Staphylococcus aureus (SA) is an important pathogen causing many diseases, especially nosocomial infections. It forms biofilms to protect itself from the host and antibiotics. Biofilm and planctonic life style is regulated by a complex Quorum-Sensing (QS) system with agr as a central regulator. To study biofilm formation and QS in SA a Boolean network was build and thoroughly validated using data from microarrays, northern blots and biofilm adherence assays. Network analysis revealed sae and agr as central regulators and showed two stable states, biofilm forming versus planctonic, with...