You have a new position at the Center for Disease Control. You have been assigne

Question

You have a new position at the Center for Disease Control. You have been assigned to characterize a new epidemic that has spread rapidly among workers at a chicken farm in California. All affected have high fever and a severe cough. A co-worker has given you a purified vial of the infectious material.

a) You add some of the infectious material to an agar plate containing all necessary nutrients, but nothing grows. Why is this?

b) You then add infectious material to ahuman cell line and see some cells begin to round up and die.

i)What is the likely infectious material and why didn't it grow on the agar plate?

The infectious material is a virus and it didn't grown on the agar plate because virus need host cells to replicate.

ii) If the cells were put into a tube with the media they grew in and spun down, Where would you find the material that could infect new cells?

In the media/supernatant In the pelleted cells

Explanation / Answer

Viruses are microbial cultures which cannot be grown in-vitro easily using simple media such as broth or agar. They can be grown only by methods where live cells / animals are being utilized as their source of energy and nutrition. In this question purified vial of the infectious material was obtained.

a) The culture did not grow on an agar plate is indicative that the culture is not a bacterial strain.

b) When regrown on some human cell lines some of the human cells were observed to round up which is indicative of their death. This feature is not observed in case of bacterial or fungal strains because they do not kill the human cells in such a way.

i) This indicates that the culture is a viral culture as the viruses need a host to replicate and their adherence to the host causes cell death of the host as the virus utilizes the replicative machinery of the human cell and multiplies itself.

ii) If the cells were put into a tube with the media they grew in and were spun down by centrifugation then the viral RNA/DNA (genetic material) would be found in the pellet where the human cells will also be found. The supernatant / media will just contain the protein coats of the viruses. Hence, the pelleted cells can infect new cells if introduced into new cells.

Related Questions

Navigate

• Browse (All)
• Browse Y
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.