Poster Session - Abstract # 24
Mutations in the Nitrogen Phosphotransferase Gene ptsP Destabilize Cooperation in P. aeruginosa
Blanca L. Rodriguez1, Rhea G. Abisado2, Brielle M. McKee3, Kade A. Townsend3, Kate Woods3 and Josephine R. Chandler3
1Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, USA; 2Department of Biology, Ateneo de Manila University, Quezon City, Philippines; 3Department of Molecular Biosciences, University of Kansas, Lawrence, KS, USA
The bacterium Pseudomonas aeruginosa regulates gene expression in a population density-dependent manner using quorum sensing, which is carried out by the LasI signal synthase and the LasR signal receptor. The LasR-LasI system coordinates cooperative activities such as exoprotease secretion for catabolism. Exoproteases are public goods that are prone to exploitation by freeloading social cheaters, such as individuals with LasR-null mutations. LasR mutant cheaters spontaneously emerge in populations growing on casein, where exoproteases are needed for growth. These LasR-null mutants proliferate in populations where casein is the sole carbon source because they avoid the metabolic burden of activating the production of exoproteases. The proliferation of LasR-null cheaters is predicted to drive the population to collapse by destabilizing cooperation under quorum sensing but, collapse rarely occurs in these conditions. It has been observed that cooperating populations with knockout mutations in the genes mdpA or ptsP do collapse as a result of spontaneous lasR cheater invasion. mdpA codes for a metallopeptidase that is involved in the catabolism of dipeptides, which may be important for taking up nutrients from proteolyzed casein. ptsP codes for the first enzyme in the nitrogen phosphotransferase (PTSNtr) system, which is thought to regulate changes in metabolism in response to nitrogen and carbon availability. These mutations may accelerate collapse by increasing competition for nutrients between cooperators and cheaters. We focused on understanding how these mutations affect nutrient uptake, metabolism and direct competition through policing effects that drive the destabilization of cooperation in P. aeruginosa communities. These studies will illuminate new insight into quorum sensing biology and the evolution of cooperation and will provide new information to address P. aeruginosa-related challenges in the medical, agricultural and industrial fields.