In biology, to describe a certain organism that belongs to the animal, fungal or plant kingdoms, its own nomenclature has been developed. It reflects belonging to one species, depending on the features of morphology and appearance. For animals, the criteria for referring to a species are applied, 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 that have morphological properties, but different biochemical and immunological features, it is impossible to apply standard nomenclature for naming. As a result, such a concept as a strain was introduced. This is a pure culture of microbes that has been isolated and isolated in a certain place at a certain hour.
Each microbe that belongs to one strain is similar to another such representative in terms of 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. Because fastthe exchange of genetic material (mutation) leads to the emergence of new organisms within a species, but with different properties, it is this definition that allows us to more accurately characterize pathogenicity and virulence factors.
Bacterial strains
The existing nomenclature of bacteria makes it possible to classify the types of organisms, but does not characterize their new properties. The latter appear as a result of rapid mutation, acquiring new properties, including those pathogenic for humans, farm animals and plants, as well as other microbes. An example of nomenclature using 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 cultures of bacteria of the Escherichia colli species that exhibit different properties. They are isolated into 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 disease, but the O157:H7 strain is exclusively pathogenic due to the presence of a large number of virulence factors. She has experienced an epidemic of enterotoxigenic diseases in the past 5 years.
Virus strains
The concept of a strain is a flexible name for organisms with the same properties that were isolated, and then identified and described in a certain area at a certain time. With its course, the virus can acquire new properties due to antigenicdrift. This will create a new viral strain, perhaps more pathogenic than its progenitor.
You can clearly show the emergence of new strains using the example of the influenza virus. It belongs to the family of Orthomyxoviruses and is named depending on the antigens (hemagglutinins and neuraminidase) HxNy. X and Y are numerical values reflecting the presence of antigens. An example is H5N1, known for the recent swine flu epidemic with rapidly progressive hemorrhagic pneumonias. According to the theory, a new and more dangerous strain can develop from this strain due to the same antigenic drift.
Fungal strains and protist strains
Of all 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. There is also an opinion that any newly discovered 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 low, so 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.
