Defense of Bacteria & Viruses

by Sruthi Boppuri

TEK 11B: What are ways bacteria and viruses defend themselves?

Bacteria Against Bacteriophages

Bacteria protect themselves from the attack of bacteriophages by building an endonuclease. This is an enzyme that cuts DNA and the bacteria uses it to cut up foreign DNA, such as the DNA of the bacteriophages. The endonucleases are in the cytoplasm of the bacteria and they are restriction enzymes.
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In order to survive in extreme conditions, some bacteria produce endospores. An endospore is a cell that is formed inside the bacteria that protects and contains the genetic material of the DNA. It is highly resistant to the harsh conditions and can survive for thousands of years. Once the conditions are favorable again, the endospore can germinate into a regular cell.
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How Viruses Protect Themselves

Viruses are always changing their genetic material through mutations. This makes it harder to cure certain viral diseases. Also, viruses are able to reproduce and mutate quickly. When their environment becomes unfavorable, the virus "pushes" all their genetic material into the center of their protein coat. Some viruses have the ability to block the protein that identifies the virus. At the beginning of the virus' DNA is a blocking structure called the stem-loop.


An endospore. Digital image. N.p., n.d. Web. 16 Mar. 2015. <>.

Goodsell, David. "RCSB PDB-101." Restriction Enzymes. N.p., Aug. 2000. Web. 16 Mar. 2015. <>.

Jones, Mike. Bacteriophages: The Most Common Life-Like Forms on Earth. Digital image. Astronomy Picture of the Day. N.p., 21 Apr. 2008. Web. 16 Mar. 2015. <>.