海洋放线菌是一类具有重要价值的药用微生物，能够产生结构类型多样的生物活性物质．对中国南海海洋生物中分离出的海洋放线菌进行抗农业病原菌活性筛选，发现两株海绵链霉菌Streptomycessp.HMH1和Streptomycessp.HML1对农业病原菌具有较强的拮抗活性．为研究菌株HMH1和HML1产生的活性代谢产物，采用正相/反相硅胶柱和SephadexLH-20凝胶柱色谱等分离方法对代谢产物进行分离纯化，通过核磁共振波谱、高分辨电喷雾质谱等波谱数据和文献数据鉴定化合物结构，测定化合物的抗菌活性．结果显示，从链霉菌Streptomycessp.HMH1的大米固体发酵产物中分离鉴定出3种放线菌素类化合物，分别为放线菌素D、放线菌素X2和放线菌素Xoβ；从链霉菌Streptomycessp.HML1的大米固体发酵产物中分离得到1个吲哚咔唑生物碱类化合物，鉴定为K-252d．化合物抗农业病原菌活性测试结果显示，放线菌素D的抗菌谱广，对供试的10种植物病原真菌和2种植物病原细菌的生长具有抑制活性．其中，对木瓜可可毛色二孢霉、木瓜拟茎点霉、小麦赤霉和辣椒疫霉等病原真菌具有较强的抑制作用，抑制率分别为（60.09±0.66）%、（48.82±0.66）%、（46.47±1.14）%和（44.13±0.66）%；对水稻白叶枯病菌、茄青枯劳尔氏菌等病原细菌也显示抑菌活性，抑菌直径分别为（36.00±0.82）mm和（15.00±0.47）mm．研究结果可为相关农业病害高效生防菌剂研发提供新的化合物和菌种资源．
Actinomycetes residing in marine habitat are an excellent treasure house of structurally novel and bioactive natural products with potent medicinal values. To exploit chemically diverse and bioactive natural products from actinomycetes living in underexplored ecological niche, we isolate a large number of marine actinomycetes from marine sponges, corals, algae, mollusks, sea grasses, and sediments collected from the South China Sea. In order to assess the values of these special marine actinomycetes in the green development of tropical agriculture, we screen the activity of marine actinomycetes against phytopathogenic fungi and bacteria. As a result, we identify two strains of sponge-derived actinobacteria Streptomyces sp. HMH1 and HML1 possessing antagonism effect against tested phytopathogenic microbes. The secondary metabolites produced by these two actinomycete strains and their anti-phytopathogenic fungi activity are investigated. The secondary metabolites from the fermentation extract of Streptomyces sp. HMH1 and HML1 are isolated and purified using various chromatography methods including silica gel column, reverse gel column and Sephadex LH-20 column chromatography. The structures of the isolated compounds are characterized by NMR, HR-ESI-MS spectroscopic data analyses and comparison with previously reported data. Three major compounds belonging to the family of actinomycin are purified from the solid fermentation extract of the sponge-derived actinobacterium Streptomyces sp. HMH1. They actinomycin D, actinomycin X2, and actinomycin Xoβ. A compound identified as K-252d belonging to the family of indolocarbazole alkaloid is isolated from the solid fermentation extract of another sponge-derived actinobacterium Streptomyces sp. HML1. The anti-phytopathogenic fungi and bacteria activities of these compounds are evaluated against ten species of plant pathogenic fungi including Fusarium oxysporum FOC4, Lasiodiplodia theobromae, Phomopsis caricae-papayae Fetrak&Cif., Corynespora cassiicola, Phytophthora capsica, Pythium aphanidermatum (Edson) Fitzp, Corynespora sp., Fusarium graminearum, Verticillium dahlia, Pestalotiopsis microspora , and two species of plant pathogenic bacteria including Xanthomonas oryzae pv. oryzae and Ralstonia solanacearum . The bioactivity test results of the compound against agricultural pathogens show that actinomycin D possesses inhibitory activity against the growth of these tested phytopathogenic fungi and bacteria. among which, actinomycin D has the most potent inhibitory activity against the plant pathogenic fungi Lasiodiplodia theobromae, Phomopsis caricae-papayae Fetrak&Cif., Fusarium graminearum and Phytophthora capsica , with inhibitory rate of (60.09 ± 0.66)% , (48.82 ± 0.66)% , (46.47 ± 1.14)% and (44.13 ± 0.66)% , respectively. In addition, actinomycin D displays strong antibacterial activity on the plant pathogenic bacteria Xanthomonas oryzae pv. oryzae and Ralstonia solanacearum with bacteriostatic diameter at (36.00 ± 0.82) mm and (15.00 ± 0.47) mm, respectively. These results provide new compounds and bacteria resources for the development of high-efficiency biocontrol agents for agricultural disease control.
