الفهرس 
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Abstract
One isolate of either Rhizobium leguminosarium bv.viciae and Bradyrhizobium japonicum was isolated from root nodules of faba bean and soybean plants, The isolated R. leguminosarum bv. Viciae was grown in liquid media containing different concentrations of NaCl The root nodule bacterial isolate exhibited high sensitivity to NaCl An isolate of halophilic bacteria. was picked up from saline soil sample Transformation was carried out using halophilic bacterial isolate as a (donor) and R. leguminosarum as a (recipient) . The transformed root nodule bacteria exhibited high tolerance to NaCl than the recipient (root nodule bacteria of vicia faba).and In this study the thermal stability of root nodule bacterial isolate of soybean (Bradyrhizobium japonicum) was tested. This isolate was grown in liquid medium (YMA broth) and incubated at different temperature degrees (30, 35, 40, 45, 50 upto 60°C). The bacterial growth was measured as optical density. The obtained results indicate that the root nodule bacteria are sensitive to the high temperature , and the most convenient temperature for their growth is ranged from 30-35 °C. One isolate of thermophilic bacteria was isolated from a compost sample. A thermophilic bacterial isolate was grown in nutrient broth medium and incubated at different temperature degrees (30, 35, 40, 45, 50 upto 60°C). The growth was measured as optical density. The highest growth value was recorded with incubation at 55°C, whereas, the lowest growth values was observed at 30°C.Using genetic transformation technique, Plasmid DNA of thermophilic bacterial isolate was transferred into root nodule bacteria (B. japonicum). Transfer of a plasmid DNA from thermophilic bacteria (Bacillus stearothermophilus) into root nodule bacterial isolate of G. max., resulted in construction of thermo-tolerant root nodule bacteria of G. max. (transformant) which exhibited much higher tolerance to high temperature than the recipient one.Moreover, no differences in the nodulation and nitrogen fixation efficiency of the recipient isolate and transformant isolate were detected, since, no significant differences were observed in number of nodules and N% of plant in plants inoculated with root nodule bacterial isolate (recipient) and those inoculated with the transformant isolate . On the basis of the antibiotic sensitivity test transfer plasmid DNA isolated from B. japonicumto R.leguminosarium . No significant differences were detected in values of fresh, dry weight of soybean plants as well as number of nodules/plant and plant nitrogen content in plants inoculated with the transformed R. leguminosarum as compared to those of soybean plants inoculated with B. japonicum. In addition, values of fresh, dry weight of faba bean plants as well as number of nodules/plant and plant nitrogen content in plants inoculated with the transformed strain were similar to those of faba bean plants inoculated with R. leguminosarum (recipient).
In conclusion, the use of such technique ( transfer of symbiotic plasmids) could be recommended to extend the host range of high presistance root nodule bacterial strains to comprise the plant groups of other strains which exhibit low presistance under certain soil conditions.