In recent years, Escherichia coli has served as one of a handful of model bacterial species for studying c-di-GMP signaling. The widely used E. coli K-12 laboratory strains possesses 29 genes encoding proteins with GGDEF and/or EAL domains, which include 12 diguanylate cyclases (DGC), 13 c-di-GMP-specific phosphodiesterases (PDE) and four 'degenerate' enzymatically inactive proteins. In addition, six new GGDEF/EAL domain-encoding genes, which encode two DGCs and four PDEs, have recently been found in genomic analyses of commensal and pathogenic E. coli strains.

 

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