The aim of this project is to define the molecular details controlling signal transduction in response to arginine during biofilm formation; we plan to define how this nutrient modulates c-di-GMP (3',5'- cyclic diguanylic acid) levels in Pseudomonas aeruginosa. This bacterium is an opportunistic human pathogen responsible for biofilm-mediated chronic infections; biofilms represents a sessile multicellular lifestyle difficult to be eradicated, which confers both antibiotic and host defence resistance to the encapsulated bacterial population. Nutrients may control intracellular levels of the second messenger C-di-GMP, which in turn trigger biofilm formation when accumulates. Among nutrients, arginine represents a strategic metabolite being at the crossroad of many metabolic processes (including carbon, nitrogen and ATP source) and also associated to chronic infections, biofilm/virulence and antibiotic resistance.
We recently found that P. aeruginosa is able to respond to environmental arginine by directly decreasing the intracellular levels of c-di-GMP via the molecular "antenna" named RmcA (Redox regulator of c-di-GMP). This multidomain membrane protein recognise extracellular arginine through a Venus Fly Trap (VFT) domain and transduces the environmental signal by a transmembrane and cytoplasmic portions containing PAS-LOV domains; their re-organization controls the downstream catalytic moiety composed by the diguanylate cyclases (GGDEF) and the phsphodiesterases (EAL) tandem, where the hydrolysis of c-di- GMP occurs.
The final goal of this proposal is to gain details on the mechanism of control of arginine on c-di- GMP hydrolysis both in terms of VFT activation and of PAS-mediated transduction of the periplasmic signal.
This mechanistic study will be useful to develop an approach to promote biofilm dispersion (where cells are more sensitive to traditional antimicrobial compounds) to finally treat chronic infection with more effective combined strategies.
