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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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Sensitivity to copper chloride and invasion in MDCK epithelial cell line, with or without copper chloride stress.A) Optical density of overnight wild type S. Typhimurium, ΔscsABCD and different ΔtrxA mutants grown in the presence of CuCl2. B) The compromised invasion of a ΔtrxA deletion mutant can be trans-complemented with cloned trxA (pFA3) but not with a plasmid coding for catalytically inactive TrxA (pFA8). C) The scsABCD deletion acts as a suppressor mutation for the decreased invasion of the ΔtrxA mutant. D) and E) The viability of ΔscsABCD and ΔtrxA under CuCl2 stress (3 mM) is compromised, yet the invasiveness is highly enhanced at this concentration. F) shows fold changes in invasion of 3 mM CuCl2 treated culture relative to the untreated culture. ns = non-significant; * = p≤0.05; ** = p≤0.01; *** = p≤0.001.The error bars indicate standard error of the mean.
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pone-0064948-g004: Sensitivity to copper chloride and invasion in MDCK epithelial cell line, with or without copper chloride stress.A) Optical density of overnight wild type S. Typhimurium, ΔscsABCD and different ΔtrxA mutants grown in the presence of CuCl2. B) The compromised invasion of a ΔtrxA deletion mutant can be trans-complemented with cloned trxA (pFA3) but not with a plasmid coding for catalytically inactive TrxA (pFA8). C) The scsABCD deletion acts as a suppressor mutation for the decreased invasion of the ΔtrxA mutant. D) and E) The viability of ΔscsABCD and ΔtrxA under CuCl2 stress (3 mM) is compromised, yet the invasiveness is highly enhanced at this concentration. F) shows fold changes in invasion of 3 mM CuCl2 treated culture relative to the untreated culture. ns = non-significant; * = p≤0.05; ** = p≤0.01; *** = p≤0.001.The error bars indicate standard error of the mean.

Mentions: TrxA also contributes to copper tolerance in E. coli[30]. We thereby set out to test whether the presence of scsABCD genes made trxA dispensable for CuCl2 tolerance in S. Typhimurium. We noted a decreased CuCl2 tolerance of a S. Typhimurium ΔtrxA mutant that in magnitude equaled to that of the ΔscsABCD mutant (Fig. 4A). S. Typhimurium lacking trxA as well as the scsABCD genes did not show any further sensitization to CuCl2 (Fig. 4A).


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

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

Sensitivity to copper chloride and invasion in MDCK epithelial cell line, with or without copper chloride stress.A) Optical density of overnight wild type S. Typhimurium, ΔscsABCD and different ΔtrxA mutants grown in the presence of CuCl2. B) The compromised invasion of a ΔtrxA deletion mutant can be trans-complemented with cloned trxA (pFA3) but not with a plasmid coding for catalytically inactive TrxA (pFA8). C) The scsABCD deletion acts as a suppressor mutation for the decreased invasion of the ΔtrxA mutant. D) and E) The viability of ΔscsABCD and ΔtrxA under CuCl2 stress (3 mM) is compromised, yet the invasiveness is highly enhanced at this concentration. F) shows fold changes in invasion of 3 mM CuCl2 treated culture relative to the untreated culture. ns = non-significant; * = p≤0.05; ** = p≤0.01; *** = p≤0.001.The error bars indicate standard error of the mean.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0064948-g004: Sensitivity to copper chloride and invasion in MDCK epithelial cell line, with or without copper chloride stress.A) Optical density of overnight wild type S. Typhimurium, ΔscsABCD and different ΔtrxA mutants grown in the presence of CuCl2. B) The compromised invasion of a ΔtrxA deletion mutant can be trans-complemented with cloned trxA (pFA3) but not with a plasmid coding for catalytically inactive TrxA (pFA8). C) The scsABCD deletion acts as a suppressor mutation for the decreased invasion of the ΔtrxA mutant. D) and E) The viability of ΔscsABCD and ΔtrxA under CuCl2 stress (3 mM) is compromised, yet the invasiveness is highly enhanced at this concentration. F) shows fold changes in invasion of 3 mM CuCl2 treated culture relative to the untreated culture. ns = non-significant; * = p≤0.05; ** = p≤0.01; *** = p≤0.001.The error bars indicate standard error of the mean.
Mentions: TrxA also contributes to copper tolerance in E. coli[30]. We thereby set out to test whether the presence of scsABCD genes made trxA dispensable for CuCl2 tolerance in S. Typhimurium. We noted a decreased CuCl2 tolerance of a S. Typhimurium ΔtrxA mutant that in magnitude equaled to that of the ΔscsABCD mutant (Fig. 4A). S. Typhimurium lacking trxA as well as the scsABCD genes did not show any further sensitization to CuCl2 (Fig. 4A).

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