Differential expression of two phenazine-producing loci mediated by deficiency of the global regulator RsmA in Psedomonas aeruginosa PAO1

Abstract:

Abstract:In many Pseudomonas，RsmA mediates the production of a set of secondary metabolites or virulence factors．［Objective］Our aim is to evaluate the function and regulation of the rsmA gene on two phenazine-producing operons in Pseudomonas aeruginosa PAO1．［Methods］ We first cloned the upstream and downstream fragments of the rsmA gene from the chromosomal DNA． With the insertion of gentamycin resistance cassette ( aacC1)，the deletion mutant PA-RG was created and verified with PCR． To complement and overexpress the rsmA gene，pME10R and pME32R were also constructed． By constructing the translational fusion plasmids phz1'-'lacZ pMEZ1and phz2'-'lacZ pMEZ2，we introduced them into the wild type strain PAO1 and the mutant PA-RG，respectively． Activities of beta-galactosidase were determined with Miller method． ［Results］In glycerol-alanine medium，overexpression of the rsmA gene results in dramatical decrease of pyocyanin production in PA-RG and PAO1 strain． In addition，beta-galactosidase activity of phz1'-'lacZ in the mutant PA-RG was much higher than that in the wild type strain． However，beta-galactosidase activity of phz2'-'lacZ in the wild type strain was 2fold more than that in the mutant PA-RG． ［Conclusion］ The regulation mediated by RsmA on two phenazine loci is specific and differential．