Karin Omer, Alon Uri
Department Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel.
Wellcome Trust-Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge, UK.
iScience. 2021 Jun 28;24(7):102796. doi: 10.1016/j.isci.2021.102796. eCollection 2021 Jul 23.
Bacterial chemotaxis is a major testing ground for systems biology, including the role of fluctuations and individual variation. Individual bacteria vary in their tumbling frequency and adaptation time. Recently, large cell-cell variation was also discovered in chemotaxis gain, which determines the sensitivity of the tumbling rate to attractant gradients. Variation in gain is puzzling, because low gain impairs chemotactic velocity. Here, we provide a functional explanation for gain variation by establishing a formal analogy between chemotaxis and algorithms for sampling probability distributions. We show that temporal fluctuations in gain implement simulated tempering, which allows sampling of attractant distributions with many local peaks. Periods of high gain allow bacteria to detect and climb gradients quickly, and periods of low gain allow them to move to new peaks. Gain fluctuations thus allow bacteria to thrive in complex environments, and more generally they may play an important functional role for organism navigation.
细菌趋化性是系统生物学的一个主要试验场，包括波动和个体变异的作用。单个细菌在翻滚频率和适应时间上存在差异。最近，在趋化增益方面也发现了较大的细胞间差异，趋化增益决定了翻滚速率对吸引剂梯度的敏感性。增益的变化令人费解，因为低增益会损害趋化速度。在这里，我们通过在趋化性和用于采样概率分布的算法之间建立形式上的类比，为增益变化提供了一个功能上的解释。我们表明，增益的时间波动实现了模拟回火，这使得能够对具有许多局部峰值的吸引剂分布进行采样。高增益期使细菌能够快速检测并攀爬梯度，而低增益期使它们能够移动到新的峰值。因此，增益波动使细菌能够在复杂环境中茁壮成长，更普遍地说，它们可能在生物体导航中发挥重要的功能作用。
