Isolation, Identification and Screening for Nitrogen Fixing Activities by Azotobacter chroococcum Isolated from Soil of Keffi, Nigeria as Agent for Bio-fertilizer Production

Free living nitrogen fixing bacteria are those that lives freely on rhizosphere of a young growing plant or those living in a close association with root of plants (Rhizobacteria) but not symbiotically. In most tropical soil, Nitrogen and other essential nutrients element are the most limiting nutrients which deficiencies could lead to slow growth and reduced crop production. Free living nitrogen fixing bacteria has the potential of secreting nitrogenase enzymes and produces organic acids such as glycolic, acetic, malic, succunic acids which fix atmospheric nitrogen directly into the soil for plants growth and development. To this end, the study on isolation, identification and screening of Azotobacter chroococcum from soil of Keffi, Nasarawa State, Nigeria was carried out from May to September 2018. Soil samples were collected from eight different locations and Azotobacter strains were isolated and identified using standard microbiological methods. The 16SrRNA gene sequence analysis of the strain showed maximum similarity of 96% with Azotobacter chroococcum of the reference type strain deposited in RDP Gen Bank database. Azotobacter strains isolated from four different locations showed coloured zone ranging between 16-10mm. Similarly, Percentage amount of nitrogen released by each Azotobacter strain in the culture broth ranging between 1.19% - 5.11% in an increasing order