The process whereby certain mutualistic bacteria convert gaseous nitrogen to a form that plants can use is called nitrogen fixation.

Here's a breakdown of the process:

1. Nitrogen gas (N₂) in the atmosphere: Nitrogen makes up about 78% of the Earth's atmosphere, but it is in an unusable form for most organisms.

2. Nitrogen-fixing bacteria: These bacteria, primarily found in the genus *Rhizobium*, live in root nodules of legumes (like beans, peas, and clover). They possess the enzyme nitrogenase, which is crucial for nitrogen fixation.

3. Nitrogenase: This enzyme breaks the strong triple bond between the nitrogen atoms in N₂, allowing them to react with hydrogen.

4. Conversion to ammonia (NH₃): Nitrogenase uses energy (usually from photosynthesis) to convert N₂ into ammonia (NH₃). This is the form that plants can readily absorb and utilize.

5. Plant uptake and use: Plants take up ammonia through their roots and use it to synthesize essential molecules like amino acids, proteins, and nucleic acids.

6. Symbiotic relationship: The bacteria receive energy (sugars) from the plant in return for providing them with a usable form of nitrogen. This mutually beneficial relationship is known as symbiosis.

Key points to remember:

* Nitrogen fixation is a vital process for life on Earth, as it converts unusable atmospheric nitrogen into a form that can be utilized by organisms.

* Nitrogen-fixing bacteria play a crucial role in the nitrogen cycle, which is the continuous movement of nitrogen between the atmosphere, biosphere, and geosphere.

* The process of nitrogen fixation requires energy, which is usually provided by the host plant.

* Nitrogen fixation is essential for plant growth and is crucial for maintaining the health of ecosystems.

Let me know if you have any other questions about nitrogen fixation or the nitrogen cycle!