Viruses cannot multiply on ordinary artificial nutrient media because they need living host cells. This lesson explains how viruses are separated from host cells, why they were once called filterable agents, and how careful specimen handling supports reliable identification.
Early investigators found that infectious material from some diseased plants could pass through porcelain filters that retained bacteria. The filtered material could still cause disease, leading scientists to describe the infectious agents as filterable agents. The discovery of tobacco mosaic virus (TMV) was an important example.
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Tissue tropism
The tendency of a virus to preferentially infect particular cell types or tissues; it helps determine a suitable host and inoculation site.
Contact inhibition
The stopping of cell division when cells contact neighboring cells, limiting crowding in many normal cell cultures.
In vivo cultivation
Growth of a virus within a whole living host, such as an animal or embryonated egg.
Continuous cell line
A cell population, often derived from transformed or tumor cells, that can be subcultured many times; some lines are immortal.
Cytopathic effect
An observable cellular change caused by viral infection, such as rounding, lysis, or formation of multinucleated cells.
Quiz questions
What do clear plaques in a bacterial lawn indicate during bacteriophage cultivation?Answer: Localized destruction of bacteria associated with phage replication.
In a hemagglutination inhibition assay, what does inhibition of red-cell clumping indicate?Answer: Relevant antibodies are present in the tested serum.
Why have embryonated eggs been used to cultivate influenza virus?Answer: They provide a living environment that supports viral growth, including for vaccine production.
In an enzyme immunoassay designed to detect viral antigen, what generates the detectable signal?Answer: An enzyme-tagged detecting antibody reacts with its substrate.
What can cytopathic effects alone establish about a virus in cultured cells?Answer: They can suggest infection but may not identify the virus.
Based on Microbiology by Nina Parker, Mark Schneegurt, Anh-Hue Thi Tu, Philip Lister, Brian M. Forster (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.