Effect Of Gene Deletion Of AveC On Avermectins Production In Streptomyces Avermitilis

The avermectins are a kind of macrolide antibiotics, composed of eight compounds (Ala, A2a, B1a, B2a, Alb, A2b, B1b, B2b), which exhibit structural differences at three positions(C5, C22-C23 and C26). Of these components, Bla exhibits the most potent antihelminthic activity.The C22-C23 dehydrase gene aveC, plays an essential role on the ratio of avermectin B1 and avermectin B2. Avermectin B1 and avermectin B2 only have structural differences on C22-C23. Avermectin Bl has a double bond, however, avermectin B2 has a single bond, with a hydroxyl on C23.Gene deletion vector aveC was used in Streptomyces avermitilis. AveC gene in the chromosome was displaced by deletion allele on the plasmid via double crossover. Disruptants were assued by PCR. Shaking flask experiments and HPLC analysis showed that the whole avermectins production were almost the same between the primary and the mutants. However, the productions of avermectin B2 of the mutants improved greatly, but the productions of avermectin B1 reduced greatly. It could prove that the partial gene deletion of aveC has the significant effect on regulation between avermectin B2a and avermectin B1a.