Multiple diguanylate cyclase-coordinated regulation of pyoverdine synthesis in P seudomonas aeruginosa.

The nucleotide signalling molecule bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di- GMP) plays an essential role in regulating microbial virulence and biofilm formation. C-di- GMP is synthesized by diguanylate cyclase ( DGC) enzymes and degraded by phosphodiesterase ( PDE) enzymes. One intrinsic feature of c-di- GMP signalling is the abundance of DGCs and PDEs encoded by many bacterial species. It is unclear whether the different DGCs or PDEs coordinately establish the c-di- GMP regulation or function independently of each other. Here, we provide evidence that multiple DGCs are involved in regulation of c-di- GMP on synthesis of the major iron siderophore pyoverdine in P seudomonas aeruginosa. Constitutive expression of the Wsp G or Yed Q DGC in P . aeruginosa is able to induce its pyoverdine synthesis. Induction of pyoverdine synthesis by high intracellular c-di- GMP depends on the synthesis of exopolysaccharides and another two DGCs, Sia D and Sad C. Sia D was found to boost the c-di- GMP synthesis together with constitutively expressing Yed Q. The exopolysaccharides and the Sia D DGC were found to modulate the expression of the Rsm Y/ Rsm Z nc RNAs. Induction of the Rsm Y/ Rsm Z nc RNAs might enhance the pyoverdine synthesis through Sad C. Our study sheds light on a novel multiple DGC-coordinated c-di- GMP regulatory mechanism of bacteria. [ABSTRACT FROM AUTHOR]