Isolation and characterization of Azotobacter species from soils.

摘要

Azotobacter is an aerobic soil-dwelling organism with a wide variety of metabolic capabilities, which include the ability to fix atmospheric nitrogen by converting it to ammonia. A total of 19 samples were collected from various sites in Dehradun, Uttar Pradesh, India. The soil samples collected were of rice-wheat, rice-maize, rice-pea rotation system and various agro-ecosystems. A total of 30 isolates were obtained from the collected soil samples. The isolates were named as APB-1 to APB-30. The isolates showed morphological characteristics like circular, pulvinate, raised and smooth colonies. Out of the 30 isolates, almost 50% were gram negative and the others were gram positive. On the basis of morphology and gram reaction, only seven cultures (APB-1, APB-5, APB-9, APB-17, APB-22, APB-24 and APB-27) were selected. Among the different isolates, the maximum IAA was produced by APB-24 (0.026) followed by APB-27 (0.023) and APB-22 (0.019). APB-1 and APB-5 also produced significant amounts of IAA, i. e. 0.014 and 0.012, respectively. The isolate APB-17 produced the least amount of IAA (0.005). Maximum PHB production was shown by isolate APB-22 (0.981), followed by APB-27 (0.968) and APB-1 (0.954). A significant amount of PHB [polyhydroxybutyrate] was also produced by the isolates APB-17 (0.824), APB-5 (0.723), APB-9 (0.625) and APB-24 (0.241). The isolates APB-1, APB-5, APB-17 and APB-22 showed 90% germination of wheat seeds. Further, the isolates showed positive results on root and shoot proliferation. The maximum root and shoot length was observed in the case of isolate APB-9 (30 and 40 mm, respectively).