Q.38 Which one of the following is an obligate anaerobe
- Halobacterium
- Thermus aquaticus
- Chlamydomonas nivalis
- Clostridium
Clostridium is the obligate anaerobe among the options. These bacteria cannot tolerate oxygen due to lacking detoxifying enzymes like superoxide dismutase.
Question Analysis
Obligate anaerobes grow only in oxygen-free environments, using fermentation or anaerobic respiration. They die in oxygen’s presence from toxic reactive oxygen species (ROS).
Option Breakdown
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Halobacterium: Extreme halophile archaeon thriving in high-salt, aerobic hypersaline conditions like salt lakes. Requires oxygen for respiration.
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Thermus aquaticus: Thermophilic bacterium from hot springs, aerobic or facultative, famous for Taq polymerase in PCR. Grows with oxygen.
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Chlamydomonas nivalis: Snow algae (chlorophyte) photosynthetic in aerobic cold environments like alpine snow. Uses oxygen and produces it via photosynthesis.
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Clostridium: Gram-positive bacteria (e.g., C. botulinum, C. tetani) strictly anaerobic, forming endospores. Lack catalase/superoxide dismutase, so oxygen is lethal.
Correct Answer: Clostridium.
Obligate anaerobe Clostridium cannot survive oxygen exposure, relying on fermentation in anaerobic niches like soil or guts. This trait sets it apart from aerobic options in exam questions.
Organism Traits
Clostridium species produce endospores for survival but perish from ROS without protective enzymes. Others adapt to oxygen-rich habitats via respiration or photosynthesis.
Organism Oxygen Requirement Key Habitat/Trait Halobacterium Aerobic Salt lakes, halophilic Thermus aquaticus Aerobic/Facultative Hot springs, thermophile Chlamydomonas nivalis Aerobic/Microaerophilic Snowfields, photosynthetic Clostridium Obligate anaerobe Soil/guts, endospore-forming Microbial Metabolism
Obligate anaerobes like Clostridium generate energy via glycolysis to acids/alcohols, yielding low ATP. Aerobes extract far more via oxidative phosphorylation. This distinction is crucial for NEET/CSIR life sciences prep.
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