Resistance and Proteomic Response of Microalgae to Ionizing Irradiation

Microalgae have been drawing much attention as a platform for food supplements and biofuel production. Advance molecular tools are not available for manipulating microalgae, and therefore, methods for strain improvement mostly depend on random mutation. Radiation is frequently used mutagen in plant as well as microalgae breeding methods. In this study, the resistance of 7 microalgae species to ionizing irradiation was measured. To monitor the growth of microalgae, optical density and staining methods were used. Based on the D 10 values, the dose required to reduce one log cycle of the cell population, Chlorella protothecoides, Zygnema circumcarinatum , and Spirogyra varians were shown to be highly resistant to ionizing radiation. The changes in protein expression levels in S. varians were further investigated. Using 2-dimensional electrophoresis and protein identification, it was shown that some proteins involved in energy and glyceride metabolisms were up-regulated. These results provide fundamental insights into metabolic changes that occur in a microalga species upon exposure to ionizing irradiation.