Bacteria Floc, but Do They Flock? Insights from Population Interaction Models of Quorum Sensing
Bacteria Floc, but Do They Flock? Insights from Population Interaction Models of Quorum Sensing
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DOI：
10.1128/mbio.00972-19
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发表时间：
2019-05-01
期刊：
影响因子：
6.4
通讯作者：
Bentley, William E.
中科院分区：
文献类型：
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作者：
Ueda, Hana;Stephens, Kristina;Bentley, William E.
群体感知(QS)实现了协调一致的全群体行为。QS活性细菌使用它们合成、收集和解释的自动诱导剂来“传递”它们的数量密度。在切线上，趋化细菌迁移，寻找营养物质和其他分子。长期以来，人们一直假设细菌的行为，如趋化性，是高级生物复杂行为的原始祖先。最近，QS与趋化性联系在一起，然而这些行为可以共同促进更高阶行为的概念还没有被证明。在这里，我们通过构建种群规模的QS中介现象的现象学模型，在数学上将鱼类和鸟类中常见的集群行为与细菌趋化和QS联系起来。具体地说，我们重新预测了之前开发的集群数学模型，发现模拟的细菌行为与众所周知的QS行为很好地吻合。这一相对简单的常微分方程组提供了渐近行为的分析分析，并描述了细胞的位置和速度、QS介导的蛋白质表达以及自身诱导剂的周围浓度。此外，对该模型的启发式探索表明，只有当趋化性与QS直接相关时，才会出现“迁徙”亚群。也就是说，模拟趋化性与QS偶联和不偶联时的行为。当结合在一起时，细菌聚集模型预测了两组不同的细胞在朝向引诱剂的旅程中以不同的速度迁移。这在性质上类似于我们的大肠杆菌趋化性实验中以及50多年前观察到的类似工作中发现的现象。重要的是，我们的建模工作展示了细胞密度如何影响趋化性；它们有助于解释细菌种群中亚群形成的根源。我们的工作也强化了这样一个概念，即细菌机制有时在更高级的生物体中表现出来。
Quorum sensing (QS) enables coordinated, population-wide behavior. QS-active bacteria "communicate" their number density using autoinducers which they synthesize, collect, and interpret. Tangentially, chemotactic bacteria migrate, seeking out nutrients and other molecules. It has long been hypothesized that bacterial behaviors, such as chemotaxis, were the primordial progenitors of complex behaviors of higher-order organisms. Recently, QS was linked to chemotaxis, yet the notion that these behaviors can together contribute to higher-order behaviors has not been shown. Here, we mathematically link flocking behavior, commonly observed in fish and birds, to bacterial chemotaxis and QS by constructing a phenomenological model of population-scale QS-mediated phenomena. Specifically, we recast a previously developed mathematical model of flocking and found that simulated bacterial behaviors aligned well with well-known QS behaviors. This relatively simple system of ordinary differential equations affords analytical analysis of asymptotic behavior and describes cell position and velocity, QS-mediated protein expression, and the surrounding concentrations of an autoinducer. Further, heuristic explorations of the model revealed that the emergence of "migratory" subpopulations occurs only when chemotaxis is directly linked to QS. That is, behaviors were simulated when chemotaxis was coupled to QS and when not. When coupled, the bacterial flocking model predicts the formation of two distinct groups of cells migrating at different speeds in their journey toward an attractant. This is qualitatively similar to phenomena spotted in our Escherichia coli chemotaxis experiments as well as in analogous work observed over 50 years ago.IMPORTANCE Our modeling efforts show how cell density can affect chemotaxis; they help to explain the roots of subgroup formation in bacterial populations. Our work also reinforces the notion that bacterial mechanisms are at times exhibited in higher-order organisms.