Salmonella biofilms: participation of the RcsCDB regulatory system

INDIANA M PÁEZ PAZ; MARIA CECILIA LECCESE TERRAF; MARÍA DE LAS MERCEDES PESCARETTI; MÓNICA A. DELGADO

San Luis

Congreso; SAMIGE; 2018

Bacterial biofilms are complex communities consisting of microorganisms embedded in a self-produced extracellular matrix. Salmonella is able to form biofilm on the surface of the gallstones in the gallbladders that produce the persistence of the bacterial colonization in the carrier patients. The RcsCDB phosphorelay system has an important role in the bacterial physiology, manly in the response to extracytoplasmic stress signaling. It was shown that the factors affecting the cell envelope lead to the activation of the system and consequently the modulation of capsule synthesis, motility behavior and biofilm formation. Previously, in our laboratory we characterize the rcsC11 mutant as a not virulent strain that can be used as an attenuated vaccine, producing RcsCDB constitutive activation. We here investigated whether the RcsCDB system activation conditions have the ability to produce red dry/rough (RDAR) morphotype and the levels of biofilm formation on polystyrene plates. For this purpose, we used the 14028s wild type strain harboring the prcsB plasmid, or tolB and rcsC11 mutants as RcsCDB system activation conditions. The ability of biofilm formation was also determined on uniform gallstones mainly composed of cholesterol, removed from a single lithiasic patient. To this end, gallstones were incubated in LB medium with and without bile salt, previously inoculated with wild type and rcsC11 Salmonella strains. After 7 days, the biofilm formed was evaluated by scanning electron microscopy. Our results demonstrated that the RcsCDB system activation negatively affects the Salmonella biofilm development. In addition, our findings on the inability of the rcsC11 strain to form biofilm highlight once again that this mutant is an excellent candidate for the development of vaccines.