| Biofilms are incredibly persistent and structured assemblages of surface associated bacteria that likely represent the predominant lifestyle of microbes in the environment. The development and coordination of biofilms is enabled by cell-to-cell communication. In the opportunistic pathogen Pseudomonas aeruginosa, quorum sensing controls a range of biofilm phenotypes, including surface attachment, motility, and virulence, but does not appear to control biofilm dispersion. Dr. Davies' lab has recently isolated a fatty acid signaling molecule, cis-2-decenoic acid, that induces the dispersion of biofilms. In this work, I have examined genes associated with dispersion induction. By sequencing a set of Tn5 insertion mutants, 11 genes were identified that may be up-regulated in response to the dispersion molecule. Putative genes responsive to the inducer included a two component regulatory system, a number of virulence factors, and also genes associated with arginine catabolism, cell proliferation, and phage pyocin. Additionally, candidate membrane receptors were chosen based on published gene and protein data, and the respective knockout mutants were tested for dispersion induction. One Tn5 strain, Tn5::PA1396, was impaired in dispersion response, which may indicate that the sensor kinase PA1396 is required for the perception of inducer molecule. All mutant strains were also assayed for growth and biofilm characteristics, and a model for the genes controlling biofilm dispersion was proposed. The goal of this work was to better understand the genetic regulation of Pseudomonas aeruginosa biofilm dispersion, in the hope of improving treatment options. |
