Abhishek Walia1* and Kritika Sharma2
1Assistant Professor, DAV University, Jalandhar, Punjab, India
2B. Sc Student, DAV University, Jalandhar, Punjab, India
*Corresponding Author: Abhishek Walia, Assistant Professor, DAV University, Jalandhar, Punjab, India.
Received: January 23, 2018; Published: March 23, 2018
Citation: Abhishek Walia and Kritika Sharma. “Nitrogen Fixation in Leguminous Plants”. Acta Scientific Microbiology 1.4 (2018).
Rhizobium is a gram negative free living soil bacteria that fix nitrogen.
Martinus beijernick was the first who isolate and cultivate
microorganisms from the nodules of legumes in 1888. He named it
Bacillus radicicola. Frank in 1889 named this bacterium Rhizobium
leguminosarum. Rhizobium sp. form symbiotic association with
most leguminous plants (e.g. pea, cloves, alfa alfa, acacia) and convert
atmospheric nitrogen into ammonium ions which is then used
by plants in formation of amino acids and nucleotides.
There are different phases in the symbiotic interaction between Rhizobia and leguminous plants.
Initiation:Rhizobia present freely in soil. The root hairs of leguminous plant secrete flavanoids or isoflavanoids. Flavanoids initiate the interaction between bacterium (Rhizobium, Bradyrhizobium, Azorhizobium) and leguminous plant root i.e. this chemical is responsible for chemotactic movement of bacteria towards root hair and it is the inducer of nodulation (nod) and other genes. The first flavanoid to be discovered to act as nod gene inducer was Luteolin that is isolated from Medicago sativa (alfalfa plant). The rhicadhesins protein present on surface of Rhizobium that help in the attachment of rhizobium with leguminous plant root. Rhicadhesins proteins are calcium binding proteins. When bacteria attach to root hairs, flavanoids promote transcription of regulatory nod D gene in bacteria. This regulatory nod D gene is constitutively expressed in bacteria. After transcription regulatory nod D gene give rise to Nod D proteins. This Nod D protein act as activator for transcription of other nod genes.
Copyright: © 2018 Abhishek Walia and Kritika Sharma. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.