Isolation, Identification And Radioresistant Characters Of Two Radioresistant Bacteria WGR700 And WGR702

Radioactive waste produced in the nuclear industry and the nuclear tests can cause serious environmental pollutions.Researches on the radioresistant microorganisms help us to elucidate the repair mechanisms of the DNA damages caused by radiation,and also have significant effects on environmental protection,human healthy and outer space exploration.In this study,two radioresistant bacterial strains WGR700 and WGR702 were isolated from water samples and add soils of Radiation Centre of Guangxi University.The water samples and add soils had been radiated by a ⁶⁰Co irradiator(0.1 kGy h^-1)for many years.Research results showed that the strain WGR700 is Gram-negative and rod-shape while the cells of WGR702 are coccus,and Gram-positive.The optimum temperature for the growth of the strains WGR700 and WGR702 was 37℃and 28～32℃,respectively.(G+C) mol%content of the strains WGR700 and WGR702 was 64.7mol%and 60.5mol%,respectively.UV and gamma radiation survival testes showed the strain WGR700 and WGR702 are extremely resistant to ionizing radiation.The D₁₀(10%survival value)of WGR700 and WGR702 are 9.8 kGy and 7.1 kGy, respectively.Phylogenetic analysis showed that the 16S rDNA sequences of WGR700(NCBI number:EU285374)shares 87.5%～95.6%similarities with other recognized Deinococcus specieses.On the other hand,the 16S rDNA sequences of the strain WGR702(NCBI number:EU315117)have 94.8%～98.5%similarities with other recognized Serratia specieses.Based on its phenotypic,biochemical and physiological characteristics,it is proposed that the new isolated strain WGR700 should be classified as a novel member in the genus Deinococcus with the name Deinococcus guangxiensis sp.nov.For the strain WGR702,it might be classified as a novel species of Serratia.The effect of gamma-radiation on the water soluble protein of the radioresistant strains WGR700,D.radiodurans R1 and radiosensitive strain E.coli DH5αcells has been compared,respectively.The results showed that the change of water soluble protein concentration in radioresistant strains and radiosensitive strain cells were different after gamma-radiation.The studies on the two radioresistant bacteria strains WGR700 and WGR702 will have the significance for cloning radioresistant genes and realizing the radioresistance mechanism.