Metabolic regulation of Escherichia coli and its glnG and zwf mutants under nitrogen limitation

The effect of nitrogen (N)-limitation on the metabolism of the wild type Escherichia coli BW25113, its glnG, and zwf mutants was investigated based on the chemostat cultures at the dilution rate of 0.2 h−1 under both carbon (C)-limitation and N-limitation. It was shown that gdhA gene expression was down-regulated, and glutamine synthetase-glutamate synthase (GS/GOGAT) pathway was mainly utilized under N-limitation in E. coli BW25113. It was also shown that the specific glucose consumption rate and the specific CO2 evolution rate (CER) were higher in glnG mutant as compared to the wild type under C-limitation. It was also shown that GOGAT is the main pathway for N assimilation under C-limitation, while GDH is the main pathway under N-limitation in glnG mutant. In zwf mutant, glnA, glnG, and gltD gene expressions were significantly down-regulated, while malic enzyme was significantly activated for NADPH production under both C-limitation and N-limitation.