Question

Which of the following is a major group of microbes involved in nitrogen fixation?

• A. Bacteria
• B. Fungi
• C. Protozoa
• D. Archaea

Hint:

• Nitrogen fixation is the conversion of atmospheric N$_2$ to ammonia (NH$_3$).
• This process is carried out by prokaryotic microorganisms called diazotrophs.
• Major groups of diazotrophs are found within Bacteria (e.g., \textit{Rhizobium}, \textit{Azotobacter}, \textit{Clostridium}, Cyanobacteria).
• Some Archaea (e.g., certain methanogens) can also fix nitrogen.
• Fungi and protozoa (eukaryotes) do not fix nitrogen.

Answer 1

The Correct Option is A

To answer the question, let's first understand the process of nitrogen fixation and the types of microorganisms involved.

1. Understanding the Concepts:

- Nitrogen Fixation: This is the process by which atmospheric nitrogen (N₂) is converted into ammonia (NH₃) or other forms of nitrogen that plants can use. This process is vital for the nitrogen cycle and supports plant growth.

- Microorganisms in Nitrogen Fixation: Nitrogen fixation is primarily carried out by certain microorganisms that can convert atmospheric nitrogen into usable forms, making it available for plants and other organisms.

2. Breakdown of the Given Options:

• Bacteria: This is the major group of microorganisms involved in nitrogen fixation. Certain bacteria, especially Rhizobium species, form symbiotic relationships with leguminous plants, fixing nitrogen in plant root nodules. Free-living nitrogen-fixing bacteria, such as Azotobacter, also play a role in nitrogen fixation in the soil.
• Fungi: Fungi are not major players in nitrogen fixation. While fungi can decompose organic matter and release nitrogen in the process, they do not directly fix nitrogen from the atmosphere.
• Protozoa: Protozoa are single-celled organisms that do not play a significant role in nitrogen fixation. Their role in the nitrogen cycle is minimal compared to bacteria.
• Archaea: Some species of archaea have been found to participate in nitrogen fixation, but they are less common and not as significant as bacteria in this process. The primary nitrogen fixers are bacteria.

3. Conclusion:

The major group of microorganisms involved in nitrogen fixation is bacteria, specifically nitrogen-fixing bacteria like Rhizobium and Azotobacter.

Final Answer:

The major group of microbes involved in nitrogen fixation is bacteria.