Kargeti Manika, Kalita Irina, Hoch Sarah, Ratnikava Maryia, Xu Wenhao, Ni Bin, Dy Ron L, Colin Remy, Sourjik Victor
Max Planck Institute for Terrestrial Microbiology and Center for Synthetic Microbiology (SYNMIKRO), Marburg, Germany.
PLoS Genet. 2025 Jul 10;21(7):e1011784. doi: 10.1371/journal.pgen.1011784. eCollection 2025 Jul.
The chemotaxis signaling pathway, which enables bacteria to follow chemical gradients in their environment, is highly conserved among motile bacteria. It is assumed that Escherichia coli contains the minimal and non-redundant set of protein activities that are necessary for bacterial chemotaxis and nearly universally conserved among bacterial chemotaxis pathways. These include stimulus sensing, signal transduction towards the flagellar motor, and adaptation-based temporal comparisons of the environment. In this study, we show that functionality of the chemotaxis signaling pathway lacking some of its proteins can be partially regained by subjecting E. coli strains to experimental evolution under selection for chemotactic spreading in porous medium. While the core signaling components are indeed essential for the pathway function, the absence of auxiliary pathway proteins required for adaptation and desensitization could be compensated by specific sets of mutations affecting the other pathway components. Further characterization of the evolved strain lacking the adaptation enzyme CheR suggested that this strain utilizes an alternative mechanism of biased drift in chemical gradients, which does not rely on short-term adaptation that is normally considered a prerequisite for bacterial chemotaxis. Although the efficiency of this alternative mechanism remains below the one that can be achieved by the original memory-based chemotaxis strategy of E. coli, it can mediate chemotaxis not only in porous medium but also in liquid. Thus, even short-term experimental evolution of microorganisms can result in the appearance of behavioral strategies that are qualitatively different from those used by parental organisms.
趋化信号通路能使细菌追踪其周围环境中的化学梯度，在运动细菌中高度保守。据推测，大肠杆菌含有细菌趋化作用所必需的最小且无冗余的蛋白质活性集合，并且在细菌趋化通路中几乎普遍保守。这些包括刺激感知、向鞭毛马达的信号转导以及基于适应的环境时间比较。在本研究中，我们表明，通过在多孔介质中对趋化扩散进行选择的实验进化，使缺乏某些蛋白质的大肠杆菌菌株可以部分恢复趋化信号通路的功能。虽然核心信号成分确实对通路功能至关重要，但适应和脱敏所需的辅助通路蛋白的缺失可以通过影响其他通路成分的特定突变集来补偿。对缺乏适应酶CheR的进化菌株的进一步表征表明，该菌株利用了化学梯度中偏向漂移的替代机制，该机制不依赖于通常被认为是细菌趋化作用先决条件的短期适应。尽管这种替代机制的效率仍低于大肠杆菌基于记忆的原始趋化策略所能达到的效率，但它不仅可以在多孔介质中，也可以在液体中介导趋化作用。因此，即使是微生物的短期实验进化也可能导致出现与亲本生物体所使用的行为策略在质上不同的行为策略。
