State Key Laboratory of Crop Stress Biology for Arid Areas, Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, People's Republic of China.
Appl Environ Microbiol. 2022 Apr 12;88(7):e0252921. doi: 10.1128/aem.02529-21. Epub 2022 Mar 24.
As a key bacterial second messenger, cyclic di-GMP (c-di-GMP) regulates various physiological processes, such as motility, biofilm formation, and virulence. Cellular c-di-GMP levels are regulated by the opposing activities of diguanylate cyclases (DGCs) and phosphodiesterases (PDEs). Beyond that, the enzymatic activities of c-di-GMP metabolizing proteins are controlled by a variety of extracellular signals and intracellular physiological conditions. Here, we report that (), (), and () are cotranscribed in the same operon and are involved in a regulatory cascade controlling the cellular level of c-di-GMP in Burkholderia thailandensis. The GGDEF domain-containing protein PdcA was found to be a DGC that modulates biofilm formation, motility, and virulence in B. thailandensis. Moreover, the DGC activity of PdcA was inhibited by phosphorylated PdcC, a single-domain response regulator composed of only the phosphoryl-accepting REC domain. The phosphatase PdcB affects the function of PdcA by dephosphorylating PdcC. The observation that homologous operons of are widespread among betaproteobacteria and gammaproteobacteria suggests a general mechanism by which the intracellular concentration of c-di-GMP is modulated to coordinate bacterial behavior and virulence. The transition from planktonic cells to biofilm cells is a successful strategy adopted by bacteria to survive in diverse environments, while the second messenger c-di-GMP plays an important role in this process. Cellular c-di-GMP levels are mainly controlled by modulating the activity of c-di-GMP-metabolizing proteins via the sensory domains adjacent to their enzymatic domains. However, in most cases how c-di-GMP-metabolizing enzymes are modulated by their sensory domains remains unclear. Here, we reveal a new c-di-GMP signaling cascade that regulates motility, biofilm formation, and virulence in B. thailandensis. While , , and constitute an operon, the phosphorylated PdcC binds the PAS sensory domain of PdcA to inhibit its DGC activity, with PdcB dephosphorylating PdcC to derepress the activity of PdcA. We also show this c-di-GMP regulatory model is widespread in the phylum . Our study expands the current knowledge of how bacteria regulate intracellular c-di-GMP levels.
作为一种关键的细菌第二信使，环二鸟苷酸（c-di-GMP）调节各种生理过程，如运动性、生物膜形成和毒力。细胞内 c-di-GMP 水平受环二鸟苷酸环化酶（DGC）和磷酸二酯酶（PDE）的拮抗活性调节。除此之外，c-di-GMP 代谢蛋白的酶活性受到各种细胞外信号和细胞内生理条件的控制。在这里，我们报告 （）、 （）和 （）在同一个操纵子中共同转录，并参与调控伯克霍尔德氏菌中细胞内 c-di-GMP 水平的调控级联。发现含有 GGDEF 结构域的蛋白 PdcA 是一种 DGC，可调节伯克霍尔德氏菌的生物膜形成、运动性和毒力。此外，磷酸化的 PdcC（仅由磷酸接受 REC 结构域组成的单域响应调节子）抑制 PdcA 的 DGC 活性。磷酸酶 PdcB 通过去磷酸化 PdcC 影响 PdcA 的功能。观察到 的同源操纵子在β变形菌和γ变形菌中广泛存在，这表明了一种普遍的机制，通过该机制调节细胞内 c-di-GMP 的浓度以协调细菌行为和毒力。从浮游细胞到生物膜细胞的转变是细菌在各种环境中生存的一种成功策略，而第二信使 c-di-GMP 在这个过程中起着重要作用。细胞内 c-di-GMP 水平主要通过调节与其酶结构域相邻的感觉域来控制 c-di-GMP 代谢蛋白的活性。然而，在大多数情况下，c-di-GMP 代谢酶如何被其感觉域调节仍不清楚。在这里，我们揭示了一个新的 c-di-GMP 信号级联，它调节泰国伯克霍尔德氏菌的运动性、生物膜形成和毒力。虽然 、 和 构成一个操纵子，但磷酸化的 PdcC 结合 PdcA 的 PAS 感觉域抑制其 DGC 活性，而 PdcB 去磷酸化 PdcC 以解除 PdcA 的活性。我们还表明，这种 c-di-GMP 调节模型在门 中广泛存在。我们的研究扩展了细菌如何调节细胞内 c-di-GMP 水平的现有知识。
