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PerR controls oxidative stress resistance and iron storage proteins and is required for virulence in Staphylococcus
M J Horsburgh1, M O Clements, H Crossley
1Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2TN, England.
Abstract:
The Staphylococcus aureus genome encodes three ferric uptake regulator (Fur) homologues: Fur, PerR, and Zur. To determine the exact role of PerR, we inactivated the gene by allelic replacement using a kanamycin cassette, creating strain MJH001 (perR). PerR was found to control transcription of the genes encoding the oxidative stress resistance proteins catalase (KatA), alkyl hydroperoxide reductase (AhpCF), bacterioferritin comigratory protein (Bcp), and thioredoxin reductase (TrxB). Furthermore, PerR regulates transcription of the genes encoding the iron storage proteins ferritin (Ftn) and the ferritin-like Dps homologue, MrgA. Transcription of perR was autoregulated, and PerR repressed transcription of the iron homeostasis regulator Fur, which is a positive regulator of catalase expression. PerR functions as a manganese-dependent, transcriptional repressor of the identified regulon. Elevated iron concentrations produced induction of the PerR regulon. PerR may act as a peroxide sensor, since addition of external hydrogen peroxide to 8325-4 (wild type) resulted in increased transcription of most of the PerR regulon, except for fur and perR itself. The PerR-regulated katA gene encodes the sole catalase of S. aureus, which is an important starvation survival determinant but is surprisingly not required for pathogenicity in a murine skin abscess model of infection. In contrast, PerR is not necessary for starvation survival but is required for full virulence (P < 0.005) in this model of infection. PerR of S. aureus may act as a redox sentinel protein during infection, analogous to the in vitro activities of OxyR and PerR of Escherichia coli and Bacillus subtilis, respectively. However, it differs in its response to the metal balance within the cell and has the added capability of regulating iron uptake and storage.
Insights
The Staphylococcus aureus PerR protein regulates genes involved in oxidative stress and iron storage. PerR is crucial for virulence in infections, acting as a peroxide sensor and influencing iron homeostasis.
Area of Science:
- Microbiology
- Molecular Biology
- Bacterial Pathogenesis
Background:
- Staphylococcus aureus possesses three Fur homologues: Fur, PerR, and Zur.
- The precise function of PerR in S. aureus remained largely undetermined.
- Understanding PerR's role is key to elucidating bacterial stress response and virulence mechanisms.
Purpose of the Study:
- To investigate the regulatory role of the PerR protein in Staphylococcus aureus.
- To identify the genes and pathways controlled by PerR.
- To determine PerR's contribution to bacterial survival and pathogenesis.
Main Methods:
- Gene inactivation of perR using allelic replacement with a kanamycin cassette.
- Transcriptional analysis of PerR-regulated genes.
- Assessment of bacterial virulence in a murine skin abscess model.
Main Results:
- PerR controls genes for oxidative stress resistance (katA, ahpCF, bcp, trx B) and iron storage (ftn, mrgA).
- PerR acts as a manganese-dependent transcriptional repressor, autoregulated, and represses Fur.
- PerR is essential for S. aureus virulence in a murine model, functioning as a peroxide sensor and regulator of iron homeostasis.
Conclusions:
- PerR is a critical regulator of oxidative stress and iron metabolism in S. aureus.
- PerR functions as a redox sentinel during infection, distinct from its in vitro activities.
- PerR plays a significant role in S. aureus pathogenesis, independent of starvation survival.