Molecular Evolution of the Negative Regulatory Gene (NifL) from Azotobacter Chroococcum and its Nitrogenase Activity

Gothandapani Sellamuthu^1,2, Prabha Shankar¹, Sekar Soundarapandian², Sangeeta Paul³ and Jasdeep C. Padaria¹

¹ICAR - National Research Centre on Plant Biotechnology, Pusa Campus, New Delhi- 110012, India.

²Department of Industrial Biotechnology, Bharathidasan University, Tiruchirappalli – 620 024, India.

³ICAR – Indian Agricultural Research Institute, Pusa Campus, New Delhi- 110012, India.

Corresponding Author E-mail: jasdeep_kaur64@yahoo.co.in

DOI : http://dx.doi.org/10.13005/bbra/2643

ABSTRACT: Two isolates of Azotobacter chroococcum (A. chroococcum CBD15 and A. chroococcum W5), were characterized for their atmospheric nitrogen fixing efficiency and ability to produce plant growth promoting hormone. The isolates, A. chroococcum CBD15 and A. chroococcum W5, were observed the production of Indole acetic acid (IAA) and nitrogen fixation in the absence of any inorganic nitrogen source. The ability nitrogen fixation was estimated by acetylene reduction studies revealed that A. chroococcum CBD15 produced 693.3 nmole C₂H₄ h^-1 mg^-1 whereas A. chroococcum W5 produced 523.4 nmole C₂H₄ h^-1 mg^-1. Nitrogenase activity of both the isolates was reduced when grown in media containing nitrogen source (ammonia or urea), in comparison to media lacking any nitrogen source. The nifL gene, which is one of the most important regulatory gene of nitrogen fixation pathway, was isolated from A. chroococcum CBD15 and A. chroococcum W5. Sequence analysis revealed that both nifL gene sequences have maximum homology with nifL gene of A. vinelandii and Pseudomonas oryzae respectively. The genetic manipulation of nifL gene of A. chrococcum will lead to development of an efficient bioinoculant for sustainable agriculture.

KEYWORDS: Acetylene Reduction; Azotobacter Chroococcum; IAA; NifL; NifA

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