Ozone-induced Fatty Acid and Viability Changes in Chlorella

Ozone-treated cells of the photosynthetic green alga Chlorella sorokiniana var. pacificensis exhibit an exponential decline in viability, as measured by their ability to form colonies on agar plates. Postexposure conditions appear to have little, if any, effect on this rate of decline. Except in young (early exponential phase) cells, culture age did not affect this rate. The decline in cell viability was correlated with the production of malondialdehyde, arising from the oxidative breakdown of an ozonide of unsaturated fatty acid material. The loss of fatty acids is substantiated by gas-liquid chromatography. A loss of 5 x 10(-15) moles of fatty acid per cell corresponds to 75% nonviable cells after 50 minutes of ozone exposure.