The D10 value represents the irradiating dose required to reduce the population by 90%. Here, the D10 value was proposed to assess the resistant ability of R1 and mntE – mutant to different stresses. As shown in Figure 5 the resistance of the mntE – mutant under different

stresses was higher than that of R1, and the D10 values of the mntE – mutant were 14000 Gy γ-radiation, 700 J/m2 UV, and 50 mM H2O2, whereas that for R1 was 11000 Gy γ-radiation, 600 J/m2 UV, and 40 mM H2O2. Moreover, when R1 and mntE – mutant were cultured in TGY supplemented with 50 μM manganese, their resistance to different stresses also increased remarkably, Ro 61-8048 and it is consistent with their intracellular manganese level (Figure 5). The results suggest that there is a correlation between the intracellular manganese level check details and cellular oxidative resistance, which is consistent with the data from Daly’s studies [8]. Although the role of manganese

in the oxidative resistance of D. radiodurans remains unclear, our study implies that an increase in the intracellular manganese level may be one of the responses to oxidative stress. Moreover, it is AZ 628 in vivo notable that the UV resistance of the mntE – mutant also increased. Generally, UV light results in DNA damage, and only high doses of UV cause oxidative damage. Therefore, it is interesting to speculate that the UV resistance of the mntE – mutant may be indirectly enhanced by manganese ions. In fact, many important DNA repair enzymes use Mn2+ as the cofactor [21], and manganese accumulation may have a positive effect on gene function. Furthermore, a high intracellular manganese level is also known to have an important effect on the expression of many genes Carnitine palmitoyltransferase II including stress response genes [10]. Figure 5 Survival curves for R1 (triangles) and mntE – (squares) following exposure

to UV (A), H 2 O 2 (B), and γ-radiation (C). R1 and mntE – were cultured in TGY broth with or without 50 μM manganese. The values represent the means ± standard deviations of four independent experiments. The mntE- mutant shows a lower protein oxidation level under oxidative stress The protein carbonylation level is an important index of intracellular oxidative damage to proteins [8]. Previous reports have shown that the proteins of IR-sensitive bacteria are more vulnerable than those of D. radiodurans to ROS-induced protein oxidative damage [7]. Therefore, we measured and compared the levels of protein carbonylation in the mntE – mutant and wild-type R1. Notably, the level of protein carbonylation in the mntE – mutant decreased to nearly 50% of that in R1 after H2O2 treatment (Figure 6), indicating that the mutation of mntE resulted in a lower level of protein oxidation than that observed in the wild type.