湛江高桥红树林沉积物放线菌多样性及其中一株链霉菌产生的germicidins类化合物的鉴定

Diversity of actinobacteria from mangrove sediment in Gaoqiao, Zhanjiang and identification of germicidins from one strain of Streptomyces

摘要:

【目的】从3种红树林植物根际沉积物中分离和鉴定放线菌，进行抑菌活性初筛获得目标菌株并研究其次级代谢产物。【方法】使用5种培养基对红树林植物根际沉积物放线菌进行分离，采用16S rRNA基因序列比对的方法研究沉积物中的放线菌多样性，结合抑菌活性筛选获得目标菌株后进行放大规模发酵和分离鉴定次级代谢产物，根据生物合成基因簇定位和分析对化合物的生物合成途径进行推导。【结果】从3种红树林植物根际沉积物中分离得到放线菌49株，包括链霉菌属(Streptomyces)31株、小单孢菌属(Micromonospora)14株、小双孢菌属(Microbispora)、链孢子囊菌属(Streptosporangium)、野野村氏菌属(Nonomuraea)和糖单孢菌属(Saccharomonospora)各1株。获得粗浸膏抑菌活性较好的菌株Streptomycessp.SCSIO 40067，从中分离鉴定了6个α-吡喃酮类化合物：germicidin A–C、germicidin I和isogermicidin A–B，并首次报道了germicidin A的晶体结构。从菌株SCSIO 40067基因组中定位到了germicidins的Ⅲ型聚酮合酶生物合成基因簇，结合文献对6个germicidins类化合物的生物合成途径进行了推导。【结论】湛江高桥红树林根际沉积物中的放线菌具有多样性，包含潜在的新物种和天然产物资源。菌株Streptomycessp. SCSIO 40067具有α-吡喃酮类化合物的生产潜力。上述研究为后续工作提供了良好的实验材料。

关键词:红树林;放线菌;α-吡喃酮;Ⅲ型聚酮合酶

Abstract:

[Objective]The present work aims to isolate and identify actinobacteria from rhizosphere sediments of 3 mangrove plants and to investigate the target strain for secondary metabolites based on antibacterial activities. [Methods] Five media were used to isolate actinobacteria from rhizosphere sediments of mangrove plants in Gaoqiao, Zhanjiang. The isolates were identified based on 16S rRNA genes and then screened for antibacterial activities against 6 indicator strains. The target strain was selected for upscaled fermentation and identification of bioactive compounds. We then analyzed the biosynthetic gene cluster of the isolated compounds to predict the biosynthetic pathways. [Results]A total of 49 actinobacterial strains were isolated and categorized into 6 genera including Streptomyces (31 strains), Micromonospora (14 strains), Microbispora (1 strain), Streptosporangium (1 strain), Nonomuraea (1 strain), and Saccharomonospora (1 strain). Six α-pyrones, including germicidins A–C, germicidin I, and isogermicidins A–B, were separated from the crude extract of Streptomyces sp. SCSIO 40067 and identified. The crystal structure of germicidin A was reported for the first time. The type Ⅲ polyketide synthase biosynthetic gene cluster of α-pyrones was localized in the SCSIO 40067 genome by bioinformatics analysis. The biosynthetic pathway of α-pyrones was then proposed. [Conclusion]Actinobacteria in the rhizosphere sediment of mangrove plants in Gaoqiao, Zhanjiang had high species diversity, from which new species capable of producing valuable natural products can be mined.Streptomyces sp. SCSIO 40067 can produce α-pyrones via the type Ⅲ polyketide synthase pathway, which can serve as a start strain for the following studies.

Key words:mangrove;actinobacteria;α-pyrones;type polyketide synthase