Riboswitches That Sense Cyclic Di-GMP

Cyclic diguanylate regulation of Bacillus cereus group biofilm formation

“…Using predicted c‐di‐GMP responsive GEMM riboswitches (Sudarsan et al ., ; Zhou et al ., ) we mined 23 B. cereus group genomes for downstream effector genes (including three representatives for the B. anthracis cluster, covering the A‐, B‐, and C‐ phylogenetic branches). The analysis revealed that each mined genome carried 1‐3 gene loci putatively responsive to c‐di‐GMP through a GEMM riboswitch, and including genes encoding a putative methyl‐accepting chemotaxis protein [orthologs to BC0422 in B. cereus ATCC 14579; c‐di‐GMP off‐riboswitch (Lee et al ., )], a collagen adhesion protein (orthologs to BC1060 B. cereus ATCC 14579; c‐di‐GMP on‐riboswitch (Lee et al ., )), and/or a cell surface protein (orthologs of CT43_CH4799 in B. thuringiensis subspecies chinensis CT‐43; c‐di‐GMP on‐riboswitch (Zhou et al ., )) (Supporting Information Table S2). Interestingly, the chemotaxis protein with its upstream riboswitch was found in all 23 genomes, while six genomes carried two riboswitch loci ( B. cereus strains 03BB108, AH1134, ATCC 14579, G9241; B. thuringiensis Al‐Hakam, B. weihenstephanensis KBAB4), and five genomes carried all three loci ( B. cereus strains B4264 and G9842; B. thuringiensis strains var.…”

“…This is in line with earlier findings that different c‐di‐GMP‐regulated phenotypes can be controlled by distinct DGCs, possibly by the formation of local c‐di‐GMP pools within subcellular microenvironments (Newell et al ., ; Massie et al ., ; Lindenberg et al ., ). Downstream effector functions under riboswitch control included a putative chemotaxis protein for which transcription is turned off in the presence of c‐di‐GMP, and various putative peptidoglycan‐linked cell surface proteins (five‐gene operon) and putative collagen adhesin for which c‐di‐GMP in both cases turns transcription on (Lee et al ., ; Zhou et al ., ). Future dissection of the molecular functions and macromolecular interactions of the various Cdg proteins and their putative downstream effectors could provide further links between c‐di‐GMP signalling and phenotypes classically important for B. cereus group bacteria in their different habitats, including sporulation, motility, cytotoxicity and biofilm formation.…”