title: The Aeromonas hydrophila wb*O34 gene cluster: genetics and temperature regulation.
abstract: 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.
authors.affiliation: Departamento Microbiología, Facultad Biología, Universidad Barcelona, Diagonal 645, 08071 Barcelona. Spain.
authors.forename: Natalia
authors.initials: N
authors.lastname: Jimenez
authors.forename: Rocío
authors.initials: R
authors.lastname: Canals
authors.forename: María Teresa
authors.initials: MT
authors.lastname: Saló
authors.forename: Silvia
authors.initials: S
authors.lastname: Vilches
authors.forename: Susana
authors.initials: S
authors.lastname: Merino
authors.forename: Juan M
authors.initials: JM
authors.lastname: Tomás
mesh_terms: D016980:Aeromonas hydrophila / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D015139:Blotting, Southern; D002238:Carbohydrate Epimerases / Q000235:genetics / Q000378:metabolism; D002240:Carbohydrate Sequence; D015964:Gene Expression Regulation, Bacterial; D008957:Models, Genetic; D008969:Molecular Sequence Data; D005810:Multigene Family; D019081:O Antigens / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D013696:Temperature; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D019081:O Antigens; D002238:Carbohydrate Epimerases