Social Evolution Selects for Redundancy in Bacterial Quorum Sensing.
Social Evolution Selects for Redundancy in Bacterial Quorum Sensing.
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DOI：
10.1371/journal.pbio.1002386
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发表时间：
2016-02
期刊：
影响因子：
9.8
通讯作者：
Eldar A
中科院分区：
文献类型：
--
作者：
Even-Tov E;Bendori SO;Valastyan J;Ke X;Pollak S;Bareia T;Ben-Zion I;Bassler BL;Eldar A
群体感应是细菌用来监测细胞密度和协调合作行为的一种化学通讯过程。群体感应依赖于细胞外信号分子和同源受体对。虽然单个群体感应系统足以探测细胞密度，但细菌经常使用多个群体感应系统来调节相同的合作行为。这些冗余网络结构的潜在好处尚不清楚。在此，我们将枯草芽孢杆菌和哈维弧菌群体感应网络的建模和实验分析结合起来，表明多个群体感应系统的积累可能是由兼性欺骗机制驱动的。我们证明，获得额外群体感应系统的菌株可以利用其拥有少一个系统的祖先，但是，当它在种群中固定时，它可以恢复与其亲属的充分合作。我们确定了这种优势所需的分子网络设计标准。我们的研究结果表明，细菌社会信号回路的复杂性增加可以在克隆群体中进化而不提供适应性优势。多个看似冗余的细菌群体感应系统的积累是由兼性欺骗行为促进的；具有多个系统的菌株在作为少数群体时欺骗其单一群体感应系统祖先，但在多数群体时返回合作。群体感应是细菌通过产生、释放和检测编码细胞种群密度信息的信号分子进行交流的一种机制。群体感应允许细菌同步它们的行为，并作为集体行动。通常，群体感应控制着有利于整个群落的合作行为，例如昂贵的代谢物的产生和分泌。一些细菌会释放多种信号分子，一旦被检测到，这些信号分子就会将信息传递到相同的细胞反应中。因此，使用多个而不是单个信号的好处是神秘的，因为信号看起来是冗余的。在此，我们将模型和实验相结合，表明多个群体感知系统的进化积累可归因于社会利用和亲属识别。当种群丰度较低时，一个额外获得群体感应系统的菌株可以避免合作，并利用其少一个群体感应系统的祖先菌株。包含额外系统的作弊者在系统充足时恢复到合作行为。我们还确定了获得额外信号系统所必需的分子机制。我们的工作表明，细菌社会信号回路的复杂性增加可以在克隆群体中不提供适应性优势的情况下进化。
Quorum sensing is a process of chemical communication that bacteria use to monitor cell density and coordinate cooperative behaviors. Quorum sensing relies on extracellular signal molecules and cognate receptor pairs. While a single quorum-sensing system is sufficient to probe cell density, bacteria frequently use multiple quorum-sensing systems to regulate the same cooperative behaviors. The potential benefits of these redundant network structures are not clear. Here, we combine modeling and experimental analyses of the Bacillus subtilis and Vibrio harveyi quorum-sensing networks to show that accumulation of multiple quorum-sensing systems may be driven by a facultative cheating mechanism. We demonstrate that a strain that has acquired an additional quorum-sensing system can exploit its ancestor that possesses one fewer system, but nonetheless, resume full cooperation with its kin when it is fixed in the population. We identify the molecular network design criteria required for this advantage. Our results suggest that increased complexity in bacterial social signaling circuits can evolve without providing an adaptive advantage in a clonal population. The accumulation of multiple, seemingly redundant, bacterial quorum-sensing systems is promoted by facultative cheating behavior; the strain with multiple systems cheats its single quorum-sensing system ancestor as a minority but returns to cooperation when in the majority. Quorum sensing is a mechanism through which bacteria communicate by producing, releasing, and detecting signal molecules encoding information about cell population density. Quorum sensing allows bacteria to synchronize their behaviors and act as collectives. Often, quorum sensing controls cooperative behaviors that benefit the entire community, such as the production and secretion of costly metabolites. Some bacteria release multiple signal molecules which, once detected, funnel information into the same cellular response. Thus, the benefit of using multiple rather than a single signal is mysterious since the signals seem redundant. Here, we combine modeling and experiments to show that the evolutionary accumulation of multiple quorum-sensing systems can be attributed to social exploitation and kin recognition. When in low abundance, a strain that has acquired an additional quorum-sensing system can avoid cooperating and can exploit its ancestor strain, which contains one less quorum-sensing system. The cheater containing the additional system returns to a cooperative behavior when it is abundant. We also identify the molecular mechanisms necessary for the acquisition of an additional signaling system. Our work demonstrates that increased complexity in bacterial social signaling circuits can evolve without providing an adaptive advantage in a clonal population.