To cheat or not to cheat: cheatable and non-cheatable virulence factors in Pseudomonas aeruginosa.

Important bacterial pathogens such as Pseudomonas aeruginosa produce several exoproducts such as siderophores, degradative enzymes, biosurfactants, and exopolysaccharides that are used extracellularly, benefiting all members of the population, hence being public goods. Since the production of public goods is a cooperative trait, it is in principle susceptible to cheating by individuals in the population who do not invest in their production, but use their benefits, hence increasing their fitness at the expense of the cooperators' fitness. Among the most studied virulence factors susceptible to cheating are siderophores and exoproteases, with several studies in vitro and some in animal infection models.

Iron limitation by transferrin promotes simultaneous cheating of pyoverdine and exoprotease in Pseudomonas aeruginosa.

Pseudomonas aeruginosa is a primary bacterial model to study cooperative behaviors because it yields exoproducts such as siderophores and exoproteases that act as public goods and can be exploited by selfish nonproducers behaving as social cheaters. Iron-limited growth medium, mainly casamino acids medium supplemented with transferrin, is typically used to isolate and study nonproducer mutants of the siderophore pyoverdine. However, using a protein as the iron chelator could inadvertently select mutants unable to produce exoproteases, since these enzymes can degrade the transferrin to facilitate iron release.

Rhamnolipids stabilize quorum sensing mediated cooperation in Pseudomonas aeruginosa.

Pseudomonas aeruginosa is one of the main models to study social behaviors in bacteria since it synthesizes several exoproducts, including exoproteases and siderophores and release them to the environment. Exoproteases and siderophores are public goods that can be utilized by the individuals that produce them but also by non-producers, that are considered social cheaters. Molecularly exoprotease cheaters are mutants in regulatory genes such as lasR, and are commonly isolated from chronic infections and selected in the laboratory upon serial cultivation in media with protein as a sole carbon source.

Characterization of FlgP, an Essential Protein for Flagellar Assembly in .

The flagellar lipoprotein FlgP has been identified in several species of bacteria, and its absence provokes different phenotypes. In this study, we show that in the alphaproteobacterium , a Δ mutant is unable to assemble the hook and the filament. In contrast, the membrane/supramembrane (MS) ring and the flagellar rod appear to be assembled.