Glutathione analogs in prokaryotes

► Biosynthesis of glutathione appears to have evolved several times in prokaryotes. ► Mycothiol is found in Actinobacteria and has functions similar to glutathione. ► Bacillithiol, a new thiol found in Firmicutes, has received only limited study. ► Ergothioneine and coenzyme A may have protective roles in some prokaryotes. ► The biochemistry of small thiols is largely unexplored in many prokaryotes.