Department of Molecular Microbiology and Biotechnology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel.
Proc Natl Acad Sci U S A. 2011 Aug 16;108(33):13635-40. doi: 10.1073/pnas.1102923108. Epub 2011 Aug 1.
In microbial "quorum sensing" (QS) communication systems, microbes produce and respond to a signaling molecule, enabling a cooperative response at high cell densities. Many species of bacteria show fast, intraspecific, evolutionary divergence of their QS pathway specificity--signaling molecules activate cognate receptors in the same strain but fail to activate, and sometimes inhibit, those of other strains. Despite many molecular studies, it has remained unclear how a signaling molecule and receptor can coevolve, what maintains diversity, and what drives the evolution of cross-inhibition. Here I use mathematical analysis to show that when QS controls the production of extracellular enzymes--"public goods"--diversification can readily evolve. Coevolution is positively selected by cycles of alternating "cheating" receptor mutations and "cheating immunity" signaling mutations. The maintenance of diversity and the evolution of cross-inhibition between strains are facilitated by facultative cheating between the competing strains. My results suggest a role for complex social strategies in the long-term evolution of QS systems. More generally, my model of QS divergence suggests a form of kin recognition where different kin types coexist in unstructured populations.
在微生物的“群体感应”（QS）通讯系统中，微生物会产生并响应一种信号分子，从而在高细胞密度下实现协同反应。许多细菌物种的 QS 途径特异性表现出快速、种内、进化上的差异——信号分子激活同种菌株中的同源受体，但不能激活、有时甚至抑制其他菌株的受体。尽管进行了许多分子研究，但信号分子和受体如何共同进化、多样性如何维持以及是什么驱动交叉抑制的进化仍然不清楚。在这里，我使用数学分析表明，当 QS 控制细胞外酶（“公共物品”）的产生时，多样化很容易进化。共进化受到受体突变的“欺骗”和信号突变的“欺骗免疫”的交替循环的正向选择。在竞争菌株之间的兼性欺骗下，菌株之间多样性的维持和交叉抑制的进化得到了促进。我的结果表明，复杂的社会策略在 QS 系统的长期进化中发挥了作用。更一般地说，我的 QS 分歧模型表明了一种亲缘识别形式，其中不同的亲缘类型在无结构的种群中共存。
