Question

Identify the function of Nitrosomonas and Nitrobacter.
A) Convert (oxidise) ammonia or ammonium compounds into nitrates
B) Convert nitrate into nitrogen.
C) Convert nitrogen into nitrates.
D) Convert carbon dioxide into carbohydrates.

Answer 1

Hint:In the nitrogen cycle, the biological nitrogen fixation starts with ammonia. The process of conversion of nitrogen to ammonia is termed as nitrogen-fixation. After, the ammonia is oxidised to nitrites, and then to nitrates. Microbes play an important role in these processes.

Complete answer:
Nitrogen, as a macronutrient, is one of the most primary essential elements in plant growth and development. Along with plants, the microorganisms that present in the soil is also in demand of nitrogen. This is because nitrogen is a constituent of most of the organic metabolites like amino acids,enzymes, chlorophylls, hormones and some other vitamins too.

Now let us analyze each of the option above-mentioned;
>Option A: The conversion or oxidation of ammonia or ammonium to nitrites is carried out by bacteria Nitrosomonas and Nitrococcus. And the nitrites are further oxidised to nitrates by the bacterium Nitrobacter. The following steps are called nitrification. Therefore, this is the correct option.
>Option B: The process of conversion of nitrate to nitrogen is referred to as denitrification, and it is carried out by Pseudomonas and Thiobacillus. Therefore, this is the incorrect option.
>Option C: They do not carry out this process. Therefore, this is the incorrect option.
>Option D: Conversion of carbon dioxide to carbohydrates is called photosynthesis, and it takes place without the help of microbes. Therefore, this is the incorrect option.

Thus, the correct answer is option (A) Convert (oxidise) ammonia or ammonium compounds into nitrates.

Note:The (oxidised) ammonia and nitrates are then absorbed by the plants and hence transporting them to different parts where nitrates are required. The main sink is the leaf, where they are converted to amino acids.