title: Mediation of serum resistance in Salmonella typhimurium by an 11-kilodalton polypeptide encoded by the cryptic plasmid.
abstract: A cosmid bank of the DNA (including cryptic plasmid DNA) of a virulent strain of Salmonella typhimurium was prepared in Escherichia coli K12, and clones that contained cryptic plasmid DNA were detected by probing. Two such clones expressed a new outer membrane protein of 11 kilodaltons (kDa) and were serum resistant (E. coli K12 is serum sensitive). The gene encoding the 11-kDa protein was subcloned in a 2.1-kilobase fragment and shown to mediate serum resistance in both E. coli K12 and a cryptic plasmid-free (serum-sensitive) strain of S. typhimurium. The cryptic plasmid-free S. typhimurium strain did not express normal lipopolysaccharide, but introduction of the 11-kDa protein gene into the strain rendered the strain serum resistant without restoration of normal lipopolysaccharide synthesis. The 11-kDa protein gene was not sufficient to restore either macrophage resistance or virulence to a cryptic plasmid-free strain of S. typhimurium.
mesh_terms: D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000502:physiology; D001770:Blood Bactericidal Activity; D003001:Cloning, Molecular; D003165:Complement System Proteins / Q000276:immunology*; D004926:Escherichia coli / Q000235:genetics; D005798:Genes, Bacterial; D051379:Mice; D010957:Plasmids; D012486:Salmonella typhimurium / Q000235:genetics* / Q000276:immunology / Q000472:pathogenicity; D014774:Virulence
chemical_list: D001425:Bacterial Outer Membrane Proteins; D003165:Complement System Proteins