CONTROL OF BIOFILM FORMATION BY A SALMONELLA-SPECIFIC TRANSCRIPTION FACTOR UNDER ENVIRONMENTAL CONDITIONS

TULIN G; CHECA SK; SONCINI FC

VIRTUAL

Congreso; LVII SAIB Meeting - XVI SAMIGE Meeting; 2021

SOCIEDAD ARGENTINA DE BIOQUIMICA Y BIOLOGIA MOLECULAR Y SOCIEDAD ARGENTINA DE MICROBIOLOGIA GENERAL

Salmonellosis is a food-borne disease caused by Salmonella, that include illness ranging from gastroenteritis to enteric/typhoid fever, with millions of cases occurring worldwide every year. One of the key aspects of Salmonella life cycle that contributes to its high prevalence is its ability to persist in the environment and to form biofilms in abiotic surfaces and in the host tissues. This multicellular behavior allows the pathogen to survive hostile environmental conditions, and confers resistance to both host defenses and antimicrobial agents. This lifestyle?s change, from motile to sessile cells attached to diverse solid surfaces, implies a drastic metabolic modification, and depends on the master transcriptional regulator CsgD. This regulator activates the production of the two major components of extracellular matrix in Salmonella, the curli fiber and the exopolysaccharide cellulose, but also other extracellular components important for biofilm development, such as colanic acid and the large cell-surface protein BapA. Because of its homology to a well-known csgD transcriptional activator, we analyzed the role of BioR, a Salmonella-specific transcription factor, in biofilm formation. Using the Congo Red dye to evaluate biofilm production in solid media, and the Cristal Violet dye to quantify the extracellular matrix production in liquid media, we determined that this factor is required for Salmonella adhesion and biofilms formation. To gain insight into the optimal conditions of BioR expression, we use lacZ and gfp transcriptional fusions to its natural promoter, as well as specific antibodies. We found that this regulator is maximally expressed when Salmonella grows at low temperatures and in minimal media. Also, we searched for genes that were differentially expressed in the presence or absence of BioR, analyzing changes in the bacterial transcriptome through an RNA-Seq approach. We uncover that BioR controls the expression of genes encoding several matrix components, as well as enzymes that take part of diverse metabolic processes. In conclusion, we identified a Salmonella-specific regulator that modulates biofilm formation at low temperatures and under nutrient limitations, favoring the of pathogen?s persistence under extreme conditions in non-host environments.