The Salmonella Typhimurium RcsCDB system is involved in the std operon regulation

FARIZANO JV; GARCÍA-PASTOR, L; CASADESÚS, J; DELGADO, MA

Mar del PLata

Congreso; 51th Reunión Anual de la Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular; 2015

SAIB

THE Salmonella typhimurium RcsCDB SYSTEM IS INVOLVED IN THE std OPERONREGULATIONFarizano, JV1; García-Pastor, L2; Casadesús, J2; Delgado, MA1.1INSIBIO-CONICET/UNT, Tucumán-Argentina. 2Dpto de Genética-Universidad de Sevilla, Sevilla-España.E-mail: jfarizano@fbqf.unt.edu.arThe genus Salmonella includes Gram-negative bacteria that cause foodborne diseases in human and animals. We areinterested in the study of the RcsCDB system role in the control of S. Typhimurium virulence factors. This pathogenproduces gastroenteritis in humans and typhoid fever in mice. The rcsC11 allele activates constitutively the RcsCDBsystem. As we previously demonstrated that the S. Typhimurium rcsC11 mutant shows reduced attachment toeukaryotic cells, we postulate that the activation of the RcsCDB system represses expression of fimbrial encodinggenes. In order to study whether fimbrial expression depends on the RcsCDB system in S. Typhimurium, we selectedthe std operon because it was demonstrated that this operon encodes for a fimbriae required for the bacteriapersistence in the distal region of the intestine. In this work, we demonstrated that the expression of the std operon isdown-regulated by RcsB, in an HdfR-independent pathway. Finally, bioinformatic analysis and EMSA assay allowedus to conclude that the RcsB regulator binds to a specific std promoter region. The results obtained suggest that thereduced adhesion of the rcsC11 mutant may be caused by repression of fimbrial genes like std.