Name two free living micro-organisms which can fix nitrogen.

Explanation

**Step-by-Step Solution:**

1. **Understanding Nitrogen Fixation**: Nitrogen fixation is the process by which atmospheric nitrogen (N₂) is converted into ammonia (NH₃) by certain microorganisms. This process is essential for making nitrogen available to plants, as they cannot utilize atmospheric nitrogen directly.

2. **Identifying Free-Living Microorganisms**: Free-living microorganisms are those that do not require a host to survive and can live independently in the soil or water. In the context of nitrogen fixation, we are looking for bacteria that can fix nitrogen without being symbiotic with plants.

3. **Listing Examples**: Two well-known free-living nitrogen-fixing bacteria are:
- **Azotobacter**: This is a genus of bacteria that is commonly found in soil and is known for its ability to fix atmospheric nitrogen.
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