Illuminated dark field micrograph of Bacillus anthracis, the spore forming bacteria that causes anthrax. B. anthracis was the first bacterium identified as the cause of a disease. When a bacterium germinates from an ingested spore, it will secrete toxins that will overwhelm the host. A single infected tissue may contain billions of bacteria. Symptoms of anthrax vary depending upon the type of exposure. With skin exposure, swollen lymph glands, and a boil-like lesion will appear. With respiratory exposure, symptoms resemble a common cold, progressing to severe breathing problems and shock. Inhalation of anthrax is usually fatal as its spores produce lethal toxins that rupture the alveoli in the lungs. Respiratory anthrax is also a potential agent in biological warfare as the spores of the bacterium can be freeze-dried and disseminated as an aerosol or powder. Magnification: 1200x at 35mm.