Cyclic di-AMP in Bacillus subtilis Biofilm Formation

Bacillus subtilis is a soil-dwelling bacterium that forms highly structured microbial communities called biofilms. Biofilm formation is important for bacterial survival, as biofilms are highly tolerant to environmental stresses. In B. subtilis, the formation of biofilms facilitates important interactions with plants. While the genetic regulation of biofilm formation is highly studied in B. subtilis, little is known regarding the molecular details of how signaling molecules feed into the biofilm regulatory network of this bacterium. Recent studies found that the second messenger cyclic di-adenylate monophosphate (cyclic di-AMP) plays an important role in B. subtilis biofilm formation and plant attachment. B. subtilis secretes cyclic di-AMP via three putative cyclic di-AMP transporters, suggesting that cyclic di-AMP can act as an extracellular signal for biofilm formation and plant attachment. Here, we discuss how cyclic di-AMP metabolism and secretion impact colony biofilm architecture, biofilm gene expression, and plant attachment in B. subtilis and speculate on future directions for the field.