Viruses multiply by taking over a host cell, using that cell to multiply their genetic material (DNA or RNA) and then spreading to nearby cells. Viruses can kill their host cells. Yet viruses are hard to kill because they use our own cells, and our body will not attack its own cells. Viruses against a type of bacteria can kill that bacteria once it finishes using it for multiplying.
In the lab, we test for viruses not through presence of viral colonies, but through absence of bacterial colonies. For example, if we wanted to test for a virus that harms a certain kind of bacteria, we would inoculate an agar plate with that bacteria and put some of the virus on the same agar plate. If the bacteria does not appear where the virus is, we know that the virus is present. We illustrated this in the lab through the following experiment.
Materials:
Agar plate
Agar slant of bacteria
3 different viruses in tubes
Disposable sterile pipet tips
Steps:
1. Inoculate the agar plate with the bacteria using aseptic technique.
2. Use a sterile pipet tip to write one's initials on one part of the inoculated agar plate. Dispose of the tip in the biohazard waste bag.
3. Repeat step 2 twice, each with a different virus. For each virus, write on a different part of the agar plate.
4. Incubate the agar plate for 24 hours.
5. Observe results.
Results:
Discussion:
There are viruses, because they used the bacteria on the agar plate to multiply.
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