Caption

Chlamydia bacteria. Coloured Transmission Electron Micrograph (TEM) of Chlamydia sp. bacteria. Here a group of such bacteria are coloured yellow. These spherical, Gram-negative bacteria include several species that parasitize humans and birds. They are obligate parasites, incapable of living outside the cells of their host. Diseases caused by Chlamydia include the sexually-transmitted disease lymphogranuloma venereum; eye diseases of trachoma and inclusion conjunctivitis; many cases of non- specific urethritis (NSU); a type of pneumonia called psittacosis; bronchitis; and sinusitis. Chlamydia are among the smallest bacteria, about the size of large viruses. Magnification: unknown.