Department of Physics and Biocenter, University of Cologne, Köln, Germany.
PLoS One. 2013 Jun 24;8(6):e67718. doi: 10.1371/journal.pone.0067718. Print 2013.
Bacterial type IV pili are essential for adhesion to surfaces, motility, microcolony formation, and horizontal gene transfer in many bacterial species. These polymers are strong molecular motors that can retract at two different speeds. In the human pathogen Neisseria gonorrhoeae speed switching of single pili from 2 µm/s to 1 µm/s can be triggered by oxygen depletion. Here, we address the question how proton motive force (PMF) influences motor speed. Using pHluorin expression in combination with dyes that are sensitive to transmembrane ΔpH gradient or transmembrane potential ΔΨ, we measured both components of the PMF at varying external pH. Depletion of PMF using uncouplers reversibly triggered switching into the low speed mode. Reduction of the PMF by ≈ 35 mV was enough to trigger speed switching. Reducing ATP levels by inhibition of the ATP synthase did not induce speed switching. Furthermore, we showed that the strictly aerobic Myxococcus xanthus failed to move upon depletion of PMF or oxygen, indicating that although the mechanical properties of the motor are conserved, its regulatory inputs have evolved differently. We conclude that depletion of PMF triggers speed switching of gonococcal pili. Although ATP is required for gonococcal pilus retraction, our data indicate that PMF is an independent additional energy source driving the high speed mode.
细菌 IV 型菌毛对于许多细菌物种的表面黏附、运动、微菌落形成和水平基因转移至关重要。这些聚合物是强大的分子马达，可以以两种不同的速度回缩。在人类病原体淋病奈瑟菌中，单个菌毛的速度可以从 2 µm/s 切换到 1 µm/s，这可以被缺氧触发。在这里，我们探讨质子动势 (PMF) 如何影响马达速度。我们使用 pHluorin 表达，并结合对跨膜 ΔpH 梯度或跨膜电位 ΔΨ 敏感的染料，在不同的外部 pH 值下测量 PMF 的两个组成部分。解偶联剂耗尽 PMF 可使速度切换发生可逆性触发。降低 PMF 约 35 mV 足以触发速度切换。抑制 ATP 合酶降低 ATP 水平不会诱导速度切换。此外，我们表明，严格需氧的粘球菌在 PMF 或氧气耗尽时无法移动，这表明尽管马达的机械性能是保守的，但它的调节输入已经进化得不同。我们得出结论，PMF 的耗尽会触发淋病奈瑟菌菌毛的速度切换。尽管 ATP 是淋病奈瑟菌菌毛回缩所必需的，但我们的数据表明 PMF 是驱动高速模式的另一个独立的能量来源。
