Bacterial second messenger cyclic di‐AMP in streptococci.

Cyclic dimeric adenosine monophosphate (c‐di‐AMP) has been well studied in bacteria, including those of the genus Streptococcus, since the first recognition of this dinucleotide in 2008. Streptococci possess a sole diadenylate cyclase, CdaA, and distinct c‐di‐AMP phosphodiesterases. Interestingly, cdaA is required for viability of some streptococcal species but not all when streptococci are grown in standard laboratory media. Bacteria of this genus also have distinct c‐di‐AMP effector proteins, diverse c‐di‐AMP‐signaling pathways, and subsequent biological outcomes. In streptococci, c‐di‐AMP may influence bacterial growth, morphology, biofilm formation, competence program, drug resistance, and bacterial pathogenesis. c‐di‐AMP secreted by streptococci has also been shown to interact with the mammalian host and induces immune responses including type I interferon production. In this review, we summarize the reported c‐di‐AMP networks in seven species of the genus Streptococcus, which cause diverse clinical manifestations, and propose future perspectives to investigate the signaling molecule in these streptococcal pathogens. [ABSTRACT FROM AUTHOR]