Question

Match LIST-I with LIST-II 

LIST-I		LIST-II
A.	Biological nitrogen fixation	I.	Nitrobacter
B.	Conversion of ammonia to nitrite	II.	Paracoccus
C.	Conversion of nitrite to nitrate	III.	Rhizobium
D.	Denitrification	IV.	Nitrosomonas

Choose the correct answer from the options given below: 
 

• A. A-II, B-III, C-IV, D-I
• B. A-III, B-IV, C-I, D-II
• C. A-I, B-III, C-II, D-IV
• D. A-I, B-II, C-III, D-IV

Hint:

For nitrification, remember the order and the names: {Nitro{so}monas} works on ammonia ({so}urce), which comes first. {Nitro{bacter}} works on the product of the first step (nitrite), coming second.

Answer 1

The Correct Option is B

Step 1: Concept Overview:
The task is to match nitrogen cycle processes (LIST-I) with the corresponding bacterial genus (LIST-II).
Step 2: Detailed Explanation:
A. Biological Nitrogen Fixation: The conversion of atmospheric \(N_2\) to ammonia \(NH_3\). III. {Rhizobium} performs this symbiotically in legume root nodules. Therefore, A matches III.
B. Ammonia to Nitrite Conversion: The first nitrification step, performed by ammonia-oxidizing bacteria such as IV. {Nitrosomonas}. Thus, B matches IV.
C. Nitrite to Nitrate Conversion: The second nitrification step, performed by nitrite-oxidizing bacteria like I. {Nitrobacter}. Hence, C matches I.
D. Denitrification: The conversion of nitrate \(NO_3^-\) back to nitrogen gas \(N_2\) under anaerobic conditions by bacteria like II. {Paracoccus} (and Pseudomonas). Therefore, D matches II.
Step 3: Solution:
The correct matches are A-III, B-IV, C-I, D-II.