The OD600 values were determined after 12 h. Data represent the means ± standard deviations of three independent experiments. To further investigate the influence of manganese ions on the mntE – mutant, different concentrations of manganese ions were added to TGY medium, and the growth of the mntE – mutant was measured (Figure 3C). The results showed that in comparison with R1, the growth of the mntE -

mutant was clearly delayed in the presence of low concentrations of manganese ions. When the manganese concentration increased, the growth defect phenotype became more pronounced. This phenotype is similar to that observed in Rosch’s study in which the growth of S. pneumoniae having a disrupted calcium efflux system was more severely inhibited at higher calcium concentrations [18]. The mntE- mutant shows high intracellular Paclitaxel order manganese concentrations To confirm that

the mntE – mutant had lost its ability to export manganese ions, the intracellular manganese ion levels of wild-type R1 and the mntE – mutant were measured by inductively coupled plasma-mass spectrometry (ICP-MS). As expected, when grown on TGY medium supplemented with manganese ions, the manganese ion level in the mntE – mutant was almost four-fold higher than that in wild-type R1. However, there was no significant difference in the intracellular Fe ion BVD-523 cell line concentrations of R1 and the mutant (Figure 4A). Similar results were obtained when the mntE – mutant and wild-type R1 were grown on TGY medium (Figure 4B). This result indicates that Dr1236 is a manganese ion exporter. Figure 4 Analysis of the intracellular ion content of wild-type R1 and mntE – cultured in medium supplemented with

or without cations. (A) R1 (white bars) and mntE – (grey bars) were cultured in TGY medium supplemented with 50 μM manganese, 10 μM ferric chloride, 100 mM magnesium, or 100 mM calcium chloride to determine the effects of these specific cations. (B) R1 (white bars) and mntE – (grey bars) were cultured in TGY medium without added cations. Cells (OD600 = 0.8) were harvested, and learn more the extracellular SIS3 cost cations were removed by washing in EDTA. The cation concentration was determined by ICP-MS. The data represent the means ± standard deviations of three independent experiments. The mntE- mutant shows higher resistance to γ-radiation, UV, and oxidative Recently, there has been a debate on whether the high intracellular Mn/Fe ratio of D. radiodurans contributes to the extreme oxidative resistance of this microorganism. Daly et al proposed that the high Mn/Fe ratio can effectively suppress protein carbonylation and increase radiation resistance [7, 8]. In contrast, Sukhi et al and Shashidhar et al argued that D. radiodurans exhibits the same radiation resistance even when the intracellular Mn/Fe ratio changed substantially [19, 20].