Multiple diguanylate cyclase-coordinated regulation of pyoverdine synthesis in Pseudomonas aeruginosa

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Bis-(3"-5")-cyclic dimeric guanosine monophosphate (c-di-GMP) is a crucial second messenger regulating bacterial processes like virulence and biofilm formation.
• Diguanylate cyclase (DGC) and phosphodiesterase (PDE) enzymes synthesize and degrade c-di-GMP, respectively, with many bacteria possessing multiple DGC and PDE enzymes.
• The coordinated function of multiple DGCs and PDEs in c-di-GMP regulation remains largely unelucidated.

Purpose of the Study:

• To investigate the role of multiple DGC enzymes in regulating c-di-GMP levels.
• To elucidate the coordinated mechanisms of DGCs in controlling bacterial virulence factors, specifically pyoverdine synthesis in Pseudomonas aeruginosa.
• To understand how c-di-GMP signaling impacts exopolysaccharide synthesis and downstream regulatory pathways.

Main Methods:

• Genetic manipulation of DGCs (WspG, YedQ, SiaD, SadC) in Pseudomonas aeruginosa.
• Analysis of pyoverdine synthesis under constitutive DGC expression.
• Investigation of the role of exopolysaccharides in c-di-GMP mediated regulation.
• Assessment of RsmY/RsmZ ncRNA expression levels.

Main Results:

• Constitutive expression of WspG or YedQ DGCs induced pyoverdine synthesis.
• High intracellular c-di-GMP levels, induced by exopolysaccharides and SiaD/SadC DGCs, were necessary for pyoverdine synthesis.
• SiaD DGC boosted c-di-GMP synthesis in conjunction with constitutively expressed YedQ.
• Exopolysaccharides and SiaD DGC modulated RsmY/RsmZ ncRNA expression, potentially enhancing pyoverdine synthesis via SadC.

Conclusions:

• Multiple DGCs are involved in a coordinated regulatory network controlling c-di-GMP levels in Pseudomonas aeruginosa.
• This DGC-coordinated mechanism influences the synthesis of the iron siderophore pyoverdine.
• The findings reveal a novel, intricate c-di-GMP regulatory pathway in bacteria.