On the mechanism of mitotic segregation induction in Aspergillus nidulans by benzene hydroxy metabolites.

The principal hydroxy-metabolites of benzene--hydroquinone, catechol and phenol--were assayed in tests for mitotic segregation induction in Aspergillus nidulans diploid strain 19. Hydroquinone was the most effective chemical, increasing the frequency of mitotic segregants up to 10-fold at 1-3 mM. Catechol was similarly active at 10-20 mM and phenol was weakly positive at 15 mM. Genetic characterization of induced abnormal segregating colonies by replating and complementary assays with haploid strain 35 suggest that gross chromosomal aberrations, instead of numerical abnormalities, are the primary genetic damages induced by hydroxybenzenes in A. nidulans. The protecting activity exerted by L-cysteine against equimolar concentrations of hydroquinone supports a free radical mechanism for hydroxybenzenes genotoxicity in A. nidulans.