Research In Technology And Mechanism Of Femtosecond Laser Induced Mutation From Streptomyces Roseosporus

Daptomycin is a lipopeptide antibiotic first approved by the FDA, which has excellent effects on killing anti-Gram-positive bacteria. Daptomycin's activity limited to gram-positive organisms, especially the antibiotic-resistant bacteria such as Staphvlococcus aureus (MRSA), vancomycin-resistant enterococci (VRE). Daptomycin was produced mainly by Streptomyces roseosporus with high costs and low production at present. Therefore, it is of great significance to search for a high productivity strain and the optimal medium composition. In this work, the high productivity strain was selected for daptomycin production using femtosecond laser induced micro-organisms mutation, and the medium composition and fermentation conditions were optimized. The major research contents and results are as follows:Streptomyces roseosporus NRRL11375 was used as an original strain. After treated with femtosecond laser irradiation (Laser mutagenesis parameters:output power 5mW-30mW, irradiation time 5-25s), a mutant strain JG-25-50 was screened out by using the medium with selective pressure of Sarcinalutea schroter. The production of daptomycin of the strain JG-25-50 was 371.40mg/L, which was 18.3% higher than that of the parental strain NRRL11375. The strain is genetically stable.Femtosecond laser induced micro-organisms mutation has became a new microbial technology, because of its characteristics of ultrafast pulse, high peak power and focusing on small size. In this paper, the femtosecond laser mutagenesis microbial mechanism was discussed, such as multi-photon absorption process, the formation of plasma, the formation of reactive oxygen species, DNA damage and self-repair mechanism. Finally, basing on the current research, some recommendations were given about the prospect of the area of femtosecond laser induced mutation technology and that of the mutation mechanism.