Question:
The DNA of the microorganisms living under conditions of extreme temperature is predominantly:
The DNA of the microorganisms living under conditions of extreme temperature is predominantly:
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The presence of reverse gyrase is a biochemical marker for hyperthermophiles. It is the only known topoisomerase that can actively introduce positive supercoils using ATP.
Updated On: Jul 13, 2026
- Negatively supercoiled
- Positively supercoiled
- Relaxed
- Extensively methylated
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The Correct Option is B
Solution and Explanation
Step 1: Understanding the Concept:
Extreme environmental temperatures can cause double-stranded DNA to denature (melt) into single strands. Thermophilic and hyperthermophilic microorganisms utilize structural and enzymatic adaptations to protect their genetic material at these high temperatures.
Step 2: Detailed Explanation:
- Most mesophilic organisms have negatively supercoiled DNA, which makes it easier to unwind the double helix during replication and transcription.
- However, hyperthermophilic archaea and bacteria contain a unique topoisomerase enzyme called reverse gyrase.
- Reverse gyrase introduces positive supercoils into the circular DNA molecule.
- Positive supercoiling increases the thermal stability of the DNA double helix, raising its melting temperature ($\text{T}_m$) and protecting it against thermal denaturation in extreme heat.
Step 3: Final Answer:
The DNA of extreme-temperature microorganisms is predominantly positively supercoiled.
Extreme environmental temperatures can cause double-stranded DNA to denature (melt) into single strands. Thermophilic and hyperthermophilic microorganisms utilize structural and enzymatic adaptations to protect their genetic material at these high temperatures.
Step 2: Detailed Explanation:
- Most mesophilic organisms have negatively supercoiled DNA, which makes it easier to unwind the double helix during replication and transcription.
- However, hyperthermophilic archaea and bacteria contain a unique topoisomerase enzyme called reverse gyrase.
- Reverse gyrase introduces positive supercoils into the circular DNA molecule.
- Positive supercoiling increases the thermal stability of the DNA double helix, raising its melting temperature ($\text{T}_m$) and protecting it against thermal denaturation in extreme heat.
Step 3: Final Answer:
The DNA of extreme-temperature microorganisms is predominantly positively supercoiled.
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