| 1. | Effect of avec gene deletion on avermectins production in streptomyces avermitilis
基因缺失对产素调控的影响 |
| 2. | The transformants were cultivated and the harvested cells were used in the procedure of conjugation by which the recombinant plasmid pid03 and pc05 were introduced into streptomyces avermitilis s - 2 respectively
经过在mym平板上的传代和抗性标记的筛选分别得到了同源双交换的菌株aved24和avecg 。 |
| 3. | In order to obtain a dna fragment containing aved gene , 5 ' end primer and 3 ' end primer , consisting of 18 and 20 nucleotides respectively , were designed and synthesized . a 2 . 2 kb dna fragment containing aved gene was obtained by pcr when genomic dna of streptomyces avermitilis s - 2 was used as a template
为了得到aved基因片段，首先根据已知的阿维菌素生物合成基因簇的核苷酸序列，设计并合成了由18和20个核苷酸组成的5端和3端引物；以streptomycesavermitiliss - 2基因组dna为模板，经pcr扩增得到了2 . 2kb的含有aved基因的dna片段。 |
| 4. | In addition to avermectins , s . avermitilis produces oligomycin , a strongly toxic compound . gene deletion vector pxl05 was used to disrupt oligomycin polyketide synthase ( pks ) encoding genes ( olma ) in streptomyces avermitilis cz8 - 73 , the producer of anthelmintic avermectins b and the cell growth inhibitor oligomycin . olma gene cluster in the chromosome was displaced by deletion allele on the plasmid via double crossover
本研究以产阿维菌素b和寡霉素的阿维链霉菌cz8 - 73为出发菌株，构建了基因缺失载体pxl05 ，并将其转入cz8 - 73中，通过缺失载体和染色体之间的同源双交换，对染色体上长达90kb的寡霉素聚酮合酶( pks )基因簇( olma )进行了缺失。 |
| 5. | In this study , the avermectin - producing strain streptomyces avermitilis was studied and the avermectin biosynthesis gene cluster in the genomic dna of streptomyces avermitilis s - 2 was altered by the method of gene engineering . insertion inactivation of aved gene in the cluster by introducing apramycin resistance gene into aved gene resulted in the disappearance of " a " components of avermectins . when avec gene was inactivated by the same way , four " 1 " components were lost and only " 2 " components , the potential precursor of ivermectin , were accumulated
将该基因簇中的aved基因通过插入外源的安普霉素抗性基因片段使其失活，导致发酵产物中4个a组分(不需要的组分)的消失；将基因簇中的avec基因通过同样手段，使其失活，导致发酵产物中4个“ 1 ”组分的消失，而主要积累“ 2 ”组分(进一步改造可成为伊维菌素的前体b _ 2组分) 。 |
| 6. | Content : avermectins are a class of drugs which have been found wide usage against a board spectrum of nematodes and arthropods , many of which are important endoparasites and ectoparasites of animals . avermectin bi is a common agriculture pesticide produced by the actinomycete streptomyces avermitilis and registered for worldwide use
正文：阿维菌素类药物( avermectins ， avms )属大环内酯类抗生素，由于其优异的驱虫活性和较高的安全性，被视为目前最为优良、应用最广泛的兽用驱虫药。 |
| 7. | Four types of colony , powdery gray , gray with white blot , white and bald were isolated from streptomyces avermitilis among them only the powdery gray one produced the highest avermectin . the gray with white blot one only produced 70 % - 80 % less than the powdery gray . and the others produced none
白色菌株和光秃型菌株经传代培养比较稳定，灰色有白点的菌落在传代过程中不断分化出灰色、白色、光秃型菌落，直接造成遗传的不稳定性，使生产效价不稳定，为生产的大害。 |
| 8. | Avermectins are a series of 16 - membered macrocyclic lactones produced by streptomyces avermitilis with potent anthelmintic and insecticidal activity . they are the most effective agricultural pesticides and antiparasitic agents , and used widely in medical , veterinary and agricultural fields
阿维链霉菌( streptomycesavermitilis )产生的阿维菌素( avermectins )是一组高效、低毒、广谱的杀虫抗生素，在医药、农业和畜牧业生产中具有良好的应用价值和广阔的市场前景。 |
