Ricerc@Sapienza

Biofilm is a microbial community whose formation is regulated by the dinucleotide cyclic-di-GMP. The GGDEF diguanylate cyclases (DGCs) and EAL or HD-GYP phosphodiesterases (PDEs) control the balance of c-di-GMP. DGCs synthesize the second messenger from two GTP molecules through the conserved GGDEF catalytic domain, while PDEs degrade it by producing pGpG through the EAL domain or GMP through the HD-GYP domain. Moreover there are proteins bearing both the GGDEF and EAL or HD-GYP domains named hybrid proteins. Most of these proteins have N-terminal sensing domains which can perceive environmental signals likely involved in modulating the catalytic moiety. The identification of extracellular signals acting on these sensory domains is crucial to understand the final output and the regulation of hybrid proteins. More in general the environmental stimuli able to regulate c-di-GMP levels (and the corresponding proteins involved) are still largely unknown.
We are currently characterizing the hybrid protein PA0575 from Pseudomonas aeruginosa, a model system for studying biofilm and a well known human pathogen. We have identified L-arginine as the small molecule able to trigger the activation of the downstream catalytic domains which lead to c-di-GMP hydrolysis to finally decrease biofilm formation.
Given that literature data suggest that arginine could be involved in controlling biofilm formation, we plan to deeply characterize the arginine dependent PA0575 signaling pathway. Moreover, since previous data indicated that the diatomic gas NO promote biofilm dispersal, we plan to design arginine analogues able to release NO to test whether a combined action on decreasing c-di-GMP levels could enhance the biological effect on biofilm dispersal.