STREPTOMYCES: CHARACTERISTICS, TAXONOMY, MORPHOLOGY, CULTURE - BIOLOGY - 2025

Streptomyces is a genus of filamentous bacteria found in many places. They are harmless bacteria, which are very rarely related to pathologies.

One of the most distinctive characteristics of this type of bacteria is that they have a secondary metabolism, through which they can synthesize various substances that have been very beneficial in the field of medicine. These include numerous antibiotics, some antifungals, and herbicides.

Streptomyces. Source: By Photo Credit: Content Providers (s): CDC / Dr. David Berd, via Wikimedia Commons

Within this genus, there are more than 500 species, many of them unknown. Due to this numerous studies and investigations are carried out to determine its properties.

Its life cycle is a fairly complex process, which involves profound changes that culminate in the production of secondary metabolites and the formation of spores. These are found in the soil and when the ideal conditions arise they germinate, generating a germ tube, from which hyphae are born that penetrate the substrate to extract the nutrients.

In the field of biotechnology, studies have been carried out with streptomyces to generate recombinant human proteins. These investigations have shown that these bacteria have fewer problems than Escherichia coli, which is the one that has traditionally been used for this purpose.

Taxonomy

The taxonomic classification of the genus Streptomyces is as follows:

Domain: Bacteria

Phylum: Actinobacteria

Order: Streptomycetales

Suborder: Streptomycineae

Family: Streptomycetaceae

Genus: Streptomyces.

Morphology

Bacteria of the genus Streptomyces are characterized by having an elongated and filamentous shape. They produce very well developed hyphae that are approximately 0.5-2 microns in diameter. These hyphae form a substrate mycelium network that helps to eliminate organic compounds.

These bacteria are characterized by producing spores. The surface of these is varied. There are hairy, smooth, rough, prickly or warty.

The genome of the Streptomyces bacteria is quite peculiar. While all bacteria have a circular chromosome, they have a linear chromosome.

Streptomyces coelicolor is the bacterium with the longest genome sequenced so far, with a total of 7,825 genes. Likewise, a large percentage of guanine and cytosine nucleotides is observed in its genome.

Likewise, they present linear or circular plasmids. There are even some that can integrate into the bacterial chromosome.

Its cell wall is type I. It does not contain mycolic acids or polysaccharides. In contrast to this, it has diaminopimelic acid and glycine.

Colonies with a powdery appearance are seen in the cultures. They frequently excrete color pigments, being able to appreciate grayish white, orange, black and brown, among others.

General characteristics

They are gram positive

Bacteria belonging to the genus Streptomyces adopt a characteristic violet color when subjected to the Gram stain method.

This is due to the presence of peptidoglycan in its cell wall, which retains the dye particles.

They are strict aerobes

These bacteria use oxygen as the main element to carry out the different metabolic processes from which they obtain energy. Due to this, the bacteria must develop in an environment with high availability of this element.

They are catalase positive

Bacteria of this genus synthesize the enzyme catalase. This enzyme is important because it allows the breakdown of hydrogen peroxide (H ₂ O ₂) into oxygen and water.

When it occurs, one of the characteristic signs is the release of bubbles, indicating that oxygen has been produced in the form of a gas.

They are chemoorganotrophic

This means that its metabolism is based on oxide reduction reactions, which are carried out in order for the cell to obtain the necessary energy.

They are slow growing

When a Streptomyces culture is done, they grow slowly, in a period of time of approximately 2 to 10 days.

Growing conditions

Streptomyces are mesophilic bacteria, with an adequate growth temperature that is located in a range between 25 and 35 ° C. The optimum growth temperature is 30 ° C.

With regard to pH conditions, these bacteria grow optimally at a pH ranging from 6.5 to 8. Despite this, species have been found that manage to grow at an acidic pH or at an alkaline pH of up to 9 o plus.

Habitat

They are widely distributed throughout the planet, in a great multitude of environments. They are mainly in the soil, constituting 80% of the actinomycetes found in the soil.

Culture

The most suitable carbon source for establishing a Streptomyces culture is glucose. According to the characteristics of these bacteria and taking into account published studies, the recommended culture media are: Glucosado Sabourad and Benett, among others.

Glucosado Sabouraud culture medium

It is the most widely used culture medium with fungi and with certain filamentous bacteria such as Streptomyces. Glucose is used as a carbon source and peptone as a nitrogen source.

It also contains agar, chloramphenicol and triptein. The pH should be kept between 5.5 and 6.

Benett culture medium

This medium is also widely used to cultivate Streptomyces. The carbon source is glucose, while the nitrogen source is meat or yeast extract.

Its components also include casein and agar. The ideal pH for this culture medium is 7.3.

Applications

Antibiotic production

Streptomyces are characterized by the fact that they produce approximately 80% of the currently known antibiotics. This production of antibiotics is mediated by environmental signals such as pH, temperature and the amount of available nutrients.

Among the antibiotics produced by the various species of Streptomyces are:

• Clavulanic acid
• Chloramphenicol
• Chlorotetracycline
• Streptomycin
• Fosfomycin
• Neomycin
• Tetracycline
• Kanamycin

Pathogeny

Streptomyces bacteria are generally not pathogenic to humans. However, in certain conditions of depression of the immune system, they can cause pathologies such as mycetomas, peritonitis, chronic pericarditis, septicemia, panniculitis, cervical lymphadenitis and endocarditis, among others.

The bacteria can enter the body through injuries or wounds on the skin. From there it can pass into the bloodstream and travel to various organs where it can wreak havoc.

If it does not enter the bloodstream, it remains in the layers of the skin, generating lesions, of which the most common are mycetomas.

References

1. Barry, S. (2009). Mycetoma. Argentine journal of dermatology. 90 (1).
2. De lima, R., Reis, I., Kassawara, M., De Azevedo, J. and De Araujo, J. (2012). Antibiotics produced by Streptomyces. The Brazilian Journal of Infectious Diseases. 16 (5). 466-471.
3. Hasani, A., Kariminik, A. and Issazadeh, K. (2014). Streptomycetes: Characteristics and Their Antimicrobial Activities. International Journal of Advanced Biological and Biomedical Research. 2 (1). 63-75
4. Hidrin, N., Goodfellow, M., Boiron, P., Moreno, M. and Serrano, J. (2001). Streptomyces. Didactic update and revision. Journal of the Venezuelan Society of Microbiology. 21 (1).
5. Sanchez, A. (1962). Constancy of characteristics in the streptomycetes. Journal of Bacteriology. 83 (6). 1183-1192
6. Streptomyc Retrieved from: Microbewiki.com
7. Obtained from: fundacionio.org.