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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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Virulence and ROS dissemination are restored in C. elegans by removing ΔscsABCD in the ΔtrxA mutant.A) Survival of wild-type N2 nematodes was compared when infected with S. Typhimurium 14028 wild-type, ΔtrxA, ΔscsABCD or the ΔscsABCD/ΔtrxA mutant. B to I). Nematodes were harvested 48 or 72 hours post infection and stained with H2DCFDA to detect intracellular ROS. In these images, ROS is shown in green and intestinal autofluorescence in blue. Images are shown at 40x magnification and are representative of at least 20 nematodes from 2 independent assays. J) Florescence intensities are compared with wild type and between different mutants. ns = non-significant, ** = p≤0.01, **** = p≤0.0001. Error bars indicate the standard error of the mean.
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pone-0064948-g007: Virulence and ROS dissemination are restored in C. elegans by removing ΔscsABCD in the ΔtrxA mutant.A) Survival of wild-type N2 nematodes was compared when infected with S. Typhimurium 14028 wild-type, ΔtrxA, ΔscsABCD or the ΔscsABCD/ΔtrxA mutant. B to I). Nematodes were harvested 48 or 72 hours post infection and stained with H2DCFDA to detect intracellular ROS. In these images, ROS is shown in green and intestinal autofluorescence in blue. Images are shown at 40x magnification and are representative of at least 20 nematodes from 2 independent assays. J) Florescence intensities are compared with wild type and between different mutants. ns = non-significant, ** = p≤0.01, **** = p≤0.0001. Error bars indicate the standard error of the mean.

Mentions: C. elegans infected with the ΔscsABCD mutant of S. Typhimurium behaved as nematodes infected with the wild type regarding life span (Fig. 7A). Still, transfer of the scsABCD deletion into the ΔtrxA mutant resulted in retrieved virulence as evidenced by a shortening of the nematode life span (Fig. 7A).


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

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

Virulence and ROS dissemination are restored in C. elegans by removing ΔscsABCD in the ΔtrxA mutant.A) Survival of wild-type N2 nematodes was compared when infected with S. Typhimurium 14028 wild-type, ΔtrxA, ΔscsABCD or the ΔscsABCD/ΔtrxA mutant. B to I). Nematodes were harvested 48 or 72 hours post infection and stained with H2DCFDA to detect intracellular ROS. In these images, ROS is shown in green and intestinal autofluorescence in blue. Images are shown at 40x magnification and are representative of at least 20 nematodes from 2 independent assays. J) Florescence intensities are compared with wild type and between different mutants. ns = non-significant, ** = p≤0.01, **** = p≤0.0001. Error bars indicate the standard error of the mean.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0064948-g007: Virulence and ROS dissemination are restored in C. elegans by removing ΔscsABCD in the ΔtrxA mutant.A) Survival of wild-type N2 nematodes was compared when infected with S. Typhimurium 14028 wild-type, ΔtrxA, ΔscsABCD or the ΔscsABCD/ΔtrxA mutant. B to I). Nematodes were harvested 48 or 72 hours post infection and stained with H2DCFDA to detect intracellular ROS. In these images, ROS is shown in green and intestinal autofluorescence in blue. Images are shown at 40x magnification and are representative of at least 20 nematodes from 2 independent assays. J) Florescence intensities are compared with wild type and between different mutants. ns = non-significant, ** = p≤0.01, **** = p≤0.0001. Error bars indicate the standard error of the mean.
Mentions: C. elegans infected with the ΔscsABCD mutant of S. Typhimurium behaved as nematodes infected with the wild type regarding life span (Fig. 7A). Still, transfer of the scsABCD deletion into the ΔtrxA mutant resulted in retrieved virulence as evidenced by a shortening of the nematode life span (Fig. 7A).

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