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Role of the dpr product in oxygen tolerance in Streptococcus mutans.

ABSTRACT: We have previously identified and characterized the alkyl hydroperoxide reductase of Streptococcus mutans, which consists of two components, Nox-1 and AhpC. Deletion of both nox-1 and ahpC had no effect on the sensitivity of S. mutans to cumene hydroperoxide or H(2)O(2), implying that the existence of another antioxidant system(s) independent of the Nox-1-AhpC system compensates for the deficiency. Here, a new antioxidant gene (dpr for Dps-like peroxide resistance gene) was isolated from the S. mutans chromosome by its ability to complement an ahpCF deletion mutant of Escherichia coli with a tert-butyl hydroperoxide-hypersensitive phenotype. The dpr gene complemented the defect in peroxidase activity caused by the deletion of nox-1 and ahpC in S. mutans. Under aerobic conditions, the dpr disruption mutant carrying a spectinomycin resistance gene (dpr::Spc(r) mutant) grew as well as wild-type S. mutans in liquid medium. However, the dpr::Spc(r) mutant could not form colonies on an agar plate under air. In addition, neither the dpr::Spc(r) ahpC::Em(r)::nox-1 triple mutant nor the dpr::Spc(r) sod::Em(r) double mutant was able to grow aerobically in liquid medium. The 20-kDa dpr gene product Dpr is an iron-binding protein. Synthesis of Dpr was induced by exposure of S. mutans cells to air. We propose a mechanism by which Dpr confers aerotolerance on S. mutans.

SUBMITTER: Yamamoto Y

PROVIDER: S-EPMC94545 | biostudies-literature | 2000 Jul

REPOSITORIES: biostudies-literature

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Role of the dpr product in oxygen tolerance in Streptococcus mutans.

Yamamoto Y Y Higuchi M M Poole L B LB Kamio Y Y

Journal of bacteriology 20000701 13

We have previously identified and characterized the alkyl hydroperoxide reductase of Streptococcus mutans, which consists of two components, Nox-1 and AhpC. Deletion of both nox-1 and ahpC had no effect on the sensitivity of S. mutans to cumene hydroperoxide or H(2)O(2), implying that the existence of another antioxidant system(s) independent of the Nox-1-AhpC system compensates for the deficiency. Here, a new antioxidant gene (dpr for Dps-like peroxide resistance gene) was isolated from the S. ...[more]

PMID: 10850989

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Project description:The Dps-like peroxide resistance protein (Dpr) is essential for H2O2 stress tolerance and aerobic growth of the oral pathogen Streptococcus mutans Dpr accumulates during oxidative stress, protecting the cell by sequestering iron ions and thereby preventing the generation of toxic hydroxyl radicals that result from the interaction of iron with H2O2 Previously, we reported that the SpxA1 and SpxA2 regulators positively regulate expression of dpr in S. mutans Using an antibody raised against S. mutans Dpr, we confirmed at the protein level the central and cooperative nature of SpxA1 and SpxA2 regulation in Dpr production. During phenotypic characterization of the S. mutans Δdpr strain, we observed the appearance of distinct colony variants, which sometimes lost the oxidative stress sensitivity typical of Δdpr strains. Whole-genome sequencing of these phenotypically distinct Δdpr isolates revealed that a putative iron transporter operon, smu995-smu998, was a genomic hot spot with multiple single nucleotide polymorphisms identified within the different isolates. Deletion of smu995 or the entire smu995-smu998 operon in the Δdpr background strain completely reversed the oxidative stress-sensitive phenotypes associated with dpr inactivation. Conversely, inactivation of genes encoding the ferrous iron transport system FeoABC did not alleviate phenotypes of the Δdpr strain. Preliminary characterization of strains lacking smu995-smu998, feoABC, and the iron/manganese transporter gene sloABC revealed the interactive nature of these three systems in iron transport but also indicated that there may be additional iron uptake systems in S. mutansIMPORTANCE The dental caries-associated pathogen Streptococcus mutans routinely encounters oxidative stress within the human plaque biofilm. Previous studies revealed that the iron-binding protein Dpr confers protection toward oxidative stress by limiting free iron availability, which is associated with the generation of toxic hydroxyl radicals. Here, we report the identification of spontaneously occurring mutations within Δdpr strains. Several of those mutations were mapped to the operon smu995-smu998, revealing a previously uncharacterized system that appears to be important in iron acquisition. Disruption of the smu995-smu998 operon resulted in reversion of the stress-sensitive phenotype typical of a Δdpr strain. Our data suggest that the Smu995-Smu998 system works along with other known metal transport systems of S. mutans, i.e., FeoABC and SloABC, to coordinate iron uptake.

Dataset Information

Role of the dpr product in oxygen tolerance in Streptococcus mutans.

Publications

Role of the dpr product in oxygen tolerance in Streptococcus mutans.

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