Inactivation of DNA repair genes leads to the induction of vitamin B₁ biosynthesis.

Extracellular oxidative stress and intracellular redox metabolism generate ROS, which can attack DNA to yield oxidatively damaged DNA. (A) In the wild-type strain, oxidatively damaged DNA is repaired by DNA repair enzymes including MutS, MutL, and MutS2. (B) In the ΔmutS, ΔmutL, and ΔmutS2 strains, the genes for vitamin B₁ biosynthesis are activated to prevent the accumulation of oxidative damage in DNA via an unknown mechanism.