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Details of the machinery some bacteria use to inject toxins in to host cells

24 June 2019

Shoot Out

Bacteria often use sophisticated weaponry to pump human cells full of toxins. Legionella pneumophila (among other bacterial invaders) use this ‘Type IV secretion system’ to inject their hosts with around 300 molecules per 'shot'. This 3D computer model pieces together clues from electron cryotomography – examining the molecular mechanics in detail – followed by fluorescence microscopy to watch how they assemble and move. With its artificially-coloured red 'barrel' imbedded in a host cell, chambers around the outside of the tiny protein machine help to trigger the release of toxins. Knowing more about how all these mechanisms work together, scientists are developing new antibiotics to specifically disarm these bacterial 'guns' in the fight against Legionnaire’s disease, whooping cough and certain types of cancer.

Written by John Ankers

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BPoD stands for Biomedical Picture of the Day. Managed by the MRC Laboratory of Medical Sciences until Jul 2023, it is now run independently by a dedicated team of scientists and writers. The website aims to engage everyone, young and old, in the wonders of biology, and its influence on medicine. The ever-growing archive of more than 4000 research images documents over a decade of progress. Explore the collection and see what you discover. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.

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