False-colour transmission electron micrograph (TEM) of a colony of Shigella sp.,a genus of Gram-negative bacteria which causes dysentery in humans. Dysentery,affecting mainly the large intestines,varies in severity from a mild attack of diarrhoea to an acute infection. Until the introduction of the sulphonamide drugs in the 1930s it was a killer disease of the world. It still is among the young,elderly & malnourished. The infection is spread by flies,direct contact,& water contaminated by faeces containing the bacillus. Here,the bacterium at centre is dividing through binary fission. Magnification: x 10,000 at 35mm size,x20,000 at 6x7cm size |