Resistance of blue-green algae to 60Co gamma radiation

Abstract

Many characteristics of blue green algae suggest that they should be excellent organisms for the investigation of biological interaction with radiation, particularly ionizing radiation. Therefore, the relative resistance to gamma radiation from a 60Co source has been measured for 23 cyanophycean algae. Since the organisms represent a wide range of cell types it was necessary to use dry weight as the end point for viability determination. Using the radiation resistant bacterium Micrococcus radiodurans as a primary standard and the bacterium Sarcina lutea as a secondary standard, the algae have been compared with one another and with S. lutea using a dry weight end point; S. lutea has also been compared with M. radiodurans on a colony count basis. The algae show a wide range of radiation resistance and have been grouped into three categories: (1) low resistance, with an ld 90 of less than 400 krads, for example, Microcystis aeruginosa, Anacystis nidulans and some species of Schizothrix calcicola; (2) moderate resistance, (equal or better than M. radiodurans) with an ld 90 of more than 400 krads but less than 1200 krads, for example, Oscillatoria brevis, Anabaena variabilis and Scytonema hoffmannii; (3) high resistance, with an ld 90 of greater than 1200 krads, for example, Plectonema boryanum, Lyngbya estuarii, Nostoc muscorum and Microcoleus vaginatus.