The Adc regulon mediates zinc homeostasis in Streptococcus mutans

Abstract

Zinc (Zn2+) is an essential divalent trace metal for living cells. Intracellular zinc homeostasis is critical to the survival and virulence of bacteria. Thus, the frequent fluctuations of salivary zinc, caused by the low physiological level and the frequent exogenous zinc introduction, present a serious challenge for bacteria colonizing the oral cavity. However, the regulation strategies to keep intracellular Zn2+ homeostasis in Streptococcus mutans, an important causative pathogen of dental caries, are unknown. Because zinc uptake is primarily mediated by an ATP‐binding ABC transporter AdcABC in Streptococcus strains, we examined the function of AdcABC and transcription factor AdcR in S. mutans in this study. The results demonstrated that deletion of either adcA or adcCB gene impaired the growth but enhanced the extracellular polymeric matrix production in S. mutans, both of which could be relieved after excessive Zn2+ supplementation. Using RNA sequencing analysis, quantitative reverse transcription polymerase chain reaction examination, LacZ‐reporter studies, and electrophoretic mobility shift assay, we showed that a MarR (multiple antibiotic resistance regulator) family transcription factor, AdcR, negatively regulates the expression of the genes adcR, adcC, adcB, and adcA by acting on the adcRCB and adcA promoters in response to Zn2+ concentration in their environmental niches. The deletion of adcR increases the sensitivity of S. mutans to excessive Zn2+ supply. Taken together, our findings suggest that Adc regulon, which consists of a Zn2+ uptake transporter AdcCBA and a Zn2+‐responsive repressor AdcR, plays a prominent role in the maintenance of intracellular zinc homeostasis of S. mutans.

Acetylation of glucosyltransferases regulates Streptococcus mutans biofilm formation and virulence

“…Next, the reconstructed plasmid was cloned to the E. coli BL21 (DE3) cells. Proteins were purified, and concentrations were determined as described previously [55]. First, overnight cultures of the transformant were diluted 1:20 with fresh LB medium containing 50 μg/ mL of kanamycin until OD 600nm of 0.6 was achieved.…”

ZccE, a P‐type ATPase contributing to biofilm formation and competitiveness in Streptococcus mutans

“…Primer3 online tool (http://simgene.com/Primer3) was used to design gene‐specific primers (Table S1). Total bacterial RNA isolation, purification, and reverse transcription were performed as previously described (Pan et al., 2021). cDNA was synthesized using a PrimeScript™ RT Master Mix kit (Takara, Japan).…”

“…In Streptococcus pneumoniae, zinc import is regulated by adc regulon, a zinc uptake system regulated by the transcription factor AdcR, and zinc toxification is prevented by the zinc exporter CzcD, a cation diffusion facilitator (CDF) family's metal/H + antiporter (Manzoor et al, 2015;Martin et al, 2017;Mikhaylina et al, 2018). According to our previous research (Pan et al, 2021), S. mutans zinc import relies mainly on the ABC transporter AdcCBA. In response to environmental zinc concentration, the transcriptional factor AdcR regulates the expression of adcCBA genes to avoid excessive Zn 2+ import when zinc is abundant and to increase the scavenging in the zinc-deprived environment to meet the growth requirements.…”

Acetylation of Lactate Dehydrogenase Negatively Regulates the Acidogenicity of Streptococcus mutans

“…The biofilm biomass was assessed using the crystal violet (CV) staining method described previously ( 61 ). Briefly, after fixing the biofilms with methanol for 15 min and staining with 0.01% (wt/vol) CV for 5 min, the dye bound to the cells was resolubilized with 33% (vol/vol) acetic acid.…”

“…Next, the reconstructed plasmids were transformed into E. coli BL21(DE3) cells. The proteins were purified, and their concentrations were determined as described previously ( 61 ). First, overnight cultures of the transformant were diluted 1:20 with fresh LB medium containing 50 μg/mL of kanamycin until an OD 600nm of 0.6 was achieved.…”