Fig. 3

Ammonium production in a strain lacking the ammonium transporter AmtB. Shown are the ammonium (top left) and OD₆₀₀ (bottom left) results of growing AZBB163 and AZBB281 (AZBB163 derivative containing the amtB deletion) in Burk’s (B) medium. Shown on the right is a graphical representation of the effects of deleting amtB within a strain of Azotobacter deregulated for nitrogen fixation. Cultures were grown at 26 °C and shaken at 180 rpm. Bottom graph optical density plotted on a log₂-based scale (y-axis). Data points indicate averages, while the error bars represent standard deviation. N = 4