Peroxide Stimulon and Role of PerR in Group A Streptococcus

Abstract

We have characterized group A Streptococcus (GAS) genome-wide responses to hydrogen peroxide and assessed the role of the peroxide response regulator (PerR) in GAS under oxidative stress. Comparison of transcriptome changes elicited by peroxide in wild-type bacteria with those in a perR deletion mutant showed that 76 out of 237 peroxide-regulated genes are PerR dependent. Unlike the PerR-mediated upregulation of peroxidases and other peroxide stress defense mechanisms previously reported in Gram-positive species, PerR-dependent genes in GAS were almost exclusively downregulated and encoded proteins involved in purine and deoxyribonucleotide biosynthesis, heme uptake, and amino acid/peptide transport, but they also included a strongly activated putative transcriptional regulator (SPy1198). Of the 161 PerR-independent loci, repressed genes (86 of 161) encoded proteins with functions similar to those coordinated by PerR, in contrast to upregulated loci that encoded proteins that function in DNA damage repair, cofactor metabolism, reactive oxygen species detoxification, pilus biosynthesis, and hypothetical proteins. Complementation of the perR deletion mutant with wild-type PerR restored PerR-dependent regulation, whereas complementation with either one of two PerR variants carrying single mutations in two predicted metal-binding sites did not rescue the mutant phenotype. Metal content analyses of the recombinant wild type and respective PerR mutants, in addition to regulation studies in metal-supplemented and iron-depleted media, showed binding of zinc and iron by PerR and an iron requirement for optimal responses to peroxide. Our findings reveal a novel physiological contribution of PerR in coordinating DNA and protein metabolic functions in peroxide and identify GAS adaptive responses that may serve to enhance oxidative stress resistance and virulence in the host.

The PerR-Regulated P 1B-4 -Type ATPase (PmtA) Acts as a Ferrous Iron Efflux Pump in Streptococcus pyogenes

“…GAS encodes the regulator PerR, which acts to sense and coordinate the bacterial response to oxidative stress. Previous research examining the PerR regulon has shown that this regulator controls the direct detoxification of reactive oxygen species, mechanisms to repair ROSmediated damage, and a number of genes involved in metal homeostasis (6,33,34). Here, we provided evidence to suggest that the PerR-regulated GAS gene pmtA encodes an Fe(II) efflux pump that contributes to defense against reactive oxygen species.…”

“…A consensus per box, the regulatory element bound by PerR, is found immediately upstream of the pmtA gene (6,25,33). We therefore sought to determine whether pmtA is upregulated by hydrogen peroxide, consistent with PerR regulation.…”

“…Streptococcus pyogenes (group A Streptococcus [GAS]) coordinates oxidative stress responses through the action of the regulator PerR, which functions as a repressor of oxidative stress defense genes under normal conditions through binding to DNA at per boxes upstream of these genes (3,4). This stable complex typically exists with Fe as a prosthetic group; in the presence of hydrogen peroxide, Fe causes metal-catalyzed oxidation and damage of the complex, leading to its dissociation and the subsequent transcription of peroxide response genes (3)(4)(5)(6). In GAS, the PerR-regulated oxidative stress response encompasses both direct mechanisms, involving the detoxification of reactive oxygen species (ROS), and indirect mechanisms, which involve the repair of biomolecules damaged by oxidative stress.…”

PolA1, a Putative DNA Polymerase I, Is Coexpressed with PerR and Contributes to Peroxide Stress Defenses of Group A Streptococcus

“…3A). We also determined the role of PolA1 in GAS adaptive defenses against peroxide damage by preincubating cultures at sublethal H 2 O 2 levels recently reported to elicit genome-wide responses in GAS (22) prior to lethal peroxide challenge. Following a 30-min preadaptation in 0.5 mM H 2 O 2 , wild-type bacteria could withstand a subsequent 60-min challenge with 10 mM H 2 O 2 , retaining over 80% viability.…”

“…In its reduced ferrous-ionbound form, PerR represses the expression of several products, including two peroxidases (KatA and AhpC/AhpF), the iron/ DNA-binding ferritin-like MrgA, and a zinc uptake protein (ZosA), and heme biosynthesis, whereas in the presence of peroxide, ferrous-ion oxidation leads to OH ⅐ , which oxidizes and inactivates PerR, thereby allowing derepression of peroxide stress defenses (20,21). Recent characterization of wild-type (WT) and perR mutant group A Streptococcus (GAS) transcriptome changes elicited by H 2 O 2 showed PerR-dependent downregulation of DNA and protein metabolism, but no upregulation of any known peroxidases or MrgA (22). Moreover, comparison of transcriptomes obtained from the same two wild-type and mutant GAS strains in the absence of H 2 O 2 indicated control by PerR of a different set of genes that included a strongly repressed putative metal transporter (23,24).…”