Question

Given below are two statements:
Statement (I): Nitrobacteria are obligate autotrophic aerobes
Statement (II): Nitrate will not be produced from NH$_4^+$ in the absence of oxygen

• A. Both Statement (I) and Statement (II) are correct
• B. Both Statement (I) and Statement (II) are incorrect
• C. Statement (I) is correct but Statement (II) is incorrect
• D. Statement (I) is incorrect but Statement (II) is correct

Hint:

Nitrifying bacteria like Nitrobacter require oxygen to convert ammonium to nitrate via nitrite.

Answer 1

The Correct Option is A

Step 1: Nitrobacter is a chemoautotroph that gains energy only by oxidising nitrite to nitrate.
Step 2: This oxidation step uses \( \text{O}_2 \) as the terminal electron acceptor in its electron transport chain.
Step 3: Without oxygen, the enzyme cannot function, so nitrate cannot form from \( \text{NH}_4^+ \).
Step 4: Both statements hold, so the correct answer is \[ \boxed{\text{Both Statement (I) and Statement (II) are correct}} \]