The mechanisms by which bacteria sense and respond to surface attachment have long been a mystery. Our understanding of the structure and dynamics of bacterial appendages, notably type IV pili (T4P), provided new insights into the potential ways that bacteria sense surfaces. T4P are ubiquitous, retractable hair-like adhesins that until recently, due to their nanoscale size, were difficult to image in the absence of fixation. This review focuses on recent microscopy innovations used to visualize T4P in live cells to reveal the dynamics of their retraction and extension. We discuss recently proposed mechanisms by which T4P facilitate bacterial surface sensing, including the role of surface-exposed PilY1, two-component signal transduction pathways, force-induced structural modifications of the major pilin, and altered dynamics of the T4P motor complex.

中文翻译：

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不仅仅是一种感觉：了解表面传感机制的显微镜方法

细菌感知和响应表面附着的机制长期以来一直是个谜。我们对细菌附属物的结构和动力学的理解，特别是 IV 型菌毛 (T4P)，为细菌感知表面的潜在方式提供了新的见解。T4P 是无处不在的、可伸缩的毛发状粘附素，直到最近，由于它们的纳米级尺寸，在没有固定的情况下难以成像。本综述侧重于最近用于可视化活细胞中 T4P 的显微镜创新，以揭示其收缩和伸展的动力学。我们讨论了最近提出的 T4P 促进细菌表面感知的机制，包括表面暴露的 PilY1 的作用，双组分信号转导途径，主要菌毛蛋白的力诱导结构修饰，