Bacillus subtilis, also known as hay bacillus or grass bacillus, is a Gram-positive, catalase-positive bacterium commonly found in soil. It is rod-shaped and a member of the genus Bacillus. It also has the ability to form a tough, protective endospore, allowing the organism to tolerate extreme environmental conditions. B. subtilis has historically been classified as an obligate aerobe, though recent research has proven this to not be strictly correct.
It is not a human pathogen although it can contaminate food and occasionally cause food poisoning. The spores can survive extreme heat during cooking. They are capable of producing a single endospore that is resistant to environmental factors and can persist in the environment for long periods of time. The endospore is formed at times of nutritional stress.
B. subtilis is a model organism used to study bacterial chromosome replication. Replication is completed when the two replication forks reach the terminus region. The terminus region has several short DNA sequences that promote replication arrest. Certain proteins mediate all the steps in DNA replication.
It has proven highly amenable to genetic manipulation, and has become widely adopted as a model organism for laboratory studies, especially of sporulation, which is a simplified example of cellular differentiation. It has approximately 4,100 genes. Of these, only 192 were shown to be indispensable; another 79 were predicted to be essential as well.