Characterization of assembly factors for type IV secretion systems

摘要 许多细菌病原体采用复杂的、专门的分泌系统来输出毒素并递送 进入哺乳动物细胞的细胞质。虽然已经做了大量的工作， 由于这些分泌系统的成分的确定，对这些分泌系统所需的因素知之甚少。 功能/功能。我们建议通过研究这些组装因子， 嗜肺军团菌IVB型分泌系统。这个系统被称为Dot/Icm，由L. 在肺泡巨噬细胞内生存和复制，从而介导肺炎样 一种叫做军团病的疾病洛杉矶嗜肺菌T4 BSS由大约30个 dot/icm基因。这些基因对于该病原体的细胞内复制和毒力是必需的，但是， 大多数不是生物体在培养基上生长所必需的。然而，dotL是一个必需的基因， 条件和大量的抑制子可以被分离，以允许一个菌株存活。这些 抑制因子包括其他dot/icm基因和许多推定的组装因子中的突变 包括DjlA和LdsA。基于这些观察结果，我们建议分离额外的致死率 使用Tn-seq的抑制子，并阐明DjlA和LdsA如何在细胞的组装/功能中发挥作用。 点/Icm T4 BSS。获得的信息将提供洞察如何L。嗜肺细胞T4 BSS组装 并可能揭示药物干预的新靶点。

Abstract Many bacterial pathogens employ complex, specialized secretion systems to export toxins and deliver effectors into the cytoplasm of mammalian cells. Although a significant amount of work has been done on identifying components of these secretion systems, less is known about the factors that are required for their assembly/function. We propose to identify and characterize these assembly factors by studying the type IVB secretion system of Legionella pneumophila. This system, called Dot/Icm, is used by L. pneumophila to survive and replicate within alveoloar macrophages, thereby mediating a pneumonia-like disease called Legionnaires’ disease. The L. pneumophila T4BSS is encoded by approximately thirty dot/icm genes. These genes are essential for intracellular replication and virulence of this pathogen, but most are not required for growth of the organism on media. However, dotL is an essential gene under all conditions and a large number of suppressors can be isolated that allow a ∆dotL strain to live. These suppressors include mutations in other dot/icm genes and in a number of putative assembly factors including DjlA and LdsA. Based on these observations, we propose to isolate additional ∆dotL lethality suppressors using Tn-seq and to elucidate how DjlA and LdsA function in the assembly/function of the Dot/Icm T4BSS. Information acquired will provide insight into how L. pneumophila’s T4BSS assembles and functions and may reveal novel targets for drug intervention.