RsaL-driven negative regulation promotes heterogeneity in Pseudomonas aeruginosa quorum sensing.
RsaL-driven negative regulation promotes heterogeneity in Pseudomonas aeruginosa quorum sensing.
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在其规范的解释中，群体感应（QS）允许细菌群体中的单个细胞同步基因表达，从而在达到群体细胞密度时集体执行特定任务。然而，越来越多的证据表明，在不同的细菌物种中，在生长过程中，QS激活状态在细胞间发生了相当大的变化，经常导致细胞亚群共存，其中QS是活跃的（定量细胞）或不活跃的（非定量细胞）。条件致病菌铜绿假单胞菌的las QS系统存在异质性。然而，这一现象背后的分子机制尚未明确。LasR QS系统由一个非相干前馈回路组成，其中LasR转录调控因子激活lasI合成酶基因和rsaL的表达，编码lasI转录抑制因子rsaL。在这里，对特殊工程生物传感器菌株和缺失突变体进行的单细胞水平基因表达分析显示，RsaL与lasI启动子区域的直接结合增加了lasqs系统的异质激活。用双荧光报告系统进行的实验表明，lasr依赖的lasI和rsaL的表达在单个细胞中并不相关，这表明在表达高水平这种负调节因子的细胞亚群中，rsaL可以随机地限制非定量细胞向定量状态的转变。有趣的是，不受类似RsaL蛋白控制的rhl QS系统相对于las系统表现出更高的均匀性。单细胞分析可以揭示，尽管经历相同的物理化学条件，单克隆群体中的单个细菌细胞可能表现出基因表达的差异。这种表型异质性已被描述为细菌生理学的几个方面，包括QS激活。本研究表明，非定量细胞向定量状态的转变是一个渐变过程，并不发生在特定的细胞密度下，非定量细胞亚群也会在高细胞密度下持续存在。本研究为这一现象提供了一种机制解释，表明整合到las系统中的负反馈调节回路在促进P. aeruginosa中QS激活状态的细胞间变异和限制非定量细胞向定量状态的转变中起着关键作用。
In its canonical interpretation, quorum sensing (QS) allows single cells in a bacterial population to synchronize gene expression and hence perform specific tasks collectively once the quorum cell density is reached. However, growing evidence in different bacterial species indicates that considerable cell-to-cell variation in the QS activation state occurs during growth, often resulting in coexisting subpopulations of cells in which QS is active (quorate cells) or inactive (non-quorate cells). Heterogeneity has been observed in the las QS system of the opportunistic pathogen Pseudomonas aeruginosa. However, the molecular mechanisms underlying this phenomenon have not yet been defined. The las QS system consists of an incoherent feedforward loop in which the LasR transcriptional regulator activates the expression of the lasI synthase gene and rsaL, coding for the lasI transcriptional repressor RsaL. Here, single-cell-level gene expression analyses performed in ad hoc engineered biosensor strains and deletion mutants revealed that direct binding of RsaL to the lasI promoter region increases heterogeneous activation of the las QS system. Experiments performed with a dual-fluorescence reporter system showed that the LasR-dependent expression of lasI and rsaL does not correlate in single cells, indicating that RsaL acts as a brake that stochastically limits the transition of non-quorate cells to the quorate state in a subpopulation of cells expressing high levels of this negative regulator. Interestingly, the rhl QS system that is not controlled by an analogous RsaL protein showed higher homogeneity with respect to the las system. Single-cell analyses can reveal that despite experiencing identical physico-chemical conditions, individual bacterial cells within a monoclonal population may exhibit variations in gene expression. Such phenotypic heterogeneity has been described for several aspects of bacterial physiology, including QS activation. This study demonstrates that the transition of non-quorate cells to the quorate state is a graded process that does not occur at a specific cell density and that subpopulations of non-quorate cells also persist at high cell density. Here, we provide a mechanistic explanation for this phenomenon, showing that a negative feedback regulatory loop integrated into the las system has a pivotal role in promoting cell-to-cell variation in the QS activation state and in limiting the transition of non-quorate cells to the quorate state in P. aeruginosa.
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影响因子：
14.9
作者：
Balasubramanian D;Schneper L;Kumari H;Mathee K
通讯作者：
Mathee K
影响因子：
4.4
作者：
Haseltine, Eric L.;Arnold, Frances H.
通讯作者：
Arnold, Frances H.
影响因子：
3.2
作者：
De Kievit, T;Seed, PC;Iglewski, BH
通讯作者：
Iglewski, BH
影响因子：
4.2
作者：
Anetzberger C;Schell U;Jung K
通讯作者：
Jung K
DOI：
10.1073/pnas.051624298
发表时间：
2001-02-27
影响因子：
11.1
作者：
Chugani, SA;Whiteley, M;Greenberg, EP
通讯作者：
Greenberg, EP