The DmeRF System Is Involved in Maintaining Cobalt Homeostasis in Vibrio parahaemolyticus

Although cobalt (Co) is indispensable for life, it is toxic to cells when accumulated in excess. The DmeRF system is a well-characterized metal-response system that contributes to Co and nickel resistance in certain bacterial species. The RIMD 2210633 genome also harbors a operon that encodes a multiple antibiotic resistance regulator family transcriptional regulator and a cation diffusion facilitator family protein. Quantitative real-time PCR, growth curves analysis, inductively coupled plasma-mass spectrometry, β-galactosidase activity assays, electrophoretic mobility shift assays, and a mouse infection experiment were performed to characterize the function of the DmeRF system in . Zinc, copper, and Co significantly increase expression, with Co inducing the greatest increase. DmeF promotes growth under high-Co conditions. Additionally, increased accumulation of cellular Co in the Δ mutant indicates that DmeF is potentially involved in Co efflux. Moreover, DmeR represses the operon by binding directly to its promoter in the absence of Co. Finally, the DmeRF system was not required for virulence in mice. Collectively, our data indicate that the DmeRF system is involved in maintaining Co homeostasis in and DmeR functioning as a repressor of the operon.