A Review of Bacillus Subtilis

Peter M. Williams, Erika Steele
  • Author
    Peter M. Williams

    Peter holds a Bachelor's degree in Microbiology and Biotechnology, and a Master's degree in Applied Microbiology. In addition, Peter has more than two years of experience in tutoring and writing academic materials for senior and junior schools, mainly in Sciences, Languages, and Humanities.

  • Instructor
    Erika Steele

    Erika has taught college Biology, Microbiology, and Environmental Science. She has a PhD in Science Education.

What is the Gram stain of Bacillus Subtilis? Learn about Bacillus Subtilis' characteristics, shape, and how it is best used to help in medical research. Updated: 11/03/2021

Table of Contents


What is Bacillus Subtilis

Bacillus subtilis is a bacteria known to produce heat-resistant spores known as the endospore. The spores are usually ellipsoidal, and they help preserve the genetic material of the bacteria under unfavorable environmental conditions. Thus, the main reason for spore production in Bacillus subtilis is survival.

Bacillus subtilis is commonly found in the soil but can also be cultured in a microbiology laboratory. This bacterium belongs to a group of gram-positive bacteria since it has a thick peptidoglycan layer. Peptidoglycan is a molecule found on the cell wall of bacteria.

In addition, Bacillus subtilis fall under the phylum Firmicute, a group of bacteria that produces endospores.


A complete set of genetic information in any living organism is referred to as a genome. Bacillus subtilis is comprised of 4100 genes that are responsible for the coding of proteins. This bacterium has a total number of 4,214,630 base pairs. The guanine-cytosine content is relatively low, and it comprises 43.5% of the total base pairs. The majority of Bacillus subtilis genes are represented once (53%), while others are duplicates. These genes are entirely used and responsible for producing secondary metabolites such as antibiotics and enzymes.

Bacillus subtilis has been genetically studied for years, and its characterization has established a model system used in cell differentiation and development. The Bacillus subtilis QB928 strain has been used in research to understand the evolution of the genetic code of this bacterium. As a result, researchers have been able to establish a complete genome sequence of Bacillus subtilis QB928. In addition, the Bacillus Subtilis 169 strain has also been broadly studied in trying to understand the behavioral and traits of Bacillus subtilis.

Bacterial Transformation of Bacillus Subtilis

Bacteria exchange genetic information through various mechanisms. Transformation occurs when naked DNA from the donor or environment is transferred into a recipient bacteria cell. This phenomenon is mainly known as DNA-mediated transformation. Surprisingly in this process, DNA molecules with high molecular weight, 100,000 times larger, can pass through the bacteria cell.

The transformation process in Bacillus subtilis begins when a double-stranded DNA from the donor attaches itself to the cell surface of the recipient bacteria. Then, an enzyme found on the cell surface known as nuclease degrades one DNA strand of the donor, and the remaining single strand enters the recipient cell. This strand then pairs with the homologous region of the recipient chromosome.

Once the pairing occurs, the single-stranded DNA from the donor is integrated into the recipient DNA through breakage and reunion. The replaced DNA recipient fragment is then removed, resulting in a transformed bacteria cell. The transformed bacteria cells then multiply through cell division.

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  • 0:00 What Is Bacillus Subtilis?
  • 0:39 Characteristics
  • 2:56 Metabolism
  • 3:27 Why B. Subtilis Is Important
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Bacillus Subtilis Arrangement and Characteristics

The ability of Bacillus subtilis to form subterminal endospores makes it unique among the other members of the genus Bacillus. The formation of an endospore is a response to nutrition deprivation or harsh environmental conditions. Bacillus subtilis has a single chromosome that replicates bidirectionally. Peptidoglycan surrounds its cell, and it utilizes a flagellum for motility.

Bacillus subtilis arrangement is quite diverse, and they may be arranged as single or chain cells. When two bacilli combine, they are diplobacillus, bacilli forming a chain are known as streptobacillus, and those appearing as oval or sphere-shaped are referred to as coccobacillus, while those touching each other on ends form palisades. The length of chains depends on the type of media used. For instance, Bacillus subtilis grown on hard agar media has been shown to have long chains.

Arrangement of Bacillus Bacteria

Genus Bacillus

Bacillus Subtilis Shape

Like most members of the genus Bacillus, the shape of Bacillus subtilis is like a cylindrical rod. Rod-shaped bacteria are also referred to as bacilliform, and they either occur singly or as a group. Observation of Bacillus subtilis under the microscope have vegetative cells appearing red while the endospores appear green in color. In addition, colonies of Bacillus subtilis can either appear as volcanic-like, crater-like, concentric rings, or jagged branches.

Bacillus Subtilis Under a Microscope- Appears as Rods

B. Subtilis

Bacillus Subtilis Metabolism

Bacillus subtilis requires essential nutrients for growth since it cannot make its own food thus, heterotrophic. These include essential salts, carbon, nitrogen, and phosphorous. This bacterium does not require oxygen to grow, and thus it is a facultative anaerobe. It can make ATP in the presence of oxygen, and it can switch to fermentation when oxygen is lacking. Under aerobic conditions, Bacillus subtilis have oxygen as the terminal electron acceptor and nitrate or nitrite as the terminal electron acceptor under anaerobic conditions.

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Frequently Asked Questions

What is the shape and arrangement of Bacillus subtilis?

Bacillus subtilis gram stain test reveals them as rod-shaped bacteria cells under a microscope. They may be arranged as clumps, singly, or as chains.

Is Bacillus subtilis harmful to humans?

Bacillus subtilis is considered non-pathogenic, and it is most useful in the production of antibiotics and its spores used as probiotics. However, this bacterium has been attributed to causing eye infections, soft tissue infections, lung infections, and also causing strong foot odor. These infections are common in immunosuppressed individuals.

What is the cell shape of Bacillus subtilis?

Bacillus subtilis cell has a rod-like shape. This shape is quite common with the members of Bacillus. Bacillus subtilis arrangement may appear as single chains (streptobacillus), or as dual (diplobacillus) chains.

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