Strain is a pure culture of microorganisms. Strains of bacteria, viruses, fungi

In biology, a specific nomenclature has been developed to describe a specific organism that belongs to the kingdoms of animals, fungi or plants. It reflects belonging to one species depending on the features of morphology and appearance. To animals, the criteria of reference to a species are applicable depending on the possibility of giving fertile offspring during fertilization. However, these regularities are applicable only to these organisms, whereas microbes can not be classified in this way.

The concept of a strain in microbiology

Due to the presence of a huge number of organisms that have morphological properties, but different biochemical and immunological features, a standard nomenclature can not be used to assign a name. As a result, a notion such as strain is introduced. This is a pure culture of microbes, which it was possible to isolate and isolate in a certain place at a certain hour.

Each microbe, which belongs to the same strain, is similar to another such representative for biochemical, morphological, immunological and genetic criteria. But within the limits of one bacterial species of such an analogy is not observed. Therefore, the strain is a more flexible name for microbial culture. Because the rapid exchange of genetic material (mutation) leads to the appearance of new organisms within the species, but with other properties, it is this definition that allows more accurately to characterize pathogenicity and virulence factors.

Bacterial strains

The existing nomenclature of bacteria allows us to classify species of organisms, but does not characterize their new properties. The latter appear due to rapid mutation, acquiring new properties, including pathogenic for humans, farm animals and plants, as well as other microbes. An example of nomenclature with the example of Escherichia coli is as follows: the kingdom is bacteria, the type is proteobacteria, the class of gamma proteobacteria, the order is Enterobacteriales, the family of enterobacteria. The genus is Escherichia, and the species is Escherichia colli. However, there are many cultures of bacteria of the species Escherichia colli, exhibiting different properties. They are isolated into separate strains of bacteria and have an additional name. For example, Escherichia colli O157: H7.

The E. coli itself is present in the human intestine and does not cause disease, but strain O157: H7 is extremely pathogenic due to the presence of more virulence factors. She noted an epidemic of enterotoxigenic diseases in the last 5 years.

Viral strains

The term strain is a flexible name for organisms with the same properties that were isolated and then identified and described in a specific locality at a specific time. With its course, the virus can acquire new properties due to antigenic drift. This will create a new viral strain, perhaps more pathogenic than its ancestor.

Visualize the emergence of new strains possible by the example of the influenza virus. It belongs to the family of orthomixoviruses and is called depending on antigens (hemagglutinins and neuraminidase) HxNy. X and Y are numerical values that reflect the presence of antigens. Example - H5N1, known for the recent epidemic of swine flu with rapidly progressing hemorrhagic pneumonia. According to the theory, a new and more dangerous strain can develop from this strain due to the same antigenic drift.

Fungal strains and protista strains

Of all microbes, mold fungi are the least variable, although their biochemistry is also complex. Due to a more complex structure than bacteria and viruses, and also because of the lack of mechanisms for rapid gene transfer, the number of new fungal strains increases insignificantly. There is also the view 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 realm of protists. Their ability to mutate is low, therefore the probability 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 before, but were not discovered.