ROLE OF THE RcsC/YojN/RcsB REGULATORY SYSTEM IN LPS MODIFICATION IN SALMONELLA TYPHIMURIUM

MÓNICA A. DELGADO

San Pablo- Brasil

Conferencia; A XXXVII Reunião Anual da Sociedade Brasileira de Bioquímica e Biologia Molecular (SBBq) and XI Reunião da Panamerican Association for Biochemistry and Molecular Biology (PABMB); 2008

SBBq and PABMB

Prokaryotic organisms respond to changing environmental conditions regulating the genes expression via two-component systems. These systems are composed by two proteins: the sensor, a histidin kinase inner membrane protein, and the cytoplasmic cognate response regulator. The lipopolysaccharide (LPS) is the outermost component of the cell envelope in Gram (-) bacteria. It consists of the hydrophobic lipid A, a short non-repeating core oligosaccharide and a distal polysaccharide termed O-antigen. We studied the role of Rcs system in the control of those genes involved in the Salmonella enterica LPS synthesis and determined that it system and PmrA/PmrB regulatory systems promote wzzB (O-antigen chain length determinant gene) transcription under different environmental conditions and independently of each other. The transcriptional induction of the wzzB gene increased the amount of O-antigen in the LPS leading to a higher resistance to the serum complement-mediated killing. In addition, we identified a new role of the WzzB protein in the lipid A modification, indicating that the WzzB is required for many biological processes. Nevertheless, we show that the absence of pbgE2 and pbgE3 genes, which are regulated by the PmrA/PmrB system and involved in the lipid A modification, resulted in an O-antigen without the region containing 1 to 15 O-antigen subunits, and that it regulatory system promotes directly the fepE transcription, which product determines the O-antigen very long chain (35 to 100 O-antigen subunits) attached to the lipid A-core. These results indicated that the PmrA/PmrB system is the master regulator of the LPS synthesis, and that both O-antigen formation and the lipid A modification are required at the same time during the Salmonella infection.