The role of two periplasmic copper- and zinc-cofactored superoxide dismutases in the virulence of Salmonella choleraesuis

• Published in: Microbiology (Society for General Microbiology) 2002-03, Vol.148 (3), p.719-726
• Main Authors: Sansone, Assunta, Watson, Patricia R, Wallis, Timothy S, Langford, Paul R, Kroll, J. Simon
• Format: Article
• Language: English
• Subjects: Animals; Bacteriology; Biological and medical sciences; Female; Fundamental and applied biological sciences. Psychology; Macrophages - microbiology; Mice; Mice, Inbred BALB C; Microbiology; Mutation; nitric oxide; Nitrogen - pharmacology; Oxygen - pharmacology; Pathogenicity, virulence, toxins, bacteriocins, pyrogens, host-bacteria relations, miscellaneous strains; Periplasm - enzymology; Salmonella - enzymology; Salmonella - genetics; Salmonella - growth & development; Salmonella - pathogenicity; Salmonella choleraesuis; Salmonella Infections, Animal - microbiology; Salmonella Infections, Animal - physiopathology; sodC gene; SodC protein; Superoxide Dismutase - genetics; Superoxide Dismutase - metabolism
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/00221287-148-3-719

Molecular Infectious Diseases Group, Department of Paediatrics, Faculty of Medicine, Imperial College, St Mary’s Hospital Campus, Norfolk Place, London W2 1PG, UK 1 Institute for Animal Health, Compton, Newbury, Berkshire, RG20 7NN, UK 2 Author for correspondence: J. Simon Kroll. Tel: [phone]. Fax: [phone]. e-mail: s.kroll{at}ic.ac.uk Periplasmic copper- and zinc-cofactored superoxide dismutases ([Cu,Zn]-SODs, SodC) of several Gram-negative pathogens can protect against superoxide-radical-mediated host defences, and thus contribute to virulence. This role has been previously defined for one [Cu,Zn]-SOD in various Salmonella serovars. Following the recent discovery of a second periplasmic [Cu,Zn]-SOD in Salmonella , the effect of knockout mutations in one or both of the original sodC-1 and the new sodC-2 on the virulence of the porcine pathogen Salmonella choleraesuis is investigated here. In comparison to wild-type, while sodC mutants – whether single or double – showed no impairment in growth, they all showed equally enhanced sensitivity to superoxide and a dramatically increased sensitivity to the combination of superoxide and nitric oxide in vitro . This observation had its correlate in experimental infection both ex vivo and in vivo. Mutation of sodC significantly impaired survival of S. choleraesuis in interferon -stimulated murine macrophages compared to wild-type organisms, and all S. choleraesuis sodC mutants persisted in significantly lower numbers than wild-type in BALB/c ( Ity s ) and C3H/HeN ( Ity r ) mice after experimental infection, but in no experimental system were sodC-1 sodC-2 double mutants more attenuated than either single mutant. These data suggest that both [Cu,Zn]-SODs are needed to protect bacterial periplasmic or membrane components. While SodC plays a role in S. choleraesuis virulence, the data presented here suggest that this is through overcoming a threshold effect, probably achieved by acquisition of sodC-1 on a bacteriophage. Loss of either sodC gene confers maximum vulnerability to superoxide on S. choleraesuis . Keywords: Superoxide dismutase, Salmonella , periplasm, bacterial [Cu,Zn]-SOD, bacterial virulence Abbreviations: [Cu,Zn]-SOD, copper- and zinc-cofactored superoxide dismutase; DEDC, diethyldithiocarbamate; FCS, foetal calf serum; IFN , interferon ; i.p., intraperitoneal; ROI/RNI, reactive oxygen/nitrogen intermediate; SOD, superoxide dismutase; SPER/NO, 2,2'-hydroxy-nitrosohydrazono bis-ethanamin