| In this experiment, Bacillus.subtilis 1831 was irradiated individually by soft X-ray from Synchrotron Radiation (SR), N- ion implantation and ultraviolet (UV). Effects of this three kinds of radiation on the survival and mutagenesis of B.subtilis 1831 were studied. The method of SR soft X-ray radiation mutagenesis on microbe was established preliminarily . Four stable mutants were obtained, that is, a two-fold defective mutant of neutral and alkaline proteaseæ¡ž.subtilis 1831SX, a low-yielding mutant of alkaline proteaseæ¡ž.subtilis 1831NL, a low-yielding mutant of neutral proteaseæ¡ž.subtilis 1831UV and a high-yielding mutant of neutral proteaseæ¡ž.subtilis 1831NH. The time courses of protease and o-amylase production of the parent strain and the protease mutants were studied, and the relations between protease and o-amylase were analysed.The survival curve of B.subtilis 1831 spores , which were treated by 3.1 nm SR soft X-ray,appeared "shoulder shape" , with LD, D37 and LD/D,7 being 107mA.s, 12300 mA.s and 813 respectively. The inactivation of SR soft X-ray on spores belonged in "single target multi-hit model", and the number of inactivation hits was 3. Protease activity of clonies on skim milk agar plate was measured and analyzed with statistical method, and the coefficient of variation(C.V) of the protease activity was expressed as index of mutagenic effect. Within a certain radiation dose, the mutagenic effect increased as the dose increased; The optimal dose of mutagenesis was 50000 mA.s. at which survival rate was 23.65%,and the C.V was 2.3 time compared with control; At high dose, the mutagenic effect tended to decline.The survival curve of B.subtilis 1831 spores ,which were implanted by 20 Kev N- ion , appeared typical "exponential shape" . with LD, D37 and LD / D37being 99.94 X 1014N+/cnr, 21.7 X 10l4N7cm2 and 4.61 respectively. The inactivation of N+ ion implantation on spores belonged in "single target single hit model". When mutation rate of resistance to streptomycin of spores was regarded as index of mutagenic effect, 20 Kev 1ST ion had striking effect. Within low dose, mutation rate increased as the dose increased; The highest mutation rate was 9 times compared with control, with implantation dose being 10.4X 1014N+/cnr,and survival rate being 59%; Like SR soft X-ray , the mutagenic effect inclined to decline at high dose.The survival curve of B.subtilis 1831 logarithmic phase cells, which were radiated by UV , appeared "exponential shape" , with LD, D37 and LD / D37 being 39.75 X 10-7J/mm2, 8.48 X 10'7J/mm2 and 4.69 respectively. When mutation rate of resistance to streptomycin of cells was taken as the index of mutagenic effect, mutagenic action showed effect of two peaks. When the dose as low as 2 X10~7J/mm2, and survival rate being 87.1%,the first peak reached the highest point , which mutation rate was 2 times of control; As the dose enhanced, the mutation rate at first fell suddenly (still higher than the control),then increased gradually until reached the second peak at the point of 20X10~7J/mnr with survival rate being 10.8%, and mutation rate was 1.6 time of the control; At higher dose, the mutation rate dropped dramatically to 0.When the B.subtilis 1831 parent strain and it' smutants were cultured at 37"C and 120rpm in media composing of bean cake flour, maize flour, wheat bran, etc, there seems no difference among those strains for the highest yield of a-amylase, and the production of neutral protease and a-amylase might be promoted by each other.
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