Cryo-EM structure of the bacteria-killing type IV secretion system core complex from Xanthomonas citri

Type IV secretion (T4S) systems form the most common and versatile class of secretion systems in bacteria, capable of injecting both proteins and DNAs into host cells. T4S systems are typically composed of 12 components that form 2 major assemblies: the inner membrane complex embedded in the inner membrane and the core complex embedded in both the inner and outer membranes. Here we present the 3.3 Å-resolution cryo-electron microscopy model of the T4S system core complex from Xanthomonas citri, a phytopathogen that utilizes this system to kill bacterial competitors. An extensive mutational investigation was performed to probe the vast network of protein–protein interactions in this 1.13-MDa assembly. This structure expands our knowledge of the molecular details of T4S system organization, assembly and evolution

Bordetella pertussis pathogenesis: current and future challenges

Pertussis, or whooping cough, has recently reemerged as a major public health threat despite high levels of vaccination against the etiological agent, Bordetella pertussis. In this Review, we describe the pathogenesis of this disease, with a focus on recent mechanistic insights into virulence factor function. We also discuss the changing epidemiology of pertussis and the challenges of vaccine development. Despite decades of research, many aspects of B. pertussis physiology and pathogenesis remain poorly understood. We highlight knowledge gaps that must be addressed to develop improved vaccines and therapeutic strategies