STRUCTURE AND CLASSIFICATION
Bacillus species are rod-shaped, endospore-forming aerobic or facultatively anaerobic, Gram-positive bacteria; in some species cultures may turn Gram-negative with age. The many species of the genus exhibit a wide range of physiologic abilities that allow them to live in every natural environment. Only one endospore is formed per cell. The spores are resistant to heat, cold, radiation, desiccation, and disinfectants.
Bacillus is a genus of Gram-positive rod-shaped bacteria and a member of the division 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 stressful 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. A third species, B. thuringiensis, is an important insect pathogen, and is sometimes used to control insect pests. The type species is B. subtilis, an important model organism. It is also a notable food spoiler, causing ropiness in bread and related food. B. coagulans is also important in food spoilage.
The soil, once considered their habitat, may simply serve as a reservoir. A growing number of studies show that Bacillus spores can be found in the intestinal tracts of animals, raising the question of whether this could be where they live and grow.
REF:Research in Microbiology
Volume 160, Issue 6, July-August 2009, Pages 375-379
Defining the natural habitat of Bacillus spore-formers
Huynh A. Honga, Ellen Toa, Saad Fakhryb, Loredana Baccigalupib, Ezio Riccab and Simon M. Cuttinga, ,
aSchool of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK
bDepartment of Structural and Functional Biology, Federico II University, Naples, Italy
Received 11 May 2009; accepted 24 June 2009. Available online 7 July 2009.