Department of Biological Sciences, Binghamton University, Binghamton, New York, USA.
Department of Biological Sciences, Binghamton University, Binghamton, New York, USA
J Bacteriol. 2014 Aug;196(15):2827-41. doi: 10.1128/JB.01628-14. Epub 2014 Jun 2.
Cyclic di-GMP is a conserved signaling molecule regulating the transitions between motile and sessile modes of growth in a variety of bacterial species. Recent evidence suggests that Pseudomonas species harbor separate intracellular pools of c-di-GMP to control different phenotypic outputs associated with motility, attachment, and biofilm formation, with multiple diguanylate cyclases (DGCs) playing distinct roles in these processes, yet little is known about the potential conservation of functional DGCs across Pseudomonas species. In the present study, we demonstrate that the P. aeruginosa homolog of the P. fluorescens DGC GcbA involved in promoting biofilm formation via regulation of swimming motility likewise synthesizes c-di-GMP to regulate surface attachment via modulation of motility, however, without affecting subsequent biofilm formation. P. aeruginosa GcbA was found to regulate flagellum-driven motility by suppressing flagellar reversal rates in a manner independent of viscosity, surface hardness, and polysaccharide production. P. fluorescens GcbA was found to be functional in P. aeruginosa and was capable of restoring phenotypes associated with inactivation of gcbA in P. aeruginosa to wild-type levels. Motility and attachment of a gcbA mutant strain could be restored to wild-type levels via overexpression of the small regulatory RNA RsmZ. Furthermore, epistasis analysis revealed that while both contribute to the regulation of initial surface attachment and flagellum-driven motility, GcbA and the phosphodiesterase DipA act within different signaling networks to regulate these processes. Our findings expand the complexity of c-di-GMP signaling in the regulation of the motile-sessile switch by providing yet another potential link to the Gac/Rsm network and suggesting that distinct c-di-GMP-modulating signaling pathways can regulate a single phenotypic output.
环二鸟苷酸（cyclic di-GMP）是一种保守的信号分子，调节多种细菌从运动状态到静止状态的转变。最近的证据表明，假单胞菌拥有独立的细胞内环二鸟苷酸（c-di-GMP）库，以控制与运动、附着和生物膜形成相关的不同表型输出，多个双鸟苷酸环化酶（DGC）在这些过程中发挥不同的作用，但关于假单胞菌物种中功能 DGC 的潜在保守性知之甚少。在本研究中，我们证明了与促进生物膜形成有关的荧光假单胞菌 DGC GcbA 的铜绿假单胞菌同源物同样通过调节游泳运动来合成 c-di-GMP 以调节表面附着，但不影响随后的生物膜形成。发现铜绿假单胞菌 GcbA 通过抑制鞭毛反转率来调节鞭毛驱动的运动，这种方式不依赖于粘度、表面硬度和多糖产生。发现荧光假单胞菌 GcbA 在铜绿假单胞菌中具有功能，并且能够将与 gcbA 失活相关的表型恢复到野生型水平。通过过度表达小调控 RNA RsmZ，可以将 gcbA 突变株的运动和附着恢复到野生型水平。此外，上位性分析表明，虽然 GcbA 和磷酸二酯酶 DipA 都有助于初始表面附着和鞭毛驱动的运动调节，但它们作用于不同的信号网络来调节这些过程。我们的研究结果通过提供另一个与 Gac/Rsm 网络的潜在联系，并表明不同的 c-di-GMP 调节信号通路可以调节单个表型输出，从而扩展了 c-di-GMP 信号在调节运动-静止开关中的复杂性。
