Pathogenesis could be one of the anti-cheating mechanisms for Pseudomonas aeruginosa society

Pseudomonas aeruginosa is the major pathogen of chronic lung infections in individuals with cystic fibrosis (CF). Traditionally, it has been regarded as living in planktonic form, and as being able to perform only simple physiological activities. Recent studies in biofilm infections in CF patients, however, show that P. aeruginosa can perform many social behaviors, like cooperation and cheating. Based on the theory of "survival of the fittest", it may be presumed that every individual will take advantage of cheating instead of cooperation to increase its fitness, at the cost of group survival. In reality, however, a bacterial society can remain stable, even though cheaters arise frequently in the population. It is therefore possible that there are anti-cheating mechanisms in a bacterial society. The cheaters of P. aeruginosa will cause the loss or the decrease of the pathogenesis of the microorganism in the cystic fibrosis host. These defects in pathogenesis will be disadvantageous to bacterial colonization and compromise the resistance to host immunity. We therefore propose the hypothesis that the pathogenesis in cystic fibrosis lung infections could be one of the anti-cheating mechanisms that contribute to the hidden costs of the cheater strains. To test this hypothesis, we designed an experiment in an animal model of CF. If this hypothesis can be confirmed, it will illustrate that nontrivial analogies exist between microbial social behaviors and the social traits that are observed in the more traditional model systems for sociobiology. This will not only provide a genetic model for sociobiology research, but also cast light on the social control of chronic bacterial infections.