Bacillus is a genus of Gram‑positive, rod‑shaped bacteria that form protective endospores. Members of this group are aerobic or facultatively anaerobic and they occur in a wide variety of environments, especially soil. Each cell produces a single spore, which allows the organism to survive extreme conditions such as drying, heat and exposure to disinfectants.
Explanation
Bacillus species have a simple cylindrical shape and reproduce by binary fission. When nutrients are limited they switch to a sporulation pathway, producing a dormant spore that can persist for long periods. These spores are highly resistant to heat, cold, radiation, desiccation and many chemicals, which explains why the genus is found in diverse habitats and can contaminate laboratory reagents or hospital equipment. The genus was formally described in the nineteenth century and today contains hundreds of species. Many are harmless saprophytes that recycle organic matter, while others are used in industry for enzyme production or fermentation. Some Bacillus species produce antibiotics and enzymes that are valuable in food processing and agriculture.
Examples and notes
Bacillus subtilis is a well‑studied soil bacterium used as a model organism for understanding spore formation and gene regulation. Bacillus cereus is associated with foodborne illness when it grows in improperly stored rice or other foods. Bacillus thuringiensis produces protein crystals toxic to certain insects and is widely used as a biological pesticide. Because of their ability to form spores, Bacillus strains are also used to test the efficacy of sterilization methods. Many species within this genus are harmless and even beneficial, but a few can cause disease or spoil food. The spores’ resilience makes careful sterilization important when working with these organisms. Related Terms: Bacteria, Bacteriology, Basal medium, Bacteriophage, Biofilm