The Effects of UVB on Growth and Anti-UV Compounds Contents in Cyanobacteria Nostoc linckia

Nostoc species have gained much interest as a natural source of many secondary metabolites that have exhibited pharmacological properties. They synthesize UV-protective substances such as mycosporine-like amino acids (MAAs) or scytonemin to minimize the deleterious effects caused by UV radiation. In this research the effects of UVB radiation on increasing amount of UV-protective substances (scytonemin, OS-MAAS), and growth parameters such as photosynthetic pigments, protein and sugar content were studied in cyanobacteria Nostoc linckia.

For this purpose, 14-day algal cultures were treated with UVB rays for 1, 2 and 3 hours per day for 5 days. After treatment, the growth rate according to fresh weight measurement and other biochemical parameters according to colorimetric methods were assayed. Data were analyzed by one-way analysis of variance, and the significance of the differences was estimated by Duncan’s multiple comparison tests.

UVB treatment resulted in lower fresh weight of Nostoc algae. Algae exposure to 3 hours UVB, showed an increase in OS-MAAS content. The amount of scytonemin increased up to 3 times in 3 hours UVB treatment. The algae treated with UVB had more chlorophyll a and total carotenoid content but phycobiliproteins content reduced in this treatment. Total protein and total sugars were not affected by UVB treatment.

The results showed that this UV treatment method, in addition to significantly enhancing the anti UV compounds of the algae, would not reduce the biomass.