Colonies of Mycobacterium ulcerans cultured on Middlebrook 7H9 agar. Mycobacterium ulcerans is a causative agent of Buruli ulcer, a chronic and destructive skin disease in humans. Serious skin ulceration is developed by the disease, and the extensive legion can even require amputation of the affected limb. The disease is the third common mycobacterial disease in humans after tuberculosis and leprosy. The colonies of the bacterium were cultivated on a Middlebrook 7H9 agar plate at 32°C for three weeks. The photo was taken under a magnification of 90×. Mineo Watanabe Ph.D. (Laboratory of Medical Microbiology, Kitasato Institute of Life Sciences, Kitasato University)