Rhamnolipids stabilize quorum sensing mediated cooperation in Pseudomonas aeruginosa

ABSTRACT 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. Despite that the production of exoproteases is exploitable, cooperators have also ways to restrict the growth and selection of social cheaters, for instance by producing toxic metabolites like pyocyanin. In this work, using bacterial competitions, serial cultivation and growth assays, we demonstrated that rhamnolipids which production is regulated by quorum sensing, selectively affect the growth of lasR mutants and are able to restrict social cheating, hence contributing to the maintenance of cooperation in Pseudomonas aeruginosa populations.

On treatment of moderate and severe forms of Flexner's dysentery 2a

The comparison of the treatment efficiency of patients with Flexner's 2a dysentery with fluochinolones (in peroral and parenteral administration) and antibacterial drugs of other groups is performed. The antibiotic sensitivity of Flexner 2a Shigella strains evolved from patients with midgrave and grave forms of dysentery (during life and postmortelly) using the methods of disks and serial cultivation is studied. It is established that the largest sensitivity of Flexner 2a Shigella is expressed in tarivid that is a highly effective antibacterial drug for the treatment of patients with midgrave and grave course of Flexner's dysentery. There is significant resistance of Flexner 2a Shigella to the traditionally used antibacterial drugs for the treatment of dysentery.