Cysteinylation, covalent bond-between protein cysteinyl residue and free cysteine; Glutathione (GSH) and cysteine (Cys)-abundant LMM thiols in mammals; Protein S-glutathionylation and S-cysteinylation; Protein thiol groups (PSHs), physiologically reversible cysteine sulfenic derivative (PSOH); Reactive oxygen species (ROS) and reactive nitrogen species (RNS)-double-face significance; Role of protein cysteine S-glutathionylation-in redox signaling and oxidative stress responses; S-cysteinylation importance, means for thiol protection-against oxidative stress in Bacillus subtilis; S-glutathionylation and S-cysteinylation-reversible post-translational modifications; S-glutathionylation and S-cysteinylation-two protein modifications in oxidative stress