Write names of two atmospheric nitrogen - fixing bacteria.

Explanation

**Step-by-Step Solution:**

1. **Understand the Concept of Nitrogen Fixation**: Nitrogen fixation is the process by which atmospheric nitrogen (N2) is converted into a form that can be used by living organisms. Certain bacteria have the ability to perform this process.

2. **Identify Types of Nitrogen-Fixing Bacteria**: There are two main types of nitrogen-fixing bacteria: those that form symbiotic relationships with plants (especially legumes) and those that are free-living in the soil.

3. **List Examples of Atmospheric Nitrogen-Fixing Bacteria**:
- The first example is **Rhizobium**, which is a genus of bacteria that forms symbiotic relationships with leguminous plants, helping them to fix nitrogen.
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