Lead (Pb) tolerance in the ectomycorrhizal fungi Suillus brevipes and S. tomentosus.

Lead (Pb) is a highly toxic metal and a contaminant of many soils across the world. Some fungi are known to be Pb tolerant, persisting in environments with high Pb levels. Here we investigate Pb tolerance in Suillus brevipes and S. tomentosus, two widespread ectomycorrhizal fungal species in the American West where soil contamination due to mining is common. We conducted in vitro growth assays, exposing previously studied isolates to a range of Pb concentrations. We found S. tomentosus to be more Pb tolerant compared to S. brevipes and that isolates from the two species showed both high and low Pb tolerance. There were no correlations between Pb tolerance and Pb soil concentration, isolate growth rate, or Zn tolerance. Lead tolerance was positively correlated with Cd tolerance in S. tomentosus. Our research contributes for understanding fungal metal tolerance variability and paves the way for future work addressing the mechanisms of Pb tolerance and the potential for using Suillus in the recovery of contaminated sites.