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Introduction Representatives of the Azotobacteriaceae family are regular inhabitants of soils of roots (rhizosphere) and on the root surface of free-living nitrogen fixing bacteria of the genera Azotobacter and Azospirillum . They are the regular associates of the roots of many tropical grasses and cereals. Their associations with medicinal plants are of paramount importance. The medicinal plants such as Aloe vera and Datura alba were selected to access the nature of association in the rhizosphere and on the roots by the above bacteria. Methods The roots of A. vera had the dominance of nitrogen fixing bacteria (132 × l0 2 /g). The characteristics of the selected bacteria revealed the presence of Azotobacter chroococcum , Azotobacter beijerinckii , Azotobacter vinelandii and Azospirillum lipoferum . The carbon sources such as sucrose, lactose, glucose, maltose, rhamnose, xylose and mannitol either individually or in combination induced the growth of selected nitrogen fixing bacteria (A. chroococcum , A. beijerinckii , and A. vinelandii) . Results The maximum growth was recovered with maltose and glucose (1.36S0.D). The mixed carbon sources such as mannitol, maltose and xylose showed elevated growth of the bacterium (A. chroococcum and A. beijerinckii) . The production of IAA, a growth promoting hormone by A. chroococcum , A. beijerinckii and A. vinelandii was studied at varying pH ranges from 6 to 9 in the growing medium. The increase in the pH stimulated the growth as well as the synthesis of IAA. Both the growth and the growth hormones are similar in the growing liquid broth. The above observations paved the way for accessing the growth of the seedling of Ocimum sanctum . The application of Azotobacter and Azospirillum species as biofertilizers is a testimony to the effect that IAA on seedlings growth. Conclusion With this we conclude that IAA with its growth promoting capacity dominates the Microbial and Agricultural Biotechnology in the years to come. |
