Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain.
FEMS Microbiol Rev. 2014 Jul;38(4):569-97. doi: 10.1111/1574-6976.12078. Epub 2014 Jul 2.
Membrane-spanning signaling pathways enable bacteria to alter gene expression in response to extracytoplasmic stimuli. Many such pathways are cell-surface signaling (CSS) systems, which are tripartite molecular devices that allow Gram-negative bacteria to transduce an extracellular stimulus into a coordinated transcriptional response. Typically, CSS systems are composed of the following: (1) an outer membrane receptor, which senses the extracellular stimulus; (2) a cytoplasmic membrane-spanning protein involved in signal transduction from the periplasm to the cytoplasm; and (3) an extracytoplasmic function (ECF) sigma factor that initiates expression of the stimulus-responsive gene(s). Members of genus Pseudomonas provide a paradigmatic example of how CSS systems contribute to the global control of gene expression. Most CSS systems enable self-regulated uptake of iron via endogenous (pyoverdine) or exogenous (xenosiderophores, heme, and citrate) carriers. Some are also implicated in virulence, biofilm formation, and cell-cell interactions. Incorporating insights from the well-characterized alginate regulatory circuitry, this review will illustrate common themes and variations at the level of structural and functional properties of Pseudomonas CSS systems. Control of the expression and activity of ECF sigma factors are central to gene regulation via CSS, and the variety of intrinsic and extrinsic factors influencing these processes will be discussed.
膜跨信号通路使细菌能够响应细胞外刺激改变基因表达。许多这样的途径是细胞表面信号（CSS）系统，这是允许革兰氏阴性细菌将细胞外刺激转导为协调的转录反应的三分体分子装置。通常，CSS 系统由以下部分组成：（1）感知细胞外刺激的外膜受体；（2）参与信号从周质到细胞质转导的跨膜蛋白；（3）启动刺激反应基因表达的胞外功能（ECF）σ因子。假单胞菌属的成员为 CSS 系统如何有助于全局控制基因表达提供了一个典范示例。大多数 CSS 系统能够通过内源性（绿脓菌素）或外源性（异源铁载体、血红素和柠檬酸）载体自我调节铁的摄取。一些还与毒力、生物膜形成和细胞-细胞相互作用有关。本综述将结合已充分研究的海藻酸盐调控回路的见解，说明假单胞菌 CSS 系统在结构和功能特性方面的常见主题和变化。通过 CSS 进行基因调控的核心是对 ECF σ因子的表达和活性的控制，将讨论影响这些过程的各种内在和外在因素。
