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

Abstract:

Abstract: 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.