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Oxidative stress tolerance is manganese (Mn(2+)) regulated in Streptococcus gordonii
Nicholas S Jakubovics1, Anthony W Smith2, Howard F Jenkinson1
1Oral Microbiology Unit, Department of Oral and Dental Science, University of Bristol Dental School, Lower Maudlin Street, Bristol BS1 2LY, UK1.
Abstract:
The Sca permease in the oral bacterium Streptococcus gordonii is a member of a family of ATP-binding cassette (ABC)-type transporters for manganese (Mn(2+)) and related cations that are associated with streptococcal virulence in a number of infection models. Since Mn(2+) has a protective function against oxidative damage in a variety of bacteria, we have investigated the role of Sca permease in oxidative stress tolerance in Streptococcus gordonii. A single Mn(2+)-dependent superoxide dismutase (SOD), encoded by sodA, is expressed by S. gordonii and was >10-fold up-regulated under oxidative stress conditions. Inactivation of sodA resulted in increased susceptibility of S. gordonii cells to growth inhibition by dioxygen (O(2)), and to killing by paraquat (a superoxide anion generator) and by hydrogen peroxide (H(2)O(2)). Expression of thiol peroxidase, encoded by the tpx gene located immediately downstream of the scaCBA operon, was also up-regulated under oxidative conditions. Inactivation of tpx led to increased susceptibility of cells to H(2)O(2), but not to O(2) or paraquat. In low-Mn(2+) medium (0.01 micro M Mn(2+)) sodA and tpx genes were transcriptionally down-regulated, SOD activity was reduced and cells were more sensitive to growth inhibition by O(2). A Sca permease-deficient (scaC) mutant showed further reduced SOD activity and hypersensitivity to O(2) in medium containing <0.1 micro M Mn(2+). These results demonstrate that the Sca (Mn(2+)) permease in S. gordonii is essential for protection against oxidative stress.
Insights
The Sca permease in Streptococcus gordonii is crucial for protecting against oxidative stress by transporting manganese (Mn2+). This transporter is essential for the function of superoxide dismutase (SOD) and overall bacterial survival under oxidative conditions.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Streptococcus gordonii is an oral bacterium.
- Manganese (Mn2+) is known to protect bacteria against oxidative damage.
- The Sca permease is an ATP-binding cassette (ABC)-type transporter involved in cation transport and linked to streptococcal virulence.
Purpose of the Study:
- To investigate the role of the Sca permease in oxidative stress tolerance in Streptococcus gordonii.
- To understand the relationship between manganese transport, superoxide dismutase (SOD) activity, and bacterial defense mechanisms against reactive oxygen species.
Main Methods:
- Genetic manipulation of Streptococcus gordonii to create mutants deficient in Sca permease (scaC) and superoxide dismutase (sodA).
- Analysis of gene expression (sodA, tpx) under varying oxidative stress conditions and manganese concentrations.
- Measurement of superoxide dismutase (SOD) activity in wild-type and mutant strains.
- Assessment of bacterial susceptibility to oxidative agents like dioxygen (O2), paraquat, and hydrogen peroxide (H2O2).
Main Results:
- Inactivation of sodA increased susceptibility to oxidative stress, highlighting the importance of Mn(2+)-dependent SOD.
- Thiol peroxidase (tpx) expression was upregulated under oxidative stress, contributing to H2O2 resistance.
- Low manganese availability led to downregulation of sodA and tpx, reduced SOD activity, and increased sensitivity to O2.
- A Sca permease-deficient mutant exhibited further reduced SOD activity and hypersensitivity to O2, especially in low-manganese conditions.
Conclusions:
- The Sca permease is essential for manganese uptake in Streptococcus gordonii.
- Manganese transport via Sca permease is critical for maintaining SOD activity and providing protection against oxidative stress.
- The Sca permease plays a vital role in the survival of Streptococcus gordonii under conditions of oxidative challenge.