Structure Revealed For Bacterial Infection Apparatus

When the pathogens that cause whooping cough and digestive disorders such as ulcers and stomach cancer infect humans, they do so with a multiprotein molecular machine, called the type IV secretion system, that introduces virulent factors into cells. A first structural glimpse of this 34-nm-long assembly has been reported by a team of researchers led by Rémi Fronzes of the Pasteur Institute, in Paris, and Elena V. Orlova and Gabriel Waksman of University College London (Nature 2014, DOI: 10.1038/nature13081). The team used electron microscopy to get an averaged 21-Å-resolution structure of the type IV secretion system. The infection apparatus has “markedly different architecture, and consequently mechanism, to other known bacterial secretion systems,” the authors note. The structure provides antibiotic developers with a needed peek at how nasty pathogens infect cells. And because the type IV secretion system is used by many kinds of benign bacteria to exchange genes, the structural information could be useful for the fundamental understanding of microbiology. Type IV secretion systems have also been touted as possible tools for genetically modifying human cells.