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The bioenergetics of denitrification
Antonie Van Leeuwenhoek
|January 1, 1982
Summary
Paracoccus denitrificans uses cytochromes b and c for anaerobic respiration, linking nitrate reduction to the respiratory chain. Energy conservation efficiency depends on reductase location and proton translocation, aligning with growth yield studies.
Area of Science:
- Microbiology
- Biochemistry
- Bioenergetics
Background:
- Dissimilatory nitrate reductase in Paracoccus denitrificans links to the respiratory chain via cytochromes b.
- Electron transport to nitrite and nitrous oxide involves c-type cytochromes.
Purpose of the Study:
- To elucidate the electron transport pathways and energy conservation mechanisms during anaerobic respiration in Paracoccus denitrificans.
- To investigate the role of proton translocation and reductase location in respiratory efficiency.
Main Methods:
- Analysis of electron transport chains involving cytochromes.
- Investigation of proton translocation across the inner membrane.
- Characterization of nitrate transport systems.
- Growth yield studies in chemostat cultures.
Main Results:
- Electron transport from NADH to nitrate involves one phosphorylation site, while transport to oxygen, nitrite, and nitrous oxide involves two.
- Proton utilization differs for reduction of oxygen/nitrate (cytoplasmic) versus nitrite/nitrous oxide (periplasmic).
- Two nitrate transport systems were identified: one proton motive force-driven and a nitrate-nitrite antiport system.
- Proton translocation during NADH oxidation is similar for nitrogenous oxides (67-71% of oxygen transfer).
Conclusions:
- Respiratory chain presentation as linear is misleading; reductase location impacts energy conservation efficiency.
- Proton translocation and electron transport mechanisms explain observed growth yields.
- Findings provide a comprehensive scheme for proton and electron flow in Paracoccus denitrificans anaerobic respiration.