Clostridium botulinum characteristics, morphology, habitat

Basil Manning

The Clostridium botulinum is a gram positive bacterium that belongs to the broad genus of the Clostridium. It is one of the bacteria in this group that has been studied the most. It was isolated for the first time by Emile Van Ermengen in the year 1896.

C. botulinum produces a series of toxins that are highly pathogenic for humans. These toxins generate a pathology generically called botulism..

Representation of Clostridium botulinum. Source: By Content Providers: CDC [Public domain], via Wikimedia Commons

When a case of botulism is diagnosed, it is mandatory to make the report to the competent health authorities, so that they take the necessary measures and thus prevent other people from being infected through the same route.

Likewise, botulinum toxin has been used for some years in the plastic surgery industry, since it is injected in small amounts and by exerting its function on the muscles of facial expression, they make expression lines disappear.

Similarly, it has been used in the treatment of certain pathologies such as blepharospasm and strabismus. Definitely, the Clostridium botulinum It is a bacterium without half measures, it can be very harmful and toxic or very beneficial for the individual.

Article index

  • 1 Taxonomy
  • 2 Morphology
  • 3 General characteristics
  • 4 Pathogenesis
  • 5 Diseases
  • 6 Symptoms
    • 6.1 Alimentary botulism
    • 6.2 Wound botulism
    • 6.3 Infant botulism
  • 7 Diagnosis
  • 8 Treatment
  • 9 References


The taxonomic classification of the Clostridium botilinum is the next:

Domain: Bacterium

Division: Firmicutes

Class: Clostridia

Order: Clostridial

Family: Clostridiaceae

Gender: Clostridium

Species: Clostridium botulinum


The Clostridium botulinum is a bacterium that is rod-shaped (bar), with rounded edges. It measures 0.5 - 2 microns wide by 1.6 - 2.2 microns long. It does not have a capsule that surrounds it.

Its cell wall is made up of a thick layer of peptidoglycan, as well as teichoic acid and lipoteichoic acid..

Its genetic material is condensed into a circular chromosome. This is one of the largest within the group of gram positive bacteria.

Various studies seem to indicate that the length is due to the fact that it contains a large number of genes that regulate the sporulation process, as well as the synthesis of toxins produced by this bacterium..

In the cultures, colonies of a whitish color, round in shape, with well-defined borders are observed.

General characteristics

It is gram positive

This bacterium acquires a violet color when the Gram stain technique is applied. This is because it has a thick layer made up of peptidoglycan. This compound has a particular structure, which retains the pigment molecules.

It is anaerobic

The Clostridium botulinum it is a strict anaerobic organism. It develops clearly in anaerobic environments (absence of oxygen). Oxygen is toxic to bacteria, so it cannot be in contact with this chemical element.

Produces toxins

The toxins synthesized by Clostridium botulinum They are known as Botulinum toxins. There are a total of eight toxins of this type, which are given by the subtypes of the bacteria, namely: A, B, C1, C2, D, E, F, G, H ...

Botulinum toxins A, B and E are those that cause pathologies in humans, while the rest cause diseases in birds, fish and other mammals.


The Clostridium botulinum It is a bacterium that is widely distributed in a wide variety of environments throughout the planet. It has been isolated mainly from the soil and marine sediments. In general, it can be said that it is found in environments with little or no oxygen availability.

Produces spores

The bacteria produce spores that are heat resistant. This means that they can survive extreme temperatures, whether they are very low or very high. These spores diffuse into many environments and in the absence of oxygen they germinate and begin to secrete toxins.

Is pathogenic

The spores of the Clostridium botulinum enter the body and germinate, the bacteria reproducing there and causing tissue damage, mainly in the gastrointestinal tract.

Growing conditions

Among the growth conditions that this bacterium needs, we can mention an optimum temperature of 30 ° C and an approximate pH of 7.


The Clostridium botulinum It is a bacterium that has a metabolism based on the fermentation of carbohydrates and amino acids. Among the carbohydrates that ferment are glucose and mannose.

Likewise, as fermentation products we can mention: acetic acid, butyric acid, isovaleric acid and propionic acid..

Presents proteolytic and non-proteolytic strains

Within the variety of strains of Clostridium botulinum that have been isolated so far, two types have been identified: proteolytic and non-proteolytic.

As its name indicates, proteolytic strains are those that cause the digestion of proteins and also produce HtwoS. Non-proteolytic ones do not cause protein lysis, they also ferment mannose and have complex nutritional requirements.

It is catalase negative

This bacterium does not have the information in its genome to encode the synthesis of the enzyme catalase. Thanks to this, it cannot split the hydrogen peroxide molecule into water and oxygen..

It is indole negative

The Clostridium botulinum it does not have in its DNA the genes that code for the synthesis of tryptophanase enzymes. Due to this, it is not able to break the indole group found in the structure of the amino acid tryptophan..

This is another of the biochemical tests that are done for the identification and differentiation of bacteria in the laboratory.

Does not reduce nitrates

This bacterium does not synthesize the enzyme nitrate reductase, so it cannot carry out the chemical reactions that involve the reduction of nitrates into nitrites..

Hydrolyzes gelatin

Thanks to the fact that it synthesizes a group of enzymes known as gelatinases, in cultures it is appreciated that they can cause gelatin to liquefy. A transparent halo can be seen around the colonies, unequivocal evidence that this process has occurred.


As mentioned above, the Clostridium botulinum produces several types of toxins, depending on the subtypes. Of all, those that cause some pathology in humans are A, B, E and E.

The spores of this bacterium survive various environmental conditions and germinate when the conditions are right (low oxygen content). Botulinum toxin has been isolated from various foods such as canned foods, some meat products such as sausages, and in vegetables such as mushrooms and beets..

The most common way in which the spore enters the body is through ingestion, through the consumption of food that does not comply with the relevant sanitary measures. Another form of entry, but much less common is through a wound or injury.

When the toxin enters the body, it goes to the nerve endings, specifically the synaptic space. There it enters the neuronal cell Already inside the neuron, it inhibits the secretion of the neurotransmitter acetylcholine, producing flaccid paralysis of the muscle.


The disease generated by the bacteria Clostridium botulinum It is known by the name of Botulism. It is classified into three types:

  • Alimentary botulism: caused by direct ingestion of bacteria toxins through unhealthy food.
  • Wound botulism: when bacteria enter the body through wounds or lesions on the skin.
  • Infant botulism: occurs when young children (under 6 months) ingest spores, which germinate in the gastrointestinal tract and cause bacteria in their vegetative form, which release toxins.


Alimentary botulism

It has an incubation period of approximately 12 to 36 hours. The symptoms that develop are the following:

  • Excessive fatigue
  • Difficulty mastering the muscles of speech and swallowing
  • Blurry vision
  • Dry mouth
  • Droopy eyelids
  • Trouble breathing
  • Diarrhea
  • Constipation
  • Sickness
  • Vomiting
Botulism patient. Source: By Herbert L. Fred, MD and Hendrik A. van Dijk ( [CC BY 2.0 ( ], via Wikimedia Commons

Wound botulism

The symptoms of wound botulism are frankly similar to those of alimentary botulism.

  • Loss of control of the muscles of speech and swallowing.
  • Blurry vision
  • Trouble breathing
  • Droopy eyelids
  • Paralysis

Infant botulism

Incubation period approximately 18 to 36 hours. The most common symptoms that it presents are:

  • Constipation
  • Weak cry
  • Drooling
  • Droopy eyelids
  • Tiredness
  • Inability to suck and feed
  • Paralysis.


The procedure used to diagnose this infection is based mainly on laboratory tests and establishment of cultures..

First, the foods that the individual has eaten are analyzed, with the aim of looking for bacteria. Likewise, samples are collected from the patient, both from feces and blood serum..

Once this is done, you can proceed to establish cultures to determine if the bacteria is present..


Treatment depends on the characteristics of the clinical picture it presents. When the person has ingested the spores that can release toxins in the body, a way is sought to inactivate it. This is achieved thanks to the application of the antitoxin immunoglobulin injection..

Likewise, an attempt is made to control the symptoms, with medications intended for this purpose. If the discomfort does not subside, then a drastic measure is covered, admitting him to the Intensive Care Unit, where he will be treated with more up-to-date drugs. Finally, the patient must go to rehabilitation to activate the affected muscles.


  1. Botulism: Symptoms and causes. Retrieved from:
  2. Botulism. Obtained from: medline. Gov
  3. Botulism. Retrieved from:
  4. Characteristics of clostridium botulinum and botulinum toxins. Retrieved from:
  5. Castro, A., Hevia, R., Escobar, M., Rubio J., Mena, O. and Riverón A. (2004). Botulism: clinical and epidemiological aspects and case reports. Surveillance technical report. 8 (5).
  6. Clostridium botulinum. Retrieved from:
  7. Shapiro, R., Hatheway, C. and Swerdlow, D. (1998). Botulism in the United States: A Clinical and Epidemiologic Review. Retrieved from:
  8. Sugiyama, H. (1980). Clostridium botulinum neurotoxin. Microbiology Reviews. 44 (3). 419- 448.

Yet No Comments