Question

DNA gyrase is inhibited by

• A. Tetracycline
• B. Cephalosporin
• C. Nalidixic acid
• D. Aurin tricarboxylic acid

Answer 1

The Correct Option is C

DNA gyrase is an essential bacterial enzyme that relieves supercoiling stress in DNA during replication and transcription. 

Step 1: Understanding DNA Gyrase Inhibition - DNA gyrase is a type II topoisomerase found in bacteria. - It introduces negative supercoils into DNA, preventing excessive twisting during replication. - Nalidixic acid, a quinolone antibiotic, inhibits DNA gyrase by blocking the enzyme’s ability to re-ligate DNA strands after cutting, leading to DNA damage and bacterial cell death. 

Step 2: Evaluating the Options 
- Option (A) - Incorrect: Tetracycline inhibits protein synthesis by targeting the 30S ribosomal subunit, not DNA gyrase. 
- Option (B) - Incorrect: Cephalosporins are beta-lactam antibiotics that inhibit cell wall synthesis, not DNA gyrase. 
- Option (C) - Correct: Nalidixic acid is a quinolone antibiotic that specifically inhibits DNA gyrase. 
- Option (D) - Incorrect: Aurin tricarboxylic acid is an inhibitor of endonucleases, not DNA gyrase. 

Step 3: Conclusion Since Nalidixic acid is a known inhibitor of DNA gyrase, the correct answer is option (C).