Abstract
Glutathione is a nearly ubiquitous, low-molecular-mass thiol and antioxidant, but it is conspicuously absent from most Gram-positive bacteria. We identify here the structure of bacillithiol, a newly described and abundant thiol produced by Bacillus species, Staphylococcus aureus and Deinococcus radiodurans. Bacillithiol is the alpha-anomeric glycoside of L-cysteinyl-D-glucosamine with L-malic acid and most probably functions as an antioxidant. Bacillithiol, like the structurally similar mycothiol, may serve as a substitute for glutathione.