Is it true that few nitrogen-fixing bacteria are autotrophic?

Some nitrogen-fixing bacteria are autotrophic, meaning that they can produce their own food through photosynthesis or chemosynthesis, while others are heterotrophic, meaning that they rely on organic matter as a source of food.

Among the nitrogen-fixing bacteria, some species are free-living and can carry out nitrogen fixation in the soil or water. Examples of free-living, autotrophic nitrogen-fixing bacteria include the cyanobacteria, such as Anabaena and Nostoc. These bacteria are capable of photosynthesis and use the energy from sunlight to drive the process of nitrogen fixation.

Other nitrogen-fixing bacteria are symbiotic and form mutualistic relationships with plants. For example, the bacteria that live in the root nodules of legumes, such as soybeans and peas, are able to fix nitrogen and provide it to the plant in exchange for a source of carbon and energy. These symbiotic bacteria are typically heterotrophic, meaning that they cannot carry out photosynthesis and rely on the plant for their energy needs.

Overall, while some nitrogen-fixing bacteria are autotrophic, the majority of nitrogen-fixing bacteria are heterotrophic and rely on organic matter for their energy needs.