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Oxidoreductases that act as conditional virulence suppressors in Salmonella enterica serovar Typhimurium.

Anwar N, Sem XH, Rhen M - PLoS ONE (2013)

Bottom Line: However, we noted a significant copper chloride sensitivity of SPI1 T3SS mediated invasiveness that strongly depended on the presence of the scs genes.Our findings thus demonstrate that the scs gene cluster conditionally affects virulence and underscore the complex interactions between oxidoreductases of the thioredoxin superfamily in maintaining host adaptation of S.Typhimurium.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.

ABSTRACT
In Salmonella enterica serovar Typhimurium, oxidoreductases of the thioredoxin superfamily contribute to bacterial invasiveness, intracellular replication and to the virulence in BALB/c mice as well as in the soil nematode Caenorhabditis elegans. The scsABCD gene cluster, present in many but not all enteric bacteria, codes for four putative oxidoreductases of the thioredoxin superfamily. Here we have analyzed the potential role of the scs genes in oxidative stress tolerance and virulence in S. Typhimurium. An scsABCD deletion mutant showed moderate sensitization to the redox-active transition metal ion copper and increased protein carbonylation upon exposure to hydrogen peroxide. Still, the scsABCD mutant was not significantly affected for invasiveness or intracellular replication in respectively cultured epithelial or macrophage-like cells. However, we noted a significant copper chloride sensitivity of SPI1 T3SS mediated invasiveness that strongly depended on the presence of the scs genes. The scsABCD deletion mutant was not attenuated in animal infection models. In contrast, the mutant showed a moderate increase in its competitive index upon intraperitoneal challenge and enhanced invasiveness in small intestinal ileal loops of BALB/c mice. Moreover, deletion of the scsABCD genes restored the invasiveness of a trxA mutant in epithelial cells and its virulence in C. elegans. Our findings thus demonstrate that the scs gene cluster conditionally affects virulence and underscore the complex interactions between oxidoreductases of the thioredoxin superfamily in maintaining host adaptation of S. Typhimurium.

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In silico analyses and localization of the ScsABCD proteins.A) Illustrates the cbpA-agp genomic region in selected strains of Eschericia coli (E. coli), Yersinia enterocolitica (Y. enterocolitica) and Salmonella enterica (S. enterica); * No cbpA or agp present. B) and C) detail and compare the Cys-X-X-Cys motives of Scs proteins with the prototype TrxA and their variability in predicted SccB and ScsD proteins. D) shows Coomassie blue stained 12%SDS-polyacrylamide gels presenting sub-cellular fractionation of the proteins E) presents immunoblot with anti-His to show the localization of Scs proteins in different subcellular fractions. In (D) and (E), cyt = cytoplasmic fraction; Tx-100 =  Triton X-100 soluble fraction; PP = periplasmic fraction and OM = Tx-100 insoluble integral outer membrane fraction. 1 =  WT/pET32a; 2 =  scsB clone (pNA15), 3 =  scsC clone (pNA16) and 4 =  scsD clone (pNA17).
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pone-0064948-g001: In silico analyses and localization of the ScsABCD proteins.A) Illustrates the cbpA-agp genomic region in selected strains of Eschericia coli (E. coli), Yersinia enterocolitica (Y. enterocolitica) and Salmonella enterica (S. enterica); * No cbpA or agp present. B) and C) detail and compare the Cys-X-X-Cys motives of Scs proteins with the prototype TrxA and their variability in predicted SccB and ScsD proteins. D) shows Coomassie blue stained 12%SDS-polyacrylamide gels presenting sub-cellular fractionation of the proteins E) presents immunoblot with anti-His to show the localization of Scs proteins in different subcellular fractions. In (D) and (E), cyt = cytoplasmic fraction; Tx-100 =  Triton X-100 soluble fraction; PP = periplasmic fraction and OM = Tx-100 insoluble integral outer membrane fraction. 1 =  WT/pET32a; 2 =  scsB clone (pNA15), 3 =  scsC clone (pNA16) and 4 =  scsD clone (pNA17).

Mentions: Many of the oxidoreductases such as TrxA, DsbA and thiol peroxidase Tpx implicated in virulence of S. Typhimurium and in redox tolerance of E. coli, are highly conserved within enterobacteria [15], [18], [23]. In contrast to laboratory E. coli strains, S. Typhimurium includes the scsABCD gene cluster that encodes four proteins each with a Cys-X-X-Cys motif characteristic for the thioredoxin superfamily [24] (Figs. 1A and 1B). When cloned into E. coli, the scs genes restore copper tolerance of selected copper-sensitive mutants [24]. However, the actual role of the scs genes for redox tolerance in S. Typhimurium and their contribution to virulence, if any, has remained enigmatic. Here we demonstrate that a S. Typhimurium scsABCD deletion mutant shows moderate sensitization to copper chloride and, surprisingly, a conditional enhanced invasiveness in epithelial cells and virulence in C. elegans.


Oxidoreductases that act as conditional virulence suppressors in Salmonella enterica serovar Typhimurium.

Anwar N, Sem XH, Rhen M - PLoS ONE (2013)

In silico analyses and localization of the ScsABCD proteins.A) Illustrates the cbpA-agp genomic region in selected strains of Eschericia coli (E. coli), Yersinia enterocolitica (Y. enterocolitica) and Salmonella enterica (S. enterica); * No cbpA or agp present. B) and C) detail and compare the Cys-X-X-Cys motives of Scs proteins with the prototype TrxA and their variability in predicted SccB and ScsD proteins. D) shows Coomassie blue stained 12%SDS-polyacrylamide gels presenting sub-cellular fractionation of the proteins E) presents immunoblot with anti-His to show the localization of Scs proteins in different subcellular fractions. In (D) and (E), cyt = cytoplasmic fraction; Tx-100 =  Triton X-100 soluble fraction; PP = periplasmic fraction and OM = Tx-100 insoluble integral outer membrane fraction. 1 =  WT/pET32a; 2 =  scsB clone (pNA15), 3 =  scsC clone (pNA16) and 4 =  scsD clone (pNA17).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3672137&req=5

pone-0064948-g001: In silico analyses and localization of the ScsABCD proteins.A) Illustrates the cbpA-agp genomic region in selected strains of Eschericia coli (E. coli), Yersinia enterocolitica (Y. enterocolitica) and Salmonella enterica (S. enterica); * No cbpA or agp present. B) and C) detail and compare the Cys-X-X-Cys motives of Scs proteins with the prototype TrxA and their variability in predicted SccB and ScsD proteins. D) shows Coomassie blue stained 12%SDS-polyacrylamide gels presenting sub-cellular fractionation of the proteins E) presents immunoblot with anti-His to show the localization of Scs proteins in different subcellular fractions. In (D) and (E), cyt = cytoplasmic fraction; Tx-100 =  Triton X-100 soluble fraction; PP = periplasmic fraction and OM = Tx-100 insoluble integral outer membrane fraction. 1 =  WT/pET32a; 2 =  scsB clone (pNA15), 3 =  scsC clone (pNA16) and 4 =  scsD clone (pNA17).
Mentions: Many of the oxidoreductases such as TrxA, DsbA and thiol peroxidase Tpx implicated in virulence of S. Typhimurium and in redox tolerance of E. coli, are highly conserved within enterobacteria [15], [18], [23]. In contrast to laboratory E. coli strains, S. Typhimurium includes the scsABCD gene cluster that encodes four proteins each with a Cys-X-X-Cys motif characteristic for the thioredoxin superfamily [24] (Figs. 1A and 1B). When cloned into E. coli, the scs genes restore copper tolerance of selected copper-sensitive mutants [24]. However, the actual role of the scs genes for redox tolerance in S. Typhimurium and their contribution to virulence, if any, has remained enigmatic. Here we demonstrate that a S. Typhimurium scsABCD deletion mutant shows moderate sensitization to copper chloride and, surprisingly, a conditional enhanced invasiveness in epithelial cells and virulence in C. elegans.

Bottom Line: However, we noted a significant copper chloride sensitivity of SPI1 T3SS mediated invasiveness that strongly depended on the presence of the scs genes.Our findings thus demonstrate that the scs gene cluster conditionally affects virulence and underscore the complex interactions between oxidoreductases of the thioredoxin superfamily in maintaining host adaptation of S.Typhimurium.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.

ABSTRACT
In Salmonella enterica serovar Typhimurium, oxidoreductases of the thioredoxin superfamily contribute to bacterial invasiveness, intracellular replication and to the virulence in BALB/c mice as well as in the soil nematode Caenorhabditis elegans. The scsABCD gene cluster, present in many but not all enteric bacteria, codes for four putative oxidoreductases of the thioredoxin superfamily. Here we have analyzed the potential role of the scs genes in oxidative stress tolerance and virulence in S. Typhimurium. An scsABCD deletion mutant showed moderate sensitization to the redox-active transition metal ion copper and increased protein carbonylation upon exposure to hydrogen peroxide. Still, the scsABCD mutant was not significantly affected for invasiveness or intracellular replication in respectively cultured epithelial or macrophage-like cells. However, we noted a significant copper chloride sensitivity of SPI1 T3SS mediated invasiveness that strongly depended on the presence of the scs genes. The scsABCD deletion mutant was not attenuated in animal infection models. In contrast, the mutant showed a moderate increase in its competitive index upon intraperitoneal challenge and enhanced invasiveness in small intestinal ileal loops of BALB/c mice. Moreover, deletion of the scsABCD genes restored the invasiveness of a trxA mutant in epithelial cells and its virulence in C. elegans. Our findings thus demonstrate that the scs gene cluster conditionally affects virulence and underscore the complex interactions between oxidoreductases of the thioredoxin superfamily in maintaining host adaptation of S. Typhimurium.

Show MeSH
Related in: MedlinePlus