Characterizations and Identification of Promoting Plant Growth and Bioagents Bacterial Strains as Indicators for its Productions

Drought-tolerant bacterial strains used for promoting plant growth include groups of bacteria that can directly enhance plant development and indirectly control fungal phytopathogens. In this study, bacteria were isolated from the nodules and rhizosphere of soybean plants. Using classical microbiological methods, two isolates were identified based on cultural, morphological, biochemical, and physiological characteristics in vitro. The first strain, designated as DTB4, was isolated from the nodules of soybean plants. It was classified as a slow grower, aerobic, gram-negative, short rod-shaped, non-spore-forming, and motile. Optimal growth occurred at 35°C and pH 7.0. It tested positive for starch, casein, and gelatin hydrolysis, as well as for the indole test. The strain was also capable of assimilating several sugars and showed resistance to certain antibiotics. The second strain, designated as DTR30, was isolated from the rhizosphere of soybean plants. It consisted of long rod-shaped, gram-positive, spore-forming, oxidase-negative bacteria. Biochemical tests revealed positive results for indole and methyl red. This strain tolerated NaCl and exhibited growth at pH 9.5. Based on identification tests, strain DTB4 was confirmed to be Bradyrhizobium japonicum, and strain DTR30 was identified as Bacillus subtilis. Biochemical analysis indicated that both strains have the potential to produce several products for using in different scales.