Adaptation by Tetrahymena pyriformis to Potassium Cyanide II. Adaptation Against Respiratory Inhibition*

Abstract

SUMMARY. Cells from a clonal culture of Tetrahymena pyriformis W were cultured in the presence of 10‐4 M KCN for a prolonged time until they became “adapted” to cyanide. The effect of 10‐3 M KCN upon respiration in the “adapted” cells was compared with the effect upon “normal” cells of the same clone grown in the absence of cyanide. The direct method of Warburg was employed. Adapted cells are more resistant against respiratory inhibition than are normal cells. Resistance is due both to a factor or factors retained within the cell and the extracellular factor(s) released into the medium by the adapted cells during their growth. The intracellular factor is acid labile, and apparently may be developed within a short time. The extracellular factor is heat labile and may cause normal cells to be more resistant against respiratory inhibition by KCN. Resistance to respiratory inhibition is lost if adapted cells are cultured in the absence of KCN. It is proposed that changes involved in gain or loss of cyanide resistance are due to physiological adaptation and not to the usual genetic influences.

Microorganisms and cyanide.

“…McCashland and Pace showed that very low concentrations of cyanide (e.g., 10-9 M) stimulate growth and respiration of T. pyriformis strain W but that higher concentrations inhibit both of these processes (98). McCashland (95,96) grew strain W in media containing gradually increasing concentrations of cyanide (from 10-12 to 10-4 M). Cells adapted to 10-4 M cyanide have 82% of the volume of normal, nonadapted cells, and their nucleus-cytoplasmic volume ratio is greater.…”