"Bacillus" can reduce themselves to oval endospores and can remain in this dormant state for years. The endospore of one species from Morocco is reported to have survived being heated to 420 °C. Endospore formation is usually triggered by a lack of nutrients: the bacterium divides within its cell wall, and one side then engulfs the other. They are not true spores (i.e., not an offspring). Endospore formation originally defined the genus, but not all such species are closely related, and many species have been moved to other genera of the "Firmicutes". Only one endospore is formed per cell. The spores are resistant to heat, cold, radiation, desiccation, and disinfectants. "Bacillus anthracis" needs oxygen to sporulate; this constraint has important consequences for epidemiology and control. In vivo, "B. anthracis" produces a polypeptide (polyglutamic acid) capsule that kills it from phagocytosis. The genera "Bacillus" and "Clostridium" constitute the family "Bacillaceae". Species are identified by using morphologic and biochemical criteria. Because the spores of many "Bacillus" species are resistant to heat, radiation, disinfectants, and desiccation, they are difficult to eliminate from medical and pharmaceutical materials and are a frequent cause of contamination. Not only they are they resistant to heat, radiation, etc., but they are also resistant to chemicals such as antibiotics. This resistance allows them to survive for many years and especially in a controlled environment. "Bacillus" species are well known in the food industries as troublesome spoilage organisms.