Antimicrobial and Phytohormone production potential of Azotobacter chroococcum and its effect on the growth of non-leguminous plants

The overuse of chemical fertilizers in agriculture leads to a decrease in the fertility of soil and increases chemical pollution, which has adverse effects on living things. Biofertilizers have a solution towards chemical fertilizer to improve soil fertility and crop production. Therefore, the present study was undertaken to isolate different isolates of Azotobacter sp. to identify effective isolates for plant growth promoting activities and biological control. Six Azotobacter sp. were isolated and their plant growth promoting activities were checked. The isolate AC3 produced the highest amount (64 μg/ml) of IAA and produced HCN and 72 μg/ml of ammonia. The isolates AC1 and AC4 lacked the HCN production. Isolate AC3 showed a 26 mm zone of clearance on Pikovaskys agar, solublized the highest 71 μg/ml of inorganic phosphate and had the ability to produce siderophores. The isolate AC3 showed good antimicrobial potential against pathogens. Isolate AC3 was identified as Azotobacter chroococcum on the basis of morphological and biochemical characteristics. The bioactive compound was produced by using Azotobacter chroococcum and purified by column chromatography. Fraction 1 showed good antimicrobial activity against all the pathogens. The highest zone of inhibition was 15 mm against F. oxysporum. FT-IR analysis of fraction 1 revealed carboxylic acid, alkane and carbonyl functional groups. Azotobacter chroococcum had a greater effect on the growth of non-leguminous plants in the bacterially inoculated pot than in the control.