Nitrogen fixation

Nitrogen is important to all organisms because it forms the basis of many compounds necessary for life. Proteins, enzymes, hormones and chlorophyll all contain nitrogen. Nucleic acids also contain nitrogen and form the long chains of nucleotides that make up the backbone of DNA and RNA. However, living things cannot use N2 in its gaseous form in the atmosphere. Nitrogen gas found in air pockets within soil is converted into a form usable by plants through a process called nitrogen fixation. Nitrogen-fixing organisms include certain types of bacteria and other micro-organisms that live on the roots of legumes such as soybeans, alfalfa and red clover. The micro-organisms convert N2 into other compounds such as ammonium and nitrate, which are taken up by plant roots. Consumers eat the plants and later deposit nitrogen compounds back into the soil through elimination or decomposition. Plants also return nitrogen to the soil when they decompose. The nitrogen-fixing micro-organisms in soil break down these compounds, and the nitrogen cycle continues.