Local c-di-GMP Signaling in the Control of Synthesis of the E. coli Biofilm Exopolysaccharide pEtN-Cellulose

J Mol Biol. 2020 Jul 24;432(16):4576-4595. doi: 10.1016/j.jmb.2020.06.006. Epub 2020 Jun 11.


In many bacteria, the biofilm-promoting second messenger c-di-GMP is produced and degraded by multiple diguanylate cyclases (DGC) and phosphodiesterases (PDE), respectively. High target specificity of some of these enzymes has led to theoretical concepts of "local" c-di-GMP signaling. In Escherichia coli K-12, which has 12 DGCs and 13 PDEs, a single DGC, DgcC, is specifically required for the biosynthesis of the biofilm exopolysaccharide pEtN-cellulose without affecting the cellular c-di-GMP pool, but the mechanistic basis of this target specificity has remained obscure. DGC activity of membrane-associated DgcC, which is demonstrated in vitro in nanodiscs, is shown to be necessary and sufficient to specifically activate cellulose biosynthesis in vivo. DgcC and a particular PDE, PdeK (encoded right next to the cellulose operon), directly interact with cellulose synthase subunit BcsB and with each other, thus establishing physical proximity between cellulose synthase and a local source and sink of c-di-GMP. This arrangement provides a localized, yet open source of c-di-GMP right next to cellulose synthase subunit BcsA, which needs allosteric activation by c-di-GMP. Through mathematical modeling and simulation, we demonstrate that BcsA binding from the low cytosolic c-di-GMP pool in E. coli is negligible, whereas a single c-di-GMP molecule that is produced and released in direct proximity to cellulose synthase increases the probability of c-di-GMP binding to BcsA several hundred-fold. This local c-di-GMP signaling could provide a blueprint for target-specific second messenger signaling also in other bacteria where multiple second messenger producing and degrading enzymes exist.

Keywords: GGDEF domain; bacterial second messenger; cellulose synthase; diguanylate cyclase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biofilms / growth & development*
  • Cellulose / metabolism
  • Cyclic GMP / analogs & derivatives*
  • Cyclic GMP / metabolism
  • Escherichia coli K12 / metabolism
  • Escherichia coli K12 / physiology*
  • Escherichia coli Proteins / metabolism*
  • Glucosyltransferases / metabolism
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Phosphoric Diester Hydrolases / metabolism
  • Phosphorus-Oxygen Lyases / metabolism
  • Polysaccharides, Bacterial / metabolism*
  • Signal Transduction


  • Escherichia coli Proteins
  • Intracellular Signaling Peptides and Proteins
  • Polysaccharides, Bacterial
  • bcsB protein, E coli
  • bis(3',5')-cyclic diguanylic acid
  • Cellulose
  • Glucosyltransferases
  • cellulose synthase
  • Phosphoric Diester Hydrolases
  • Phosphorus-Oxygen Lyases
  • diguanylate cyclase
  • Cyclic GMP