For the first time, scientists film 'giant' Mimivirus in action

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The COVID-19 pandemic led to heightened public interest in learning about viruses and how they can cause diseases. There has been a lot of focus on communicating virology concepts to the general public in order to increase awareness about the spread and prevention of viral diseases.

When it comes to teaching biology, however, how do we explain microscopic processes like viral infections to students in the classroom?

In modern science education, seeing is believing—educators are now attempting to capture the attention of students by using eye-catching visuals and videos, instead of just relying on diagrams in a textbook. In the case of viruses, however, one major issue arises.

Viruses typically cannot be seen under the familiar 'light microscope' available in school and university classrooms, requiring highly specialized and expensive equipment for visualization.

Now, in a study published in the Journal of Microbiology & Biology Education on November 8, 2024, a team led by Professor Masaharu Takemura at the Tokyo University of Science has successfully captured the viral infection process under a light microscope, creating a stunning video showcasing their results.

The key to this process was a unique 'giant' virus known as Mimivirus. This research was co-authored by Ms. Kanako Morioka and Ms. Ayumi Fujieda at Tokyo's Yone Production Co., Tokyo, Japan.

Mimivirus has a much larger particle size than most viruses and can actually be seen under a light microscope, making it an ideal candidate for use as an educational tool. The researchers sought to visualize how the Mimivirus infects a microbe called Acanthamoeba.

It is difficult to visualize amoebae under a microscope since they are constantly moving in a liquid medium; therefore, they used a modified growth medium containing a jelly-like substance called agar. This growth medium also contained viruses which infected the amoebae, and after infection, the Acanthamoeba cells moving under the agarose gel gradually slowed down.

The researchers were able to film individual cells as they were infected; indeed, we can observe all the steps of the viral infection process in their footage. While healthy Acanthamoeba cells are initially moving around, they gradually slow down and come to a stop following Mimivirus infection.

As the amoeba cells stopped moving, the researchers observed the development of a 'virion factory' inside the amoeba cell, which produced more 'virions' or viral particles. The infected cell ultimately dies as its membrane ruptures.

Prof. Takemura says, "For the first time in the world, we have succeeded in continuously visualizing the events that are believed to occur in viral infection over a long period of time—such as the proliferation of the virus, its release from cells, and the death of cells during the process."

The film showing how a single Acanthamoeba cell is infected by Mimivirus was then screened in a biology classroom at the Tokyo University of Science and garnered positive reactions. The researchers observed that the movie influenced the perception of some students regarding viruses and seems to have shifted their views towards more scientific and biological perspectives.

This study also ensures that there is no violation of biological safety guidelines since the Acanthamoeba cells and viruses are grown in an appropriately equipped laboratory. The students in the classroom do not actually handle any of the equipment; the focus is only on screening the filmed video in a classroom setting.

Prof. Takemura explains, "It enhances students' understanding of virus proliferation mechanisms and highlights the biological significance of viruses, their impact on host cell fate, and their role in ecosystems."

More information: Kanako Morioka et al, Visualization of giant Mimivirus in a movie for biology classrooms, Journal of Microbiology & Biology Education (2024). DOI: 10.1128/jmbe.00138-24

Provided by Tokyo University of Science