What is the Difference Between Azotobacter and Rhizobium?

Azotobacter and Rhizobium are both nitrogen-fixing bacteria, but they have distinct characteristics that differentiate them:

1. Lifestyle: Azotobacter is a free-living nitrogen-fixing bacterium found in the soil, while Rhizobium is a symbiotic nitrogen-fixing bacterium that forms a mutually beneficial association with legume plants.
2. Shape: Azotobacter bacteria are oval or spherical in shape, whereas Rhizobium bacteria are rod-shaped.
3. Symbiotic relationships: Azotobacter does not form any specific symbiotic relationships with plants, whereas Rhizobium forms nodules on the roots of legume plants.

Both Azotobacter and Rhizobium contribute to nitrogen fixation, which is the process of converting free atmospheric nitrogen into more readily available nitrates or nitrites in the soil. They can both be used as biofertilizers, which are organisms that are used as fertilizers for their ability to fix nitrogen in the soil. However, their methods of nitrogen fixation and interactions with plants differ, with Azotobacter being free-living and Rhizobium forming symbiotic relationships with plants.

Comparative Table: Azotobacter vs Rhizobium

Here is a table comparing the differences between Azotobacter and Rhizobium:

In summary, Azotobacter is a free-living nitrogen-fixing bacterium that belongs to the class Gammaproteobacteria and can be found in neutral and alkaline soils, specifically in association with plants. On the other hand, Rhizobium is a symbiotic nitrogen-fixing bacterium that belongs to the class Alphaproteobacteria and forms mutually beneficial associations with the roots of legume plants for nitrogen fixation.