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
BPoD stands for Biomedical Picture of the Day. Managed by the MRC London Institute of Medical Sciences (the new name for the MRC Clinical Sciences Centre) the website aims to engage everyone, young and old, in the wonders of biomedicine. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.