Anthrax bacteria (Bacillus anthracis) colonies (white) being cultured on an agar growth medium in a petri dish. Anthrax bacteria infect humans in two ways. The skin infection is usually treatable with antibiotics. Inhalation of anthrax spores and the development of pulmonary (lung) anthrax is often fatal unless antibiotics can be administered before the symptoms appear. Anthrax spores are easily cultured, and there is concern that anthrax bacteria could be used in an act of bioterrorism. Grown on tryptic soy agar (TSA), a nutrient agar.