Among eight components of avermectin, B1 fractions have the most effective antiparasitic activities and the lowest level of toxic side-effects and are used widely in veterinary and agricultural fields. In-traspecific ...Among eight components of avermectin, B1 fractions have the most effective antiparasitic activities and the lowest level of toxic side-effects and are used widely in veterinary and agricultural fields. In-traspecific protoplast fusion between two strains of Streptomyces avermitilis, one an avermectin high producer (strain 76-05) and the other a genetically engineered strain containing the mutations aveDˉ and olmAˉ (strain 73-12) was performed for enhancement and selective production of avermectin B in the absence of oligomycin. Two recombinant strains (F23 and F29) were isolated and characterized with regards to the parental merits. F23 and F29 produced only the four avermectin B components with high yield and produced no oligomycin. The avermectin production of F23 and F29 was about 84.20% and 103.45% of the parental strain 76-05, respectively, and increased about 2.66-fold and 3.50-fold, re-spectively, compared to that of parental strain 73-12. F23 and F29 were genetically stable prototrophic recombinants and F29 was quite tolerant of fermentation conditions compared to avermectin high producer parental strain 76-05. The ability to produce avermectin B with high yield without the produc-tion of other avermectin components and oligomycin will make F23 and F29 useful strains for aver-mectin production. Strain F29's tolerance of fermentation conditions will also make it suitable for in-dustrial applications.展开更多
In Streptomyces griseus, AdpA, the key transcriptional activator in the A-factor regulatory cascade, switches on the transcription of multiple genes required for secondary metabolism and morphological differentiation....In Streptomyces griseus, AdpA, the key transcriptional activator in the A-factor regulatory cascade, switches on the transcription of multiple genes required for secondary metabolism and morphological differentiation. Streptomyces avermitilis also contains an ortholog of adpA, which is named adpA-a. To clarify the in vivo function of adpA-a, an adpA-a-disrupted strain was constructed by double crossover recombination. No difference in avermectin production was found between the adpA-a-disruptant and the wild-type strain. However, this disruptant neither formed spores nor produced melanin and its phenotype was restored to the original wild-type by a single copy of the adpA-a gene integrated into the chromosome. This report shows that adpA-a is involved in regulation of morphological differentiation and melanin production in S. avermitilis.展开更多
基金Supported by National Basic Research Project (Grant No. 2003CB114205)Key Technologies R&D Programme (Grant No. 2004BA713B02-03)
文摘Among eight components of avermectin, B1 fractions have the most effective antiparasitic activities and the lowest level of toxic side-effects and are used widely in veterinary and agricultural fields. In-traspecific protoplast fusion between two strains of Streptomyces avermitilis, one an avermectin high producer (strain 76-05) and the other a genetically engineered strain containing the mutations aveDˉ and olmAˉ (strain 73-12) was performed for enhancement and selective production of avermectin B in the absence of oligomycin. Two recombinant strains (F23 and F29) were isolated and characterized with regards to the parental merits. F23 and F29 produced only the four avermectin B components with high yield and produced no oligomycin. The avermectin production of F23 and F29 was about 84.20% and 103.45% of the parental strain 76-05, respectively, and increased about 2.66-fold and 3.50-fold, re-spectively, compared to that of parental strain 73-12. F23 and F29 were genetically stable prototrophic recombinants and F29 was quite tolerant of fermentation conditions compared to avermectin high producer parental strain 76-05. The ability to produce avermectin B with high yield without the produc-tion of other avermectin components and oligomycin will make F23 and F29 useful strains for aver-mectin production. Strain F29's tolerance of fermentation conditions will also make it suitable for in-dustrial applications.
基金Supported by the National Basic Research Program of China (Grant No. 2003CB114205)
文摘In Streptomyces griseus, AdpA, the key transcriptional activator in the A-factor regulatory cascade, switches on the transcription of multiple genes required for secondary metabolism and morphological differentiation. Streptomyces avermitilis also contains an ortholog of adpA, which is named adpA-a. To clarify the in vivo function of adpA-a, an adpA-a-disrupted strain was constructed by double crossover recombination. No difference in avermectin production was found between the adpA-a-disruptant and the wild-type strain. However, this disruptant neither formed spores nor produced melanin and its phenotype was restored to the original wild-type by a single copy of the adpA-a gene integrated into the chromosome. This report shows that adpA-a is involved in regulation of morphological differentiation and melanin production in S. avermitilis.
