Bacterial copper‐ and zinc‐cofactored superoxide dismutase contributes to the pathogenesis of systemic salmonellosis

Abstract

SummaryCopper/zinc-cofactored superoxide dismutase ([Cu,Zn]-SOD) has been found in the periplasm of many bacterial species but its biological function is unknown. Here we report the cloning and characterization of sodC, encoding [Cu,Zn]-SOD, from Salmonella typhimurium. The predicted protein sequence shows only 58% identity to Escherichia coli SodC, and from this its chromosomal location and its immediate proximity to a phage gene, sodC, in Salmonella is speculated to have been acquired by bacteriophagemediated horizontal transfer from an unknown donor. A sodC mutant of S. typhimurium was unimpaired on aerobic growth in rich medium but showed enhanced sensitivity in vitro to the microbicidal action of superoxide. S. typhimurium, S. choleraesuis and S. dublin sodC mutants showed reduced lethality in a mouse model of oral infection and persisted in significantly lower numbers in livers and spleens after intraperitoneal infection, suggesting that [Cu,Zn]-SOD plays a role in pathogenicity, protecting Salmonella against oxygen radical-mediated host defences. There was, however, no observable difference compared with wild type in the interaction of sodC mutants with porcine pleural, mouse peritoneal or J774 macrophages in vitro, perhaps reflecting the hierarchical capacity of different macrophage lines to kill Salmonella, the most efficient overwhelming the proposed protective effect of periplasmic SOD.

Epitope tagging of chromosomal genes in Salmonella

“…Prophage Gifsy-2 encodes a superoxide dismutase, SodCI, implicated in bacterial protection against macrophage oxidative burst (35,36) and recently proposed to be involved in the ''avirulence'' phenotype conferred by another Gifsy-2 gene, grvA (33). Consistent with these findings, we show here that the sodCI gene is highly expressed during active proliferation of Salmonella in epithelial cells (Hep-2) and in murine spleens.…”

“…Two Gifsy-1 loci were chosen, both are at the right end of the prophage map: the gogB locus, which specifies a putative leucinerich protein similar to several type III-translocated proteins, and an unknown ORF named gogC (9). The Gifsy-2 genes that were tagged include the sodCI gene coding for a [Cu, Zn] superoxide dismutase implicated in virulence (30,35,36), an uncharacterized ORF named gtgE, and the gtgB gene (9). The latter, variably called sseI or srfH, is under the control of the SsrB activator protein and directs the synthesis of a protein translocated inside eukaryotic cells (24,34).…”

Presence of Copper- and Zinc-Containing Superoxide Dismutase in Commensal Haemophilus haemolyticus Isolates Can Be Used as a Marker To Discriminate Them from Nontypeable H. influenzae Isolates

“…Bacterial CuZnSODs are enzymes found in the periplasms of various gram-negative bacteria and, in the case of pathogens, are thought to have a role in the protection of organisms against host defense-derived free-radical-mediated damage (1,2,6,11,12,15,27). In extensive studies, we have established that capsulated or noncapsulated H. influenzae sensu stricto strains do not produce active CuZnSOD (11,12,14,16).…”

Copper- and zinc-containing superoxide dismutase (Cu/ZnSOD) is required for the protection of Candida albicans against oxidative stresses and the expression of its full virulence

“…Generally, SODs are categorized into four classes according to their metal cofactors -copper-and zinc-containing SOD (Cu\ ZnSOD), manganese-containing SOD (MnSOD), ironcontaining SOD (FeSOD) and nickel-containing SOD (Fridovich, 1989(Fridovich, , 1995Youn et al, 1996a, b). Cu\ ZnSOD is found mostly in the cytosol (Fridovich, 1989(Fridovich, , 1995 and mitochondria of eukaryotic cells (OkadoMatsumoto & Fridovich, 2001) and in the periplasmic space of some prokaryotes (Battistoni et al, 1998 ;Farrant et al, 1997 ;Wilks et al, 1998). This enzyme has been shown to play a role in protecting cells against oxygen toxicity (Fridovich, 1989(Fridovich, , 1995 and to act as a major repository for copper ions in virtually all eukaryotes (Culotta et al, 1995) ; however, the loss of Cu\ZnSOD activity has various pleiotropic consequences on organisms, which include slow growth, conditional auxotrophies and DNA damage (Fridovich, C.-S. others 1989, 1995).…”

“…For example, a Cu\ZnSOD-null yeast strain was shown to be oxygen-sensitive, hypermutable, auxotrophic for lysine and methionine and defective in sporulation (Liu et al, 1992). In some pathogenic organisms, Cu\ZnSOD has also been proposed as being a virulence determinant that could decompose the superoxide radical anions generated by phagocytic cells (Hong et al, 1992 ;Farrant et al, 1997 ;Wilks et al, 1998 ;Battistoni et al, 1998).…”