Question

What are the main steps in nitrogen cycle? Mention the microbes involved in each step.

Answer 1

Nitrogen cycle - Atmospheric nitrogen is converted into chemical forms by bacteria and brought back into the atmosphere is called the nitrogen cycle.

The major steps involved in the nitrogen cycle are:-

Nitrogen fixation- In this step atmospheric nitrogen is fixed by nitrogen fixation bacteria like Anabaena, Nostoc, and, Rhizobium and conversion of nitrogen into ammonia takes place. N₂ to NH_3.

1. Nitrification- In this step, the nitrifying bacteria convert ammonia into nitrates. NH₃ to NO^-₃.
2. Assimilation- Nitrogen compounds are now taken up by plants and animals in various forms like NH₄⁺ NH_3, NO₂^- to make proteins.
3. Ammonification- Nitrogen is added back to the soil by plants and animals through waste material and dead bodies.
4. Denitrification- The nitrogen present in the soil break down by the denitrifying bacteria and nitrogen is converted back to the atmospheric nitrogen.

The bacteria involved in the steps are:

1. Nitrogen fixation- Anabaena, Nostoc and Rhizobium.
2. Nitrification- Nitrosomes, Nitrosospira, Nitrococcus and Nitrosolobus.
3. Ammonification- Paracoccus denitrificans, and Myxococcota.
4. Denitrification- Serratia, pseudomonas and achromobacter.