Mechanistic study for mutual interactions of Pb2+ and Trichoderma viride

Abstract

Fungi play significant roles in the geochemical processes of heavy metals in the environment. However, the interaction between heavy metals and fungi, especially at the cellular level, is quite complicated and remains unknown. This study explored the mutual interaction mechanism between Pb2+ and Trichoderma viride by combining batch experiments, spectroscopy, and in vitro approaches. Batch experiments revealed that Pb2+ had toxic effect on T. viride, originally causing the biomass of T. viride decreased from 1.3 g in the control group to 0 g in the presence of 200 mg/L Pb2+. The difference in biomass further led to varied pH, even decreasing from 5.7 at the outset to 3.4 due to the acid-production properties of T. viride. Moreover, structural deformation and damage of T. viride mycelium appeared when exposed to Pb2+, and were more evident at a higher dose of Pb2+ exposure. The growth curve exhibited that T. viride gradually adapted to Pb2+ exposure, which related to Pb2+ exposure concentration. Further, intracellular and extracellular secretions of T. viride changed with varying exposure concentrations of Pb2+, indicating that T. viride adapted differently to different concentrations of Pb2+, and MT participated in the detoxification of T. viride. SEM-EDX showed that T. viride could bio-adsorb and bioaccumulate more Pb2+ when exposed to more Pb2+, which was closely related to the content of P. And carbonyl, phosphate, and amino groups of T. viride participated in the Pb2+ biosorption onto T. viride, as evidenced by FT-IR and XPS. Meanwhile, the biomineralization and reduction of Pb2+ by T. viride were observed by XRD and XPS, which might be a possible factor for Pb2+ biosorption and bioaccumulation. CLSM showed that the bio-adsorbed and bioaccumulated Pb2+ were mainly distributed in the membrane of T. viride mycelium.