Influence of very low doses of ionizing radiation on Synechococcus lividus metabolism during the initial growth phase

• Published in: Archives of microbiology 1986-04, Vol.144 (3), p.286-290
• Main Authors: Conter, A, Dupouy, D, Delteil, C, Planel, H
• Format: Article
• Language: English
• Subjects: Action of physical and chemical agents on bacteria; Bacteriology; Biological and medical sciences; Chlorophyll - analysis; Chlorophyll A; Cyanobacteria - genetics; Cyanobacteria - growth & development; Cyanobacteria - metabolism; Cyanobacteria - radiation effects; DNA - analysis; enzyme activity; Fundamental and applied biological sciences. Psychology; Gamma Rays; Glucose - metabolism; glucose-6-phosphate 1-dehydrogenase; Glucosephosphate Dehydrogenase - metabolism; glutathione reductase; Glutathione Reductase - metabolism; Glyceraldehyde-3-Phosphate Dehydrogenases - metabolism; glycerol-3-phosphate dehydrogenase; ionizing radiation; metabolism; Microbiology; oxidation; Phycocyanin - analysis; superoxide dismutase; Superoxide Dismutase - metabolism; Synechococcus
• ISSN: 0302-8933; 1432-072X
• DOI: 10.1007/BF00410964

Previous results from this laboratory have shown that very low chronic doses of gamma radiation can stimulate proliferation of the Cyanobacterium Synechococcus lividus. This modification of cell proliferation occurred during the first doubling. In this paper, we have compared the metabolism of cells cultivated in a normal environment or under chronic irradiation. Incubation of the cells in a new medium induced a high superoxide dismutase (EC 1.15.1.1, SOD) activity at the 18th hour and a degradation of phycocyanin, thus demonstrating that cells were submitted to a photooxidative stress. This increase in superoxide dismutase activity was followed by concomitant peaks of glutathione reductase (EC 1.6.4.2, GR) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49, G6P-DH) at the 24th hour. Irradiated cultures at a dose of 53.5 mGray/year show an earlier and higher peak of SOD, GR, and G6P-DH. In a second stage, cultures showed an earlier onset of photosynthesis under irradiation, as evidenced by an increase in pigment content and an enhancement of glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.13, GAP-DH). These results show that the radiostimulation is related to the activation of enzymes protecting against peroxides that were induced under oxidative circumstances and to the activation of a glucose catabolism via the oxidative pentose phosphate pathway.