<div>Background: Molecular identification of a wide range of organisms capable of carrying out biological nitrogen fixation (BNF) are diverse in nature and significantly improves plant growth. Biological N2 fixation reflects the activity of a phylogenetically diverse list of microorganisms. Molecular characterization provides efficient means to identify organisms with the potential of N2 fixation. Applying these techniques in an array of environments has considerably broadened our understanding of the suite of organisms that can carry out BNF. 
 
Methods: Thirty-four strains of free living N2 fixing bacterial strains were isolated from diverse plants cultivated in North Gujarat, including wheat, cotton, castor and pearl millet, using a nitrogen-free selective medium. Acetylene reduction assay was used to check the ability of all bacteria to fix nitrogen. Hybridization with nifH probe derived from Azotobacter vinelandii with isolated free-living nitrogen-fixing bacteria showed a positive result. The selected strains were characterized by molecular analysis like; ARDRA and 16S rDNA sequencing.&nbsp; 
 
Result:&nbsp;Based on molecular characterization 17 strains to known groups of nitrogen-fixing bacteria, including organisms from the genus Azotobacter, Pseudomonas, Enterobacter, Arthrobacter, Bacillus, Variovorax, Nocardiodies, Rhodococcus, Mycobacterium, Planococcus, Microbacterium have been identified. One of the strains was identified as unknown bacteria. The potential strains were identified by 16srDNA analysis and also corroborated by morphological and biochemical characterization.</div>

Molecular Characterization of Free Living N2 Fixing Bacteria Isolated from Agricultural Soils of North Gujarat, India

<div style="text-align: justify;">A total of 22 endophytic bacteria were isolated from roots and nodules of Vigna radiata (mungbean) obtained from Jind district, Haryana. These were characterized on the basis of plant growth promoting traits. Almost all the endophytic bacteria produced IAA with maximum production of 81.63&micro;g/ml by isolate MJiR8. Among these, 100% root isolates and 84.6% nodule isolates resulted in in vitro root growth promotion of mungbean seedlings. All the isolates produced ammonia; eighteen (all root and nine nodule isolates) produced organic acid while only four root isolates were positive for siderophore production. The four isolates produced hydrogen cyanide and out of these only MJiR9 inhibited the growth of fungal pathogens Fusarium oxysporium and Aspergillus niger. All the endophytes were used to determine molecular diversity by ARDRA (Amplified Ribosomal DNA Restriction Analysis) Results revealed that the nodule isolates were more diverse, being present in separate clusters, in comparison to root isolates which were grouped together in cluster III.</div>

Molecular Characterization of Free Living N₂ Fixing Bacteria Isolated from Agricultural Soils of North Gujarat, India

Isolation and characterization of plant growth promoting endophytic bacteria isolated from Vigna radiata