We wanted our interface to produce a protein that would inhibit the development of S. aureus in the environment of the implant, but we didn’t want this protein to be secreted continuously and to accumulate outside the biofilm. We wanted our biofilm to start producing growth inhibiting molecules only in the presence of a pathogen.

We decided to use the Biobrick BBa_I746100 from iGEM Cambridge 2007 Team and to improve it by optimizing it for our chassis: E. coli BL21 strain.

We engineered the bacteria composing our biofilm by introducing the genes encoding for AgrC and AgrA proteins, the two proteins responsible for the detection of AIPs. They are encoded under the constitutive promotor BBa_J23107, from iGEM Berkeley 2006 Team.

When AIPs are detected in the environment by the transmembrane protein AgrC, AgrA is phosphorylated and has an increased affinity for the promoter P2. In our engineered bacteria, P2 encodes for a protein called RIP (RNAIII Inhibiting Peptide), that inhibits the formation of a pathogenic biofilm.