Why is Rhizobium categorized as a 'symbiotic bacterium'? How does it act as a biofertiliser?

cbse
microbesinhuman

#1

Rhizobium is a ‘symbiotic bacteria’ living in the root nodule of leguminous plants, it fixes atmospheric nitrogen into organic forms to be used by plants.
It is a biofertilizer as it is a living organism that enriches nutrient content of the plant / soil.