细菌群体感应参与铜绿假单胞菌胞内聚羟基脂肪酸酯合成的调控

Involvement of quorum-sensing in biosynthesis of polyhydroxyalkanoates in Pseudomonas aeruginosa

群体感应是细菌根据细胞密度变化调控基因表达的一种调节机制。铜绿假单胞菌中QS系统由lasI和rhlI合成的信号分子3OC12-HSL和C4-HSL以及各自的受体蛋白LasR、RhlR组成,它们以级联方式调控多个基因表达。【目的】研究细菌群体感应(QS)对聚羟基脂肪酸酯合成的调控。【方法】利用铜绿假单胞菌PAO1及其QS突变株为材料通过气相色谱、荧光定量PCR在生理和分子水平上研究QS对聚羟基脂肪酸酯合成的调控。【结果】QS信号分子合成抑制剂阿奇霉素处理铜绿假单胞菌PAO1和QS突变株导致胞内PHA积累量显著减少;铜绿假单胞菌PAO1中C4-HSL合成酶基因rhlI缺失突变株PAO210胞内PHA积累量与野生型无差别;而3OC12-HSL合成酶基因lasI缺失突变株PAO55、3OC12-HSL受体合成酶基因lasR缺失突变株PAO56以及lasI/lasR双缺失突变株PAO57胞内PHA含量与野生型相比明显减少;lasI和lasR的突变株体内PHA合成酶基因phaC1的表达量显著降低,信号分子3OC12-HSL回补实验使phaC1的表达量可恢复到野生株水平,但只可部分恢复lasI缺失导致的胞内PHA合成。【结论】由此推测,铜绿假单胞菌群体感应系统中lasI/lasR系统参与胞内聚羟基脂肪酸酯合成的调控。

Quorum-sensing（QS） is a regulatory mechanism with which bacteria regulate the gene expression according to their population density.Pseudomonas aeruginosa regulates the expression of multiple genes via a hierarchical quorum-sensing cascade through LasR and RhlR and their cognate signal molecules N-（3-oxododecanoyl）-L-homoserine lactone（3O-C12-HSL） and N-（butanoyl）-L-homoserine lactone（C4-HSL）.[Objective] It aims to explore the regulation of QS on biosynthesis of polyhydroxyalkanoates（PHA） in P.aeruginosa.[Methods] Wild-type P.aeruginosa PAO1 and its QS mutants were used to investigate the effects of quorum-sensing on biosynthesis of PHA by GC and real-time PCR at physiological and molecular level.[Results] After treated with QS signal molecule synthesis inhibitor azithromycin,the accumulation of PHA significantly decreased in P.aeruginosa PAO1 and its QS mutant strains.The content of PHA in C4-HSL synthase gene rhlI mutant strain PAO210 had no significant difference compared with that of the wild type.However,the PHA contents were significantly affected in 3OC12-HSL synthase gene lasI mutant strain PAO55,3OC12-HSL transcriptional regulator gene lasR mutant strain PAO56 and lasI/lasR double mutant strain PAO57.PHA synthase gene phaC1 expression exhibited a significant reduction in lasI mutant and lasR mutant strains.3OC12-HSL signal molecules complementary experiment shows that the expression of phaC1 can be recovered to the level of the wild type,but the synthesis of PHA is only partially restored in lasI mutant strain.[Conclusion] The results implicates that lasI/lasR system might be involved in the regulation of intracellular PHA biosynthesis in P.aeruginosa PAO1.