Characterization of the rdar morphotype, a multicellular behaviour in Enterobacteriaceae

Cell Mol Life Sci. 2005 Jun;62(11):1234-46. doi: 10.1007/s00018-005-4557-x.


The rdar morphotype, a multicellular behaviour of Salmonella enterica and Escherichia coli is characterized by the expression of the adhesive extracellular matrix components cellulose and curli fimbriae. The response regulator CsgD, which transcriptionally activates the biosynthesis of the exopolysaccharide cellulose and curli, also transforms cell physiology to the multicellular state. However, the only role of CsgD in cellulose biosynthesis is the activation of AdrA, a GGDEF domain protein that mediates production of the allosteric activator cyclic-di-(3'-5')guanylic acid (c-di-GMP). In S. enterica serovar Typhimurium a regulatory network consisting of 19 GGDEF/EAL domain-containing proteins tightly controls the concentration of c-di-GMP. c-di-GMP not only regulates the expression of cellulose, but also stimulates expression of adhesive curli and represses various modes of motility. Functions of characterized GGDEF and EAL domain proteins, as well as database searches, point to a global role for c-di-GMP as a novel secondary messenger that regulates a variety of cellular functions in response to diverse environmental stimuli already in the deepest roots of the prokaryotes.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Animals
  • Biofilms / growth & development
  • Cellulose / biosynthesis
  • Cyclic GMP / analogs & derivatives*
  • Cyclic GMP / metabolism
  • Enterobacteriaceae* / cytology
  • Enterobacteriaceae* / growth & development
  • Enterobacteriaceae* / metabolism
  • Escherichia coli Proteins
  • Humans
  • Models, Biological
  • Phylogeny
  • Trans-Activators / metabolism


  • CsgD protein, E coli
  • Escherichia coli Proteins
  • Trans-Activators
  • bis(3',5')-cyclic diguanylic acid
  • Cellulose
  • Cyclic GMP