The process by which bacteria convert nitrogen gas in the air to ammonia is called nitrogen fixation. This process is essential for the growth of plants, as nitrogen is a key component of proteins and nucleic acids.

Nitrogen fixation is carried out by a variety of bacteria, including Rhizobium, which live in the root nodules of leguminous plants such as beans, peas, and alfalfa. These bacteria form a symbiotic relationship with the plants, providing them with nitrogen in exchange for carbohydrates and other nutrients.

The nitrogen fixation process begins with the uptake of nitrogen gas from the air by the bacteria. The nitrogen gas is then converted to ammonia by the enzyme nitrogenase. Nitrogenase is a complex enzyme that requires a number of cofactors, including iron, molybdenum, and sulfur.

The ammonia produced by nitrogen fixation can then be used by the plant to synthesize proteins and nucleic acids. In addition, some of the ammonia may be released into the soil, where it can be used by other plants.

Nitrogen fixation is an important process that helps to maintain the balance of nitrogen in the environment. Without nitrogen fixation, the amount of nitrogen available for plant growth would be severely limited.