Study On Mutation Breeding And Genome Comparison Of Streptomyces Lavendulae X33 Produce Active Substance Inhibit Citrus Green Mold

Streptomyces lavendulae X33 was screened from Citrus Root Soil in our laboratory.Previous studies showed that it had a good inhibitory effect on a variety of Citrus pathogenic fungi such as Penicillium digitatum and Penicillium italicum.In this paper,a series of mutation breeding were carried out after natural separation and purification of Streptomyces lavendulae X33.The optimization of fermentation medium,fermentation conditions and metabolism of the whole genome of the high-yield strain obtained by mutagenesis were studied.The results are as follows.(1)A strain of Streptomyces lavendulae BP39 with high yield and inhibitory activity against Penicillium digitatum was screened by UV,NTG,5-bromouracil and 2-aminopurine mutagenesis.Its relative antifungal activity was about 140.07 U/ml,which was 2.8 times higher than that of the original strain of Streptomyces lavendulae X33.After 10 times of subculture,it was found that its heredity was stable.(2)Compared with the original strain X33,the high-yield strain BP39 was found to have more abundant mycelial growth,lower sporulation and longer growth cycle.There was no difference in mycelial and spore morphology between strain BP39 and strain X33.(3)Single factor method and response surface method were used respectively to optimize the fermentation medium of high-yield strain BP39 in shaking flask.The optimum fermentation medium was:soybean meal powder 12.4 g/L,dextrin 17.9 g/L,sodium chloride 11.2 g/L,dipotassium phosphate 0.02 g/L,pH 7.0.Compared with the original fermentation medium,the cost of the culture medium decreased by 218%,the composition of the culture medium was simplified,and the cost of the raw materials of the culture medium was greatly reduced.(4)The optimal fermentation conditions of strain BP39 were established by single factor analysis,that is:30 mL/150 mL shaking flask,initial pH 7.0,104-105 spores/mL spore suspension concentration of culture medium,28℃,180 r/min for 4 days.(5)By sequencing and preliminary comparative analysis of the whole genome of strain BP39 with high antimicrobial activity and strain S2 without antimicrobial activity,it is concluded that:the genome of strian S2 chromosome is small,maybe due to the absence of some signal regulation or resistance genes,which results in the loss of antimicrobial activity;in addition,strain S2 has a large number of plasmids,which suggests that the resistance genes may also be related to the plasmid genome.There is no significant difference between the two genes in the function of genomic components and coding proteins.The specific genes can be compared for further analysis and experimental verification.