Copper tolerance in Saccharomyces cerevisiae

A commercial strain of Saccharomyces cerevisiae was serially cultured in media containing copper up to a final concentration of 10 mmol l^-1. This copper-tolerant subculture was assessed for its capacity to accumulate further quantities of copper. It was found that after Cu²⁺ accumulation the total copper content of this yeast was lower than the parent culture when exposed to similar conditions, indicating that the subculture was copper-resistant owing to reduced copper bioaccumulation properties. Although a low mass copper binding compound was isolated from the copper-tolerant subculture, no metallothionein was found. Scanning electron microscopy of S. cerevisiae showed the cell surface to be smooth except for bud scars. After exposure to copper ion-containing solutions the surface of copper-tolerant yeast became convoluted, the cell was generally more spherical and somewhat smaller.