The PmrA/PmrB and RcsC/YojN/RcsB systems control expression of the Salmonella O-antigen chain length determinant

DELGADO, MONICA ALEJANDRA; MOUSLIM, CHAKIB; GROISMAN, EDUARDO A.

Pinamar

Conferencia; X Congreso PABMB; XXXXI Reunión Anual de SAIB and XX Annual meeting of SAN; 2005

SAIB

THE PMRA/PMRB AND RCSC/YOJN/RCSB SYSTEMS CONTROL EXPRESSION OF THE SALMONELLA OANTIGEN CHAIN LENGTH DETERMINANT Delgado MA, Mouslim C, Groisman EA. Department of Molecular Microbiology, Washington University School of Medicine, 660 S. Euclid, St. Louis, Missouri, 63110, USA. E-mail: monaledel@hotmail.com The lipopolysaccharide (LPS) is the outermost component of the Gram-negative envelope. It consists of the hydrophobic lipid A, a short non-repeating core oligosaccharide and a distal polysaccharide known as O antigen. The cld gene product determines the modal distribution of chain length on the O-antigen. However, little is known about how cld expression is regulated. We now report that the PmrA/PmrB and RcsC/YojN/RcsB two-component systems independently promote cld transcription. We show that the response regulators PmrA and RcsB footprint different regions of the cld promoter but promote transcription using the same start site. Conditions that promote cld expression increase the amount of O-antigen L-type in the LPS, leading to heightened resistance to serum complement. The LPS profile of the rcsB mutant was also altered in the size of the O-antigen subunits attached to the lipid Acore. The lipid A structure of a cld null mutant differed from that of the wild-type strain, suggesting a novel role for the Cld protein in lipid A modification. The participation of the Cld protein in the modification of lipid A and in the regulation of O-antigen length may be the reason cld expression is controlled by multiple regulatory systems.