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Injurious Injections
12 April 2012

Injurious Injections

Many bacteria possess their own biological ‘needles’, for injecting toxins (shown in yellow in the image) into our cells. Using electron microscopy and computer graphics scientists were able to model one such instrument (shown in cross-section and lengthways) from bacterium Shigella flexneri, the cause of bacillary dysentery in humans. The needle is made from 25 identical proteins, arranged in a spiral shape. Its structure is similar to that of a flagellum, the tubular propeller some bacteria use to move around. Less than one millionth of a centimetre wide, Shigella's needle is 25,000 times smaller than the finest hypodermic needles used today in medical environments. The researchers hope that understanding how bacteria produce such finely structured needles will lead to better ways of fighting infectious disease.

Written by Charles Harvey

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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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