海洋动物寄生白僵菌Beauveria felina EN-135代谢产物分子多样性与活性研究

The species of the fungal genus Beauveria are generally regarded as entomopathogens and are widespread with various hosts. Most species in this genus are widely used to protect crops from insects and pathogenic diseases. Presently, the study on Beauveria is mainly focus on those derived from terrestrial sources, and very few reports were found from marine origii. We recently isolated and identified a fungal strain Beauveria felina EN-135 associated from marine animal in the southeast China sea. In the bioassay, this fungus exhibited inhibitory activity against five agro-pathogens including Alternaria brassicae, Coniella diplodiella, Valsa mali, Physalospora piricola, and Fusarium oxysporium f. sp. vasinfectum. Preliminary chemical examination of this fungal strain indicated the presence of destruxin depsipeptide and conduritol derivatives, which might responsible for the activity. Cultivation of this fungus on various culture media could induce the production of various metabolites. Based on the above work, this project will focus on the investigation of the secondary metabolites of Beauveria felina EN-135. Various cultural fermentation strategies, the so called epigenetic manipulations, such as cultivated on nutrition-rich or limited media, on higher or lower level of salt content of the media with different pH values, will be used to induce the fungus for the production of new secondary metabolites with more potent biologically active in a higher yield. The results from this project is hopefully to provide scientific value for the utilization of fungus Beauveria felina EN-135.

白僵菌(Beauveria)是一类寄主范围广、致病性与适应性强的昆虫病原菌（但对人类无害），已广泛应用于农林病害的防治。目前有关白僵菌的研究大多针对陆地来源，来自海洋的研究非常少见。我们从海洋动物中分离鉴定了一株白僵菌Beauveria felina EN-135。活性筛选显示，该菌在固体培养条件下的代谢产物对5种植物病原菌具有较强抑制活性（其中对棉花枯萎病菌的抑制活性最强），初步的代谢产物研究表明其主要作用成分为结构新颖的destruxin缩酚酸肽类和含共轭炔烯取代的conduritol类化合物。改变培养条件发现该菌能产生结构多样性的代谢成分。本课题拟在前期工作的基础上系统研究其代谢成分的多样性，采取表观遗传修饰的策略，通过富营养与寡营养，高盐与低盐、不同的酸碱度等环境胁迫的方法，刺激、诱导其产生结构新颖、活性更强、含量更高的代谢产物，为白僵菌在防治植物病原菌的应用提供依据。

白僵菌是一类重要的昆虫致病菌，陆地来源的白僵菌已有较多研究，但海洋来源的白僵菌尚未见系统研究。本项目按计划开展了海洋动物来源白僵菌(Beauveria felina)代谢产物的分子多样性与抗菌活性研究，采用表观遗传技术和微生物共培养技术开展了培养条件优化，在优化的条件下进行了规模发酵和代谢产物分离纯化与结构鉴定，从中分离获得了62个单体化合物并鉴定了所有化合物的分子结构，发现13个为首次报道的新化合物，包括缩酚酸肽类化合物、萜类化合物、橘青霉素类化合物等，其中发现的橘青霉素类化合物具有新颖的四环结构，系自然界中首次发现。对所有分离获得的单体化合物进行了抗菌活性评价，发现若干化合物具有显著的活性，有进一步研究开发的潜力。研究结果丰富了海洋天然产物化合物类型，为海洋来源的白僵菌开发利用提供了科学依据。