阿维链霉菌bkdAB的基因中断对阿维菌素合成的影响

Effects of bkdAB Interruption on Avermectin Biosynthesis

以阿维菌B组分菌株StreptomycesavermitilisBjbm0 0 0 6为出发菌株 ,用PCR的方法构建bkdAB基因簇(Branched_chainα_ketoaciddehydrogenasegeneAB)的基因置换质粒pHJ582 1(pHZ13 58∷bkdAB&erm) ,并对其进行基因中断 ,得到重组菌株Bjbm582 1。Bjbm582 1的发酵产物经HPLC检测发现 ,除了产生B1a和B2a外 ,还产生一种原菌株没有的新组分 ,3个组分的总含量只有出发菌株Bjbm0 0 0 6的 2 5%。结果表明bkdAB的中断不仅部分阻断了阿维菌素的合成 ,还阻断了阿维菌素b组分的合成 ,可以推测bkdAB的产物在阿维菌素合成途径中主要承担了α酮基异戊酸脱氢酶 (α_ketoisovalericaciddehydrogenase)

In this study, \%Streptomyces avermitilis\% Bjbm0006 which produces four avermec tin B components was used as an original test strain. A replacement plasmid cont aining a gene cluster \%bkdAB\%(branched_chain α-keto acid dehydrogenase gene) involued in the biosynthesis of avermectin B in \%S.avermitilis\% Bjbm0006 was constructed by means of PCR technique and then named as pHJ5821(pHZ1358∷\%bkdAB &erm\%). A recombinant strain Bjbm5821 was obtained after the gene cluster was i nterrupted by double crossover. This strain was tested in laboratory conditions and analysed by PCR using the total DNA as template. The HPLC analysis showed th at the strain Bjbm5821 synthesized the same ‘a′components B1a and B2a as the o riginal strain did. However, It lost the ability for the production of ‘b′comp onents for example B1b and B2b. A novel compound was detected in fermentation pr oducts. The results of present study suggests that the production of gene cluste r \%bkdAB\% may play a main role similar to α-ketoisovaleric acid dehydrogenas e in the pathway of avermectin synthesis.