In biology, to describe a specific organism that belongs to the kingdoms of animals, fungi or plants, its own nomenclature has been developed. It reflects belonging to one species, depending on the characteristics of morphology and appearance. Criteria for referring to a species are applicable to animals, depending on the ability to produce fertile offspring during fertilization. However, these patterns apply only to these organisms, while microbes cannot be classified in this way.
The concept of strain in microbiology
Due to the presence of a huge number of organisms with morphological properties, but various biochemical and immunological features, it is impossible to use standard nomenclature for naming. As a result of this, a concept such as a strain was introduced. This is a pure culture of microbes, which was able to isolate and isolate in a certain place at a certain hour.
Each microbe that belongs to one strain is similar to another such representative according to biochemical, morphological, immunological and genetic criteria. But within the same bacterial species, such an analogy is not observed. Therefore, a strain is a more flexible name for a microbial culture. Since the rapid exchange of genetic material (mutation) leads to the appearance of new organisms within the species, but with different properties, it is this definition that allows a more accurate characterization of pathogenicity and virulence factors.
Bacterial strains
The existing nomenclature of bacteria allows the classification of species of organisms, but does not characterize their new properties. The latter appear due to rapid mutations, acquiring new properties, including pathogenic ones for humans, domestic animals and plants, as well as other microbes. An example of the nomenclature on the example of Escherichia coli looks like this: kingdom - bacteria, type - proteobacteria, class of gamma-proteobacteria, order - Enterobacteriales, family of enterobacteria. The genus is Escherichia, and the species is Escherichia colli. However, there are many bacterial cultures of the Escherichia colli species exhibiting various properties. They are isolated in separate strains of bacteria and have an additional name. For example, Escherichia colli O157: H7.
E. coli itself is present in the human intestine and does not cause diseases, but strain O157: H7 is exclusively pathogenic due to the presence of more virulence factors. She was marked by an epidemic of enterotoxigenic diseases in the last 5 years.
Viral strains
The concept of strain is a flexible name for organisms with the same properties that were isolated, then identified and described in a particular area at a specific time. With its course, the virus can acquire new properties due to antigenic drift. This will create a new viral strain, possibly more pathogenic than its progenitor.
The emergence of new strains can be clearly illustrated by the example of the influenza virus. It belongs to the Orthomyxovirus family and is called HxNy depending on the antigens (hemaglutinins and neuraminidases). X and Y are numerical values reflecting the presence of antigens. An example is H5N1, known for the recent swine flu epidemic with rapidly progressing hemorrhagic pneumonia. In theory, a new and more dangerous strain can develop from this strain due to the same antigenic drift.
Fungal and protist strains
Of all the microbes, molds are the least variable, although their biochemistry is also complex. Due to a more complex structure than bacteria and viruses, and also due to the lack of mechanisms for rapid gene transfer, the number of new fungal strains increases slightly. It is also believed that any new recently found fungal strain is a pre-existing organism that simply did not come across to researchers.
A similar situation exists in the kingdom of protists. Their ability to mutate is small, because the likelihood that new strains will appear quickly is extremely small. However, new variants of organisms of the same species still appear. Therefore, apparently, they also existed earlier, but were not discovered.