Regulation of the N-acyl homoserine lactone-dependent quorum-sensing system in rhizosphere Pseudomonas putida WCS358 and cross-talk with the stationary-phase RpoS sigma factor and the global regulator GacA
Regulation of the N-acyl homoserine lactone-dependent quorum-sensing system in rhizosphere Pseudomonas putida WCS358 and cross-talk with the stationary-phase RpoS sigma factor and the global regulator GacA
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DOI：
10.1128/aem.70.9.5493-5502.2004
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发表时间：
2004-09-01
影响因子：
4.4
通讯作者：
Venturi, V
中科院分区：
文献类型：
--
作者：
Bertani, I;Venturi, V
群体感应是革兰氏阴性菌中的一种细胞密度依赖性调节系统，其通常涉及N-酰基高丝氨酸内酯（AHLs）的产生和检测。一些恶臭假单胞菌菌株已被报道产生AHLs，并已确定一个群体感应位点。然而，似乎大多数菌株不产生AHLs。在这项研究中，我们报告的AHL依赖系统的根际恶臭假单胞菌WCS 358的鉴定和调节。该系统与最近鉴定的恶臭假单胞菌菌株IsoF的系统相同，并且与铜绿假单胞菌的las系统非常相似。它由三个基因组成，luxI家族成员ppuI、推定的阻遏物rsaL和luxR家族成员ppuR。菌株WCS 358的基因组ppuR：：Tn 5突变体通过其在靠近阿勒生物传感器处交叉划线时不能产生AHL来鉴定，而rsaL：：Tn 5基因组突变体通过其过量产生阿勒分子的能力来鉴定。使用转录启动子融合，我们研究了在各种遗传背景的rsaL，ppuI和ppuR启动子的表达谱。在稳定期开始时，自诱导物合酶ppuI基因表达受PpuR-AHL的正调控，受RsaL的负调控，表明分子可能竞争结合在ppuI启动子。在基因组rsaL：：Tn 5突变体中，ppuI的表达和阿勒水平的产生显著增加;然而，这两个过程仍处于生长期调节下，表明RsaL不参与抑制低细胞密度下的阿勒产生。还研究了全局响应调节器GacA和稳定相sigma因子RpoS在稳定相开始时对阿勒系统的调节作用。将恶臭假单胞菌WCS 358 gacA基因克隆并在基因组中失活。已确定这三个全局调节系统紧密相连，群体感应和RpoS相互调节，GacA正调节ppuI表达。阿勒群体感应系统的调控研究已经落后于其他研究，并且对于理解这些系统如何整合到细胞的整体生长阶段和代谢状态中是重要的。
Quorum sensing is a cell population-density dependent regulatory system which in gram-negative bacteria often involves the production and detection of N-acyl homoserine lactones (AHLs). Some Pseudomonas putida strains have been reported to produce AHLs, and one quorum-sensing locus has been identified. However, it appears that the majority of strains do not produce AHLs. In this study we report the identification and regulation of the AHL-dependent system of rhizosphere P. putida WCS358. This system is identical to the recently identified system of P. putida strain IsoF and very similar to the las system of Pseudomonas aeruginosa. It is composed of three genes, the luxI family member ppuI, the putative repressor rsaL, and the luxR family member ppuR. A genomic ppuR::Tn5 mutant of strain WCS358 was identified by its inability to produce AHLs when it was cross-streaked in close proximity to an AHL biosensor, whereas an rsaL::Tn5 genomic mutant was identified by its ability to overproduce AHL molecules. Using transcriptional promoter fusions, we studied expression profiles of the rsaL, ppuI, and ppuR promoters in various genetic backgrounds. At the onset of the stationary phase, the autoinducer synthase ppuI gene expression is under positive regulation by PpuR-AHL and under negative regulation by RsaL, indicating that the molecules could be in competition for binding at the ppuI promoter. In genomic rsaL::Tn5 mutants ppuI expression and production of AHL levels increased dramatically; however, both processes were still under growth phase regulation, indicating that RsaL is not involved in repressing AHL production at low cell densities. The roles of the global response regulator GacA and the stationary-phase sigma factor RpoS in the regulation of the AHL system at the onset of the stationary phase were also investigated. The P. putida WCS358 gacA gene was cloned and inactivated in the genome. It was determined that the three global regulatory systems are closely linked, with quorum sensing and RpoS regulating each other and GacA positively regulating ppuI expression. Studies of the regulation of AHL quorum-sensing systems have lagged behind other studies and are important for understanding how these systems are integrated into the overall growth phase and metabolic status of the cells.