DataSheet2_Natural products, including a new caboxamycin, from Streptomyces and other Actinobacteria isolated in Spain from storm clouds transported by Northern winds of Arctic origin.DOCX

Actinobacteria, mostly Streptomyces species, are the main source of natural products essential in medicine. While the majority of producer microorganisms of secondary metabolite are reported from terrestrial or marine environments, there are limited reports of their isolation from atmospheric precipitations. Clouds are considered as atmospheric oases for microorganisms and there is a recent paradigm shift whereby atmospheric-derived Actinobacteria emerge as an alternative source for drug discovery. In this context, we studied a total of 18 bioactive Actinobacteria strains, isolated by sampling nine precipitation events with prevailing Northern winds in the Cantabrian Sea coast, Northern Spain. Backward trajectories meteorological analyses indicate that air masses were originated mostly in the Arctic Ocean, and their trajectory to downwind areas involved the Atlantic Ocean and also terrestrial sources from continental Europe, and in some events from Canada, Greenland, Mauritania and Canary Islands. Taxonomic identification of the isolates, by 16S rRNA gene sequencing and phylogenetic analyses, revealed that they are members of three Actinobacteria genera. Fifteen of the isolates are Streptomyces species, thus increasing the number of bioactive species of this genus in the atmosphere to a 6.8% of the total currently validated species. In addition, two of the strains belong to the genus Micromonospora and one to genus Nocardiopsis. These findings reinforce a previous atmospheric dispersal model, extended herein to the genus Micromonospora. Production of bioactive secondary metabolites was screened in ethyl acetate extracts of the strains by LC-UV-MS and a total of 94 secondary metabolites were detected after LC/MS dereplication. Comparative analyses with natural products databases allowed the identification of 69 structurally diverse natural products with contrasted biological activities, mostly as antibiotics and antitumor agents, but also anti-inflammatory, antiviral, antiparasitic, immunosuppressant and neuroprotective among others. The molecular formulae of the 25 remaining compounds were determined by HRMS. None of these molecules had been previously reported in natural product databases indicating potentially novel metabolites. As a proof of concept, a new metabolite caboxamycin B (1) was isolated from the culture broth of Streptomyces sp. A-177 and its structure was determined by various spectrometric methods. To the best of our knowledge, this is the first novel natural product obtained from an atmospheric Streptomyces, thus pointing out precipitations as an innovative source for discovering new pharmaceutical natural products.

放线菌，尤其是链霉菌属，是医药领域不可或缺的天然产物的主要来源。尽管已报道的大多数次级代谢产物生产微生物主要来自陆地或海洋环境，但关于从大气降水分离出的这类微生物的报告却极为有限。云层被视为微生物的大气绿洲，近期研究范式发生了转变，大气起源的放线菌已成为药物发现的新兴替代来源。在此背景下，我们研究了从西班牙北部加利西亚海岸九次主要受北风影响的降水事件中分离出的18种生物活性放线菌菌株。向后传播气象分析表明，气团主要源自北极海洋，其流向下游区域的过程中涉及了大西洋以及来自欧洲大陆的陆地来源，在某些事件中还包括了加拿大、格陵兰、毛里塔尼亚和加那利群岛。通过16S rRNA基因测序和系统发育分析对分离菌株进行分类鉴定，发现它们属于三个放线菌属。其中15个菌株为链霉菌属，从而将大气中该属生物活性物种的数量提升至已验证物种总数的6.8%。此外，有两个菌株属于单座菌属，一个菌株属于诺卡氏菌属。这些发现强化了之前的气传扩散模型，并将其扩展至单座菌属。通过LC-UV-MS对菌株的乙酸乙酯提取物进行生物活性次级代谢产物筛选，经过LC/MS去重复分析后，共检测到94种次级代谢产物。与天然产物数据库的比较分析，允许识别出69种结构多样的天然产物，其生物活性各异，主要包括抗生素和抗癌剂，但也有抗炎、抗病毒、抗寄生虫、免疫抑制剂和神经保护剂等多种活性。通过高分辨质谱确定了25种剩余化合物的分子式。这些分子在天然产物数据库中均未有过报道，表明它们可能是新型代谢产物。作为概念验证，从链霉菌属菌株A-177的培养液中分离出了一种新的代谢产物——卡泊沙霉素B（1），并利用多种光谱学方法确定了其结构。据我们所知，这是首次从大气链霉菌中获得的 novel natural product，从而指出降水是发现新药理天然产物的一种创新来源。