Figure 3.

Suggested model of glycogen metabolism in E. coli wherein major determinants of glycogen accumulation include availability of ATP for ADPG synthesis, levels of (p)ppGpp (which accumulates in a RelA- SpoT- and/or Gpp-dependent manner under conditions of limited provision of nutrients such as amino acids, sulphur, Mg²⁺, iron, etc.), factors determining intercellular communication, aggregative and social behaviour modes (which in turn determine the nutritional status of the cell), expression levels of the general stress regulator RpoS and of the global regulator CsrA, availability of a carbon source, redox status of the cell and less well-defined systems sensing the cell energy status through the activity of the electron transport chain. CsrB and CsrC small non-coding RNAs, represented by stem-loops, are likely involved in the regulation of functions strongly affecting glycogen accumulation through interaction with CsrA (Adk, adenylate kinase; c-di-GMP, cyclic diguanylate; ETC, electron transport chain).