OXYGEN-TOXICITY IN A POLYAMINE-DEPLETED SPE2-DELTA MUTANT OF SACCHAROMYCES-CEREVISIAE

When a mutant of Saccharomyces cerevisiae (spe2DELTA) that cannot make spermidine or spermine was incubated in a polyamine-deficient medium in oxygen, there was a rapid cessation of cell growth and associated c ell death. In contrast, when the mutant cells were incubated in the po lyamine-deficient medium in air or anaerobically, the culture stopped growing more gradually, and there was no significant loss of cell viab ility. We also found that the polyamine-deficient cells grown in air, but not those grown anaerobically, showed a permanent loss of function al mitochondria (''respiratory competency''), as evidenced by their in ability to grow on glycerol as the sole carbon source. These data supp ort the postulation that polyamines act, in part, by protecting cell c omponents from damage resulting from oxidation. However, since the mut ant cells still required spermidine or spermine for growth when incuba ted under strictly anaerobic conditions, polyamines must also have oth er essential functions.