Effects of heavy metals on the production of thiol compounds by the aquatic fungi Fontanospora fusiramosa and Flagellospora curta.

The aquatic hyphomycetes Fontanospora fusiramosa and Flagellospora curta isolated from a clean and a metal-contaminated site, respectively, were tested for the production of thiol compounds when exposed to Cd, Zn, and Cu for short- and long-term periods. After 8 days, control cultures of F. curta had a total thiol (T-SH) concentration in mycelia of 3.46 +/- 0.37 micromol g(-1) dry mass, which was 2.4 times greater than that of F. fusiramosa. In both species, nonprotein (NP-SH) and protein-bound (PB-SH) thiols accounted for 30% and 70% of T-SH, respectively. F. curta increased the production of thiol compounds, namely NP-SH, more rapidly than F. fusiramosa when exposed to Cd or Zn. The greater increases in either NP-SH or PB-SH occurred in F. fusiramosa after long-term exposure to all metals; in this case, the increases of PB-SH overwhelmed those of NP-SH. Long-term exposure to metals also increased the mycelial protein concentration.