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Nitrate reduction as a marker for hypoxic shiftdown of Mycobacterium tuberculosis
1Medical Research Service, Department of Veterans Affairs Medical Center, Long Beach, California 90822, USA.
Tubercle and Lung Disease : the Official Journal of the International Union Against Tuberculosis and Lung Disease
|January 25, 2000
Summary
Nitrate reduction increases in Mycobacterium tuberculosis during hypoxic shiftdown to non-replicating persistence (NRP). This hypoxically induced nitrate reduction supports survival in oxygen-depleted tissues and serves as a marker for NRP.
Area of Science:
- Microbiology
- Tuberculosis Research
- Bacterial Physiology
Background:
- Mycobacterium tuberculosis (M.tb.) exhibits complex metabolic adaptations to survive host-imposed stresses.
- Understanding M.tb. persistence mechanisms is crucial for developing effective tuberculosis treatments.
Purpose of the Study:
- To characterize nitrate reduction kinetics in M.tb. during aerobic growth and transition to non-replicating persistence (NRP).
- To investigate the role of nitrate reduction in M.tb. survival under hypoxic conditions.
Main Methods:
- In vitro cultures of M.tb. were used to measure nitrate reduction rates.
- Cultures were subjected to aerobic growth and hypoxic shiftdown to NRP stages 1 and 2.
- Nitrate and nitrite concentrations were monitored over time.
Main Results:
- Aerobically growing M.tb. reduced nitrate proportionally to substrate concentration.
- Hypoxic shiftdown induced a marked, substrate-independent increase in nitrate reduction, inhibited by high nitrite levels.
- Nitrate reduction initiation varied based on the timing of nitrate availability during shiftdown.
Conclusions:
- Hypoxically induced nitrate reduction likely functions as a respiratory process supporting M.tb. entry into non-replicating persistence.
- This metabolic shift aids M.tb. survival in oxygen-limited environments within inflammatory tissues.
- Nitrate reduction serves as a potential biomarker for monitoring M.tb. hypoxic adaptation.
