Mediation of serum resistance in Salmonella typhimurium by an 11-kilodalton polypeptide encoded by the cryptic plasmid

J Infect Dis. 1987 Mar;155(3):540-9. doi: 10.1093/infdis/155.3.540.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacterial Outer Membrane Proteins / genetics*
  • Bacterial Outer Membrane Proteins / physiology
  • Blood Bactericidal Activity*
  • Cloning, Molecular
  • Complement System Proteins / immunology*
  • Escherichia coli / genetics
  • Genes, Bacterial
  • Mice
  • Plasmids*
  • Salmonella typhimurium / genetics*
  • Salmonella typhimurium / immunology
  • Salmonella typhimurium / pathogenicity
  • Virulence


  • Bacterial Outer Membrane Proteins
  • Complement System Proteins