Molecular and mechanistic basis for spatiotemporal organization of polar flagella

许多细菌通过鞭毛活动，这为它们在环境中繁殖提供了显著的优势。鞭毛是一种蛋白质纤维，由复杂复杂的纳米机器旋转，允许细菌按照化学梯度移动。长期以来，鞭毛的位置和数量(鞭毛模式)在物种之间是不同的。有两种基本的鞭毛模式存在：一种或多种纤维出现在一个或两个细胞极上，或者它们出现在远离细胞极的横向位置。在大量的细菌物种中，鞭毛的数量、鞭毛的定位模式和鞭毛的活性是由两个相互作用的蛋白质在时空上调节的，即SRP型GTP酶FlhF和类大脑的ATPase FlhG。这两种蛋白质的作用机制大多仍不清楚。在这项研究中，我们将结合两个参与小组的互补专业知识，进一步研究FlhF和FlhG如何利用我们成熟的模式物种腐烂希瓦氏菌建立非常常见的单极鞭毛模式。更具体地说，我们将进一步确定FlhG如何将鞭毛组装与相应构建块的转录控制联系起来，以及如何调节及时的鞭毛合成。此外，我们将研究FlhF如何将新生的鞭毛结构定向到指定的细胞极点，以及FlhF和FlhG之间的直接相互作用是如何在时空上受到控制的。我们预计，这些方法将能够在细菌中产生第一个FlhF/FlhG介导的机制的全面模型，并对这两种蛋白质如何发挥作用以建立其他不同的鞭毛模式提供见解。

Many bacteria are motile by flagella, which provides them with a significant advantage in environmental proliferation. Flagella are proteinaceous fibers rotated by intricate sophisticated nanomachines, which allow bacteria to move in accordance with chemical gradients. It has long been established that place and number of flagella (flagellation pattern) vary among the species. There are two basic flagellation patterns existing: either one or more filaments emerge at one both cell poles or they occur at lateral positions away from the cell pole. The number of flagella, flagellar localization pattern and flagellar activity in a huge number of bacterial species is regulated in a spatiotemporal fashion by two interacting proteins, the SRP-type GTPase FlhF and the MinD-like ATPase FlhG. The mechanism by which the two proteins act are still mostly elusive. In this study, we will combine the complementary expertises of the two participating groups to further investigate how FlhF and FlhG establish the very common monopolar flagellation pattern using our well-developed model species Shewanella putrefaciens. More specifically, we will further determine how FlhG links flagella assembly with transcriptional control of the corresponding building blocks, and how timely flagella synthesis is regulated. Furthermore, we will investigate how FlhF directs the nascent flagellar structure to the designated cell pole, and how direct interaction between FlhF and FlhG is spatiotemporally controlled. We expect that the approaches will enable to generate the first comprehensive model of an FlhF/FlhG-mediated mechanism in bacteria and to give insights into how the two proteins may function to establish other, different flagellar patterns.