Hormesis and Low Toxic Effects of Three Lanthanides in Microfungi Isolated from Rare Earth Mining Waste in Northwestern Russia.

The low-dose toxicity of chloride and nitrate salts of three lanthanides (La, Ce and Nd) was tested on six microfungal species. Five of them (, , , and ) were isolated from the loparite ore tailings on the Kola Peninsula, northwestern Russia. was a control strain. In the case of nitrate salts, the toxicity of REEs to four of six microorganisms was significantly ( < 0.5) lower compared to chloride salts. In this case, nitrates can play the role of exogenous nutrients, compensating for the toxic effect of REEs. Interestingly, only showed an opposite response, indicating the highest toxicity of nitrate (IC = 9-20 mg/L) REEs' salts compared to chlorides (IC = 80-195 mg/L) at low concentration levels. In addition, treatment with lanthanides showed a "hormesis effect" on fungal growth with stimulation at low doses and inhibition at high doses. However, and demonstrated the absence of hormetic response under the treatment of REEs' nitrate salt. Taking into account the specific hormetic responses and high tolerance of and to lanthanides, our findings may be useful in the assessment of the potential application of the selected fungi to bioremediation and REE bioleaching.