Elastase A (LasA), elastase B (LasB) and the alkaline protease (AprA) are three major metalloproteases expressed by Pseudomonas aureus strains. Our hydrogels were then tested with mutant strains which did not express either lasB, aprA, or lasRI. These strains were used in Bonchi et. al . LasR and lasI are part of the las quorum sensing system of P. aeruginosa strains and regulate the expression and secretion of virulence factors. This las system was shown to activate the expression of lasA, lasB and aprA. Hence lasRI mutants result in quorum sensing deficient strains. A strain deficient in all three genes coding for LasA, LasB and AprA proteases was also tested.