Enhancement of glutamine synthetase activity in Paenibacillus polymyxa by optimization of different growth conditions

Abstract

Biological nitrogen fixation is highly regulated at the transcriptional level by sophisticated regulatory networks that respond to multiple environmental signals. Glutamine synthetase (GS) occupies a central position in cellular metabolism and offer to the cell, a potential point for regulation of biosynthetic function. The aim of this work is to enhance the activity of GS in Paenibacillus polymyxa through altering the constituents of the growth medium, thereby increasing the nitrogen fixation capability. Two bacterial strains were identified as P. polymyxa by 16S rRNA gene (Accession No AB727983). High GS activity was recorded in the two strains, in presence of the divalent cations Mg⁺² and Mn⁺². Western blot analysis confirmed the presence of the GS at approximately ~60 kDa. GS activity was found to be affected by growth medium, carbon source, nitrogen source and sodium chloride. LB supplemented with 7% glycerol, 0.4% asparagine and 0.15% sodium chloride gave the highest GS activity.

Key words: Glutamine, Paenipacillus polymyxa, 16S rRNA, nitrogen fixation, western blot, Mg⁺² and Mn⁺².