Cold Shock Syndrome in Anacystis nidulans

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Abstract
The phenomenon of cold shock in A. nidulans was explored further in terms of loss of viability and immediate and subsequent metabolic effects. Cold shock was observed in 2 closely related strains [Synechococcus] in which unsaturated fatty acid contents are known to be low and temperature-dependent. Loss of viability was maximum for cells grown at temperatures above 40.degree. C (< 10-4 survivors after 5 min at 0.degree. C) became negligibly small for cells grown below 34.degree. C. Development of the cold-sensitive condition after transfer 25 .fwdarw. 39.degree. C was slow and comparable to the rate of growth; development of the insensitive condition after transfer 39 .fwdarw. 25.degree. C was rapid, implying rapid in situ alteration. An immediate metabolic effect, observed as a decrease in the rate of photosynthetic O2 evolution measured at growth temperature, was less severe than loss of viability. Continued light incubation under growth conditions led to a slow decay in the rate of O2 evolution accompanied by loss of membrane chlorophyll. The multiple effects which comprise the cold shock syndrome appear to be membrane-related phenomena and provide an experimental probe of normal membrane function.