Proteins involved in signal transduction

The method relates to a method of modulating quorum sensing in bacteria. Quorum sensing is inhibited using peptide hydrolases. This inhibition is used to prevent biofilm formation or to break down established biofilms and may also be used to downregulate the production of virulence determinants by pathogenic bacteria. The invention also relates to the use of peptide hydrolase inhibitors for the upregulation of quorum sensing in bacteria, resulting in the overproduction of proteins and the use of this system as an expression system.