Effects of organotin and organolead compounds on yeasts

Four methods were used to screen nine organotin and two organolead compounds for toxicity to 29 yeasts, representing 10 genera. Center well diffusion plates were useful in comparing the sensitivity of yeasts to the most toxic organometals but were not useful for comparisons between compounds because of differences in diffusion rates and lack of sensitivity. Two-layer diffusion plates (density gradient plates) were also of limited use for comparisons between compounds but provided quantitative information on toxicity and allowed comparisons between organisms. Two-dimensional diffusion plates were useful for estimating the effect of pH on organometal toxicity. Release of K⁺ from cell suspensions measured using a K⁺-electrode provided quantitative information and allowed comparisons between compounds and organisms. The presence of 3% NaCl in cell suspensions decreased the rates and extent of organotin-induced K⁺ release. Yeasts varied in their sensitivity from strain to strain, but tributyltin was the most toxic compound tested. Mono- and dimethyltins were the least toxic. Triphenyltin, dibutyltin, monobutyltin, trimethyltin, triethyltin, diethyllead, diethyltin, and dimethylleads showed intermediate toxicity, but triphenyltin and monobutyltin were the most toxic among the group.