Screening for Salmonella factors regulating biofilm formation

CISANA, P.; ECHARREN, M. L.; SONCINI, F. C.

On-Line

Congreso; LVI Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB) y XV Congreso Sociedad Argentina de Microbiología General (SAMIGE); 2020

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB) y Sociedad Argentina de Microbiología General (SAMIGE)

Salmonellosis is among the most common foodborne diseases, with millions of human cases occurring worldwide every year. One of the key aspects that contributes to Salmonella high prevalence is its ability to form biofilms. This multicellular behaviour allows the pathogen to survive hostile conditions, and confers resistance to both host defences and antimicrobial agents. Such resilience against extreme challenges is provided in part by means of a self-produced extracellular matrix which also contributes to the attachment of sessile bacteria to each other and to both biotic and abiotic surfaces. Although curli fibrils and cellulose are the main components of Salmonella biofilms, the BapA protein, the flagellum, colanic acid and O-antigen capsules also structure the extracellular matrix. Their production is strictly controlled by a complex regulatory network that modulates the expression and activity of the biofilm master regulator CsgD. We previously identified Salmonella Typhimurium orf319 as a new member of this complex regulatory network. orf319 is a species-specific gene coding for a factor involved in biofilm formation. We carried out a random transposon mutagenesis to identify factors that modulate orf319 expression. This will allow us to better understand the metabolic as well as the physiological conditions that control the expression of this gene. With this screen we selected 40 transposon insertion mutants that showed an affected expression of orf319 and that we are currently analysing. Among them we first focused on rfbK¸ whose gene product is involved in O-antigen synthesis. orf319 expression decreases more than three folds in the rfbK deleted mutant in cells grown in minimal but not in rich media, indicating that this factor exerts its positive control over orf319 according to the environmental condition. Furthermore, the mutant exhibits an abnormal biofilm morphotype underscoring its role in biofilm regulation. Overall, our study set the bases for the discovery of the metabolic, physiologic as well as genetic conditions controlling the expression of a Salmonella-specific biofilm modulator which, by its characteristics, can be placed as a target for the generation of new strategies against salmonellosis.