A Novel Transcriptional Regulator Of The PhzA1 Operon In Pseudomonas Aeruginosa

Pseudomonas aeruginosa is an opportunistic pathogen. A number of secretable virulence factors contribute to its pathogenicity, including phenazines. P. aeruginosa releases at least four phenazine compounds. They are 1-hydroxy-phenazine (1-OH-PHZ),PCA,phenazine-1-carboxamide (PCN) and pyocyanin. Pyocyanin is an important phenazine compound, and it is suggested to be involved in lung infecion of cystic fibrosis patients. Quorum sensing network controls the production of phenazines.A novel regulator of phzA1 operon in Pseudomoas aeruginosa had been identified by screening a transponson mutagenesis library in the presence of subinhibitory concentrations of tetracycline (Tet). Three mutants that exhibited changed expression of the phzA1 operon were obtained. The transposon insertion sites were determined by arbitrary PCR and subsequent PCR product sequencing. Two sites found to be at the promoter region of gene PA0487, and one at the promoter region of gene PA0207. PA0487 was required for the expression of phzA1 operon, and in the knockout mutant some of the genes involved in quorum sensing were down-regulated. The activation of phzA1 by subinhibitory concentrations of Tet was abolished in PAM0487, probably due to that PA0487 is involved in subinhibitory antibiotic regulation pathway. In conclusion, our results indicate that PA0487 is involved in regulating the expression of phzA1, possibly through the quorum sensing system.