Heavy metal tolerance traits of filamentous fungi isolated from gold and gemstone mining sites

Abstract

tIncreased environmental pollution has necessitated the need for eco-friendly clean-upstrategies. Filamentous fungal species from gold and gemstone mine site soils were iso-lated, identified and assessed for their tolerance to varied heavy metal concentrations ofcadmium (Cd), copper (Cu), lead (Pb), arsenic (As) and iron (Fe). The identities of the fungalstrains were determined based on the internal transcribed spacer 1 and 2 (ITS 1 and ITS 2)regions. Mycelia growth of the fungal strains were subjected to a range of (0–100 Cd), (0–1000Cu), (0–400 Pb), (0–500 As) and (0–800 Fe) concentrations (mgkg−1) incorporated into maltextract agar (MEA) in triplicates. Fungal radial growths were recorded every three days overa 13-days’ incubation period. Fungal strains were identified as Fomitopsis meliae, Trichodermaghanense and Rhizopus microsporus. All test fungal exhibited tolerance to Cu, Pb, and Fe atall test concentrations (400–1000 mgkg−1), not differing significantly (p > 0.05) from the con-trols and with tolerance index >1. T. ghanense and R. microsporus demonstrated exceptionalcapacity for Cd and As concentrations, while showing no significant (p > 0.05) differencecompared to the controls and with a tolerance index >1 at 25 mgkg−1Cd and 125 mgkg−1As. Remarkably, these fungal strains showed tolerance to metal concentrations exceedingglobally permissible limits for contaminated soils. It is envisaged that this metal tolerancetrait exhibited by these fungal strains may indicate their potentials as effective agents forbioremediative clean-up of heavy metal polluted environments