Cryo-Microscope Allows High-Res 3-D Model of Salmonella’s Needle Complex

Some of the most dread diseases in the world such as plague, typhoid, and cholera are caused by bacteria that have one thing in common: they possess an infection apparatus which is a nearly unbeatable weapon. When attacking a cell of the body, they develop numerous hollow-needle-shaped structures that project from the bacterial surface. Through these needles, the bacteria inject signal substances into the host cells, which re-program these cells and thereby overcome their defense. The pathogens can then invade the cells unimpeded and in large numbers. The biochemist and biophysicist Dr. Thomas Marlovits, a group leader at the Vienna Institutes IMP (Research Institute of Molecular Pathology) and IMBA (Institute of Molecular Biotechnology) has been occupied for several years with the infection complex of salmonellae. As early as in 2006 Dr. Marlovits showed how the needle complex of Salmonella typhimurium develops. Together with his doctoral student Oliver Schraidt, he has now been able to demonstrate the three-dimensional structure of this complex at extremely high resolution. The team was able to show details with dimensions of just 5 to 6 angstroms, which are nearly atomic orders of magnitude. Their work is presented in the March 4, 2011 issue of Science. Never before has the infection tool of salmonellae been presented in such precision. This was achieved by the combined use of high-resolution cryo-electron microscopy and specially developed imaging software. "Austria's coolest microscope" makes it possible to shock-freeze biological samples at minus 196 degrees centigrade and view them in almost unchanged condition.
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