The Microbial Battlefield: Streptomyces Anti-Phage Chemical Warfare

这项拨款将用于研究链霉菌产生抗噬菌体次级代谢物。噬菌体是感染并杀死细菌的病毒。它们是地球上最丰富的生物实体，数量是细菌的十倍。据估计，地球上每秒钟发生的噬菌体感染是阿伏伽德罗数。这种普遍存在的选择压力与环境中无处不在的噬菌体相结合，导致了一系列细菌抗噬菌体防御机制的进化。例如，细菌可以抑制噬菌体在细胞表面的附着，阻断基因组复制，或使用限制性内切酶或CRISPR-Cas系统降解噬菌体基因组。鉴于噬菌体军备竞赛的强度，很可能还有其他防御机制有待研究。这些机制的表征将为噬菌体-宿主相互作用如何塑造微生物世界提供重要的见解。******先前的研究寻找抑制大肠杆菌噬菌体复制的化合物，发现了许多由不同种类的链霉菌产生的次级代谢物，这些代谢物可以有效地阻断噬菌体的繁殖。我们在链霉菌菌株中发现这些次生代谢物的高频率使我们假设次生代谢物提供了以前未被表征的抗噬菌体防御系统。在本研究中，我们将确定链霉菌是否利用次生代谢物作为内源性抗噬菌体防御机制，并将确定这些分子合成的遗传途径。我们已经开发了一个独特的平台来进行这些研究，将高通量筛选与详细的生化和遗传研究相结合，使我们能够识别分子并将它们与抗噬菌体活性直接联系起来。这项工作将把生物学功能归因于以前未被表征的次级代谢物，并为细菌和噬菌体之间的进化军备竞赛提供新的见解，细菌和噬菌体在营养循环、全球气候、生物多样性和物种分布中起着重要作用。

This grant will investigate the production of anti-phage secondary metabolites by Streptomyces bacteria. Phages are viruses that infect and kill bacteria. They are the most abundant biological entity on earth, outnumbering bacteria by a factor of ten. It is estimated that Avogadro's number of phage infections occurs each second on earth. This pervasive selection pressure combined with the ubiquity of phages in the environment has led to the evolution of a wide array of bacterial anti-phage defense mechanisms. For example, bacteria can inhibit phage attachment at the cell surface, block genome replication, or degrade the phage genome using restriction enzymes or the CRISPR-Cas system. Given the intensity of the bacteria-phage arms race, it is highly probable that other defense mechanisms remain to be delineated. Characterization of these mechanisms will provide important insight into how phage-host interactions shape the microbial world. ******Previous studies searching for compounds that inhibit E. coli phage replication identified a number of secondary metabolites produced by different species of Streptomyces that actively block phage propagation. The high frequency with which we identified these secondary metabolites among Streptomyces strains led us to hypothesize that secondary metabolites provide a previously uncharacterized anti-phage defense system. In this proposal, we will determine if Streptomyces use secondary metabolites as an endogenous anti-phage defense mechanism and will identify genetic pathways through which these molecules are synthesized. We have developed a unique platform for pursuing these studies that combines high-throughput screening with detailed biochemical and genetic studies that will allow us to identify molecules and directly link them with anti-phage activities. This work will ascribe biological functions to previously uncharacterized secondary metabolites and provide new insight into the evolutionary arms race between bacteria and phages, which plays important roles in nutrient cycling, global climate, biodiversity, and species distribution.