ABOVE: A tomogram and corresponding 3-D rendering of a Salmonella typhimurium minicell (green) interacting with a HeLa cell (membrane in red) via protein secretion (indicated by small blue arrow). Also shown are the host cell’s actin filaments (orange) and ribosomes (purple).

Bacterial pathogens such as Salmonella interact with host cells via a suite of complex mechanisms known as type III protein secretion systems. These processes allow a pathogen to directly inject its proteins into eukaryotic host cells, helping the bacteria subvert host defenses and avoid an immune response.

The details of these protein secretion systems have been murky because of the difficulty of imaging cell-cell interactions in high resolution. But now, a team led by researchers at Yale University has used cryo-electron tomography to image the interaction between bacterial minicells—nanoparticles that contain all bacterial components except chromosomes—and mammalian cells in vitro. The...

D.Park et al., “Visualization of the type III secretion mediated Salmonella-host cell interface using cryo-electron tomography,” eLife, 7:e39514, 2018.

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