Nitrogen-Fixing Bacteria

About Nitrogen-Fixing Bacteria

• These are prokaryotic microorganisms that are capable of transforming nitrogen gas from the atmosphere into “fixed nitrogen” compounds, such as ammonia, that are usable by plants.
• Types: There are two main types of nitrogen-fixing bacteria.
  • Symbiotic or mutualistic: These species live in root nodules of certain plants. Plants of the pea family, known as legumes which are some of the most important hosts for nitrogen-fixing bacteria.
  • Examples: Rhizobium, which is associated with plants in the pea family and various Azospirillum species, which are associated with cereal grasses.
  • Other nitrogen-fixing bacteria are free-living and do not require a host. They are commonly found in soil or in aquatic environments.
  • Examples: Cyanobacteria Anabaena and Nostoc and genera such as Azotobacter, Beijerinckia, and Clostridium.
• Significance
  • Nitrogen is a component of proteins and nucleic acids and is essential to life on Earth. Although nitrogen is abundant in the atmosphere, most organisms cannot use it in that form.
  • Nitrogen-fixing bacteria accomplish more than 90 percent of all nitrogen fixation and thus play an important role in the nitrogen cycle.

Q1: What is Mutualism?

It is an association between organisms of two different species in which each benefits. Mutualistic arrangements are most likely to develop between organisms with widely different living requirements.

Source: Evolution in action? New study finds possibility of nitrogen-fixing organelles