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Mycothiol peroxidase MPx protects Corynebacterium glutamicum against acid stress by scavenging ROS

Tietao Wang, Fen Gao, Yiwen Kang, Chao Zhao, Tao Su, Muhang Li, Meiru Si and Xihui Shen

Corynebacterium glutamicum mycothiol peroxidase (MPx) is a novel CysGPx family peroxidase that uses both the mycoredoxin and thioredoxin reducing systems as proton donors for peroxide detoxification. In this study, we revealed that MPx is also important for cellular survival under acid stress. A Δmpx mutant exhibited significantly decreased resistance to acid stress and markedly increased accumulation of reactive oxygen species (ROS) and protein carbonylation levels in vivo. Overexpression of mpx increased the resistance of C. glutamicum to acid stress by reducing ROS accumulation. Elevated expression of the mpx gene was consistently observed when the C. glutamicum wild-type strain was exposed to acid stress conditions, which in turn directly contributed to tolerance to acid stress. The acid-induced expression of mpx was mediated by the stress-responsive extracytoplasmic function-sigma (ECF-σ) factor, SigH. The results unequivocally show that MPx is essential for combating acid stress by reducing intracellular ROS levels induced by acid stress in C. glutamicum, which adds a new dimension to the general physiological functions of CysGPx.