The Aeromonas hydrophila wb*O34 gene cluster: genetics and temperature regulation

J Bacteriol. 2008 Jun;190(12):4198-209. doi: 10.1128/JB.00153-08. Epub 2008 Apr 11.


The Aeromonas hydrophila wb*(O34) gene cluster of strain AH-3 (serotype O34) was cloned and sequenced. This cluster contains genes necessary for the production of O34-antigen lipopolysaccharide (LPS) in A. hydrophila. We determined, using either mutation or sequence homology, roles for the majority of genes in the cluster by using the chemical O34-antigen LPS structure obtained for strain AH-3. The O34-antigen LPS export system has been shown to be a Wzy-dependent pathway typical of heteropolysaccharide pathways. Furthermore, the production of A. hydrophila O34-antigen LPS in Escherichia coli K-12 strains is dependent on incorporation of the Gne enzyme (UDP-N-acetylgalactosamine 4-epimerase) necessary for the formation of UDP-galactosamine in these strains. By using rapid amplification of cDNA ends we were able to identify a transcription start site upstream of the terminal wzz gene, which showed differential transcription depending on the growth temperature of the strain. The Wzz protein is able to regulate the O34-antigen LPS chain length. The differential expression of this protein at different temperatures, which was substantially greater at 20 degrees C than at 37 degrees C, explains the previously observed differential production of O34-antigen LPS and its correlation with the virulence of A. hydrophila serotype O34 strains.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aeromonas hydrophila / genetics*
  • Aeromonas hydrophila / metabolism
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Blotting, Southern
  • Carbohydrate Epimerases / genetics
  • Carbohydrate Epimerases / metabolism
  • Carbohydrate Sequence
  • Gene Expression Regulation, Bacterial
  • Models, Genetic
  • Molecular Sequence Data
  • Multigene Family*
  • O Antigens / chemistry
  • O Antigens / genetics*
  • O Antigens / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sequence Analysis, DNA
  • Temperature
  • Transcription, Genetic


  • Bacterial Proteins
  • O Antigens
  • Carbohydrate Epimerases