Related Study Of The Biosynthetic Genes Of Novel Antibiotic Bagremycins

The widespread use of antibiotics lead to serious drug resistance for various pathogenic bacteria, whereas the screening of new kinds of antibiotics and discovery of their biosynthetic mechanisms provide abundant material and information resources for implementing combinatorial biosynthesis and metabolic pathway engineering strategies. Bagremycin A and B are two novel secondary metabolites produced by Streptomyces sp. Tii4128with bioactivities against fungus, bacteria and tumour cell and have potential application values in the fields of medicine and agriculture.In the present study, firstly, an efficient intergeneric conjugal transfer system between Escherichia Coli and Streptomyces sp. Tu4128is developed and we investigated and optimized the related influencing factors including medium component, MgCl2concentration added into medium and conjugal temperature. Secondly, according to the structures of bagremycins, two aldolase and3-dehydroquinate synthase-encoding genes bagB and bagC were cloned from the chromosome of Streptomyces sp. Tu4128, respectively and inactivation of either bagB or bagC suggests that these two genes are involved in the biosynthesis of bagremycins. Simultaneously, bagA gene, which is located immediately upstream of bagB gene, was cloned by chromosome walking, whose deduced protein product shows high homologous with aromatic amino acid ammonia lyase. BagA gene was expressed in E. coli and the enzymatic activity was measured, identifying as a novel tyrosine ammonia lyase-encoding gene from microorganism. The inactivation of the bagA gene in bagremycins-producing strain indicated that bagA gene is responsible for the biosynthesis of p-coumaric acid and bagremycin, and p-coumaric acid is one of essential precusors of bagremycin biosynthesis. Then, we presented the draft geome sequence of bagremycins-producing strain Streptomyces sp. Tu4128by Solexa/Illumina. On the one hand, we analyses the basic features of strain Tu4128genome, and on the other hand, we carried out genome mining to acquire the biosynthetic gene clusters of other candidate secondary metabolites by bioinformatics. Meanwhile, we also analyzed the sturcture of candidate bagremycin biosynthetic gene cluster and its possible functions of resistance gene, pathway-specific regulator genes and biosynthetic genes.