Bacteria push the limits of chemotactic precision to navigate dynamic chemical gradients
Bacteria push the limits of chemotactic precision to navigate dynamic chemical gradients
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DOI：
10.1073/pnas.1816621116
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发表时间：
2019-05-28
影响因子：
11.1
通讯作者：
Stocker, Roman
中科院分区：
文献类型：
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作者：
Brumley, Douglas R.;Carrara, Francesco;Stocker, Roman
细菌的短暂聚集体在环境中无处不在，在那里它们充当代谢活动、营养循环和水平基因转移的温床。在许多情况下，这些高细菌浓度的区域被认为是在运动细胞使用趋化性导航到化学热点时形成的。然而，是什么控制了细菌聚集的动力学尚不清楚。在这里，我们使用一个实验平台来创建具有受控营养浓度的真实亚毫米级营养脉冲。通过结合实验，数学理论，和基于代理的模拟，我们表明，个别奥氏弧菌细菌开始趋化性向热点的溶解有机物（DOM）的化学梯度的幅度上升到足够远的感官噪声，是随机遇到化学引诱分子。每个DOM热点被一个动态的化学趋化细胞环包围，这些细胞聚集在高DOM浓度的区域，然后随着DOM扩散和梯度变得太嘈杂而无法响应。我们证明，V. ordalii操作接近理论上的趋化精度的限制。趋化细菌的数值模拟，其中分子计数噪声被明确考虑在内，在营养物质的收购和趋化精度的成本之间的权衡点。更一般地说，我们的研究结果说明了如何限制感官精度可以用来了解生态相关环境中的细菌行为反应的位置，空间范围和寿命。
Ephemeral aggregations of bacteria are ubiquitous in the environment, where they serve as hotbeds of metabolic activity, nutrient cycling, and horizontal gene transfer. In many cases, these regions of high bacterial concentration are thought to form when motile cells use chemotaxis to navigate to chemical hotspots. However, what governs the dynamics of bacterial aggregations is unclear. Here, we use an experimental platform to create realistic submillimeter-scale nutrient pulses with controlled nutrient concentrations. By combining experiments, mathematical theory, and agent-based simulations, we show that individual Vibrio ordalii bacteria begin chemotaxis toward hotspots of dissolved organic matter (DOM) when the magnitude of the chemical gradient rises sufficiently far above the sensory noise that is generated by stochastic encounters with chemoattractant molecules. Each DOM hotspot is surrounded by a dynamic ring of chemotaxing cells, which congregate in regions of high DOM concentration before dispersing as DOM diffuses and gradients become too noisy for cells to respond to. We demonstrate that V. ordalii operates close to the theoretical limits on chemotactic precision. Numerical simulations of chemotactic bacteria, in which molecule counting noise is explicitly taken into account, point at a tradeoff between nutrient acquisition and the cost of chemotactic precision. More generally, our results illustrate how limits on sensory precision can be used to understand the location, spatial extent, and lifespan of bacterial behavioral responses in ecologically relevant environments.