Question

A student wants to decide electron acceptor for aerobic, facultative and anaerobic bacteria. In this context, read the following statements:
(i) Dissolved Oxygen (DO) can act as electron acceptor for aerobic bacteria.
(ii) Nitrite can act as electron acceptor for aerobic bacteria.
(iii) Dissolved Oxygen (DO) can act as electron acceptor for anaerobic bacteria.
(iv) Nitrite can act as electron acceptor for facultative bacteria.
The correct choice is:

• A. (i) is correct; (iv) is correct
• B. (ii) is correct; (iii) is incorrect
• C. (ii) is correct; (iii) is correct
• D. (i) is correct; (ii) is correct

Hint:

- Aerobic: O$_2$ is the electron acceptor. - Anaerobic: Use alternate acceptors like NO$_3^-$, SO$_4^{2-}$, CO$_2$. - Facultative: Flexible; can use O$_2$ or nitrite/nitrate.

Answer 1

The Correct Option is A

Step 1: Aerobic bacteria.
Aerobic bacteria require oxygen as the terminal electron acceptor. Thus, (i) is correct.
Step 2: Anaerobic bacteria.
Anaerobic bacteria grow without oxygen. They use other compounds (like nitrate, sulfate, CO$_2$), not DO. Thus, (iii) is incorrect.
Step 3: Facultative bacteria.
Facultative bacteria can switch between oxygen (if available) and other acceptors like nitrate/nitrite. Thus, (iv) is correct.
Step 4: Check nitrite for aerobic bacteria.
Aerobic bacteria do not need nitrite as an electron acceptor because they directly use oxygen. Thus, (ii) is incorrect. So, the correct statements are (i) and (iv). Final Answer: \[ \boxed{\text{(A) (i) is correct; (iv) is correct}} \]