Bacillus is a genus of gram-positive, rod-shaped bacteria and a member of the phylum Firmicutes. Bacillus species can be obligate aerobes or facultative anaerobes, and test positive for the enzyme catalase. Ubiquitous in nature, Bacillus includes both free-living and pathogenic species. Under unfavourable environmental conditions, the cells produce oval endospores that can stay dormant for extended periods. These characteristics originally defined the genus, but not all such species are closely related, and many have been moved to other genera.
Two Bacillus species are considered medically significant: B. anthracis, which causes anthrax, and B. cereus, which causes a foodborne illness similar to that of Staphylococcus. The type species is B. subtilis, an important model organism. It is also a notable food spoiler, causing ropiness in bread and related food. Some environmental and commercial strains B. coagulans may play a role in food spoilage of highly acidic, tomato based products.
The dehydrated culture media that Merck provides for cultivating Bacillus meet the strict performance standards as set out in ISO 11133. The unique granulated format causes much less dust than powdered media and guarantees excellent solubility and homogeneity. The granules dissolve readily in water, with almost no component separation or clumping, even under warm or humid conditions. The exceptional properties of Merck dehydrated culture media make them very easy to handle and highly productive.
Bacillus cereus is responsible for 2 to 5% of foodborne illnesses, causing severe nausea, vomiting and diarrhea. This happens because bacterial endospores survive when food is improperly cooked. If the food is then not adequately refrigerated, the endospores are allowed to germinate. Bacterial growth results in enterotoxin production. One such endotoxin is highly resistant to heat and to a wide pH range. Ingestion leads to two two types of illness: one is characterized by diarrhea and the other by nausea and vomiting.