Prediction of metal cation toxicity to the bioluminescent fungus Gerronema viridilucens

A correlation between the physicochemical properties of mono‐ [Li(I), K(I), Na(I)] and divalent [Cd(II), Cu(II), Mn(II), Ni(II), Co(II), Zn(II), Mg(II), Ca(II)] metal cations and their toxicity (evaluated by the free ion median effective concentration, EC50 F ) to the naturally bioluminescent fungus Gerronema viridilucens has been studied using the quantitative ion character–activity relationship (QICAR) approach. Among the 11 ionic parameters used in the current study, a univariate model based on the covalent index ( X 2 m r ) proved to be the most adequate for prediction of fungal metal toxicity evaluated by the logarithm of free ion median effective concentration (log EC50 F ): log EC50 F  = 4.243 (±0.243) −1.268 (±0.125)· X 2 m r (adj‐ R 2  = 0.9113, Alkaike information criterion [AIC] = −60.42). Additional two‐ and three‐variable models were also tested and proved less suitable to fit the experimental data. These results indicate that covalent bonding is a good indicator of metal inherent toxicity to bioluminescent fungi. Furthermore, the toxicity of additional metal ions [Ag(I), Cs(I), Sr(II), Ba(II), Fe(II), Hg(II), and Pb(II)] to G. viridilucens was predicted, and Pb was found to be the most toxic metal to this bioluminescent fungus (EC50 F ): Pb(II) > Ag(I) > Hg(I) > Cd(II) > Cu(II) > Co(II) ≈ Ni(II) > Mn(II) > Fe(II) ≈ Zn(II) > Mg(II) ≈ Ba(II) ≈ Cs(I) > Li(I) > K(I) ≈ Na(I) ≈ Sr(II)> Ca(II). Environ. Toxicol. Chem. 2010;29:2177–2181. © 2010 SETAC