Researchers have identified a cell signaling system that may help the bacterium Pseudomonas aeruginosa establish itself in the lungs of cystic fibrosis patients. The researchers used a new technology to seek insights into an important and elusive enemy, and say the findings are important for biology and potentially important for therapy. The researchers identified the activation of this signaling system by the use of new quantitative proteomic technology that analyzed Pseudomonas samples from the lungs of children with cystic fibrosis. Proteomics is the method for analyzing and cataloguing a complete cellular complement of proteins, which are produced based on information encoded by genes and are the workhorses of all living cells.