Summary auto-generated
This mini-review examines cyclic di-GMP (c-di-GMP) as a bacterial second messenger that regulates cell surface properties and adhesiveness. The authors describe how proteins containing GGDEF and EAL domains control c-di-GMP levels in diverse bacteria. The GGDEF domain functions as a cyclase synthesizing c-di-GMP from GTP, while the EAL domain acts as a phosphodiesterase degrading c-di-GMP. Originally discovered in Gluconacetobacter xylinus regulating cellulose production, c-di-GMP signaling is now recognized as a conserved system across many bacterial species. Genetic evidence links c-di-GMP metabolism to the production of exopolysaccharides and proteinaceous appendages that promote bacterial adhesion and biofilm formation. Examples include wrinkled colony formation in Pseudomonas species, rugose morphology in Vibrio cholerae, rdar phenotype in Salmonella, and autoaggregation in Yersinia pestis. The review highlights how c-di-GMP signaling integrates multiple environmental signals through sensor domains and coordinates bacterial cell-to-cell interactions and surface adhesion, representing a unifying regulatory theme across bacterial species.
Key findings
- GGDEF domains function as c-di-GMP synthases while EAL domains function as c-di-GMP phosphodiesterases, allowing fine-tuned regulation of this second messenger
- c-di-GMP signaling controls production of extracellular matrices containing exopolysaccharides and adhesive proteins that promote biofilm formation and surface attachment across diverse bacteria
- Proteins with GGDEF and EAL domains are widespread in bacterial genomes (e.g., 33 in Pseudomonas aeruginosa, 41 in Vibrio cholerae) and often include additional regulatory domains like CheY phosphorylation receivers and PAS oxygen sensors
- c-di-GMP-regulated adhesiveness phenotypes are conserved across evolutionarily distant bacteria, including wrinkled colonies, rugose morphotypes, and autoaggregation linked to virulence and transmissibility
- c-di-GMP signaling coordinates bacterial responses to environmental cues and facilitates both cell-to-cell interactions and adhesion to plant and animal surfaces
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Abstract
Environmental signals trigger changes in the bacterial cell surface, including changes in exopolysaccharides and proteinaceous appendages that ultimately favour bacterial persistence and proliferation. Such adaptations are regulated in diverse bacteria by proteins with GGDEF and EAL domains. These proteins are predicted to regulate cell surface adhesiveness by controlling the level of a second messenger, the cyclic dinucleotide c-di-GMP. Genetic evidence suggests that the GGDEF domain acts as a nucleotide cyclase for c-di-GMP synthesis while the EAL domain is a good candidate for the opposing activity, a phosphodiesterase for c-di-GMP degradation.