OhrRA functions as a redox-responsive system controlling toxinogenesis in Bacillus cereus

Clair , Gérémy
        INRA
        , Avignon .
         UMR 0408 Sécurité et Qualité des Produits d'Origine Végétale; Lhorphelin , Alain
        . Laboratoire de Biochimie des Systèmes Perturbés; Armengaud , Jean
        . Laboratoire de Biochimie des Systèmes Perturbés; Duport , Catherine
        INRA
        , Avignon .
         UMR 0408 Sécurité et Qualité des Produits d'Origine Végétale

OhrRA functions as a redox-responsive system controlling toxinogenesis in Bacillus cereus

2013

Clair , Gérémy (INRA , Avignon (France). UMR 0408 Sécurité et Qualité des Produits d'Origine Végétale) | Lhorphelin , Alain (Commissariat à l'Energie Atomique et aux Energies Alternatives, Bagnols - sur - Cèze(France). Laboratoire de Biochimie des Systèmes Perturbés) | Armengaud , Jean (Commissariat à l'Energie Atomique et aux Energies Alternatives, Marcoule - Banols - sur- Cèze(France). Laboratoire de Biochimie des Systèmes Perturbés) | Duport , Catherine(auteur de correspondance) (INRA , Avignon (France). UMR 0408 Sécurité et Qualité des Produits d'Origine Végétale)

Bacillus cereus OhrR is a member of the subgroup of the MarR (multiple antibiotic resistance) family of transcriptional regulators that use a cysteine-based redox sensing mechanism. OhrA is a thiol-dependent, peroxidase-like protein. The dual OhrRA system triggers B. cereus adaptation in response to redox changes, such as those encountered in the environment of the gastrointestinal tract. Here, we investigated the role of OhrRA in toxinogenesis. Comparative shotgun analysis of exoproteomes from ΔohrA, ΔohrR and wild-type cells revealed significant changes in the abundance levels of toxin-related proteins depending on the extracellular redox potential.We complemented these data by measuring the DNA binding activity of reduced and oxidized recombinant OhrR on toxin and putative toxin promoter regions. Furthermore, transcriptomic data and OhrRA-dependent, antiproliferative activity of the B. cereus exoproteome on Caco-2 human epithelial cells were recorded. The results indicate that OhrR controlled toxin gene expression directly or indirectly in a redox- and toxin-dependent manner, and may function as a repressor or an activator. Moreover, we found that OhrR restricts toxindependent antiproliferative activity of the B. cereus exoproteome whatever the growth conditions, while the restrictive impact of OhrA occurs only under low ORP anoxic conditions.

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