| Summary: | Staphylococcus aureus is a major pathogen causing both community and hospital-acquired infections. The diversity of diseases caused by this organism can be attributed to its ability to colonize a range of niches and to adapt to the stressful environments of the host. As part of this, successful utilization of host nutrients is crucial for pathogenesis. Sulfur is an essential element required for many cellular components. S.aureus can use glutathione as sole sulfur source and as it cannot synthesize this molecule, it must acquire it from the host. Glutathione utilization is facilitated by gammaglutamyltranspeptidase (GGT) in many organisms. To analyse the role of GGT in S.aureus, the putative ggt gene was identified and insertionally inactivated. The ggt mutant was still able to grow on glutathione, which suggests a novel alternative pathway for catabolism. The role of a putative glutathione transporter was also investigated. Mutant strains, although still able to grow on glutathione showed a stress defect, in particular to tellurite. S.aureus is well known as having high level tellurite resistance. Resistance occurs via reduction leading to cytoplasmic deposits of tellurium. Purification of tellurite reductase activities resulted in the identification of alkylhydroperoxidase subunit F (AhpF) and thioredoxin reductase (TrxB). The relative roles of these two enzymes in tellurite reduction was examined.
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