The tolerance and Zn2+, Ba2+ and Fe3+ accumulation by Trichoderma atroviride and Mortierella exigua isolated from contaminated soil

Abstract

This paper presents the results of studies on tolerance to and bioaccumulation of selected heavy metals by filamentous fungi, as a result of natural adaptation and improved resistance of fungal cells. The fungal communities were selected from soils highly contaminated with Zn, Ba and Fe in the vicinity of the chemical plant in Tarnowskie Gory (South Poland, the Silesia Region). The isolates of Trichoderma atroviride and Mortierella exigua were most frequently present in soil with high contents of metals; however, they did not occur in non-contaminated soil samples. The metal tolerance of fungi was determined by measuring growth by means of mycelium diameter on solid medium, dry weight of mycelium on Czapek-Dox solid and Sabouraud liquid media amended with increasing concentrations of Zn2+, Ba2+ and Fe 3+ up to 1000 mg Lr-1. Zn2+, Ba2+ and Fe3+ affected the fungal growth, dry weight and metal uptake. The studied fungi were able to grow at high Zn2+ and Ba2+, but not Fe concentrations. The weight of biomass was dependent on the medium used. The highest accumulation by both T. atroviride and M. exigua was found in the case of Ba2+. Maximal concentrations in T. atroviride mycelium were 21.3, 25.0 and 4.5 mg g-1, in the case of Zn2+, Ba2+ and Fe, respectively. Maximal concentrations in M. exigua mycelium were equal to 32.9 mg L-1 (Zn2+), 15.3 mg L -1 (Ba2+) and 1.2 mg g-1 (Fe3+). Worldwide occurrence of T. atroviride and M. exigua and their easy adaptation to different conditions is promising for their use as bioagents in remediation processes.