“Rhizobium is a soil bacteria that fixes atmospheric nitrogen once it finds a base inside the roots of the leguminous plants”.
Table of Contents
Rhizobium is the bacteria that live in symbiotic association with the root nodules of the leguminous plants. Fixation of nitrogen cannot be done independently. That is why rhizobium requires a plant host. Rhizobium is a vital source of nitrogen to agricultural soils including those in arid regions. They convert dinitrogen into ammonia. Ammonia, being toxic in nature. is rapidly absorbed into organic compounds.
Nitrogen fixation helps in increasing soil productivity and soil fertility. The various behavioural factors such as drought stress, nutrient deficiency, salt stress, fertilizers, pesticides of nitrogen-fixing systems are reviewed.
Classification of Rhizobium Bacteria
Rhizobium can be classified on the basis of the types of the plant they are associated with and also the rate of growth. Few species of Rhizobium bacteria include:
• Rhizobium leguminosarum
• Rhizobium alamii
• Rhizobium lantis
• Rhizobium japonicum
• Rhizobium trifolii
• Rhizobium phaseolii
Role of Rhizobium
Rhizobium plural form rhizobia are prokaryotes whose main function involves the conversion of stable nitrogen gas in the atmosphere to a biologically useful form. Nitrogenase is an enzyme complex that reduces dinitrogen to ammonia.
A huge amount of energy is consumed during the nitrogen fixation and the nitrogenase enzymes are irreversibly inactivated by oxygen. Acetylene reduction assay is used to measure the nitrogenase activity. A very less portion of species is capable of carrying out nitrogen fixation. That is around two genera of archaea, twenty genera of cyanobacteria and much more