Gonorrhoea bacteria. Coloured transmission electron micrograph (TEM) of three sectioned Neisseria gonorrhoeae bacteria during conjugation. These are the cause of the sexually-transmitted disease gonorrhoea. During conjugation, bacteria exchange genetic material along structures known as pili (thin lines). N. gonorrhoeae infects the genital mucous membranes of both sexes, causing pain on urination and a discharge of pus from the vagina or penis. Some cases pass unnoticed, but in others complications develop that may lead to sterility. Treatment is with antibiotics. Magnification unknown.