Studies On UV Mutagenic Breeding And Identification Of An Antibiotic-producing Strain AP19-1

Studies on UV mutagenic breeding and identification of an antibiotic-producing strain AP19-1 were carried out.Based on the results of phenotypic characteristics and 16S rDNA sequence analysis, the isolate was assigned to the genus Streptomyces.In order to improve the antibiotic-producing trait of strain AP19-1, we exposed its protoplasts and spores to UV and isolated a mutant strain Y207. The antibiotic's relative liter of the mutant's fermented broth was 4 times as high as the parent strain through MIC experiment. And its high capacity for producing antibiotic remained stable after 4 times of subcultures. It was also found that the effect of protoplasts' UV mutagenic breeding was better than spores'.UV irradiated spores of strain AP19-1 were incubated at 27℃ and 33℃ close to inhibiting growth temperature. Results showed that among the offspring from UV irradiated spores grown at 33℃ , the amount of forward mutants whose antibiotics-producing ability were over the original strain's were many more than that at 27℃. The percentage of the forward mutants was 25.8% at 27℃ and 58.1% at 33 ℃ respectively. Total DNA of the progeny strain and the original strain was tested by RAPD with 17 primers. It was demonstrated that the variations occurred in the chromosomal DNA of the progeny strains grown at 33℃ were more than that at 27 ℃. This method improved the efficiency of UV mutagenic breeding and put forward a new way in researching into the mechanisms of mutation formation in Streptomyces sp. cells irradiated by UV.