J. Gen. Appl. Microbiol

Corynebacterium glutamicum is not only well known as a very important industrial microorganism (mainly used in the production of amino acids and vitamins), but also as a model organism in microbial research, and for the disclosing of catabolism mechanisms of aromatic compounds in high G+C content Gram-positive bacteria (Shen et al., 2012). It is inevitable that bacteria will be subject to a variety of environmental stresses, resulting in the production and accumulation of various reactive oxygen and nitrogen species (ROS, RNS), causing the oxidation of biological macromolecules, breaking the intracellular redox balance, resulting in cell dysfunction and leading to cell damage and even apoptosis (Davies, 2005; Si et al., 2014). To survive under hostile conditions, bacteria adopt a variety of resistant mechanisms, including several antioxidant enzymes, such as catalases, superoxide dismutases, peroxiredoxins, alkyl hydroperoxide reductases, organic hydroperoxide resistance protein and thiol peroxidase, which have been characterized to resist oxidative stresses (An et al., 2010; Baysse et al., 2000; Hassett et al., 1995; Liu et al., 2016; Ochsner et al., 2001). Amino acid residues in proteins represent one of the major targets of ROS and cellular oxidants (Vogt, 1995). Methionine (Met) ranks as one of the most sensitive amino acids to oxidation and it can be oxidized into methionine sulfoxide (MetO) which contains two classes, methionineS-sulfoxide (Met-S-O) and methionine-R-sulfoxide (MetR-O), leading to changes in protein conformation and causing a loss of biological activities (Couturier et al., 2012; Stadtman et al., 2002, 2003). Methionine sulphoxide reductases (Msr) present in most living organisms are antioxidant repair enzymes that catalyze the reduction of MetO Functional comparison of methionine sulphoxide reductase A and B in Corynebacterium glutamicum