Cyclic di-GMP riboswitch

Cyclic di-GMP riboswitches are a class of riboswitch that specifically bind cyclic di-GMP, [cite journal|author=Sudarsan N, Lee ER,Weinberg Z,Moy RH,Kim JN, Link KH, Breaker RR|title=Riboswitches in eubacteria sense the second messenger cyclic di-GMP|journal=Science|volume=321|issue=5887|pages=411–3|year=2008|doi=10.1126/science.1159519] which is a second messenger that is used in a variety of microbial processes including virulence, motility and biofilm formation. Cyclic di-GMP riboswitches were originally identified by bioinformatics as a conserved RNA-like structure called the "GEMM motif". [cite journal |author=Weinberg Z, Barrick JE, Yao Z, "et al" |title=Identification of 22 candidate structured RNAs in bacteria using the CMfinder comparative genomics pipeline |journal=Nucleic Acids Res. |volume=35 |issue=14 |pages=4809–19 |year=2007 |pmid=17621584 |doi=10.1093/nar/gkm487] These riboswitches are present in a wide variety of bacteria, and are most common in Clostridia and certain varieties of Proteobacteria. The riboswitches are present in pathogenes such as "Clostridium difficile", "Vibrio cholerae" (which causes cholera) and "Bacillus anthracis" (which causes anthrax). "Geobacter uraniumreducens" is predicted to have 30 instances of this riboswitch in its genome. A bacteriophage that infects "C. difficile" is predicted to carry a cyclic di-GMP riboswitch, which it might use to detect and exploit the physiological state of bacteria that it infects.

The discovery of this riboswitch class answers the question of how genes are regulated in response to cyclic di-GMP levels in many different bacteria. However, some bacteria in which cyclic di-GMP has been studied lack cyclic di-GMP riboswitches, e.g. "Pseudomonas aeruginosa". Cyclic di-GMP riboswitches are the first kind of riboswitch to be discovered whose role is not primarily in regulating metabolism, but is instead part of signaling.

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