Inactivation of DNA repair genes leads to the induction of vitamin B<sub>1</sub> biosynthesis.

<p>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 Δ<i>mutS</i>, Δ<i>mutL</i>, and Δ<i>mutS2</i> strains, the genes for vitamin B<sub>1</sub> biosynthesis are activated to prevent the accumulation of oxidative damage in DNA via an unknown mechanism.</p>