Summary
Rhizobium and others convert atmospheric nitrogen into ammonia for plants.
In depth
Nitrogenase converts N2 to NH3 and is inhibited by oxygen. Rhizobium in legume root nodules uses leghaemoglobin to protect it. Free-living fixers include Azotobacter and cyanobacteria (Anabaena).
This reduces the need for fertiliser.
Nitrogenase requires lots of ATP and anaerobic conditions. Symbiotic fixers supply plants; free-living fixers enrich soils. Industrial nitrogen fertiliser mimics this.
Key idea: fixation converts N2 to NH3.
Nitrogenase needs a lot of energy (16 ATP per N2 fixed) and contains iron-molybdenum. Free-living fixers include Azotobacter, Clostridium and cyanobacteria with heterocysts (Anabaena), which separate nitrogenase from oxygen-producing photosynthesis. In symbiosis, plants signal with flavonoids, bacteria respond with Nod factors, and root hairs curl and form infection threads and nodules.
Legumes allow crop rotation and green manure, adding nitrogen to soils. The aim of transferring nitrogen fixation to cereals is a major research goal. Rhizobia are specific to certain hosts, and seeds are often inoculated with the right strain.
Frequently asked questions
What is Nitrogen-Fixing Bacteria?
Rhizobium and others convert atmospheric nitrogen into ammonia for plants.
Which area of biology covers Nitrogen-Fixing Bacteria, and how advanced is it?
Nitrogen-Fixing Bacteria is one of the 54 topics in Microbiology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Cyanobacteria, Bioremediation, Microorganisms.
Why does Nitrogen-Fixing Bacteria matter?
Biological fixation supplies about 60 percent of the new reactive nitrogen in natural and agricultural ecosystems, which reduces fertiliser needs.
Can you give an example of Nitrogen-Fixing Bacteria?
Soybean cultivation fixes up to 300 kg N per hectare per year.
What should I learn before Nitrogen-Fixing Bacteria?
Work through the Beginner topics in Microbiology first, such as Microorganisms, Bacteria, Archaea, then return to Nitrogen-Fixing Bacteria. Intermediate topics assume the Beginner vocabulary.
What topics are related to Nitrogen-Fixing Bacteria?
The closest topics to Nitrogen-Fixing Bacteria are Cyanobacteria, Bioremediation, Microorganisms, Bacterial Metabolism. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Nitrogen-Fixing Bacteria?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Nitrogen-Fixing Bacteria. To practise the whole of Microbiology, use the Microbiology quiz.
How is Nitrogen-Fixing Bacteria different from Cyanobacteria?
Nitrogen-Fixing Bacteria: Rhizobium and others convert atmospheric nitrogen into ammonia for plants. Cyanobacteria: Photosynthetic bacteria that oxygenated Earth's atmosphere billions of years ago. Read both side by side and note what each one explains.
How should I study Nitrogen-Fixing Bacteria step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Cyanobacteria and explain the difference aloud. Finally, take the Microbiology quiz and come back to this page for any question you miss.