Expression of and secretion through the Aeromonas salmonicida type III secretion system

• Published in: Microbiology (Society for General Microbiology) 2006-05, Vol.152 (5), p.1275-1286
• Main Authors: Ebanks, Roger O, Knickle, Leah C, Goguen, Michel, Boyd, Jessica M, Pinto, Devanand M, Reith, Michael, Ross, Neil W
• Format: Article
• Language: English
• Subjects: Aeromonas salmonicida; Aeromonas salmonicida - genetics; Aeromonas salmonicida - growth & development; Aeromonas salmonicida - metabolism; Animals; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Bacteriology; Biological and medical sciences; Calcium - pharmacology; Electrophoresis, Gel, Two-Dimensional; Electrophoresis, Polyacrylamide Gel; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Bacterial; Genetics; Iron - pharmacology; Metabolism. Enzymes; Microbiology; Pathogenicity, virulence, toxins, bacteriocins, pyrogens, host-bacteria relations, miscellaneous strains; Peritoneal Cavity - microbiology; Plasmids; Protein Transport - genetics; Proteome - analysis; Reverse Transcriptase Polymerase Chain Reaction; RNA, Bacterial - biosynthesis; RNA, Messenger - biosynthesis; Salmo salar - microbiology; Salmonidae; Sodium Chloride - pharmacology; Temperature; Transcription, Genetic; Virulence Factors - genetics; Virulence Factors - metabolism
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/mic.0.28485-0

National Research Council Canada – Institute for Marine Biosciences, 1411 Oxford Street, Halifax, NS, B3H 3Z1, Canada Correspondence Roger Ebanks roger.ebanks{at}nrc-cnrc.gc.ca Aeromonas salmonicida subsp. salmonicida is the aetiological agent of furunculosis, a disease of farmed and wild salmonids. The type III secretion system (TTSS) is one of the primary virulence factors in A. salmonicida . Using a combination of differential proteomic analysis and reverse transcriptase (RT)-PCR, it is shown that A. salmonicida A449 induces the expression of TTSS proteins at 28 °C, but not at its more natural growth temperature of 17 °C. More modest increases in expression occur at 24 °C. This temperature-induced up-regulation of the TTSS in A. salmonicida A449 occurs within 30 min of a growth temperature increase from 16 to 28 °C. Growth conditions such as low-iron, low pH, low calcium, growth within the peritoneal cavity of salmon and growth to high cell densities do not induce the expression of the TTSS in A. salmonicida A449. The only other known growth condition that induces expression of the TTSS is growth of the bacterium at 16 °C in salt concentrations ranging from 0·19 to 0·38 M NaCl. It is also shown that growth at 28 °C followed by exposure to low calcium results in the secretion of one of the TTSS effector proteins. This study presents a simple in vitro model for the expression of TTSS proteins in A. salmonicida . Abbreviations: ACN, acetonitrile; 2-DE, 2-dimensional gel electrophoresis; OMP, outer-membrane protein; TTSS, type III secretion system Present address: Fisheries and Oceans Canada/Pêches et Océans Canada, 343 Université Ave, Moncton NB, E1C 5K4, Canada.