Q.39 Endospores can be formed by which of the following:
- Gram (−) negative bacteria
- Gram (+) positive bacteria
- Both of the above
- None of the above
Gram-positive bacteria form endospores as a survival mechanism under stress. This trait is exclusive to certain low G+C Gram-positive rods like Bacillus and Clostridium.
Question Analysis
Endospores are dormant, resistant structures produced inside bacterial cells during nutrient scarcity or harsh conditions. Only Gram-positive bacteria possess the required cellular machinery for canonical endospore formation.
Option Breakdown
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Gram (−) negative bacteria: Cannot form true endospores; their thin peptidoglycan and outer membrane complicate sporulation. Rare spore-like variants (e.g., Coxiella burnetii SCVs) exist but differ structurally and lack full resistance.
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Gram (+) positive bacteria: Primary endospore formers due to thick peptidoglycan providing a stable sporulation framework. Examples include Bacillus (aerobic) and Clostridium (anaerobic).
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Both of the above: Incorrect, as Gram-negatives do not produce endospores routinely or equivalently.
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None of the above: False, since Gram-positives demonstrably form them.
Correct Answer: Gram (+) positive bacteria.
Endospores formed by gram positive bacteria enable survival in extreme heat, radiation, and desiccation. This adaptation, absent in Gram-negatives, is vital for understanding microbial resilience in exams.
Formation Process
Sporulation involves asymmetric division, engulfment, cortex formation, and coat deposition—feasible only in Gram-positive cells with robust peptidoglycan. Triggers include nutrient depletion; one spore per cell emerges highly resistant.
Option Endospore Capability Examples/Notes Gram (−) negative No Outer membrane blocks process Gram (+) positive Yes Bacillus, Clostridium Both No Gram-negatives incapable None No Gram-positives confirmed Biological Relevance
These spores resist autoclaving, impacting sterilization and pathogenesis (e.g., C. difficile infections). Gram-positive exclusivity stems from evolutionary cellular architecture. Crucial for NEET/CSIR microbiology prep.
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