Blanca Rodriguez
University of Kansas
Lawrence, KS
Elucidating how quorum sensing reprogramming alters cooperativity in Pseudomonas aeruginosa
Blanca Rodriguez, Tom Chao, Nicole Smalley, Maxim Kostylev, Ajai Dandekar
The gram-negative bacterium Pseudomonas aeruginosa uses quorum sensing (QS) to sense and respond to population density-dependent changes. One type of P. aeruginosa QS involves LasR, which activates cooperative activities such as exoprotease production. Exoproteases can be exploited by social cheaters that avoid the metabolic burden of public goods production. If unchecked, cheaters can overrun cooperators and cause a population collapse. In some P. aeruginosa strains, LasR mutants are deficient for exoprotease production, and are also unable to activate a secondary QS regulator, RhlR. In other strains, the QS architecture is reprogrammed such that RhlR functions in parallel to LasR. In these strains, RhlR can activate protease production. I hypothesize that QS reprogramming alters cooperator-cheater dynamics. To test this hypothesis, I use an experimental evolution model. In populations serially passaged on casein, which requires digestion by exproteases for carbon and energy, lasR mutants spontaneously emerge and proliferate to high levels, and sometimes cause collapse. My results show that lasR mutants are conditional cooperators in strains with parallel QS systems; they fail to grow by themselves at low population density but can produce sufficient exoprotease at high density. I also show that lasR mutants highly activate exoprotease production when grown with LasR-intact cooperators. This represents a type of coercion of lasR mutants to cooperate and might have implications for the long-term stability of QS. These results have relevance to understanding the prevalence of diverse QS architectures and how cooperative traits evolve.
SACNAS National Diversity in STEM Conference, Phoenix, AZ, October 30-November 2, 2024
