[Objective] The rhizobacterium Pseudomonas sp. Ml8 can produce two antibiotics,phenazine-1-carboxylic acid (PCA) and pyoluteorin (Plt). PsrA belongs to the TetR family bacterial transcription regulator. To investigate the effect of PsrA on the PCA and Plt biosynthesis, the psrA gene was amplified from Ml8 strain genome. [Methods] The psrA mutant (M18psrA) was constructed through gene replacement of psrA by gentamicin resistance cassette and homologous recombination. Gene complement experiment and lacZ gene fusion report analysis further identified whether PsrA regulates the expression of antibiotics biosynthesis gene clusters. [Results] PCA and Plt production was respectively assayed in PPM and KMB media. PCA production of psrA mutant was significantly lower than that of its parent strain Ml8. However, Pit production of M18psrA was obviously increased 10-15 times as much as that of Ml8 strain. Gene complement experiment and lacZ gene fusion report analysis further confirmed that PsrA strongly up-regulated PCA biosynthesis and down-regulated Plt biosynthesis. [Conclusion] PsrA regulates distinctively on the PCA and Plt biosynthesis.%[目的]假单胞菌M18是一株能同时合成吩嗪-1-羧酸(PCA)和藤黄绿菌素(Plt)两种抗生素的植物根际促生细菌.PsrA为细菌TetR家族转录调控因子.为了研究PsrA对PCA与Plt生物合成的影响,从M18菌株基因组中扩增psrA基因.[方法]通过同源重组技术,构建庆大霉素抗性片段置换psrA的突变菌株M18psrA.利用基因互补、lacZ报告基因融合分析实验,验证PsrA对抗生素合成基因的调控作用.[结果]在PPM和KMB培养基中,分别比较野生型菌株M18和突变菌株M18psrA的PCA与Plt产量,突变菌株M 18psrA的PCA产量显著下降；Plt产量显著升高,为野生型菌株的10-15倍.基因互补、lacZ报告基因融合分析,进一步证明了psrA正调控PCA的phz2合成基因簇,负调控Plt的合成基因簇.[结论]PsrA区别性调控抗生素PCA与Plt的生物合成.
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