title: Molecular characterization of an Aeromonas salmonicida mutant with altered surface morphology and increased systemic virulence.
abstract: The asoA gene of Aeromonas salmonicida is located approximately 7 kb downstream of the A-layer structural gene, vapA. A 6 kb BamHI fragment containing asoA was cloned and marker-exchange mutagenesis using a kanamycin-resistance cassette was performed to generate an asoA mutation in the low-virulence strain A449L. When analysed by electron microscopy, the mutant A449L-MB exhibited an altered surface morphology. Strands and blebs of membranous material were observed protruding from the disorganized cell surface. This material was shown to contain lipopolysaccharide and A-layer subunit protein. The disorganization of the surface of A449L-MB had no apparent effect on virulence when the bacteria were administered to rainbow trout (Oncorhynchus mykiss) by bath immersion. However, when administered by intraperitoneal injection, the mutant A449L-MB was found to exhibit significantly increased virulence. The predicted amino acid sequence of AsoA shows homology to a number of polytopic membrane proteins involved in translocation across the cytoplasmic membrane.
authors.affiliation: Department of Biochemistry and Microbiology, University of Victoria, British Columbia, Canada.
authors.forename: B
authors.initials: B
authors.lastname: Noonan
authors.forename: T J
authors.initials: TJ
authors.lastname: Trust
mesh_terms: D000333:Aeromonas / Q000737:chemistry / Q000235:genetics* / Q000472:pathogenicity* / Q000648:ultrastructure; D000595:Amino Acid Sequence; D000818:Animals; D001345:Autoradiography; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D002462:Cell Membrane / Q000737:chemistry / Q000648:ultrastructure; D003001:Cloning, Molecular; D017124:Conserved Sequence; D005798:Genes, Bacterial; D007150:Immunohistochemistry; D008070:Lipopolysaccharides / Q000032:analysis; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D008969:Molecular Sequence Data; D016296:Mutagenesis; D017686:Oncorhynchus mykiss / Q000382:microbiology*; D010641:Phenotype; D017386:Sequence Homology, Amino Acid; D014774:Virulence
chemical_list: C093540:AsoA protein, Aeromonas salmonicida; D001426:Bacterial Proteins; D008070:Lipopolysaccharides; D008565:Membrane Proteins