Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China.
Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ 85721.
Proc Natl Acad Sci U S A. 2024 Nov 19;121(47):e2408082121. doi: 10.1073/pnas.2408082121. Epub 2024 Nov 13.
Microorganisms have evolved sophisticated sensor-actuator circuits to perform taxis in response to various environmental stimuli. How any given circuit can select between different taxis responses in noisy vs. saturated stimuli conditions is unclear. Here, we investigate how can select between positive vs. negative phototaxis under low vs. high light intensities, respectively. We propose three general selection mechanisms for phototactic microswimmers, and biophysical modeling demonstrates their effectiveness. Perturbation and high-speed imaging experiments show that of these three mechanisms, the "photoresponse inversion mechanism" is implemented in : a fast, light-intensity-dependent switching between two flagellar beat states responsible for swimming and turning causes positive vs. negative phototaxis at low vs. high light intensity via run-and-tumble vs. helical klinotaxis strategies, respectively. This coordinated beat-switching mechanism then also accounts for a larger set of previously reported behaviors; furthermore, it suggests key design principles for other natural as well as synthetic microswimmers.
微生物已经进化出复杂的传感器-执行器电路，以响应各种环境刺激进行趋性运动。在嘈杂和饱和刺激条件下，任何给定的电路如何在不同的趋性运动反应之间进行选择还不清楚。在这里，我们研究了 在低光和高光强度下，如何分别在正趋光性和负趋光性之间进行选择。我们提出了三种用于趋光微游泳者的一般选择机制，生物物理建模证明了它们的有效性。扰动和高速成像实验表明，在这三种机制中，“光响应反转机制”在 中得到了实现：两种鞭毛拍打状态之间的快速、光强度依赖性切换负责游泳和转向，分别通过跑-转和螺旋趋旋策略在低光和高光强度下产生正趋光性和负趋光性。这种协调的拍打切换机制还解释了更大的一组之前报道的 行为；此外，它为其他天然和合成微游泳者提供了关键的设计原则。
