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Superoxide dismutase activity in antarctic and temperate strains of chroococcidiopsis.  A. L. Price, J. L. Liles and D. J. Thomas.  Science Division, Lyon College, Batesville, AR  72501.

     Superoxide dismutases (SOD’s) are critical components of the antioxidant systems of aerobic (and some anaerobic) organisms.  The antioxidant systems of photosynthetic organisms are particularly well-developed in order to detoxify reactive forms of oxygen that occur as a by-product of photosynthesis.  The amount of reactive oxygen produced during photosynthesis increases when the organism is under environmental stress.  SOD’s have been shown to provide protection against moderate chilling stress in chilling-sensitive cyanobacterium, Synechococcus.  We are currently screening for SOD’s that retain their activity in cyanobacteria that grow at temperatures below 17° C.  Temperate and Antarctic strains of Chroococcidiopsis were grown in liquid culture then passed through a French press to rupture cells without denaturing the SOD’s. Total SOD activity was measured in the resulting cell homogenates using the photochemical nitro-blue tetrazolium (NBT) assay.  NBT is converted to a blue-colored formazan when reactive oxygen is formed.  Preliminary data indicate that the Antarctic strains grow well under chilling conditions (12°C).  At least one Antarctic strain has increased SOD activity as compared to temperate strains.  The results of research in progress will be presented.  This research could be used to develop chilling and other stress-resistant crops for use on a space station or planetary exploration base, such as on Mars, where the average ambient temperature is much lower than that of Earth.  

     (Supported by an Arkansas SILO Undergraduate Research Fellowship to ALP and by the Arkansas Space Grant Consortium.)