title: Growth-phase regulation of lipopolysaccharide O-antigen chain length influences serum resistance in serovars of Salmonella.
abstract: The amount of lipopolysaccharide (LPS) O antigen (OAg) and its chain length distribution are important factors that protect bacteria from serum complement. Salmonella enterica serovar Typhi produces LPS with long chain length distribution (L-OAg) controlled by the wzz gene, whereas serovar Typhimurium produces LPS with two OAg chain lengths: an L-OAg controlled by Wzz(ST) and a very long (VL) OAg determined by Wzz(fepE). This study shows that serovar Enteritidis also has a bimodal OAg distribution with two preferred OAg chain lengths similar to serovar Typhimurium. It was reported previously that OAg production by S. Typhi increases at the late exponential and stationary phases of growth. The results of this study demonstrate that increased amounts of L-OAg produced by S. Typhi grown to stationary phase confer higher levels of bacterial resistance to human serum. Production of OAg by serovars Typhimurium and Enteritidis was also under growth-phase-dependent regulation; however, while the total amount of OAg increased during growth, the VL-OAg distribution remained constant. The VL-OAg distribution was primarily responsible for complement resistance, protecting the non-typhoidal serovars from the lytic action of serum irrespective of the growth phase. As a result, the non-typhoidal species were significantly more resistant than S. Typhi to human serum. When S. Typhi was transformed with a multicopy plasmid containing the S. Typhimurium wzz(fepE) gene, resistance to serum increased to levels comparable to the non-typhoidal serovars. In contrast to the relevant role for high-molecular-mass OAg molecules, the presence of Vi antigen did not contribute to serum resistance of clinical isolates of serovar Typhi.
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, PO Box 174 Correo 22, Santiago, Chile.
authors.forename: Denisse
authors.initials: D
authors.lastname: Bravo
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, PO Box 174 Correo 22, Santiago, Chile.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Silva
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, PO Box 174 Correo 22, Santiago, Chile.
authors.forename: Javier A
authors.initials: JA
authors.lastname: Carter
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, PO Box 174 Correo 22, Santiago, Chile.
authors.forename: Anilei
authors.initials: A
authors.lastname: Hoare
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, PO Box 174 Correo 22, Santiago, Chile.
authors.forename: Sergio A
authors.initials: SA
authors.lastname: Álvarez
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, PO Box 174 Correo 22, Santiago, Chile.
authors.forename: Carlos J
authors.initials: CJ
authors.lastname: Blondel
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, PO Box 174 Correo 22, Santiago, Chile.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Zaldívar
authors.affiliation: Department of Microbiology and Immunology, Siebens-Drake Research Institute, University of Western Ontario, London, ON N6A 5C1, Canada.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Valvano
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, PO Box 174 Correo 22, Santiago, Chile.
authors.forename: Inés
authors.initials: I
authors.lastname: Contreras
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D024881:Drug Resistance, Bacterial; D007700:Kinetics; D008070:Lipopolysaccharides / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification; D016296:Mutagenesis; D019081:O Antigens / Q000737:chemistry / Q000378:metabolism*; D010957:Plasmids; D019779:Salmonella enterica / Q000235:genetics / Q000254:growth & development*; D012477:Salmonella enteritidis / Q000235:genetics / Q000254:growth & development
chemical_list: D001426:Bacterial Proteins; D008070:Lipopolysaccharides; D019081:O Antigens; C075969:rol protein, Bacteria