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Elucidating how quorum sensing reprogramming alters cooperativity in Pseudomonas aeruginosa
Rodriguez, Blanca
Rodriguez, Blanca
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Abstract
The gram-negative bacterium Pseudomonas aeruginosa uses quorum sensing (QS) to sense and respond to changes in population density. QS in general involves the production of a signal, which binds to a receptor, activating gene expression. In P. aeruginosa the QS receptor LasR activates cooperative activities such as exoprotease production. Like most cooperative behaviors, these activities can be exploited by social cheaters that do not cooperate. If unchecked, cheaters can overrun cooperators and cooperative behaviors can be lost from the population. LasR mutants are a type of cheater. In some P. aeruginosa strains, LasR mutants do not make exoproteases, and are also unable to activate another QS regulator, RhlR. In other strains, RhlR functions in parallel to LasR. In these strains, RhlR can activate protease production. I hypothesize that QS architecture affects 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. I 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 these lasR mutants activate exoprotease production when grown with LasR-intact cooperators; this is a type of coercion of lasR mutants to cooperate. Coercive interactions have implications for the long-term stability of QS. These results have relevance to understanding diverse QS architectures and how cooperative behaviors evolve.
Description
These are the slides from a presentation given at National Diversity in STEM Conference on 11/01/2024.
Date
2024-11-01
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University of Kansas
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Keywords
Pseudomonas aeruginosa, Cooperation, Cheating, Quorum sensing