[5][6][7][8] As a member of the genus Bacillus, B. subtilis is rod-shaped, and can form a tough, protective endospore, allowing it to tolerate extreme environmental conditions.

B. subtilis 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.

In terms of popularity as a laboratory model organism, B. subtilis is often considered as the Gram-positive equivalent of Escherichia coli, an extensively studied Gram-negative bacterium.

[6] Note: + = Positive, – =Negative This species is commonly found in the upper layers of the soil and B. subtilis is thought to be a normal gut commensal in humans.

Studies have shown that the bacterium exhibits vegetative growth in soil rich in organic matter, and that spores were formed when nutrients were depleted.

[17] Additionally, B. subtilis has been shown to form biofilms on plant roots, which might explain why it is commonly found in gut microbiomes.

[17] Bacillus subtilis can divide symmetrically to make two daughter cells (binary fission), or asymmetrically, producing a single endospore that can remain viable for decades and is resistant to unfavourable environmental conditions such as drought, salinity, extreme pH, radiation, and solvents.

The endospore is formed at times of nutritional stress and through the use of hydrolysis, allowing the organism to persist in the environment until conditions become favourable.

Comparison between the proteins involved in chromosomal DNA replication in B. subtilis and in Escherichia coli reveals similarities and differences.

Although the basic components promoting initiation, elongation, and termination of replication are well-conserved, some important differences can be found (such as one bacterium missing proteins essential in the other).

[6][7] B. subtilis strain WS1A genome contains many potential genes, such as those encoding proteins involved in the biosynthesis of riboflavin, vitamin B6, and amino acids (ilvD) and in carbon utilization (pta).

[41] Cultures of B. subtilis were popular worldwide, before the introduction of antibiotics, as an immunostimulatory agent to aid treatment of gastrointestinal and urinary tract diseases.

[43] It was marketed throughout America and Europe from 1946 as an immunostimulatory aid in the treatment of gut and urinary tract diseases such as Rotavirus and Shigellosis.

[45] The antibiotic bacitracin was first isolated from a variety of Bacillus licheniformis named "Tracy I"[46] in 1945, then considered part of the B. subtilis species.

[48] It has been used as an extremophile survival indicator in outer space such as Exobiology Radiation Assembly,[49][50] EXOSTACK,[51][52] and EXPOSE orbital missions.

[53][54][55] Wild-type natural isolates of B. subtilis are difficult to work with compared to laboratory strains that have undergone domestication processes of mutagenesis and selection.

These strains often have improved capabilities of transformation (uptake and integration of environmental DNA), growth, and loss of abilities needed "in the wild".

[citation needed] On the other hand, several feed additives containing viable spores of B. subtilis have been positively evaluated by the European Food Safety Authority, regarding their safe use for weight gaining in animal production.

Molecular assays (randomly amplified polymorphic DNA PCR assay, denaturing gradient gel electrophoresis analysis, and sequencing of the V3 region of 16S ribosomal DNA) revealed greater Bacillus species variety in ropy breads, which all seems to have a positive amylase activity and high heat resistance.

In the United States, an opinion letter issued in the early 1960s by the Food and Drug Administration (FDA) designated some substances derived from microorganisms as generally recognized as safe (GRAS), including carbohydrase and protease enzymes from B. subtilis.

This includes consumption of Japanese fermented soy bean, in the form of Natto, which is commonly consumed in Japan, and contains as many as 108 viable cells per gram.

The fermented beans are recognized for their contribution to a healthy gut flora and vitamin K2 intake; during this long history of widespread use, natto has not been implicated in adverse events potentially attributable to the presence of B. subtilis.