Bacillus subtilis characteristics, morphology, diseases

Abraham McLaughlin

The Bacillus subtilis it is a catalase positive bacterium that is widely distributed throughout the globe. It constitutes one of the specimens of the genus Bacillus most studied.

Generally, when people hear about bacteria, they imagine disease-causing pathogens. However, these microorganisms do not always cause harm to their host. Some bacteria are capable of generating benefits, not only to man but to the environment..

Bacillus subtilis cells. Source: By Doc. RNDr. Josef Reischig, CSc. (Author's archive) [CC BY-SA 3.0 (], via Wikimedia Commons

This is the case of the Basillus subtilis, gram positive bacterium that reports enormous benefits in several and diverse fields. The biochemical properties of this bacterium have been studied for years..

This is how it has been concluded that it is harmless to man, since it does not cause any harm when in contact with it. On very rare occasions, a harmful effect has been described, but this has been determined by other aspects beyond the pathogenicity of the bacteria as such..

On the contrary, the many proven benefits of this bacterium, whether in agriculture, medicine or industry, have made it one of the best options when it comes to exposing the positive effect of certain bacteria on humanity..

Article index

  • 1 Taxonomy
  • 2 Morphology
  • 3 General characteristics
  • 4 Related pathologies
  • 5 Clinical picture
  • 6 Applications of Bacillus subtilis
    • 6.1 Antifungal activity
    • 6.2 Preparation of detergents
    • 6.3 In the pharmacological area
    • 6.4 In gastronomy
  • 7 References


The taxonomic classification of the bacteria Bacillus subtilis is the next:

Domain: Bacterium

Edge: Firmicutes

Class: Bacilli

Order: Bacillales

Family: Baacillaceae

Gender: Bacillus

Species: Bacillus subtilis


Like all those belonging to this genus, the cells of the Bacillus subtillis They are rod-shaped with rounded edges. They are approximately 1 micron wide by 2-3 microns long. They are found individually or in small chains.

When observed under a microscope, a spherical spore can be seen in the center of the bacterial cell, which does not change the shape of the bacteria.

On blood agar cultures, they form colonies that may appear smooth, rough, or mucoid. Its edges can be extended in the middle or be wavy.

Likewise, the average size of the colonies is 2 to 4mm in diameter..

The bacterial cell has a thick cell wall, made up of a peptidoglycan, known as murein..

Regarding its genome, the bacterium has a single circular chromosome, which contains 4100 genes that encode the expression of certain proteins.

From the cell surface some extensions, the flagella, come off. These contribute to the mobility of the cell.

General characteristics

When subjected to the Gram staining process, the bacteria take on the typical violet coloration of Gram positive bacteria. This is due to the peptidoglycan present in its cell wall..

On the other hand, when bacteria are grown on blood agar, a complete hemolysis pattern is observed. This places them within the group of Beta hemolytic bacteria, capable of causing complete lysis of erythrocytes..

When it comes to metabolism, Bacillus subtilis  is capable of hydrolyzing triglycerides, not phospholipids or casein.

Until recently it was believed that this bacterium was strict aerobic. However, recent studies have shown that it can survive in environments without oxygen availability. Under anaerobic conditions it can carry out fermentation via the butanediol pathway. You can also carry out ammonification with nitrate.

The Bacillus subtilis it is a bacterial species that can be found in various environments. It has been isolated from terrestrial and aquatic environments. However, when it is in an environment with hostile conditions it has a mechanism to survive.

Bacillus subtilis culture. The green dots are the spores. Source: By WMrapids [CC0], from Wikimedia Commons

This mechanism is the production of spores, which are highly resistant to the changing conditions of the external environment. Once the environment is favorable again, the spores germinate and the bacteria begin to reproduce again.

Among its attributes, it can be mentioned that it presents the catalase enzyme, which allows it to divide the hydrogen peroxide molecule into its constituents: water and oxygen..

Other enzymes of importance that it has are nitrate reductases, especially two, which are unique. One of them is used in the assimilation of hydrogen nitrate and the other is used in the respiration of nitrate..

Regarding environmental requirements, the Basillus subtilis It can grow and develop in temperature ranges from 15 ° C to 55 ° C. It is also capable of surviving in saline concentrations of up to 7% NaCl..

Related pathologies

The Bacillus subtilis it is a bacterium that is considered safe and harmless for man. However, because it is found in the soil and in the intestines of some animals, it is possible that it infects some foods..

Despite this, there are very few cases that have been documented of food poisoning by this bacterium. Most refer to immunosuppressed patients, whose immune system is not fully capable of fulfilling its function..

Clinical picture

In the few cases of food poisoning from Bacillus subtilis, the symptoms described are similar to the poisoning generated by the bacteria Bacillus cereus. Among the most prominent are:

  • Diarrhea
  • Sickness
  • Fever
  • General discomfort.

It is important to note that these are isolated cases, so rare that there is little literature on them.

As a general rule, and based on studies that have been carried out using the Bacillus subtilis, it is claimed to be harmless bacteria for humans.

Applications of the Bacillus subtilis

The Bacillus subtilis It is a bacterium that has been beneficial in various areas or fields. Studies are still being carried out today to determine the usefulness it may have.

Antifungal activity

Among the pathogenic microorganisms that affect various crops are fungi. They are among the main causes of damage and deterioration of certain plants.

In experimental studies it has been possible to determine the antifungal effect of the Bacillus subtilis. Releases certain substances that have the ability to break down the cell walls of other organisms, such as fungi, causing their lysis.

Taking this characteristic into account, the Bacillus subtilis It is widely used for pest control in crops.

 Detergent production

The Bacillus subtilis produces a class of enzymes, known as proteases, which have been used for many years as additives in detergents. Among the proteases produced by this bacterium, the most widely used industrially in the manufacture of detergents is subtilisin.


The usefulness of these enzymes lies in the fact that they are capable of degrading substances of protein origin, which translates into the effectiveness of the detergent in eliminating these types of stains..

In the pharmacological area

The Bacillus subtilis produces certain substances that have an antibiotic effect. This means that they are capable of eliminating other bacterial strains that are pathogenic..

An example of this is the drug Bacitracin, which is an ointment that is applied to wounds, injuries, or burns and is effective against other gram-positive bacteria. Bacitracin is made up of polypeptides produced by one of the isolated strains of this species of bacteria.

Likewise, this bacterium produces approximately two dozen substances with antibiotic qualities, which include ribosomal synthesis peptides and others that are not..

They are substances whose effects are still under study to determine all their potentialities..

In gastronomy

There is a strain of Bacillus subtilis that acts on the soybean seed, carrying out the fermentation process. The result of this process is a food of Japanese origin known by the name of Natto.

It is a food whose flavor is unconventional, but this makes up for it with the large amount of nutrients it provides.

The Bacillus subtilis It is a bacterium known for the large number of benefits it brings to humans. Despite this, there are still many of its properties to be discovered. It is a microorganism that will give much to talk about in the area of ​​biotechnology.


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