Targeting biofilm formation by human pathogenic bacteria: functional and inhibition studies of diguanylate cyclases

Bacteria react to adverse environmental stimuli by forming biofilms, difficult to eradicate and highly resistant to antimicrobials and to the host immune system. Pseudomonas aeruginosa is an opportunistic pathogen, able to invade lung of cystic fibrosis (CF) patients by forming a drug-resistant biofilm that results in fatal pneumonia. The intracellular second messenger 3',5' diguanylic acid (c-di-GMP) is crucial for biofilm formation. C-di-GMP levels are modulated by the opposite activity of diguanylate cyclases (DGCs), which catalyze its synthesis and specific phosphodiesterases (PDEs), which hydrolyze it. Targeting c-di-GMP metabolism represents thus an attractive strategy for the development of anti-biofilm drugs. Structural and functional studies of selected DGCs from P. aeruginosa are needed for specific drug design and inhibition studies. Synthesis of c-di-GMP analogues as inhibitors may represent an effective approach to minimize side effects due to binding to eukaryotic enzymes/proteins. In order to provide a novel tool in treating drug-resistant bacterial infections, we are testing several compounds that target selectively c-di-GMP synthesis and biofilm formation in vitro. Our results identify at least 1 compound able to significantly decrease DGC activity. These promising results pave the way to test more compounds both in vitro and in vivo in P. aeruginosa.