Roles of Pseudomonas aeruginosa las and rhl quorum-sensing systems in control of elastase and rhamnolipid biosynthesis genes
Roles of Pseudomonas aeruginosa las and rhl quorum-sensing systems in control of elastase and rhamnolipid biosynthesis genes
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DOI：
10.1128/jb.179.18.5756-5767.1997
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发表时间：
1997-09-01
影响因子：
3.2
通讯作者：
Iglewski, BH
中科院分区：
文献类型：
--
作者：
Pearson, JP;Pesci, EC;Iglewski, BH
两个群体感应系统(LAS和RHL)调节铜绿假单胞菌毒力基因的表达。LAS系统由转录激活剂LasR和LASI组成，用于指导自身诱导剂N-(3-氧代十二烷酰)高丝氨酸内酯(PAI-1)的合成。LasB(编码弹性酶)和其他毒力基因的诱导需要LasR和PAI-1。该系统由一个可能的转录激活子RhlR和RhlI组成，它指导N-丁酰高丝氨酸内酯(PAI-2)的合成。据报道，在铜绿假单胞菌中生产鼠李糖脂需要同时需要rh l系统和rh lAB(编码鼠李糖基转移酶)，本文报道了一个Delta lasi突变体的产生，以及菌株PAO1的Delta lasi Delta rh lI和Delta lasR rh lR：：Tn501双突变体的产生。鼠李糖脂的产量和弹性裂解在Delta Lasi单突变株中减少，而在双突变株中取消。这些菌株在对数生长期中期未检测到rh lAB m RNA、Vas，但在亲本菌株中表达丰富。进一步对野生型菌株的RNA分析表明，rhlAB是以操纵子的形式组织的。我们绘制了rHlAB转录起始的图谱，并在上游确定了可能的sigma(54)和sigma(70)启动子，为了确定rh lAB表达所需的组分，我们在大肠杆菌中建立了一种生物测定方法，证明了PAI-2和RhlR是表达rh lA所必需的且充分的。为了研究PAI-2和Rh1R之间可能的相互作用，我们证明了[H-3]PAI-2与表达Rh1R的大肠杆菌细胞结合，而不是与表达LasR的大肠杆菌细胞结合，最后，我们在大肠杆菌生物检测中检测了LAS和rhL系统的特异性。INS系统能轻度激活rh lA，类似地，rh l系统部分激活lasB。然而，这些影响远远小于rHL系统和lasB系统对rH1A和lasB的激活。本文的结果进一步表征了rHL和LAS群体感应系统在毒力基因表达中的作用。
Two quorum-sensing systems (las and rhl) regulate virulence gene expression in Psendomonas aeraginosa. The las system consists of a transcriptional activator, LasR and LasI, which directs the synthesis of the autoinducer N-(3-oxododecanoyl) homoserine lactone (PAI-1). Induction of lasB (encoding elastase) and other virulence genes requires LasR and PAI-1. The rhl system consists of a putative transcriptional activator, RhlR, and RhlI, which directs the synthesis of N-butyryl homoserine lactone (PAI-2). Rhamnolipid production in P. aeruginosa has been reported to require both the rhl system and rhlAB (encoding a rhamnosyltransferase), Here we report the generation of a Delta lasI mutant and both Delta lasI Delta rhlI and Delta lasR rhlR::Tn501 double mutants of strain PAO1. Rhamnolipid production and elastolysis were reduced in the Delta lasI single mutant and abolished in the double-mutant strains. rhlAB mRNA,vas not detected in these strains at mid-logarithmic phase but was abundant in the parental strain. Further RNA analysis of the wild-type strain revealed that rhlAB is organized as an operon. The rhlAB transcriptional start was mapped, and putative sigma(54) and sigma(70) promoters were identified upstream, To define components required for rhlAB expression, we developed a bioassay in Escherichia coli and demonstrated that PAI-2 and RhlR are required and sufficient for expression of rhlA. To characterize the putative interaction between PAI-2 and RhlR, we demonstrated that [H-3]PAI-2 binds to E. coli cells expressing RhlR and not to those expressing LasR, Finally, the specificity of the las and rhl systems was examined in E. coli bioassays. The Ins system was capable of mildly activating rhlA, and similarly, the rhl system partly activated lasB. However, these effects were much less than the activation of rhlA by the rhl system and lasB by the [as system, The results presented here further characterize the roles of the rhl and las quorum-sensing systems in virulence gene expression.