O'Neal Lindsey, Ryu Min-Hyung, Gomelsky Mark, Alexandre Gladys
Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee, USA.
Department of Molecular Biology, University of Wyoming, Laramie, Wyoming, USA.
J Bacteriol. 2017 Aug 22;199(18). doi: 10.1128/JB.00020-17. Print 2017 Sep 15.
Bacterial chemotaxis receptors provide the sensory inputs that inform the direction of navigation in changing environments. Recently, we described the bacterial second messenger cyclic di-GMP (c-di-GMP) as a novel regulator of a subclass of chemotaxis receptors. In , c-di-GMP binds to a chemotaxis receptor, Tlp1, and modulates its signaling function during aerotaxis. Here, we further characterize the role of c-di-GMP in aerotaxis using a novel dichromatic optogenetic system engineered for manipulating intracellular c-di-GMP levels in real time. This system comprises a red/near-infrared-light-regulated diguanylate cyclase and a blue-light-regulated c-di-GMP phosphodiesterase. It allows the generation of transient changes in intracellular c-di-GMP concentrations within seconds of irradiation with appropriate light, which is compatible with the time scale of chemotaxis signaling. We provide experimental evidence that binding of c-di-GMP to the Tlp1 receptor activates its signaling function during aerotaxis, which supports the role of transient changes in c-di-GMP levels as a means of adjusting the response of to oxygen gradients. We also show that intracellular c-di-GMP levels in change with carbon metabolism. Our data support a model whereby c-di-GMP functions to imprint chemotaxis receptors with a record of recent metabolic experience, to adjust their contribution to the signaling output, thus allowing the cells to continually fine-tune chemotaxis sensory perception to their metabolic state. Motile bacteria use chemotaxis to change swimming direction in response to changes in environmental conditions. Chemotaxis receptors sense environmental signals and relay sensory information to the chemotaxis machinery, which ultimately controls the swimming pattern of cells. In bacteria studied to date, differential methylation has been known as a mechanism to control the activity of chemotaxis receptors and modulates their contribution to the overall chemotaxis response. Here, we used an optogenetic system to perturb intracellular concentrations of the bacterial second messenger c-di-GMP to show that in some chemotaxis receptors, c-di-GMP functions in a similar feedback loop to connect the metabolic status of the cells to the sensory activity of chemotaxis receptors.
细菌趋化性受体提供感官输入，以告知在不断变化的环境中导航的方向。最近，我们将细菌第二信使环二鸟苷酸（c-di-GMP）描述为趋化性受体一个亚类的新型调节剂。在[具体内容未提及]中，c-di-GMP与趋化性受体Tlp1结合，并在趋氧性过程中调节其信号传导功能。在此，我们使用一种新型双色光遗传学系统进一步表征c-di-GMP在趋氧性中的作用，该系统经设计可实时操纵细胞内c-di-GMP水平。该系统包括一个红/近红外光调节的二鸟苷酸环化酶和一个蓝光调节的c-di-GMP磷酸二酯酶。它允许在用适当的光照射后几秒钟内细胞内c-di-GMP浓度产生瞬时变化，这与趋化性信号传导的时间尺度相匹配。我们提供了实验证据，表明c-di-GMP与Tlp1受体的结合在趋氧性过程中激活其信号传导功能，这支持了c-di-GMP水平的瞬时变化作为调节[具体内容未提及]对氧梯度反应的一种方式的作用。我们还表明，[具体内容未提及]中的细胞内c-di-GMP水平随碳代谢而变化。我们的数据支持一种模型，即c-di-GMP的功能是用最近的代谢经历记录给趋化性受体留下印记，以调整它们对信号输出的贡献，从而使细胞能够不断微调趋化性感官感知以适应其代谢状态。运动细菌利用趋化性来响应环境条件的变化改变游动方向。趋化性受体感知环境信号并将感官信息传递给趋化性机制，该机制最终控制细胞的游动模式。在迄今为止研究的细菌中，差异甲基化一直被认为是一种控制趋化性受体活性并调节它们对整体趋化性反应贡献的机制。在此，我们使用光遗传学系统干扰细菌第二信使c-di-GMP的细胞内浓度，以表明在一些趋化性受体中，c-di-GMP在类似的反馈回路中起作用，将细胞的代谢状态与趋化性受体的感官活性联系起来。
