Heavy metals and thiol compounds in Mucor racemosus and Articulospora tetracladia

The influence of Cd(II), Cu(II) and Zn(II) on growth and thiol production i n an aquatic hyphomycete (Articulospora tetracladia) and a zygomycete (Muco r racemosus) were studied. Growth of a strain of M. racemosus, isolated fro m effluents contaminated by heavy metals, was not inhibited by Cd concentra tions of up to 100 mum. M. racemosus was more sensitive to Cu and Zn. The p roduction of SH-containing compounds by M. racemosus was positively correla ted with Cd concentration in the nutrient medium. By contrast, glutathione concentration in the mycelium was negatively correlated with Cd concentrati on. Addition of Zn or Cu to the medium had no significant effect on mycelia l levels of thiol compounds or glutathione. One strain of A. tetracladia, i solated from a clean stream (At-BB), significantly increased the production of thiol compounds and of glutathione in the presence of Cd; the other str ain from a Cu enriched stream (At-CS) showed no significant response. Addit ion of Zn or Cu did not significantly change levels of thiols or glutathion e, with one exception: glutathione levels in At-CS were negatively correlat ed with external Cu levels. Declining glutathione levels in M. racemosus ex posed to Cd was coupled with the appearance of several phytochelatins. No s uch compounds were found in A. tetracladia.