Match List – I with List – II

List – I	List – II
A. Nitrobacter	I. Oxidation of sulphur
B. Nitrosomonas	II. Asymbiotic fixation of nitrogen
C. Clostridium	III. Conversion of NH₄–N to NO₂–N
D. Thiobacillus	IV. Conversion of NO₂–N to NO₃–N

Choose the correct answer from the options given below

Correct option is A

Nitrosomonas oxidizes ammonium nitrogen into nitrite nitrogen during the first step of nitrification, which is an essential soil nitrogen transformation process. Nitrobacter converts nitrite nitrogen into nitrate nitrogen during the second step of nitrification, completing the nitrification pathway. Clostridium is an anaerobic bacterium capable of asymbiotic nitrogen fixation, allowing it to fix nitrogen independently in soil. Thiobacillus oxidizes sulphur compounds present in soil and is responsible for biological oxidation of sulphur.
Information booster: Nitrification is a two-step biological oxidation process carried out by different groups of specialized bacteria. Nitrogen transformation processes are essential for nutrient availability and balance in soil ecosystems. Sulphur oxidizing bacteria play an important role in soil acidification and nutrient cycling. Understanding microbial functions helps in effective soil fertility management and fertilizer use efficiency.
Why other options are incorrect: (b) This option mismatches nitrifying bacteria with incorrect biochemical processes. (c) This option assigns sulphur oxidation and nitrogen fixation incorrectly. (d) This option does not correctly pair nitrification steps with the responsible bacteria.