A 2ND N-ACYLHOMOSERINE LACTONE SIGNAL PRODUCED BY PSEUDOMONAS-AERUGINOSA
A 2ND N-ACYLHOMOSERINE LACTONE SIGNAL PRODUCED BY PSEUDOMONAS-AERUGINOSA
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DOI：
10.1073/pnas.92.5.1490
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发表时间：
1995-02-28
影响因子：
11.1
通讯作者：
GREENBERG, EP
中科院分区：
文献类型：
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作者：
PEARSON, JP;PASSADOR, L;GREENBERG, EP
群体感应系统被许多革兰氏阴性细菌物种用于以细胞密度依赖的方式调节特定的基因集。群体感应涉及合成和检测称为自诱导剂的细胞外信号。结果表明，在重组大肠杆菌中，铜绿假单胞菌（Pseudomonas aeruginosa）自身诱导剂（PAI） N-（3-氧十二烷基）同丝氨酸内酯与lasR基因产物一起激活了P. aeruginosa lasB基因，在lac启动子控制下，PAI在含有lasR质粒的P. aeruginosa lasR突变体中激活了lasB- lacz的表达，使lasB- lacz融合达到半最大激活所需的PAI浓度约为1 μ M。在铜绿假单胞菌培养液中发现的PAI水平范围内，PAI对铜绿假单胞菌lasR突变体的影响也进行了测试，该突变体含有lasR的质粒，在其自身启动子的控制下，含有lasB- lacz融合，尽管培养液提取物激活了该构建体中的lasB启动子，但高达10 μ M的PAI浓度没有激活。这表明当lasR受自身启动子控制时，铜绿假单胞菌中存在第二种细胞外因子（因子2），该因子是激活lasB所必需的，而当lasR受强外源启动子控制时则不存在，因子2被证明是n -丁酰基高丝氨酸内酯。尽管含有PAI合成酶基因lasI的重组大肠杆菌细胞产生PAI，但这些细胞不产生因子2。P. aeruginosa突变体产生约0.1%的野生型PAI，产生约5%的野生型因子2，这表明因子2的合成是由基因产物的活性引起的，而不是由PAI合成酶引起的。因子2在毒力基因调控中的作用尚不清楚，但这种化合物可能影响lasR的表达，而lasR反过来在足够PAI的存在下激活许多毒力基因的转录。显然，在单个细菌物种中可以发生多个群体感应系统并相互作用。
Quorum sensing systems are used by a number of Gram-negative bacterial species to regulate specific sets of genes in a cell density-dependent manner. Quorum sensing involves synthesis and detection of extracellular signals termed autoinducers. As shown in recombinant Escherichia coli, the Pseudomonas aeruginosa autoinducer (PAI) N-(3-oxododecanoyl)homoserine lactone, together with the lasR gene product, activate the P. aeruginosa lasB gene, In this study, PAI was shown to activate lasB-lacZ expression in a P, aeruginosa lasR mutant containing a plasmid with lasR under the control of the lac promoter, The concentration of PAI necessary for half-maximal activation of the lasB-lacZ fusion was approximate to 1 mu M, which is within the range of PAI levels found in P. aeruginosa culture fluids, The effect of PAI on a P. aeruginosa lasR mutant containing a plasmid with lasR under the control of its own promoter and containing the lasB-lacZ fusion was also tested, Although extracts of culture fluid activated the lasB promoter in this construct, concentrations of PAI as high as 10 mu M did not, This indicates the presence of a second extracellular factor (factor 2) that is required for lasB activation in P. aeruginosa when lasR is controlled by its own promoter but not when lasR is controlled by a strong foreign promoter, Factor 2 was shown to be N-butyrylhomoserine lactone, Although recombinant E. coli cells containing the PAI synthase gene, lasI, produce PAI, these cells do not produce factor 2, Furthermore, a P. aeruginosa mutant that produced about 0.1% of the wild-type level of PAI made about 5% of the wild-type level of factor 2, This indicates that factor 2 synthesis results from the activity of a gene product other than PAI synthase. The role of factor 2 in virulence gene regulation remains to be determined, but this compound may affect the expression of lasR, which in turn activates transcription of numerous virulence genes in the presence of sufficient PAI, Apparently, multiple quorum sensing systems can occur and interact with each other in a single bacterial species.