A Nitrogen Fixation: The Story of the Frankia Symbiosis

a large input of energy and can occur either biologically, within the cells of various bacteria, or chemically, in fertilizer factories or during lightning storms. Among all living organisms, only bacteria have evolved the complex biochemical mechanisms required for nitrogen fixation. All "higher" plants and animals that are said to fix nitrogen are really only the symbiotic partners of the bacteria that do the actual work. Among plants, the cultivated legumes (peas, beans, peanuts, etc.) are the best-known nitrogenfixers, but many plant families besides the Leguminosae can also fix nitrogen. On a worldwide scale, these nonlegumes, as they are somewhat negatively called, fix as much nitrogen