以基因组信息为指导的深海放线菌SCSIO-5802次级代谢产物挖掘及其活性研究

The genomes of actinomycetes from the deep-sea sediment encode many genes or gene clusters capable of synthesizing various secondary metabolites regulating its own growth or as chemical weapons for defense. Yet the gene clusters were in large extent not expressed in the usual laboratory fermentation conditions. During the course of our investigations on the secondary metabolites from the deep-sea derived actinomycetes, we have isolated strain Streptomyces sp. SCSIO 5802 from a sediment sample collected in the South China Sea at a depth of 3536 m. All of its crude extracts fermented with different media showed bioactivities such as antibacterial, cytotoxicities, etc; a type of new polyketides with rare tandem lactone bridging were structurally elucidated form the strain SCSIO 5802. Bioinformatics analysis of its genome revealed that about 20 gene clusters are silent, indicating the genome of this strain holds great potential of producing more and more secondary metabolites. Therefore, in this application, the following 4 items would be applied to discover novel marine lead compounds: 1) using OSMAC methods, to design and optimize various media to activate more of its biosynthetic pathway thereby stimulating the production of more secondary metabolites; 2) the target gene or gene clusters would be activated and regulated by metabolic engineering and heterologous expression, to isolate targeted secondary metabolites encoded certain gene cluster/s; 3) the secondary metabolites would be isolated and structures elucidated by using various kind of chromatography technologies and spectroscopic and chemical methods; and 4) the biological activities on antibacterial, cytotoxic, antivirus and cardiovascular effects will be screened by using various models to screen compound/s with significant bioactivities. The results of this project will potentially offer novel lead compounds for new marine drug discovery.

深海放线菌基因组编码合成多种次级代谢产物的基因簇，用于调控自身生长和化学防御，但这些基因簇在实验室条件下较少表达。申请人前期发现深海沉积物链霉菌SCSIO 5802，其多种发酵粗提物显示抗感染和细胞毒等生物活性，并从中分离鉴定了一类具有串联内酯桥结构的聚酮类新化合物。基因组生物信息学分析发现，有20个编码基因簇未表达。本项目拟：1）通过OSMAC（one strain-many compounds）方法，优选和设计多种培养基激活多条生物合成途径，刺激化合物生产；2）利用代谢工程和异源表达手段方法对目标基因（簇）进行激活和调控，定向挖掘基因簇编码的新颖次级代谢产物；3）运用多种色谱和波谱手段分离鉴定目标化合物；4）对获得的单体化合物进行抗菌、抗病毒、细胞毒、心血管作用等生物活性筛选，发现结构新颖、显著活性的化合物。研究工作将为开发具有自主知识产权的海洋药物提供新分子实体。

基于深海放线菌特殊的生产结构新颖活性次级代谢产物的潜力，本项目对深海放线菌SCSIO 5802等菌株，在OSMAC策略下，以基因组信息为指导，对其活性次级代谢产物的生产潜力进行了系列挖掘，并开展了相关活性研究。结果如下：1）激活了深海放线菌SCSIO 5802等菌株多个沉默基因簇，先后发现了系列深渊霉素类、抗霉素类、5-烷基-丁烯酸内酯类、多烯类、PTM类、二吲哚生物碱类、四氢异喹啉类等骨架的活性化合物43个，其中结构新颖的化合物21个；2）发现具有抗菌、抗肿瘤活性的先导化合物1个；3）发明具有治疗柑橘溃疡潜力的微生物制剂1种。4）先后发表SCI论文6篇，申请专利2项，授权专利1项。该项目的开展，为开发具有我国自主知识产权的海洋药物提供了新的分子实体和开发新型农药制剂提供了来源。