Importance of Bacillithiol in the Oxidative Stress Response of Staphylococcus aureus

Abstract

In Staphylococcus aureus, the low-molecular-weight thiol called bacillithiol (BSH), together with cognate S-transferases, is believed to be the counterpart to the glutathione system of other organisms. To explore the physiological role of BSH in S. aureus, we constructed mutants with the deletion of bshA (sa1291), which encodes the glycosyltransferase that catalyzes the first step of BSH biosynthesis, and fosB (sa2124), which encodes a BSH-S-transferase that confers fosfomycin resistance, in several S. aureus strains, including clinical isolates. Mutation of fosB or bshA caused a 16-to 60-fold reduction in fosfomycin resistance in these S. aureus strains. High-pressure liquid chromatography analysis, which quantified thiol extracts, revealed some variability in the amounts of BSH present across S. aureus strains. Deletion of fosB led to a decrease in BSH levels. The fosB and bshA mutants of strain COL and a USA300 isolate, upon further characterization, were found to be sensitive to H 2 O 2 and exhibited decreased NADPH levels compared with those in the isogenic parents. Microarray analyses of COL and the isogenic bshA mutant revealed increased expression of genes involved in staphyloxanthin synthesis in the bshA mutant relative to that in COL under thiol stress conditions. However, the bshA mutant of COL demonstrated decreased survival compared to that of the parent in human wholeblood survival assays; likewise, the naturally BSH-deficient strain SH1000 survived less well than its BSH-producing isogenic counterpart. Thus, the survival of S. aureus under oxidative stress is facilitated by BSH, possibly via a FosB-mediated mechanism, independently of its capability to produce staphyloxanthin.

Isobaric Tags for Relative and Absolute Quantitation Proteomics Analysis of Gene Regulation by SprC in Staphylococcus Aureus

“…In the process of infection, the organism faces metabolic and environmental stresses from the host such as reactive oxygen species and lipid peroxides [33,34]. If the bacterium has an ineffective response to the injury generated by oxidative stress, it is in danger of amassing harmful mutations, membrane breakdown and cell death [35].…”

“…If the bacterium has an ineffective response to the injury generated by oxidative stress, it is in danger of amassing harmful mutations, membrane breakdown and cell death [35]. Generation of low-molecular-weight (LMW) thiols is a wise strategy applied by bacteria to maintain its cellular redox balance and soften the effects of reactive oxygen species [34]. In eukaryotes and Gram-negative bacteria, LMW thiol glutathione (GSH) is prevalent [36,37], while in S. aureus, bacillithiol (BSH) is the major LMW thiol [38].…”

Characterization of RNA Helicase CshA and Its Role in Protecting mRNAs and Small RNAs of Staphylococcus aureus Strain Newman

“…Reverse transcription-quantitative PCR (qRT-PCR) was performed as previously described (33). Briefly, cDNA was obtained using qScript cDNA Supermix (Quanta Biosciences) and DNase I-treated RNA as a template.…”

Characterization of a Novel Two-Component Regulatory System, HptRS, the Regulator for the Hexose Phosphate Transport System in Staphylococcus aureus

“…Resistance to fosfomycin could be induced by (i) the impaired uptake of fosfomycin through UhpT and GlpT (33), (ii) overexpression or mutation in MurA (33), (iii) biochemical modifications of fosfomycin (bacillithiol conjugation) by FosB (34), and (iv) impaired bacillithiol synthesis by downregulation of the bacillithiol synthesis enzyme, BshA (35). It is noteworthy that the wild-type LAC strain is highly sensitive to the fosfomycin, although it harbors both the fosB and bshA genes.…”