Résumé
Objective: To investigate a new method for altering the secondary metabolism of inactive actinomycete strain by magnetic nanoparticle-aided microwave mutagenesis to obtain antitumor mutants. Methods: HLF-43, a marine-derived actinomycete strain without antitumor activity with the inhibition rate of 3.9% at the 1000 μg/ml sample concentration on K562 cells, was used as the initial strain in the present study. The spore suspension of HLF-43 was exposed to the microwave radiation (the frequency 2450 MHz, the power 464 W)under the presence of Fe3O4 magnetic nanoparticles, then spread on neomycin-containing plates and the neomycin-resistant (neo) mutants were selected during incubation at 28°C for 4-14 days. The initial strain HLF-43 and its neo mutants were fermented to obtain fermentation samples and the antitumor neo mutants were obtained by the test of antitumor activity for these samples at 100 μg/ml. The antitumor activity was assayed by the MTT method using K562 cells. Results: A new method has been created for altering the secondary metabolism of actinomycete strain by magnetic nanoparticle-aided microwave mutagenesis. By the method coupled with the neo mutant selection, a total of 80 neo mutants were obtained from the inactive-initial strain HLF-43 and 28 of them were antitumor mutants with the inhibition rates over 20% at the 100 μg/ml sample concentration on the K562 cells. The antitumor mutants could be obtained at quite high frequency of 35% (28/80). Conclusion: Compared with the microwave mutagenesis without the aid of Fe3O4 magnetic nanoparticles, the Fe3O4 magnetic nanoparticle-aided microwave mutagenesis is more favorable to obtain the neo mutants resistant to higher concentration of neomycin and to obtain the antitumor neo mutants at higher frequency.
Résumé
Microwave mutagenesis has become a new physical mutation technique by non-ionizing electromagnetic radiation, which has been used in the breeding of crops, plants and microorganisms, and has revealed bright future development in its application in the microorganism breeding for medicinal source strain improvement for providing high productivity or diverse bioactive mutants. This article reviews bioeffects of microwave, possible mechanisms of microwave mutagenesis, methods of microwave mutation technique together with main factors probably affecting microwave mutagenesis, and research advances in the application of microwave mutagenesis in microorganism breeding for medicinal source strain improvement. Meanwhile, the present research status, advantage and disadvantage, and prospect of this technique are also discussed focusing on its application in the microorganism breeding for medicinal source strain improvement.