Types of Nitrogen-Fixing Bacteria

The growth and survival of all organisms depends on the availability of mineral nutrients, including nitrogen, an important component of proteins and other cellular constituents which also makes up 78 percent of the atmosphere. However, animals and plants can't absorb gaseous nitrogen from the air. According to the Department of Horticulture and Crop Science at Ohio State University, bacteria naturally occurring in the soil are the only organisms able of fixing nitrogen in a process that combines it with hydrogen to make ammonia. Nitrogen-fixing bacteria include aerobic, anaerobic and symbiotic species.

Aerobic

• Aerobic bacteria develop in the presence of oxygen. According to John Innes Centre, soil-dwelling aerobic bacteria of the genus Azotobacter and Klebsiella can fix atmospheric nitrogen by converting it to ammonia. Beijerinckia is another genus of aerobic bacteria capable of fixing nitrogen, according to the Institute of Cell and Molecular Biology at the University of Edinburgh.

Anaerobic

• According to University of Florida IFAS Extension, Anaerobic bacteria thrive in environments such as grassland and waterlogged soils, as well as soil where moisture conditions and organic substrates are available but oxygen supply is restricted. Anaerobic nitrogen-fixing bacteria include some species of the genuses Clostridium and Desulfovibrio, as well as purple and green sulphur bacteria, according to the Institute of Cell and Molecular Biology at the University of Edinburgh.

Symbiotic

• Rhizobium, Frankia and Azospirillum are among the symbiotic nitrogen-fixing bacteria, the Institute of Cell and Molecular Biology at the University of Edinburgh says. Symbiosis is a beneficial interaction between creatures of different species, such as these bacteria and plants. Rhizobium interacts with the roots of clover, forming nitrogen-fixing nodules. Frankia fix nitrogen when interacting with sea buckthorn (Hippophae rhamnoides) and Casuarina, a Mediterranean tree.