Effect of γ-irradiation on Euglena gracilis Algae

Given the prospects for using Euglena algae as part of the biological systems of human life support in long-term space flights, we studied the effects of low doses of radiation and genotype influence on the radiosensitivity of Euglena cells. Irradiation of several Euglena gracilis strains with 60Co γ-rays shows that strain Z is the most radioresistant. Its chloroplastless derivate OFL strain shows increased radiosensitivity. The E. bacillaris strain and its derivates W3 and W10 without chlorophyll have intermediate radiosensitivity. Irradiation up to 10 Gy had the hormesis effect on the initial strains, and it is only above 100 Gy that cell death was observed. The hormesis effect was observed concerning both radioresistance and growth rate. The use of methylen blue and fluorochrome dyes allows a rapid estimation of the share of the living and dead cells. A comparison of two survival rate tests shows that the classical method of plating on a growth medium yields an increased death rate because this method does not take into account the living non-dividing cells