Nutritional influence on fungal colony growth and biomass distribution in response to toxic metals

This work examines nutritional influence on fungal colony growth and biomas s distribution in response to toxic metals. In low-substrate solid medium, 0.1 mM Cd, Cu and Zn caused a decrease in radial expansion of both Trichode rma viride and Rhizopus arrhizus. However, as the amount of available carbo n source (glucose) increased, the apparent toxicity of the metals decreased . These metals also affected the overall length of the fungal mycelium and branching patterns. In low-nutrient conditions, T viride showed a decrease in overall mycelial length and number of branches in response to Cu, result ing in an extremely sparsely branched colony. Conversely, although Cd also reduced overall mycelial length to about one-third of the control length, t he number of branches decreased only slightly which resulted in a highly br anched colony with many aberrant features. Cu and Cd induced similar morpho logical changes in R. arrhizus. A large-scale mycelial-mapping technique sh owed that disruption of normal growth by Cu and Cd resulted in altered biom ass distribution within the colony. When grown on metal-free low-substrate medium, T. viride showed an even distribution of biomass within the colony with some allocation to the periphery. However, Cu caused most of the bioma ss to be allocated to the colony periphery, while in the presence of Cd, mo st biomass was located at the interior of the colony. These results imply t hat such alterations of growth and resource allocation by Cu and Cd may inf luence success in locating nutrients as well as survival, and that these me tals have individual and specific effects on the growing fungus. (C) 2001 F ederation of European Microbiological Societies. Published by Elsevier Scie nce B.V. All rights reserved.