A type of bacteria lives in the roots of plants. The bacteria helps the plants obtain nutrients. The roots are a moist home, which helps the bacteria grow and reproduce

Rhizobium.

Explanation:

The roots of most of these plants have nitrogen-fixing bacteria known as rhizobium. It helps to change nitrogen which is present in the air into the nitrates which are plants, and that is need to synthesize proteins.

Rhizobium bacteria occupy the root hairs which are present on the plants, they help the plant to grow and keep up with other plants. When the one plant dies, the fixed nitrogen which is present in it will release, and making it available for other plants, and this process helps to fertilize the soil in the environment.