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

Abstract

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 Vibrio parahaemolyticus RIMD 2210633 genome also harbors a dmeRF 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 V. parahaemolyticus. Zinc, copper, and Co significantly increase dmeF expression, with Co inducing the greatest increase. DmeF promotes V. parahaemolyticus growth under high-Co conditions. Additionally, increased accumulation of cellular Co in the ΔdmeF mutant indicates that DmeF is potentially involved in Co efflux. Moreover, DmeR represses the dmeRF operon by binding directly to its promoter in the absence of Co. Finally, the DmeRF system was not required for V. parahaemolyticus virulence in mice. Collectively, our data indicate that the DmeRF system is involved in maintaining Co homeostasis in V. parahaemolyticus and DmeR functioning as a repressor of the operon.

ZntA maintains zinc and cadmium homeostasis and promotes oxidative stress resistance and virulence in Vibrio parahaemolyticus

“… 40 In V. parahaemolyticus , dmeF is significantly induced by Zn, Cu, and Co, whereas the growth of Δ dmeF is inhibited only under excess Co conditions. 22 In Streptococcus suis , Δ pmtA grow poorly only in the presence of elevated concentrations of Fe(II) and Co, although pmtA expression is significantly upregulated in response to Fe(II), Co, and Ni. 41 It is probable that excessive amounts of Zn, Cu, Co, Ni, or Cd can bind to ZntR and affect its activity, leading to the induction of zntA expression.…”

“…Indeed, only recently we have characterized a metal-response system, DmeRF, which facilitates V. parahaemolyticus growth under high Co conditions. 22 Zn is the second most abundant trace metal in living beings and is implicated in the host-pathogen interface. 38 , 39 By exploring the transcriptome changes during V. parahaemolyticus response to Zn repletion, we can focus on zntA which potentially functions in Zn homeostasis.…”

“…Similar observations have also been described in other studies. 22 , 40 , 41 In Sinorhizobium meliloti , although Cu, Co, and Ni strongly induce the expression of the dmeRF operon, Δ dmeF exhibits a growth defect only under high Co and Ni concentrations. 40 In V. parahaemolyticus , dmeF is significantly induced by Zn, Cu, and Co, whereas the growth of Δ dmeF is inhibited only under excess Co conditions.…”

“…β-galactosidase activity assays were performed as previously described. 22 The LacZ fusion strains were cultured in TSB until the mid-exponential phase. Aliquots (1 mL) were removed and treated with the indicated metals.…”

“… 21 Recently, we reported that the DmeRF system is required for Co homeostasis in V. parahaemolyticus , where DmeF functions as a Co efflux pump and DmeR acts as a repressor the dmeRF operon. 22 Moreover, the Zur-regulated Zn-binding protein ZrgA plays a predominant role in Zn acquisition in V. parahaemolyticus . 23 RNA sequencing revealed that zntA ( VP_RS04700 ) encoding a metal-transporting ATPase is the most highly upregulated gene of V. parahaemolyticus grown under Zn-replete conditions compared with that under Zn-deficient conditions.…”