Cross-Regulation between the phz1 and phz2 Operons Maintain a Balanced Level of Phenazine Biosynthesis in Pseudomonas aeruginosa PAO1

Abstract

Gene duplication often provides selective advantages for the survival of microorganisms in adapting to varying environmental conditions. P. aeruginosa PAO1 possesses two seven-gene operons [phz1 (phzA1B1C1D1E1F1G1) and phz2 (phzA2B2C2D2E2F2G2)] that are involved in the biosynthesis of phenazine-1-carboxylic acid and its derivatives. Although the two operons are highly homologous and their functions are well known, it is unclear how the two phz operons coordinate their expressions to maintain the phenazine biosynthesis. By constructing single and double deletion mutants of the two phz operons, we found that the phz1-deletion mutant produced the same or less amount of phenazine-1-carboxylic acid and pyocyanin in GA medium than the phz2-knockout mutant while the phz1-phz2 double knockout mutant did not produce any phenazines. By generating phzA1 and phzA2 translational and transcriptional fusions with a truncated lacZ reporter, we found that the expression of the phz1 operon increased significantly at the post-transcriptional level and did not alter at the transcriptional level in the absence of the phz2 operon. Surprisingly, the expression the phz2 operon increased significantly at the post-transcriptional level and only moderately at the transcriptional level in the absence of the phz1 operon. Our findings suggested that a complex cross-regulation existed between the phz1 and phz2 operons. By mediating the upregulation of one phz operon expression while the other was deleted, this crosstalk would maintain the homeostatic balance of phenazine biosynthesis in P. aeruginosa PAO1.

Novel mechanism of metabolic co-regulation coordinates the biosynthesis of secondary metabolites in Pseudomonas protegens

“…The biosynthesis of different secondary metabolites by a microorganism is often coordinated (Bosello et al, 2011; Tsunematsu et al, 2013; Hidalgo et al, 2014; Vingadassalon et al, 2015; Cano-Prieto et al, 2015; Cui et al, 2016). Co-regulation of different secondary metabolites is thought to be selected during microbial evolution because it confers competitive advantages to the producing organism in microbial interactions (Challis and Hopwood, 2003).…”

Characterization of the multiple molecular mechanisms underlying RsaL control of phenazine‐1‐carboxylic acid biosynthesis in the rhizosphere bacterium Pseudomonas aeruginosa PA1201

“…All P. aeruginosa strains contain the two conserved gene clusters phzA 1 B 1 C 1 D 1 E 1 F 1 G 1 (abbreviated as phz1) and phzA 2 B 2 C 2 D 2 E 2 F 2 G 2 (abbreviated as phz2). biosynthesis (Mentel et al, 2009;Li et al, 2011;Recinos et al, 2012;Cui et al, 2016;Sun et al, 2016). The genome of most P. aeruginosa strains also contains the phzM, phzS, and phzH genes, which encode terminalmodifying enzymes responsible for PCA conversion into the phenazine derivatives PCN and PYO (Chin-A-Woeng et al, 2001;Mavrodi et al, 2001).…”

Construction of a β-galactosidase-gene-based fusion is convenient for screening candidate genes involved in regulation of pyrrolnitrin biosynthesis in <i>Pseudomonas chlororaphis</i> G05

“…After being mixed thoroughly for 2 min on a vortex mixer, chloroform extracts were clarified by centrifugation at 10,000 ¥ g for 5 min. Phenazine samples were diluted with chloroform appropriately, and phenazine-1-carboxylic acid was quantified spectrophotometrically at 252 nm (Cui et al, 2016;Kim, 2000). The equation of linear regression [concentration (mg/mL) = 2.9667 ¥ OD 252 -0.0979, R 2 = 0.9998] was created with a purified sample of phenazine-1-carboxylic acid provided by Dr. Xu (Shanghai Jiaotong University, Shanghai, China).…”

“…Samples were harvested after specified periods of growth. After treatment of cells with SDS and chloroform in appropriate amounts, b-galactosidase activities were quantified with the Miller method (Cui et al, 2016;Sambrook and Russell, 2001).…”