CdpA Is a Burkholderia pseudomallei Cyclic di-GMP Phosphodiesterase Involved in Autoaggregation, Flagellum Synthesis, Motility, Biofilm Formation, Cell Invasion, and Cytotoxicity

Cyclic diguanylic acid (c-di-GMP) is an intracellular signaling molecule involved in regulation of cellular functions such as motility, biofilm formation and virulence. Intracellular level of c-di-GMP is controlled through opposing diguanylate cyclase (DGC) and phosphodiesterase (PDE) activities of GGDEF and EAL domain proteins, respectively. We report the identification and characterization ofcdpA , a gene encoding a protein containing an EAL domain in the Gram-negative soil bacillus and human pathogenBurkholderia pseudomallei KHW. Purified recombinant CdpA protein exhibited PDE activityin vitro . Evidence that CdpA is a major c-di-GMP-specific PDE inB. pseudomallei KHW was shown by an 8-fold-higher c-di-GMP level in thecdpA- null mutant as compared to the wild type and the complementedcdpA mutant. The presence of higher intracellular c-di-GMP levels in thecdpA- null mutant was associated with increased production of exopolysaccharides, increased cell-to-cell aggregation, absence of flagella and swimming motility, and increased biofilm formation. The relevance of CdpA inB. pseudomallei virulence was demonstrated by a 3-fold reduction in invasion of human lung epithelial cells and a 6-fold reduction in cytotoxicity on human macrophage cells infected with thecdpA mutant.