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 C u reduced radial growth of most strains by 50% at concentrations betwe en 150-400 mu M; in a liquid medium, the strains were more sensitive. The inhibitory effects of zinc were much less severe. Two isolates (Ar ticulospora tetracladia and Tetracladium marchalianum) from a copper-m ine stream were more resistant against copper than conspecific strains from a non-polluted stream. Heliscus lugdunensis and Varicosporium el odeae responded to Cd exposure, but not to Cu or Zn exposure, by incre ased synthesis of SH-containing compounds. Glutathione levels showed a unimodal response to increasing Cd and Zn exposure. With copper, glut athione decreased at intermediate levels of contamination. In the pres ence of Cd, H. lugdunensis synthesized several unknown sulfur-rich sub stances that were absent or produced at reduced rates in control cultu res.