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Techniques of Virus Cultivation

In this techniques of virus cultivation post we have briefly explained about cultivation of viruses in microbiology, bacteriophage method, embryo method, cell culture method, and plant cultivation of viruses in microbiology.

While growing bacteria in the lab usually merely requires a supply of the right nutrients and the right atmosphere, keeping viruses alive poses a unique set of problems. Consider why this is the case: all viruses are obligatory intracellular parasites that require a specific host cell to proliferate.

Techniques of Cultivation of Viruses In Microbiology

Bacteriophage Method

Bacteriophages, for instance, are cultured alongside their bacterial hosts. By allowing phages to infect a broth culture of the appropriate bacterium, stock cultures of phages can be created. The turbidity of the culture is cleared after successful phage propagation; centrifugation removes any remaining bacteria, leaving the phage particles in the supernatant.

By mixing phages with a significantly larger number of bacteria and immobilising them in agar, a quantitative measure of phages, known as the titre, may be achieved. The bacteria develop as a confluent lawn as a result of their abundance. Some are infected by phage, and when fresh virus particles are produced after their host is lysed, they infect further host cells.

The phages can only infect cells in their local area since they are immobilised on agar. As more cells in the same region are lysed, a cleared area known as a plaque emerges in the bacterial lawn. The premise behind the quantification is that each visible plaque is the result of a single phage particle infection. As a result, plaque-forming units are used.

Virus Cultivation Methods

The plague assay for bacteriophages

Embryo Method

Previously, animal viruses were propagated in the host animal; however, this has obvious limits, not least when the host is a person. In 1931, Alice Woodruff and Ernest Goodpasture demonstrated that fertilised chicken eggs could act as a host for a variety of animal and human viruses, including those that cause rabies and influenza.

This was a major achievement in the field of cultivation of viruses in microbiology. According to legend, the cultivation of viruses in embryonated eggs did for virus culture what agar did for bacterium growth. Inoculation can be done into the growing embryo itself or into one of the numerous membranes and cavities, such as the chorioallantoic membrane or the allantoic cavity, depending on the virus. The death of the embryo or the formation of lesions on the membranes is both signs of viral proliferation.

Virus Cultivation Methods

Cultivation of Viruses in Embryonated Eggs

Cell culture Method

Cell culture techniques advanced in the 1950s, thanks in part to the widespread availability of antibiotics, making bacterial contamination much easier to manage. In tissue culture flasks containing an appropriate liquid growth media, cells are normally cultivated as monolayers.

The protease trypsin dissolves the connective tissue matrix between the cells, allowing the cells to be collected and seeded into new cultures. Changes in cell shape, referred to as cytopathic effects in general, are indications of viral infection and can be utilised to diagnose specific viral kinds.

Plant Virus Cultivation

Plant viruses must penetrate the plant’s cellulose cell wall; in nature, this is generally accomplished by penetrating the mouthparts of an insect vector or entering areas of damaged tissue. Viruses can be introduced into an appropriate host in the laboratory by scratching the surface of a leaf containing the virus with a mild abrasive to generate a tiny lesion.

Further Readings

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