Aerotolerance and Peroxide Resistance in Peroxidase and PerR Mutants of Streptococcus pyogenes

Abstract

Survival in aerobic conditions is critical to the pathogenicity of many bacteria. To investigate the means of aerotolerance and resistance to oxidative stress in the catalase-negative organism Streptococcus pyogenes, we used a genomics-based approach to identify and inactivate homologues of two peroxidase genes, encoding alkyl hydroperoxidase (ahpC) and glutathione peroxidase (gpoA). Single and double mutants survived as well as the wild type under aerobic conditions. However, they were more susceptible than the wild type to growth suppression by paraquat and cumene hydroperoxide. In addition, we show that S. pyogenes demonstrates an inducible peroxide resistance response when treated with sublethal doses of peroxide. This resistance response was intact in ahpC and gpoA mutants but not in mutants lacking PerR, a repressor of several genes including ahpC and catalase (katA) in Bacillus subtilis. Because our data indicate that these peroxidase genes are not essential for aerotolerance or induced resistance to peroxide stress in S. pyogenes, genes for a novel mechanism of managing peroxide stress may be regulated by PerR in streptococci.

Catalase (KatA) and Alkyl Hydroperoxide Reductase (AhpC) Have Compensatory Roles in Peroxide Stress Resistance and Are Required for Survival, Persistence, and Nasal Colonization inStaphylococcus aureus

“…Similarly, in the catalase-deficient bacterium Streptococcus pyogenes, the ahpC mutant strain has a growth defect when grown aerobically in the presence of 10 mM paraquat, which can be complemented by supplementing the medium with catalase (27). As the ahpC katA perR mutant of S. aureus was no more resistant to paraquat than ahpC katA, derepression of the PerR regulon is not effective in protecting against superoxide stress.…”

Oxidative stress tolerance is manganese (Mn2+) regulated in Streptococcus gordonii

“…Staphylococcus aureus PerR controls the expression of at least eight genes (Horsburgh et al, 2001). In S. pyogenes, PerR is essential for induced resistance to peroxide (King et al, 2000), although it does not apparently regulate expression of ahpC, encoding alkyl hydroperoxide reductase. It is possible therefore that a PerR orthologue may be involved in co-ordinating gene regulation in response to metal ions and ROS in S. gordonii.…”

“…The expression of sodA is also enhanced under oxidative stress in some streptococci (Gibson & Caparon, 1996 ;Yesilkaya et al, 2000). However, relatively little is known about the function or regulation of streptococcal peroxidase enzymes, which In silico analysis of the Streptococcus pyogenes genome revealed genes encoding glutathione peroxidase (GpoA) and alkyl hydroperoxide reductase (AhpC) that were found to be involved in protection against O − # and organic peroxides (King et al, 2000). In mitis-group streptococci (Whiley & Beighton, 1998), including Streptococcus gordonii, Streptococcus parasanguis and Streptococcus pneumoniae, orthologous genes encoding proteins with about 50 % amino acid sequence identities to Escherichia coli thiol peroxidase (Tpx) have been identified Dintilhac & Claverys, 1997 ;Kolenbrander et al, 1998).…”

Regulation of inducible peroxide stress responses

“…Interestingly, fur is not peroxide inducible in either S. aureus or B. subtilis, indicating that not all members of the PerR regulon are members of the peroxide stimulon (Horsburgh et al, 2001;. In S. pyogenes, a catalase-negative bacterium, PerR co-ordinates an adaptive response to peroxide stress, but the targets of PerR regulation have not yet been identified (King et al, 2000). Like B. subtilis, C. jejuni perR was identified during analysis of proteins induced by iron starvation (van Vliet et al, 1998;.…”

“…PerR and PerR-like regulators have now been described in a wide variety of organisms including Staphylococcus aureus, Streptococcus pyogenes and the Gram-negative pathogen Campylobacter jejuni (van Vliet et al, 1999;King et al, 2000;Horsburgh et al, 2001). The S. aureus PerR regulon is very similar to that in B. subtilis: PerR mediates repression of catalase, alkyl hydroperoxide reductase, PerR, Fur and thioredoxin in response to Mn(II).…”