Characterization of assembly factors for type IV secretion systems

摘要

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.