Link between phosphate starvation and glycogen metabolism in Corynebacterium glutamicum, revealed by metabolomics

In this study, we analyzed the influence of phosphate (P(i)) limitation on the metabolism of Corynebacterium glutamicum. Metabolite analysis by gas chromatography-time-of-flight (GC-TOF) mass spectrometry of cells cultivated in glucose minimal medium revealed a greatly increased maltose level under P(i) limitation. As maltose formation could be linked to glycogen metabolism, the cellular glycogen content was determined. Unlike in cells grown under P(i) excess, the glycogen level in P(i)-limited cells remained high in the stationary phase. Surprisingly, even acetate-grown cells, which do not form glycogen under P(i) excess, did so under P(i) limitation and also retained it in stationary phase. Expression of pgm and glgC, encoding the first two enzymes of glycogen synthesis, phosphoglucomutase and ADP-glucose pyrophosphorylase, was found to be increased 6- and 3-fold under P(i) limitation, respectively. Increased glycogen synthesis together with a decreased glycogen degradation might be responsible for the altered glycogen metabolism. Independent from these experimental results, flux balance analysis suggested that an increased carbon flux to glycogen is a solution for C. glutamicum to adapt carbon metabolism to limited P(i) concentrations.