Two Genes From the Capsule of Aeromonas Hydrophila (Serogroup O:34) Confer Serum Resistance to Escherichia Coli K12 Strains

Res Microbiol. Jul-Aug 1999;150(6):395-402. doi: 10.1016/s0923-2508(99)80074-6.


The Escherichia coli DH5alpha strain as well as other K12-derived strains are unable to produce O-specific lipopolysaccharide and are thus rough and serum-sensitive. One representative recombinant clone (COS-SR1) containing Aeromonas hydrophila (serogroup O:34) chromosomal DNA conferred serum resistance to E. coli K12 strains. Genetic, biochemical, and immunological studies suggested that the two genes (orf1 and wcaJ) identified in a subclone (pAC-SR9) of COS-SR1 are necessary for the production of the colanic acid capsule at 37 degrees C on E. coli DH5alpha, rendering the strain serum-resistant. A. hydrophila strains from serogroup O:34 are able to produce capsule when they grow both in synthetic medium and in an autolysate of fish viscera. However, defined wcaJ insertion mutants of A. hydrophila 1051-88 (serogroup O:34) are unable to produce capsule on these media. This strongly suggests that both genes belong to the gene cluster responsible for capsule production (wca) of A. hydrophila 1051-88 (serogroup O:34).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aeromonas hydrophila / genetics*
  • Aeromonas hydrophila / immunology*
  • Amino Acid Sequence
  • Animals
  • Bacterial Capsules / genetics
  • Bacterial Capsules / immunology
  • Base Sequence
  • Complement Activation / genetics
  • Complement Activation / immunology
  • Escherichia coli / genetics*
  • Escherichia coli / immunology*
  • Genetic Engineering
  • Humans
  • Molecular Sequence Data
  • O Antigens / immunology*
  • Polysaccharides / genetics
  • Polysaccharides / immunology
  • Rabbits
  • Sequence Analysis


  • O Antigens
  • Polysaccharides
  • colanic acid