False-colour shadow transmission electron micro- graph (TEM) of a single Serratia sp. bacterium dividing. The wall separating the new sister cells can be seen,including their cytoplasm; whip-like flagellae (hairs,green) are used to propel the bacterium. Species of Serratia occur as commensal fauna in the intestinal mucous membrane of humans. Occasionally they are pathogenic,presenting in long term,chronically sick patients in whom they may cause septicaemia. This shadow TEM was made by coating the bacterium in a metal such as gold,to produce a surface replica used as the microscope specimen. Magnification: x32,000 at 6x7cm size |