Negative fungal chemotropism to toxic metals

Hyphal growth responses of Geotrichum candidum, Gliocladium roseum, Humicola grisea and Trichoderma viride to Cu and Cd were studied using a simple tessellated agar tile system. Negative chemotropic behaviour of hyphae, which included curling and growth away from metal-containing domains, occurred in all species and with both metals. Both toxic metal and sucrose concentrations in the medium modulated the magnitude of the negative chemotropic effects observed. In general, greater concentrations of metals led to a higher level of negative chemotropism in response to Cu and Cd, which could be reduced with increasing concentrations of sucrose in the medium. This suggests that resource availability affects the ability of these fungi to grow into metal-laden domains.