of surface-associated behaviors, a key prerequisite to identifying ways to control the formation of biofilm communities.