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Abstract
Nitrogen is one of the major important nutrients essential for plants growth. The atmosphere contains about 1015 tonnes of N2 gas and the nitrogen cycle involves the transformation of some 3x109 tonnes of N2 per year on the Global basis. However, transformations eg. N2 fixation is not exclusively biological. Lightning probably accounts for about 10 per cent of the world's supply of fixed nitrogen. The fertilizer industry also provides very important quantities of chemically fixed nitrogen. World’s production of fixed nitrogen from dinitrogen for chemical fertilizer accounts for about 25 per cent of earth's newly fixed nitrogen and the biological process accounts for about 60 per cent. The international emphasis on environmentally sustainable development with the use of renewable sources is likely to focus attention on the potential role of biological nitrogen fixation in supplying N for agriculture. Annually, biological nitrogen fixation is estimated to be around 175 million tonnes of which 79 per cent is accounted by terrestrial fixation. Legume-Rhizobium symbiotic association observed to fix 60-100 kg N ha-1 crop-1. The phenolate type of siderophore production by the isolates ranged from 1.49 mg l-1 to 4.95 mg l-1. The isolates GNBJ-9 produced maximum siderophore 4.95 mg l-1 which was followed by GNBJ-4, GNBJ-8 and GNBJ-28 respectively. The Intrinsic antibiotic resistances (IAR) of the 30 isolates were assessed against 5 antibiotics. The isolate GNBJ-9 possessed high level of antibiotic tolerance upto 200 ppm for Kanamycin, 300 ppm for Streptomycin, 250 ppm for Rifampicin and 200 ppm for Pencillin and sensitive to Gentamycin. The effect of salinity towards the growth of all thirty isolates was tested using different concentration of salt. All the isolates grew well in YEM liquid broth without salt, as the concentration increased, the growth get decreased.