The chemistry of life depends on a handful of elements – mainly carbon, hydrogen, nitrogen and oxygen, with a little sodium, chlorine, phosphorus and sulfur, and some iron, calcium, magnesium, and traces of other substances. The cycling of the major elements carbon and nitrogen, from the atmosphere through the bodies of living things and back to the atmosphere, is essential to all life on this planet. Take a closer look at factors affecting the nitrogen cycle.
Nitrogen-fixing bacteria free-living in the soil
Culture free-living nitrogen-fixing bacteria from soil on a selective medium.
Nitrogen-fixing bacteria in root nodules of leguminous plants
Culture nitrogen-fixing bacteria (Rhizobium) from root nodules of leguminous plants on a suitable medium.