Biofilm Dispersal in Bacillus velezensis FZB42 Is Regulated by the Second Messenger c-di-GMP

Cyclic diguanosine monophosphate (c-di-GMP) is a second messenger that plays a crucial role in regulating biofilm development, yet the role in Gram-positive bacteria remains elusive. Here, we demonstrated that dispersed cells from biofilms of <i>Bacillus velezensis</i> FZB42 exhibit a unique phenotype and gene expression compared to planktonic cells. Transcriptomic analysis revealed 1327 downregulated and 1298 upregulated genes, among which the c-di-GMP phosphodiesterase coding <i>yuxH</i> gene was remarkably upregulated. Deletion of the <i>yuxH</i> gene led to elevated c-di-GMP levels accompanied by reduced amounts of "actively dispersed cells" from the pellicle and the capacity of motility. Deletion of <i>spoIIIJ</i>, <i>spo0J</i>, and <i>kinA</i> resulted in increased c-di-GMP levels and reduced biofilm dispersal ability. Also, the level of c-di-GMP was increased when adding the cues of inhibition biofilm dispersal such as glucose and calcium ions. Collectively, these present findings suggest the c-di-GMP level is negatively correlated with biofilm dispersal in <i>Bacillus velezensis</i> FZB42, which sheds new light on biofilm regulation in <i>Bacillus velezensis</i> FZB42.