假单胞菌株M18中pqsA突变株的构建及其对plt的调控

Construction of Pseudomonas sp. M18 pqsA mutant and its regulation on the plt operon

【目的】根际铜绿假单胞菌M18能产生藤黄绿菌素(Plt)和吩嗪-1-羧酸(PCA)两种主要的抗生素。其PqsR/PQS群体感应系统由应答调控蛋白PqsR与信号分子PQS组成。前期研究已经表明pqsR负调控Plt生物合成及基因簇表达。本论文旨在研究PQS分子对Plt合成及基因表达的调控作用。【方法】从M18基因组中扩增PQS合成基因pqsA,通过同源重组技术构建假单胞菌M18的pqsA突变菌株M18pqsA。利用lacZ报告基因分析、信号分子添加实验等,研究PQS对Plt合成及基因表达的调控作用。【结果】在KMB培养基中,分别比较野生型菌株M18和突变菌株M18pqsA的Plt产量,突变菌株的Plt产量存在较小幅度的升高,约为野生型菌株的1.53倍。添加PQS对plt表达存在一定程度但不是很显著的负调控作用。【结论】PQS分子对Plt生物合成及基因表达存在部分负调控作用。

[Objective] The rhizobacterium P. aeruginosa M18 can produce two antibiotics,pyoluteorin（Plt） and phenazine-1-carboxilic acid（PCA）. The PqsR/PQS quorum sensing system consists of the response regulatory protein PqsR and the signaling molecule PQS. Previous studies have shown that the pqsR gene negatively controls Plt biosynthesis and its gene expression. This study aims to investigate the effect of PQS on Plt biosynthesis and its gene expression. [Methods]The pqsA gene was amplified from the M18 genome. A chromosomal pqsA inactivated mutant strain of M18 was constructed by the homologous recombination technique. Plt production assay and lacZ reporter analysis were utilized to assess the influence of PQS on Plt biosynthesis and its gene expression. [Results] In KMB media, Plt production of pqsA mutant was partially increased 1.53 times as much as that of M18 strain. The addition of PQS caused a certain degree of down-regulation of plt expression. [Conclusion] PQS partially down-regulates Plt biosynthesis and its gene expression in M18.