PARENT SESSION
1A Chemical, biological, and combined methods for the detection of pollutants
9:00 AM to 7:00 PM, Wednesday, 09 May 2001

(W/EH025) A Study On Gamma Ray Effects On the Stress Responses And Cellular Toxicity Using Bacterial Cells.

Gu, Man Bock¹, Min, Jiho¹, Lee, Hyun Joo¹, Lee, Chang-Woo ², ^{1 2}

ABSTRACT- Effects of ionizing gamma radiation on recombinant Escherichia coli cells containing stress promoters, recA, fabA, grpE, or katG, fused to luxCDABE originating from Vibrio fischeri were characterized by monitoring transcriptional responses reflected by the bioluminescent output. Quantification of gamma-ray intensity was possible using the recA and fabA promoter fusion since a linear enhancement in the bioluminescence emission with increasing gamma-ray intensities was observed. Other strains sensitive to either oxidative stress (DPD2511, katG::luxCDABE) or protein-damaging stress (TV1061, grpE::luxCDABE) were also irradiated by gamma-rays but resulted in no noticeable bioluminescent output, while DPD2794, with the recA promoter, and DPD2540, with the fabA promoter, irradiated by the same intensities of gamma-rays gave a significant bioluminescent output. This would indicate that the main stresses caused by ionizing radiation in bacteria are DNA and membrane-damage, not protein- or oxidative-damage. In addition, in this study, to investigate the relationship between the radiation dose rate and bacterial responses, two recombinant Escherichia coli strains, DPD2794 and GC2, which has the lac promoter fused to luxCDABE originating from Photorhapdus luminescences, were used for detecting DNA damage and general cellular toxicity under various radiation dose rates. Throughout this study, it was found that these bacteria showed quantitative stress responses to DNA damage and general toxicity caused by gamma ray dependent on the radiation dose rates, indicating that the bacterial stress responses and general toxicity were significantly influenced by the dose rates. <Acknowledgement> This work was supported by the Science and Technology Policy Institute (STEPI) in Korea and in part by KOSEF through the Advanced Environmental Monitoring Research Center (ADEMRC) at the Kwangju Institute of Science and Technology (K-JIST). Authors are grateful for their support.

Key words: Gamma ray, stress response, recombinant bioluminescent bacteria, dose rate effect