title: Interaction of the fish pathogen Aeromonas salmonicida with rainbow trout macrophages.
abstract: A procedure was developed to culture rainbow trout macrophages (M phi) on supported glass coverslips. Using this method and a variety of well-characterized Aeromonas salmonicida strains with normal or altered cell surfaces, we investigated the role of this unusual bacterial surface in the bacterium-M phi interaction. An intact crystalline protein array, the A-layer, mediated adherence of A. salmonicida cells to M phi even in the absence of opsonins. In contrast, unopsonized cells of an A-layer-negative (A-) mutant with a smooth lipopolysaccharide (LPS) layer were unable to interact with M phi. However, this ability was recovered when the A-layer was reconstituted onto the smooth LPS surface of these A- LPS+ cells. Two A. salmonicida mutants possessing the A-layer in different disorganized states had a reduced ability to interact with M phi. A+ cells grown under calcium limitation produced A-layers locked into an alternative conformation which mediated the highest levels of M phi association in the absence of opsonins or any other surface coating. Coating A+ cells with hemin greatly increased their levels of M phi association, and bacterial cells grown on trout blood agar plates also had a dramatic increase in their ability to interact with M phi. Only A+ A. salmonicida cells were highly cytotoxic to trout M phi, especially after being coated with hemin, presumably due to a more focused targeting of the bacterial cell onto the M phi surface and/or into the intracellular regions of the M phi.
authors.affiliation: Department of Biochemistry and Microbiology, University of Victoria, British Columbia, Canada.
authors.forename: R A
authors.initials: RA
authors.lastname: Garduño
authors.forename: W W
authors.initials: WW
authors.lastname: Kay
mesh_terms: D000333:Aeromonas / Q000276:immunology* / Q000648:ultrastructure; D000818:Animals; D001422:Bacterial Adhesion; D001770:Blood Bactericidal Activity; D002478:Cells, Cultured; D006427:Hemin / Q000378:metabolism; D066298:In Vitro Techniques; D008264:Macrophages / Q000382:microbiology*; D008855:Microscopy, Electron, Scanning; D012474:Salmon / Q000276:immunology*
chemical_list: D006427:Hemin