CHANGES OF PROLINE CONTENT IN A CYANOBACTERIUM UNDER OXIDATIVE STRESS

Changes of free proline content in Plectonema boryanum cells after cultivation at oxidative stress inducing conditions were studied. It was found that the excess of light had more pronounced affect on the proline accumulation than the extreme temperatures applied individually. Proline content increased up to 58.1 mu mol proline g(-1) dry weight, which was equivalent to 186% increase above the control variant, when the cyanobacterium was grown at 300 mu mol photons m(-2) s(-1) light intensity and 14.5 degrees C temperature. Extreme high temperature 44.5 degrees C, combined with high irradiance led to 162% proline enhancement as compared to control. Herbicide paraquat (PQ), well known as an inductor of oxidative stress, caused most considerable increase of proline in Pl. boryanum cells - 79.4 mu mol proline g(-1) dry weight at 20 x 10(-7) M PQ concentration. Iron supply was also studied in order to reveal some stress effects. Fe-deficiency provoked insignificant decrease of proline while iron excess (sublethal concentration of 188 mg Fe l(-1) in nutrition medium) enhanced the proline content up to 66.2 mu mol proline g(-1) dry weight.