The core of the chemotaxis system of Shewanella oneidensis is made of the CheA3 kinase and the CheY3 regulator. When appropriated, CheA3 phosphorylates CheY3, which, in turn, binds to the rotor of the flagellum to modify the swimming direction. In this study, we showed that phosphorylated CheY3 (CheY3-P) also plays an essential role during biogenesis of the solid-surface-associated biofilm (SSA-biofilm). Indeed, in a ΔcheY3 strain, the formation of this biofilm is abolished. Using the phospho-mimetic CheY3D56E mutant, we showed that CheY-P is required throughout the biogenesis of the biofilm but CheY3 phosphorylation is independent of CheA3 during this process. We have recently found that CheY3 interacts with two diguanylate cyclases (DGCs) and with MxdA, the c-di-GMP effector, probably triggering exopolysaccharide synthesis by the Mxd machinery. Here, we discovered two additional DGCs involved in SSA-biofilm development and showed that one of them interacts with CheY3. We therefore propose that CheY3-P acts together with DGCs to control SSA-biofilm formation. Interestingly, two orthologous CheY regulators complement the biofilm defect of a ΔcheY3 strain, supporting the idea that biofilm formation could involve CheY regulators in other bacteria.

奥尼希瓦氏菌趋化系统的核心由CheA3激酶和CheY3调节剂组成。适当时，CheA3使CheY3磷酸化，然后将CheY3结合到鞭毛的转子上以改变泳向。在这项研究中，我们表明磷酸化的CheY3（CheY3-P）在与固体表面相关的生物膜（SSA-biofilm）的生物合成过程中也起着至关重要的作用。实际上，在ΔcheY3菌株中，该生物膜的形成被消除。使用模拟磷酸酯的CheY3D56E突变体，我们表明在整个生物膜的生物发生过程中都需要CheY-P，但是在此过程中，CheY3的磷酸化与CheA3无关。我们最近发现，CheY3与两个双鸟苷酸环化酶（DGC）和c-di-GMP效应物MxdA相互作用，可能通过Mxd机制触发胞外多糖合成。这里，我们发现了另外两个与SSA生物膜发育有关的DGC，并显示其中一个与CheY3相互作用。因此，我们建议CheY3-P与DGC一起控制SSA生物膜的形成。有趣的是，两个直系同源的CheY调节剂弥补了ΔcheY3菌株的生物膜缺陷，从而支持了生物膜形成可能涉及其他细菌中的CheY调节剂的观点。