Synechococcus has the ability to grow at temperatures lower than their normal growth temperature, although at a relatively reduced rate. Gel electrophoretic analysis of cellular proteins from cold - treated and heat shocked cells labeled with 14C-protein hydrolysate revealed differences in the pattern of protein synthesis. The molecular weights of polypeptides induced at low temperatures (10-22°C) were estimated to be 74, 64.5, 23, 17 and 14.7 kDa. Time course studies indicated progressive induction of some cold shock proteins (CSPs) at 13°C. Heat shock (HS) involved immediate repression of most non heat shock proteins and identification of newly synthesized protein bands with molecular weights estimated to fall into the range characteristic for HS. The results revealed that in Synechococcus, the photosynthetic activity and the midpoint value for critical temperature regions are dependent on growth temperature The reduction in O2 - evolution ranged between 37% to 47% within the studied low temperature range. Treatment at 10 and 13°C showed rapid loss of activity (50%) after 17 and 29 min, respectively, furthermore, treatment at 13°C produced a change in light absorption spectrum A pattern which indicated the involvement of a common mechanism in the cold susceptibility of photosynthesis and absorption spectrum. It is suggested that cold induced particle movement which lead to functional detachment of phycobilisomes away from the Chl-protein complex or vice versa.
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