Competition between hydrogen peroxide and nitrate for electrons from the respiratory chains of Thiosphaera pantotropha and Rhodobacter capsulatus

David J. Richardson, Stuart J. Ferguson

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


Thiosphaera pantotropha and some strains of Rhodobacter capsulatus express both a periplasmic nitrate reductase and cytochrome c peroxidase when grown under aerobic conditions. Harvested cell suspensions of either species can respire nitrate in the presence of 200 μM O2 (≈ 80% air saturation), at 70-80% of the anaerobic rate. Addition of hydrogen peroxide to such cells causes a 90% inhibition of nitrate reduction under anaerobic or aerobic conditions. The duration of the inhibition is proportional to the concentration of hydrogen peroxide added and can be ascribed to the expression of periplasmic peroxidases that compete with the nitrate reductase for electrons from the respiratory chain. The results reveal a hitherto unrecognised interaction between reactions of denitrification and the reduction of hydrogen peroxide by a periplasmic peroxidase that may have implications for the denitrification in microaerobic environments. The creation of aerobic conditions in bacterial cultures by addition of hydrogen peroxide, and relying on the generation of oxygen by endogenous catalase activity, is a commonly used technique for studying respiratory processes. The observations presented here demonstrate that results derived from such experiments should be interpreted with caution.

Original languageEnglish
Pages (from-to)125-129
Number of pages5
JournalFEMS Microbiology Letters
Issue number1-2
Publication statusPublished - 1 Oct 1995


  • Cytochrome c peroxidase
  • Denitrification
  • Nitrate reductase
  • Nitrate reduction
  • Periplasm
  • Rhodobacter capsulatus
  • Thiosphaera pantotropha

Cite this