AUTHOR=Linzner Nico , Loi Vu Van , Fritsch Verena Nadin , Tung Quach Ngoc , Stenzel Saskia , Wirtz Markus , Hell Rüdiger , Hamilton Chris J. , Tedin Karsten , Fulde Marcus , Antelmann Haike 

TITLE=Staphylococcus aureus Uses the Bacilliredoxin (BrxAB)/Bacillithiol Disulfide Reductase (YpdA) Redox Pathway to Defend Against Oxidative Stress Under Infections

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.01355

DOI=10.3389/fmicb.2019.01355

ISSN=1664-302X

ABSTRACT=<p><italic>Staphylococcus aureus</italic> is a major human pathogen and has to cope with reactive oxygen and chlorine species (ROS, RCS) during infections. The low molecular weight thiol bacillithiol (BSH) is an important defense mechanism of <italic>S. aureus</italic> for detoxification of ROS and HOCl stress to maintain the reduced state of the cytoplasm. Under HOCl stress, BSH forms mixed disulfides with proteins, termed as <italic>S</italic>-bacillithiolations, which are reduced by bacilliredoxins (BrxA and BrxB). The NADPH-dependent flavin disulfide reductase YpdA is phylogenetically associated with the BSH synthesis and BrxA/B enzymes and was recently suggested to function as BSSB reductase (<xref ref-type="bibr" rid="B35">Mikheyeva et al., 2019</xref>). Here, we investigated the role of the complete bacilliredoxin BrxAB/BSH/YpdA pathway in <italic>S. aureus</italic> COL under oxidative stress and macrophage infection conditions <italic>in vivo</italic> and in biochemical assays <italic>in vitro</italic>. Using HPLC thiol metabolomics, a strongly enhanced BSSB level and a decreased BSH/BSSB ratio were measured in the <italic>S. aureus</italic> COL Δ<italic>ypdA</italic> deletion mutant under control and NaOCl stress. Monitoring the oxidation degree (OxD) of the Brx-roGFP2 biosensor revealed that YpdA is required for regeneration of the reduced BSH redox potential (<italic>E</italic><sub>BSH</sub>) upon recovery from oxidative stress. In addition, the Δ<italic>ypdA</italic> mutant was impaired in H<sub>2</sub>O<sub>2</sub> detoxification as measured with the novel H<sub>2</sub>O<sub>2</sub>-specific Tpx-roGFP2 biosensor. Phenotype analyses further showed that BrxA and YpdA are required for survival under NaOCl and H<sub>2</sub>O<sub>2</sub> stress <italic>in vitro</italic> and inside murine J-774A.1 macrophages in infection assays <italic>in vivo</italic>. Finally, NADPH-coupled electron transfer assays provide evidence for the function of YpdA in BSSB reduction, which depends on the conserved Cys14 residue. YpdA acts together with BrxA and BSH in de-bacillithiolation of <italic>S</italic>-bacillithiolated GapDH. In conclusion, our results point to a major role of the BrxA/BSH/YpdA pathway in BSH redox homeostasis in <italic>S. aureus</italic> during recovery from oxidative stress and under infections.</p>