Furthermore , it produced 2 unusual components d24 - 1 and d24 - 2 . it was basically confirmed , by hplc and ms , that d 24 - 1 was oligomycin a ; while d24 - 2 was 5 - oxo - avermectin la 此外，该菌株还产生两个异常的组分d24和d242 ，经hplc及质谱进一步分析，初步确定异常组分d241为寡霉素a ，而d24 2为5
2.
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。
3.
In this study , we attempted to construct an engineering strain producing only avermectin bl through the replacement of dna encoding dh2 - kr2 domains of the avermectin pks ( avedh2 - kr2 ) with dna encoding dh2 - kr2 domains from the pikromycin pks in s . avermitilis olm73 - 12 , producing only avermectins b and no oligomycin . gene replacement vector pxl201 ( pkc1139 : : 5 ' flank + pia : dh2 - kr2 + 3 ' flank ) was used to transform 5 . avermitilis olm73 - 12 protoplasts 我们以不产寡霉素而仅产阿维菌素b的工程菌olm73 - 12为出发菌株，用委内瑞拉链霉菌( streptomycesvenezuelae )中编码pikromycinpks模块2上完全活性的dh和酮基还原酶( kr )的dna区域对olm73 - 12染色体上编码阿维菌素pks模块2中dh和kr的区域进行取代，试图构建仅产b1组分的基因工程菌。
4.
Shaking flask experiments and hplc analyses showed that the four mutants no longer produced the toxic oligomycin , and only made four components of avermectins b , which were avermectin b1a , b1b , b2a , b2b . the yields of avermectins b in these mutants were separately equal to those in cz8 - 73 . this revealed that olma genes deletion did n ' t affect the biosynthesis of avermectins 将4株经southern杂交验证正确的基因缺失突变株进行摇瓶发酵和hplc检测，发现4个突变株均不再产生寡霉素而仅产阿维菌素b组分，阿维菌素的总产量和b1的产量与出发菌株相当，说明寡霉素pks基因簇的缺失并不影响阿维菌素的生物合成。
