Phage resistance and mobile genetic elements in Vibrio cholerae

霍乱弧菌等水传播病原体对全球健康构成重大威胁。霍乱弧菌可持续存在 水环境，它可能会在流行地区造成毁灭性的霍乱暴发 缺乏足够的水和卫生基础设施的脆弱地区。寄主-病原体的相互作用 疾病结局和霍乱传播动态发生在复杂的微生物环境中 包括捕食性细菌病毒(噬菌体)的生态系统。噬菌体深刻地影响了它们的进化 细菌宿主，既通过捕食，选择具有克服噬菌体杀灭和 通过动员和传播遗传物质。某些被称为噬菌体卫星的移动元件 进化出复杂的机制来利用噬菌体进行自私的传播。这些元素干扰了 通过它们寄生的噬菌体的复制，从而为它们的细胞宿主提供了一种限制 噬菌体捕食。我们的实验室在V。 霍乱弧菌对ICP1提供了特异而强大的防御，ICP1是与霍乱弧菌共同循环的优势溶解噬菌体。 霍乱流行地区的霍乱。当感染ICP1时，PLE从霍乱弧菌染色体上切除， 复制到高拷贝并组装成病毒粒子，将PLE基因组传播到新细胞，同时 同时取消噬菌体生产。PLE是唯一有效的、高度特异的抗噬菌体屏障 通过多种机制采取行动，确保ICP1不会传播和传播到邻近的V。 霍乱杆菌细胞。然而，对ICP1的直接干扰机制鲜为人知，而且都不是必需的 对于PLE活动，这表明在此系统中还有其他机制等待发现。这项建议的基础是 我们之前的工作定义了PLE生命周期以响应噬菌体感染，以获得对 PLE如何执行其异常强大的抗噬菌体活性。我们的数据表明，PLE最强大的抗- 噬菌体抑制剂的重点是阻止病毒粒子的组装。为了了解PLE活动的机械性细节，我们 将追求以下具体目标：1)我们将定义病毒粒子和衣壳的结构组成 ICP1和PLE的组装中间体2)我们将询问三个PLE编码的ORF的功能，它们 每个都足以抑制噬菌体3)我们将确定PLE编码的小RNA是如何干扰噬菌体基因的 表情。拟议的研究有望揭示新的机械论范式，而不是以前的 在噬菌体卫星或其他反噬菌体防御系统中记录。霍乱弧菌的长期协同进化 PLE和ICP1是理解临床相关噬菌体防御的强大模型系统 为噬菌体治疗工作提供信息并了解推动细菌进化的力量的机制 病原体。

Waterborne pathogens like Vibrio cholerae pose significant threats to global health. V. cholerae can persist in the aquatic environment, and it can emerge to cause devastating cholera outbreaks in endemic regions and vulnerable areas lacking adequate water and sanitation infrastructure. The host-pathogen interactions that dictate disease outcome and cholera transmission dynamics occur in the context of a complex microbial ecosystem that includes predatory bacterial viruses (phages). Phages profoundly impact the evolution of their bacterial hosts, both through predation, which selects for hosts with defenses that overcome phage killing and through mobilization and dissemination of genetic material. Certain mobile elements called the phage satellites have evolved sophisticated mechanisms to exploit phages for their own selfish spread. Such elements interfere with the replication of the phages they parasitize, and as such, provide their cellular hosts with a means to limit phage predation. Our lab discovered PLEs (for phage-inducible chromosomal island-like elements) in V. cholerae that provide specific and robust defense against ICP1, the dominant lytic phage co-circulating with V. cholerae in cholera endemic regions. Upon infection by ICP1, PLEs excise from the V. cholerae chromosome, replicate to high copy and are assembled into virions to spread the PLE genome to new cells while concurrently abolishing phage production. PLEs are uniquely potent, highly specific, anti-phage barriers that act through multiple mechanisms to ensure that ICP1 does not propagate and spread to neighboring V. cholerae cells. However, few mechanisms of direct interference with ICP1 are known, and none are essential for PLE activity, indicating that additional mechanisms await discovery in this system. This proposal builds on our prior work defining the PLE lifecycle in response to phage infection to gain a mechanistic understanding of how PLEs execute their unusually potent anti-phage activity. Our data indicate that PLE’s most potent anti- phage inhibitors are focused on blocking virion assembly. To understand PLE activity in mechanistic detail, we will pursue the following specific aims: 1) We will define the structural composition of virions and capsid assembly intermediates for ICP1 and PLE 2) We will Interrogate the functions of three PLE-encoded ORFs that are each sufficient to inhibit phage 3) We will determine how a PLE-encoded small RNA perturbs phage gene expression. The proposed studies are expected to reveal novel mechanistic paradigms not previously documented in phage satellites or other anti-phage defense systems. The long-term coevolution of V. cholerae PLE and ICP1 serves as a powerful model system to understand clinically relevant phage defense mechanisms to inform phage therapy efforts and understand the forces driving the evolution of bacterial pathogens.