Cabeen, Matthew T.2014-03-112014Cabeen, Matthew T. 2014. “Stationary Phase-Specific Virulence Factor Overproduction by a lasR Mutant of Pseudomonas aeruginosa.” PLoS ONE 9 (2): e88743. doi:10.1371/journal.pone.0088743. http://dx.doi.org/10.1371/journal.pone.0088743.1932-6203http://nrs.harvard.edu/urn-3:HUL.InstRepos:11879811Secreted virulence factors of the human pathogen Pseudomonas aeruginosa are often under quorum sensing control. Cells lacking the quorum-sensing regulator LasR show reduced virulence factor production under typical laboratory conditions and are hypo-virulent in short-term animal infection models, yet lasR mutants are frequently associated with long-term infection in cystic fibrosis patients. Here, I show that in stationary-phase or slow-growth conditions, lasR cells continuously and strongly produce the important virulence factor pyocyanin while wild-type cells do not. Pyocyanin overproduction by lasR cells is permitted by loss of repression by RsaL, a LasR-dependent negative regulator. lasR cells also contribute pyocyanin in mixed cultures, even under “cheating” conditions where they depend on their wild-type neighbors for nutrients. Finally, some clinical P. aeruginosa isolates with lasR mutations can overproduce pyocyanin in the laboratory. These results imply that slow-growing clinical populations of lasR cells in chronic infections may contribute to virulence by producing pyocyanin under conditions where lasR+ cells do not.en-USBiologyDevelopmental BiologyMicrobial Growth and DevelopmentMicrobiologyBacterial PathogensGram NegativeBacteriologyBacterial BiofilmsMicrobial PathogensMicrobial PhysiologyMedicineInfectious DiseasesBacterial DiseasesPseudomonas InfectionsJournal Article2014-03-1110.1371/journal.pone.0088743