Effects of UV-B and UV-C radiation on the accumulation of scytonemin in a terrestrial cyanobacterium, Nostoc flagelliforme

Scytonemin which is derived from cyanobacteria, has been reported to possess a variety of potent properties, including UV-screening, anti-inflammatory and anti-proliferative. Since ultraviolet radiation played a positive role in the scytonemin synthesis, we used UV-B and UV-C to study the stimulative effects on the scytonemin production in a terrestrial cyanobacterium, Nostoc flagelliforme. The results showed that UV-B or UV-C could induce the synthesis of scytonemin in N. flagelliforme. The UV-B and low level of UV-C (0.5 W/m²) radiation continually stimulated the scytonemin production without any inhibition in 48 hours. The scytonemin produced by N. flagelliforme showed positive correlation to the radiation levels and exposure time. In contrast, high levels of UV-C (1.5 and 2.5 W/m²) radiation had negative effects on the scytonemin synthesis after a long exposure time. After all, we presumed that the optimal UV source and intensity for stimulation of scytonemin in our experiment was UV-B at 3.5 W/m², which could induce an increase of scytonemin up to 135% as compared to the initial level after 48 hours.