Pyocyanin Restricts Social Cheating in Pseudomonas aeruginosa

Abstract

Quorum sensing (QS) in Pseudomonas aeruginosa coordinates the expression of virulence factors, such as exoproteases and siderophores, that are public goods utilized by the whole population of bacteria, regardless of whether they invested or not in their production. These public goods can be used by QS defective mutants for growth, and since these mutants do not contribute to public goods production, they are considered social cheaters. Pyocyanin is a phenazine that is a toxic, QS-controlled metabolite produced by P. aeruginosa. It is a redox-active compound and promotes the generation of reactive oxygen species; it also possesses antibacterial properties and increases fitness in competition with other bacterial species. Since QS-deficient individuals are less able to tolerate oxidative stress, we hypothesized that the pyocyanin produced by the wild-type population could promote selection of functional QS systems in this bacterium. Here, we demonstrate, using competition experiments and mathematical models, that, indeed, pyocyanin increases the fitness of the cooperative QS-proficient individuals and restricts the appearance of social cheaters. In addition, we also show that pyocyanin is able to select QS in other bacteria such as Acinetobacter baumannii.

Isolation and characterization of nutrient dependent pyocyanin from Pseudomonas aeruginosa and its dye and agrochemical properties

“…These authors noticed that the pyocyanin was exhibited as a tremendous growth inhibiting agent against M. phaseolina and could suppress the associated diseases very effectively at low concentration, and the inhibitory action of 100 µl of purified pyocyanin against various phytopathogens and saprophytic molds was also reported 36 . The quorum sensing P. aeruginosa producing pyocyanin is correlated with siderospores activity that possesses antibacterial property 37 . In another independent research, it was observed that the phenazin pigment 50 µg produced by P. aeruginosa inhibit the growth of Candida albicans and Aspergillus fumigatus fungal growth 38 .…”

More than Simple Parasites: the Sociobiology of Bacteriophages and Their Bacterial Hosts

“…However, P. aeruginosa and other bacteria have genetically encoded mechanisms that can deter social cheating (10,27,28). For example, the redox-active phenazine pyocyanin restricts social cheating in P. aeruginosa by selecting for individuals with intact QS systems, which are required to induce antioxidant defense systems that offset phenazine toxicity (29).…”

Temperate Bacteriophages (Prophages) in Pseudomonas aeruginosa Isolates Belonging to the International Cystic Fibrosis Clone (CC274)

“…Virulence factors as pyocyanin production, biofilm and motility are regulated by QS and also influenced by the phage infections (Morkunas et al, 2012;Hosseinidoust et al, 2013;Latino et al, 2014;Castañeda-Tamez et al, 2018;Tariq et al, 2019). The infection with the wild type phage, AUS531phi, carrying the bci gene, increased the production of virulence factors, pyocyanin and biofilm, whose presence is characteristic in the lung of CF patients (Castañeda-Tamez et al, 2018). The increase in both biofilm and pyocyanin and a reduction in the swarming motility, are a response to the phage infection which is higher when the bci gene is present, but also due to the integration of the temperate phage and the bci gene in the bacterial genome, as was described previously.…”