Nitrogen Fixation
Molecular nitrogen enters biological pathways through Nitrogen Fixation
N2 ? NH3 (ammonia)
- Lightning can fix nitrogen
- very small amount
- momentary conditions of high pressure and temperature
- Primarily done by bacteria
- Azotobacter (free-living)
- Rhizobium (lives in symbiotic association with roots of some leguminous plants)
- Blue-green cyanobacteria (in lakes and ocean)
- Requires energy
- Free-living bacteria get energy by metabolizing organic detritus
- Rhizobium lives symbiotically with leguminous plants (plants provide them with sugars produced from photosynthesis)
- Cyanobacteria are photosynthetic