Effects of cadmium, copper, and zinc on growth and thiol content of aquatic hyphomycetes

The effects of cadmium, copper, and zinc on the growth of ten strains of aquatic hyphomycetes were investigated. On a solid medium, Cd and Cu reduced radial growth of most strains by 50% at concentrations between 150-400 mu M; in a liquid medium, the strains were more sensitive. The inhibitory effects of zinc were much less severe. Two isolates (Articulospora tetracladia and Tetracladium marchalianum) from a copper-mine stream were more resistant against copper than conspecific strains from a non-polluted stream. Heliscus lugdunensis and Varicosporium elodeae responded to Cd exposure, but not to Cu or Zn exposure, by increased synthesis of SH-containing compounds. Glutathione levels showed a unimodal response to increasing Cd and Zn exposure. With copper, glutathione decreased at intermediate levels of contamination. In the presence of Cd, H. lugdunensis synthesized several unknown sulfur-rich substances that were absent or produced at reduced rates in control cultures.