An Agent-Based Model to Study Selection of Pseudomonas aeruginosa Quorum Sensing by Pyocyanin: A Multidisciplinary Perspective on Bacterial Communication

Abstract

Although bacteria are unicellular organisms, they use a sophisticated mechanism to cooperate with other bacteria which allows them to carry out multicellular-like processes, such as swarming, biofilm formation, induce infections, luminescence, etc. This mechanism is known as quorum sensing (QS) and it functions through the individual release, diffusion and collective sensing of small molecules, called autoinducers, which under their accumulation lead to changes in gene regulation. A range of approaches have been used to study the complex way in which QS works, these tools combine biology, physics, and mathematics. We discuss here how a multidisciplinary perspective is ideal to study QS and present an example of QS in Pseudomonas aeruginosa, a human pathogen. In this bacterial species, QS coordinates the expression of virulence factors, that are public goods utilized by the whole population of bacteria regardless if they invested or not in their production. Hence, public good production is a cooperative behavior, susceptible to be exploited by non-public good producers, known as social cheaters. These individuals, which are QS-deficient, are also less able to tolerate oxidative stress. Our group has shown that pyocyanin (which promotes the generation of reactive oxygen species) produced by the wild-type population may work as a policing mechanism to select functional QS systems in this bacterium. Using an agent-based model (ABM) we are able to confirm that indeed this compound increases the fitness of the cooperative QS proficient individuals. We further explore, with the ABM, how the bacterial environment diffusion properties may be contributing to stabilize QS in certain growth conditions.