aeruginosa and E. faecalis secrete serine proteases and metalloproteases, some from the same family. Metalloproteases possess one or two metal ions in their catalytic site, Zn being the most frequent one. In the M4 thermolysin family, the metal centre is tetrahedrally coordinated by two Glu residues, one His residue and a water molecule. During catalysis, the water molecule gets activated and acts as a nucleophile for protein cleavage. In this study we set out to design a simple gelatin hydrogel film that would degrade in the presence of the 'gelatinases' which could in principle include serine and metalloproteases released by S. aureus, E. faecalis and P. aeruginosa. Surprisingly, in our study the hydrogels were only degraded by P. aeruginosa and remained stable when exposed to proteases from S. aureus and E. faecalis. This was unexpected given that all three bacterial species can express S1 proteases and/or M4 gelatinase (Table ). It should be noted that the presence of a protease gene does not necessary correlate with enzymatic activity. Several reports show that the gelE gene coding for gelatinase in E. faecalis does not always lead to expression of the active protein. However, out of the 36 strains tested only P. aeruginosa was capable of degrading the gel in less than 48 hours. Among the P. aeruginosa strains tested, 69.2% caused degradation.