Q.82 A new isolate of a facultative anaerobe utilizes either oxygen or pyruvate as terminal electron acceptor.
This bacterium was grown either anaerobically with glucose as sole carbon source; or aerobically with lactose as the sole carbon source.
Net increase in ATP production (per mole of the carbon source) during the aerobic growth would be
ATP Yield Comparison in Facultative Anaerobes Using Oxygen vs Pyruvate
Facultative anaerobic bacteria can grow both in the presence and absence of oxygen.
Depending on the terminal electron acceptor used, the ATP yield per mole of carbon
source changes drastically. This article explains the net increase in ATP
production during aerobic growth in a facultative anaerobe.
Key Concepts
- Glycolysis
- Fermentation
- Aerobic respiration
- Terminal electron acceptors
- Disaccharide metabolism
Step-by-Step Solution
1. Anaerobic Growth on Glucose
Under anaerobic conditions, pyruvate acts as the terminal electron acceptor.
The metabolic pathway involved is glycolysis followed by fermentation.
ATP yield:
- Glycolysis: 2 ATP per glucose
- Fermentation: 0 ATP
Total ATP (anaerobic) = 2 ATP per mole of glucose
2. Aerobic Growth on Lactose
Lactose is a disaccharide composed of:
Lactose = Glucose + Galactose
Galactose is converted into glucose-6-phosphate and enters glycolysis.
Hence:
1 lactose = 2 glucose equivalents
Under aerobic conditions, complete oxidation occurs through glycolysis,
TCA cycle, and electron transport chain.
ATP yield per glucose:
1 glucose → 38 ATP
Therefore:
1 lactose → 2 × 38 = 76 ATP
Net Increase in ATP Production
Fold increase is calculated as:
(ATP during aerobic growth) / (ATP during anaerobic growth)
= 76 / 2 = 38
ATP Yield Summary
| Condition | Carbon Source | ATP Yield |
|---|---|---|
| Anaerobic | Glucose | 2 ATP |
| Aerobic | Lactose | 76 ATP |
| Net Increase | 38-fold | |
Final Answer
The net increase in ATP production during aerobic growth is 38-fold.
