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Regulation of the intracellular free iron pool by Dpr provides oxygen tolerance to Streptococcus mutans

Yuji Yamamoto1, Kôichi Fukui, Naoko Koujin

  • 1Department of Microbial Biotechnology, Graduate School of Agricultural Science, Tohoku University, Aoba-ku, Sendai 981-8555, Japan.

Journal of Bacteriology
|September 3, 2004
PubMed

Insights

The Dpr protein in Streptococcus mutans sequesters iron to prevent toxic radical formation, enabling oxygen tolerance. A dpr mutant shows decreased viability and DNA damage when exposed to air, highlighting Dpr's essential role.

Area of Science:

  • Microbiology
  • Biochemistry
  • Oxidative Stress

Background:

  • Dpr is an iron-binding protein crucial for oxygen tolerance in Streptococcus mutans.
  • Previous research suggested Dpr prevents toxic radical generation by sequestering intracellular iron.
  • Intracellular free iron can catalyze the formation of harmful reactive oxygen species.

Purpose of the Study:

  • To investigate the intracellular free iron levels in wild-type (WT) and dpr mutant strains of S. mutans.
  • To determine the role of Dpr in regulating intracellular iron under aerobic conditions.
  • To assess the impact of Dpr deficiency on S. mutans viability and genomic integrity upon air exposure.

Main Methods:

  • Electron spin resonance (ESR) spectrometry was used to measure intracellular free iron concentrations.
  • S. mutans WT and dpr mutant strains were analyzed under both anaerobic and aerobic conditions.
  • Cell viability and genomic DNA degradation were assessed after exposure to air.

Main Results:

  • Under anaerobic conditions, dpr mutants had higher free iron levels (333.0 microM) than WT (225.9 microM).
  • Exposure to air induced Dpr expression in WT, reducing intracellular iron to 22.5 microM.
  • dpr mutants exposed to air maintained high iron levels (230.3 microM), showing decreased viability and DNA damage.

Conclusions:

  • Regulation of the intracellular free iron pool by the Dpr protein is essential for oxygen tolerance in S. mutans.
  • Dpr functions by reducing the availability of free iron that can generate toxic radicals under aerobic conditions.
  • Loss of Dpr function compromises bacterial survival and genomic stability in the presence of oxygen.

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