Rhizobia

Definition - What does Rhizobia mean?

Rhizobia are a form of soil bacteria that fix nitrogen (diazotrophs) after they are established inside the root nodules of legumes (Fabaceane). Rhizobia require a plant host as they cannot fix nitrogen independently.

After they have found a plant host, rhizobia express genes for nitrogen fixation. Rhizobia are motile (consuming energy when moving spontaneously), gram-negative, and non-sporulating rods.

MaximumYield explains Rhizobia

Nitrogen is the most commonly deficient nutrient in many soils around the world. As a result, nitrogen is the most commonly supplied plant nutrient to said soils. Thus, rhizobia are very important for the nitrogen fixation process.

The rhizobia fix nitrogen gas from the atmosphere by turning it into a more readily usable form of nitrogen. It is then exported from the nodules and helps the growth in the legume. Once the legume dies, the nodule breaks down and releases the rhizobia. The rhizobia then go back to the soil where they either live individually or infect another new legume plant host.

So, while the legumes provide shelter for the bacteria in special root nodules, the bacteria help the legumes with nitrogen fixation and the forming of important nitrogen compounds. Thus, the plant and the bacteria work in unison to activate special genes and to create necessary proteins and other compounds.
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