9120 Nucleic Acids Research, 2012, Vol. 40, No. 18 Figure 2. Continued. transition-metal homeostasis (38–40). Thioredoxins are found in nearly all organisms, acting as antioxidants by facilitating the reduction of other proteins by cysteine thio-disulﬁde exchange (41). It seems unlikely that PT DNA can substitute the known anti-oxidizing mechanisms, such as thioredoxin. Indeed, the growth curve experiment presented here clearly demonstrate that dnd mutants survive treatment with 2 mM H2O2 (Figure 4), which might be explained by the activity of catalase, peroxidase, thioredoxin or a combination of