Nitrogen Fixation: Essential Element for Life

Nitrogen Fixation and Its Importance

• Nitrogen is a required component for chlorophyll molecules to form in plants, and without it, plants cannot produce chlorophyll, photosynthesize, or produce their own food.
• Nitrogen-fixing bacteria develop a symbiotic connection with plants in a mutually beneficial relationship called mutualism.
• The chemical formula for nitrogen fixation is the transformation of atmospheric nitrogen into ammonia.

The Nitrogen Cycle

• The nitrogen cycle consists of five steps: biological nitrogen fixation, nitrification, ammonification, assimilation, and denitrification.
• Biological nitrogen fixation: Atmospheric nitrogen is transformed into ammonia by free-living prokaryotic organisms in the soil or mutualistic bacteria in the roots of plants.
• Nitrification: Prokaryotic nitrifying bacteria in the soil further convert ammonia into nitrates and nitrites.
• Ammonification: A natural process that occurs when nitrogen-containing compounds are returned to the soil via animal waste products or from dead, decomposing organisms.
• Assimilation: Bioavailable nitrogen is absorbed by eukaryotic organisms in the soil like plants.
• Denitrification: Some microorganisms take bioavailable nitrogen and transform it back into nitrogen gas, which is returned to the atmosphere.

Why Nitrogen Fixation is Important

• Nitrogen fixation is a vital biochemical step in the nitrogen cycle, without which plants and animals could not grow.
• Plants are primary producers, creating food from sunlight by photosynthesis, and are dependent on nitrogen-fixing bacteria and archaea for their metabolic and biological needs.
• Nitrogen is used not only for chlorophyll but for many other cellular and reproductive processes that involve proteins and DNA.

Nitrogen Fixation in Ecosystems

• Nitrogen fixation is essential for ecosystems, as it moves nitrogen from the air into the soil where it is transformed by prokaryotes into bioavailable forms for plants and animals.
• Human beings require nitrogen for the proteins and DNA in their bodies, and obtain it through dietary sources.
• Nitrogen fixation is necessary for agricultural systems, as it provides the necessary nitrogen for crop growth.

Nitrogen Fixation Examples

• Terrestrial nitrogen fixation examples involve mutualistic bacteria like Rhizobium, which forms nodules on the roots of legumes like beans, lentils, and clover.
• Marine nitrogen fixation examples involve free-floating diazotrophic microorganisms, like cyanobacteria, that fix atmospheric nitrogen into bioavailable forms.