False-colour transmission electron micrograph of a colony of Neisseria gonorrhoeae, the bacterium which causes the sexually-transmitted disease gonorrhoea. The bacteria are Gram-negative, non- motile & kidney- shaped & often occur in pairs, being flattened on the side facing the partner. Infection occurs through the genital mucous membranes of either sex: symptoms include pain on passing urine & a discharge of pus from the penis or vagina. Some women may experience no initial symptmoms. Untreated, the infection spreads & may cause sterility in women & urethral blockage in men. Magnification: x7500 at 6x4.5cm size.