How the bacteria present in soil and root nodules of leguminous plants are useful ?

Explanation

i. Bacterial like Rhizobia present in root nodules of leguminous plants help in nitrogen fixation.
ii. These microbes fix atmospheric nitrogen and make it available for leguminous plants. Thus, such plants are rich in proteins due to nitrogenous compounds made available by Rhizobia.
iii. Micro-organisms such as Azotobacter, that aer present free-living in soil, are capable of fixing atmospheric nitrogen and hence improve soil fertility by enriching its nitrogen content.