Study On The Effect Of Ionizing Radiation On Vibrio Qinghaiensis Sp.Q67

In recent years,for the main reason that once leakage accident occurs,radioactive pollution will harm environment organisms,the construction of inland nuclear power plants has been constantly controversial.Microorganisms,as the most widely distributed,would affected toxic substances firstly,therefore,it is important to find a sensitive microorganism to monitor and evaluate the biological toxicity of radioactivity.In this paper,we took vibrio qinghaiensis sp.Q67 as the research object.Twoγ-ray sources,⁶⁰Co and ¹³⁷Cs,and two radioactive solutions Na¹³¹I and UO₂（NO₃）₂ were used to to investigate the toxicity of radiation.By measuring the bioluminescence intensity of Q67 in dirrerent radiation doses（activities）and searching relative bioluminescence intensity(I^rel)as physiological parameter,curves of effect with doses were constructed.Then,the growth curves of Q67,contents of malondialdehyde and the activities of FMN:NADH oxidoreductase after ⁶⁰Co irradiantion were studied to investigate the injury of radiation on Q67.Results of the study are as follows:（1）Experimental results show that bioluminescence intensity of Q67is immediately inhibited after ⁶⁰Co irradiantion for short time(d>0.05Gy·min^-1).I^rel in 15 minutes after irradiation decreases with the increase of dose rates（d）and irradiation time（t）for acute radiation,and linear bivariate associations is found between I^rel and the logarithm value of d and t.（2）Irradiatied by ¹³⁷Cs at low dose rates（100μGy/h¹0 mGy/h）,two main stages of I^rel can be divided:hormesis stage(I^rel>1)and inhibition stage(I^rel<1).Among hormesis stage,three stages can be subdivided:initial stage,I^rel being declined,recovery stage,I^rel fluctuated,and decline stage,I^rel fell again,but still greater than 1.Inhibition stage occurred when I^rel was less than 1.The time when I^rel drops to less than 1（transition time T₀）is linear with the logarithm of dose rate.（3）About Na¹³¹I solution,three successive stages in the bioluminescent response at the activity over 5000 Bq/ml are found:initial stage（stress recognition）,hormesis stage（adaptive response）and inhibition stage（radiation toxicity）.While to UO₂（NO₃）₂,Bioluminescent inhibition are observed under uranyl concentrations exceeding 0.05 ppm.I^rel at exposure 15 minutes is approximate linear decrease over the concentration of uranium.The main toxic factor of ¹³¹I is radiation,while chemical component for U.（4）After irradiated by ⁶⁰Co for a short time（0.2 Gy/min）,the OD₆₀₀value in the stationary phase is decreased when transfer Q67 to culture medium for culture,and logarithmic phase is postponed while stationary phase is advanced.It indicates that irradiation caused part of cells death and part of cellular activity inhibitory.Malondialdehyde contents and activity of t FMN:NADH oxidoreductase also decline after irradiation but the amplitude is small.（5）Comprehensive analysis,Vibrio qinghaiensis Q67 is sensitive to radioactivity and can potentially be used as a biomaterial to monitor radiation.In the case of high radiation dose rates or heavy radionuclides,I^rel at 15 minutes after irradiation or adding radionuclides can be used as physiological parameter,while for low dose rates,T₀ as the physiological parameter.