Chemical and Genetic Triggers of Secondary Metabolite Production

五十多年来，天然产物是新药先导的主要来源，在许多情况下，未经修饰就从隔离进入临床使用。这些化合物大多是从细菌和真菌中分离出来的，这是一项大规模工业努力的产物，目的是从全球每个角落分离可培养的菌株。这种搜索在20年前基本结束，部分原因是对已知化合物的持续重新分离带来的回报不断减少。新天然产物的缺乏对抗癌和抗生素研究的打击最大，因为大约40%和80%的小分子抗生素和抗癌药物是以天然产物为基础的。*生物信息学的最新进展使我们能够识别参与天然产物生物合成的基因和蛋白质，而不需要分离每个化合物。这些工具表明，早期对天然产品的搜索错过了绝大多数化合物，在正常的实验室生长过程中，即使是最高产的菌株也只产生了约20%的生物合成谱系。有趣的是，控制这些沉默基因的调控元件似乎是高度保守的，这表明大多数沉默的生物合成基因依赖于一小部分化学触发因素。*以相关的Photorhabdus和Xnowhabdus家族的细菌为模型，我们将使用高通量筛选来发现激活天然产物生物合成的天然产物。结合遗传学研究，这些激活剂将提供一个句柄，通过它我们可以探索控制细菌次级新陈代谢的调节途径。将天然产品的生物合成与特定的化学触发因素联系起来，也将使细菌产生的次生代谢物与特定的环境压力联系在一起，从而揭示这些化合物是如何让细菌适应环境的。化学诱因也将对工业药物发现工作有利，显著提高天然产品筛选的效率。*同时，这种方法将激活Photorhabdus和Xnowhabdus物种中未表征的基因簇，然后将对其进行识别和表征。这些化合物可能有广泛的应用，因为这些物种的菌株是农业中重要的生防剂(通过它们与杀虫线虫的共生关系)，以及未被开发的抗微生物化合物的来源。发光杆菌的代谢物特别令人感兴趣，因为这种细菌被认为是“天使的发光”背后的病原体。在美国内战期间在夏洛战役中受伤的士兵报告说，他们的伤口在黑暗中会发光，这种令人不安的效果似乎可以防止感染和帮助愈合。发光杆菌及其近亲是唯一已知的显示生物发光的陆地细菌。**

For over fifty years natural products were the primary source of new drug leads, in many cases moving from isolation to clinic use without modification. Most of these compounds were isolated from bacteria and fungi, the product of a massive industrial effort to isolate cultivable strains from every corner of the globe. This search largely ended two decades ago, due in part to diminishing returns from continual re-isolation of known compounds. The absence of new natural products has hit anticancer and antibiotic research the hardest, as approximately 40% and 80% of small molecule antibiotics and anticancer drugs are natural product based.*** Recent advances in bioinformatics allow us to identify the genes and proteins involved in natural product biosynthesis, without needing to isolate each compound. These tools reveal that earlier searches for natural products have missed the vast majority of compounds, with even the most productive strains producing only about 20% of their biosynthetic repertoire during normal lab growth. Interestingly, the regulatory elements that control these silent genes appear to be heavily conserved, suggesting that the majority of silent biosynthesis genes rely on a small set of chemical triggers.*** With bacteria from the related Photorhabdus and Xenorhabdus families as a model, we will use high throughput screening to discover natural products that activate natural product biosynthesis. In concert with genetic studies these activators will provide a handle by which we can probe the regulatory pathways that control secondary metabolism in bacteria. Linking natural product biosynthesis to specific chemical triggers will also make it possible to tie the secondary metabolites bacteria produce to specific environmental stresses, shedding light on how these compounds allow bacteria to adapt to their environment. The chemical triggers will also be a boon to industrial drug discovery efforts, significantly improving the efficiency of natural product screening.*** At the same time, this approach will activate uncharacterized gene clusters in Photorhabdus and Xenorhabdus species, which will then be identified and characterized. These compounds are likely to have broad applications, as strains from these species are important biocontrol agents in agriculture (through their symbiotic relationship with insecticidal nematodes), as well as an underexplored source of antimicrobial compounds. The metabolites of Photorhabdus luminescens are of particular interest, as this bacteria is thought to be the causative agent behind “Angel's Glow.” Soldiers injured in the Battle of Shiloh during the American Civil War reported that their wounds glowed in the dark, an unsettling effect that nevertheless appeared to prevent infection and aid healing. P. luminescens and its close relatives are the only known terrestrial bacteria to exhibit bioluminescence. **