Effect of UV-B radiation on physiological and biochemical changes in a freshwater cyanobacterium, Scytonema hofmannii

Abstract

The effect of ultraviolet-B (UV-B) radiation and UV-B supplemented with low photosynthetically active radiation was investigated on photosynthesis, photosynthetic pigments, phycobilisomes, peroxidation of membrane lipids, fatty acids, and UV-B absorbing pigments in the freshwater cyanobacterium, Scytonema hofmannii. The present work aimed to study the UV-B radiation effect on photosynthesis and relate it to oxidative damage and protection provided by the UV-B absorbing compounds in a freshwater cyanobacterium. The results showed that photosynthesis and photosynthetic pigments were primarily affected by UV-B radiation, which seems to be the consequence of the generation of reactive oxygen species (ROS), as both ROS generation and oxidative damage to membrane lipids were observed, resulting in decreased survival of the test organisms. There was no significant change in the saturation and unsaturation level of fatty acids due to the treatments. We also suggest the role of mycosporine-like amino acids (MAAs) and scytonemin in protection against UV-B damage. Our results suggest that changes in photosynthesis, pigments, and peroxidation of membrane lipids may be a consequence of damage. In contrast, changes in fatty acids essentially resulted from the adaptation process against UV-B, and changes in UV-B absorbing compounds such as MAAs and scytonemin provided protection against the harmful effect of UV-B radiation.