GlnA1 enzyme activity and protein expression of mycobacterial strains in low nitrogen and high nitrogen medium. A. Enzyme activity in the intracellular fractions (black bars) and extracellular fractions (grey bars). ***, ** The p-value given show the statistical significant of the change in GS specific activity between low nitrogen to high nitrogen. P < 0.001 for *** and P < 0.01 for ** was regarded as a statistically significant change in specific activity from low nitrogen to high nitrogen. B. Western blots of the intracellular fractions analyzed by the anti-GS antibodies. LN, low nitrogen; HN, high nitrogen.