Isolation and Characterization of Salinity Tolerant Azotobacter sp

The research work was conducted to isolate and characterize salinity tolerant Azotobacter sp . to be use as biofertilizer. In this study, soil samples were collected from different salinity affected areas, namely Pankhali Bazar of Dakop Upazilla, Khulna, Bangladesh and Dargapur Village, Assasuni Upazilla, Satkhira, Bangladesh. Thirty- five colonies were isolated from pore-plate containing Ashby's medium. Out of thirty -five isolates, fifteen were finally selected for detail study. All the isolates were rod-shaped, gram negative and non spore-forming. Biochemical tests indicated that they were obligate aerobes, catalase, oxidase and starch hydrolysis positive. Most of them were motile except four isolate nos. 02, 05, 09 and 13. Five isolates of Azotobacter were found which could tolerate 6% NaCl concentration whereas only two isolates of Azotobacter were found which could stand for at 10% NaCl concentration, which may become a promising source for further study regarding salinity tolerant Azotobacter sp . Finally, nitrogen fixation potentiality of the selected isolates was estimated ranging from 04.95 to 10.55 mg N/g substrate.