Effect of High Oxygen Tension on Potassium Retentivity and Colony Formation of Bakers' Yeast

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Abstract
The ability of yeast cells to retain K and to form colonies was studied after exposure to pressures ranging from 2 to 143 atmospheres of O2. The investigations allow comparison of these responses with those found after x-ray exposure. Exposure to 2 to 8 atmospheres of O2 for 2, 20, and 40 hours showed decreased K leakage as measured by an elution technique. Further experiments using 0.5 to 22 hour exposures to 10 to 143 atmospheres of O2 showed decreased K leakage when glucose was present in the test media, but increased leakage (as did x-ray effects) in the absence of substrate. There was increased K leakage into the suspending media (distilled water) during O2 exposure but this usually did not affect the leakage rates measured subsequently. Marked inability to form colonies was observed after 20 hour exposures to 100 atmospheres of O2, with a much smaller response at lower pressures. Increased O2 concentrations, not pressure, evidently caused these effects, since comparable pressures of N produced almost no change. The ratio of potassium leakage to survival sensitivity was found to be approximately unity when comparing exposures causing 50% damage. This is quite different from that seen with x-ray or ultraviolet irradiation.