Link between Phosphate Starvation and Glycogen Metabolism in Corynebacterium glutamicum , Revealed by Metabolomics

Abstract

ABSTRACT 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.