Hefei National Research Center for Physical Sciences at the Microscale and Department of Physics, University of Science and Technology of China, Hefei, China.
Elife. 2024 Jun 4;12:RP91452. doi: 10.7554/eLife.91452.
Bacteria in biofilms secrete potassium ions to attract free swimming cells. However, the basis of chemotaxis to potassium remains poorly understood. Here, using a microfluidic device, we found that can rapidly accumulate in regions of high potassium concentration on the order of millimoles. Using a bead assay, we measured the dynamic response of individual flagellar motors to stepwise changes in potassium concentration, finding that the response resulted from the chemotaxis signaling pathway. To characterize the chemotactic response to potassium, we measured the dose-response curve and adaptation kinetics via an Förster resonance energy transfer (FRET) assay, finding that the chemotaxis pathway exhibited a sensitive response and fast adaptation to potassium. We further found that the two major chemoreceptors Tar and Tsr respond differently to potassium. Tar receptors exhibit a biphasic response, whereas Tsr receptors respond to potassium as an attractant. These different responses were consistent with the responses of the two receptors to intracellular pH changes. The sensitive response and fast adaptation allow bacteria to sense and localize small changes in potassium concentration. The differential responses of Tar and Tsr receptors to potassium suggest that cells at different growth stages respond differently to potassium and may have different requirements for potassium.
生物膜中的细菌分泌钾离子来吸引自由游动的细胞。然而，向钾的趋化作用的基础仍知之甚少。在这里，我们使用微流控装置发现，细胞可以在几毫摩尔的数量级上快速积累在高钾浓度的区域。通过珠粒测定法，我们测量了单个鞭毛马达对钾浓度逐步变化的动态响应，发现该响应源自趋化信号通路。为了表征对钾的趋化反应，我们通过荧光共振能量转移（FRET）测定法测量了剂量反应曲线和适应动力学，发现趋化途径对钾表现出敏感的反应和快速的适应。我们进一步发现，两种主要的化学感受器 Tar 和 Tsr 对钾的反应不同。Tar 受体表现出双相反应，而 Tsr 受体则将钾作为一种吸引剂。这些不同的反应与两个受体对细胞内 pH 变化的反应一致。敏感的反应和快速的适应使细菌能够感知和定位钾浓度的微小变化。Tar 和 Tsr 受体对钾的不同反应表明，不同生长阶段的细胞对钾的反应不同，并且可能对钾有不同的需求。
