content, followed by post-hoc Bonferroni test when the overall p value was less than 0.05. For SKN-1::GFP fluorescence analysis, unpaired two-tailed T-test was used to assess statistical differences in mean values. In all figures, error bars represent SEM; * refers to differences between genotypes; # refers to differences between doses; */# p,0.05; **/## p,0.01; and ***/### p,0.001. Supporting Information Figure S1 mod-5 loss of function does not affect Mn-induced lethality. The serotonin re-uptake transporter (SERT) mutant mod- 5(n3314) is not significantly different from wild type (p.0.05) regarding Mn sensitivity, and is characterized by an LD50 = 45 mM. Found at: doi:10.1371/journal.pgen.1001084.s001 (0.12 MB TIF) Figure S2 cat-2(e1112) exhibits higher ROS levels than wild type upon Fe exposure. 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