Functional Characterization of c-di-GMP Signaling-Related Genes in the Probiotic .

The bacterial second messenger cyclic diguanylate monophosphate (c-di-GMP) regulates a series of cellular functions, including biofilm formation, motility, virulence, and other processes. In this study, we confirmed the presence of several c-di-GMP related genes and evaluated their activities and functions in species. Bioinformatic and biochemical analyses revealed that La-14 have an active c-di-GMP phosphodiesterase (PdeA) that may act in the metabolic cycle of c-di-GMP. A GGDEF protein (DgcA) induced two c-di-GMP-dependent phenotypes (low motility and high production of curli fimbriae) in by heterologously expressed but showed no diguanylate cyclases activity while in the expression without the N-terminal transmembrane domain. The degenerated EAL-domain protein (PdeB), encoded by the last gene in the operon, serve as a c-di-GMP receptor which may be associated with exopolysaccharide (EPS) synthesis in . Heterologously expressed GtsA and GtsB, encoded by the operon, stimulated EPS and biofilm formation in BL21. Constitutive expression in revealed that a high concentration of intracellular DgcA levels increased EPS production in and enhanced the co-aggregation ability with MG1655, which may be beneficial to the probiotic properties of species. Our study imply that the c-di-GMP metabolism-related genes, in , work jointly to regulate its functions in EPS formation and co-aggregation.