Once Pseudomonas aeruginosa colonizes the lungs of a cystic fibrosis patient, it begins transforming itself from a squatter into a fully-invested resident, eventually establishing a chronic airway infection. A study just released by mBio tracked the gene expression patterns of P. aeruginosa during this transformation in three individual patients and reveals that 24 genes were commonly regulated in each of the lineages. Although the number of traits that evolved in parallel (24) is small compared to gene expression changes within lineages (up to 441) they may represent a core set of changes necessary to establish chronic infections in the host.
Several of the 24 commonly regulated genes are known to encode traits important for growth in the host, but many encode proteins of unknown function. Future studies aimed at understanding the role of these genes could provide unique insight into selective pressures in the lungs of cystic fibrosis patients.