Salmonella enterica is the most frequently reported cause of foodborne illness. As in other microorganisms, chemotaxis affords key physiological benefits, including enhanced access to growth substrates, but also plays an important role in infection and disease. Chemoreceptor signaling core complexes, consisting of CheA, CheW and methyl-accepting chemotaxis proteins (MCPs), modulate the switching of bacterial flagella rotation that drives cell motility. These complexes, through the formation of heterohexameric rings composed of CheA and CheW, form large clusters at the cell poles. RecA plays a key role in polar cluster formation, impairing the assembly when the SOS response is activated. In this study, we determined that RecA protein interacts with both CheW and CheA. The binding of these proteins to RecA is needed for wild-type polar cluster formation. In silico models showed that one RecA molecule, attached to one signaling unit, fits within a CheA-CheW ring without interfering with the complex formation or array assembly. Activation of the SOS response is followed by an increase in RecA, which rises up the number of signaling complexes associated with this protein. This suggests the presence of allosteric inhibition in the CheA-CheW interaction and thus of heterohexameric ring formation, impairing the array assembly. STED imaging demonstrated that all core unit components (CheA, CheW, and MPCs) have the same subcellular location as RecA. Activation of the SOS response promotes the RecA distribution along the cell instead of being at the cell poles. CheA- and CheW- RecA interactions are also crucial for chemotaxis, which is maintained when the SOS response is induced and the signaling units are dispersed. Our results provide new molecular-level insights into the function of RecA in chemoreceptor clustering and chemotaxis determining that the impaired chemoreceptor clustering not only inhibits swarming but also modulates chemotaxis in SOS-induced cells, thereby modifying bacterial motility in the presence of DNA-damaging compounds, such as antibiotics.

中文翻译：

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趋化性要求RecA与CheA和CheW都相互作用。

肠沙门氏菌是最常报告的食源性疾病原因。与其他微生物一样，趋化性提供关键的生理益处，包括增加对生长底物的利用，但在感染和疾病中也起着重要作用。由CheA，CheW和接受甲基的趋化蛋白（MCP）组成的化学感受器信号转导核心复合物可调节细菌鞭毛旋转的开关，从而驱动细胞运动。这些复合物通过形成由CheA和CheW组成的异六聚体环，在细胞极形成大簇。RecA在极性簇形成中起关键作用，当激活SOS响应时会损害装配。在这项研究中，我们确定RecA蛋白与CheW和CheA相互作用。这些蛋白与RecA的结合是野生型极性簇形成所必需的。在计算机模型中，一个附着在一个信号单元上的RecA分子适合CheA-CheW环内，而不会干扰复杂的结构或阵列装配。SOS响应的激活之后是RecA的增加，这增加了与此蛋白相关的信号复合物的数量。这表明在CheA-CheW相互作用中存在变构抑制作用，从而形成了异六聚体环，从而损害了阵列装配。STED成像表明，所有核心单元组件（CheA，CheW和MPC）都具有与RecA相同的亚细胞位置。SOS响应的激活促进了RecA沿着细胞分布，而不是处于细胞极。CheA-和CheW-RecA相互作用对于趋化性也至关重要，当诱导SOS反应且信号单元分散时，趋化性得以维持。我们的结果为RecA在化学感受器簇和趋化性中的功能提供了新的分子水平的见解，确定受损的化学感受器簇不仅抑制了SOS诱导的细胞群，而且还调节了趋化性，从而在存在DNA破坏性化合物的情况下改变了细菌的运动性，例如抗生素。