C. Bacteriophage Flashcards
What is bacteriophage?
Bacteriophage are viruses that attack bacteria.
It is also known as “phage”
It was discovered in 1915
What are the steps in the Lytic Cycle of E.coli cells?
- Absorption of the phage to the host cell and attachment of the bacteriophage to the bacterial surface
- Injection of the genetic material/ nucleic acid into the host host cell
- Phage proteins synthesized and genetic material replicated.
- Assembly of the virions to make the whole virus’ body
- Cell body lyse and the new phage are released to continue the cycle
Who is Max Delbruck and what is he known for?
He is a German-American biophysicist who participated in launching molecular biology. Together with Alfred D. Hershey and Salvador Luria won the noble prize for discovering the replication mechanism and the genetic structure of viruses.
What did Delbruck discovered in 1939?
He discovered a one step process for growing bacteriophage that, after a one-hour latent period, would multiply to produce several hundred thousands of progeny.
Cells don’t show continuous growth over time. What do they do instead?
There is a latent period after infection where a ton of virus particles are released when the cell explodes.
Explain the One-Step Growth Experiment done by Max Delbruck
- Cells are infected with phage
- T different time points yield is calculated
- No particles are detected until about 24 minutes post infection, which defines the latent period
- Rise period does not look like normal bacterial growth curve, it is One-Step
- Number of phage particles does not keep increasing but is instead a constant amount
Explain the Hershey/Chase Experiment of 1952
- They radioactively labeled both protein and nucleic acid. Protein is labeled with 32P and the second T2 phage was labeled with 35S
- E. coli was infected and grown in 32P and 35S medium respectively
- After lysis progeny phages with 32P was labeled with DNA and progeny pages with 35S was labeled with protein
- They let the phage bind to the coat and blended them
- They found 32P passed onto phage progeny
- They concluded that DNA was the genetic material
What happens when you put nucleic acid and protein together at the right pH and temperature?
You can have different molecules banging into each other, making them stick
What does ribosome self assembly shows?
It shows that all different proteins can go together and cell assembly is not only in viruses
What hides the bacteria away?
Integration into the host chromosome
Explain the Virulent phage. What are some examples
Are viruses that always enter the lytic cycle, multiply rapidly, and kill the host.
They kill the cells directly
They are the simplest of the phages
Example are T4 and T2
Explain the Temperate phage
Are viruses that can either enter the lytic cycle or the lysogenic cycle.
What happens during the Temperate phage? What hides DNA during Temperate phage?
Viruses could either hide away, wait to strike, and when the host is stressed, it begins to replicate.
DNA being integrated into the host
What is Lysogeny? What kind of DNA is it?
The integration of bacteriophage DNA into the host. Lysogeny is a lambda DNA with 47 kb with numerous attachment sites
What are 3 ways to get DNA into bacteria? Or the 3 types of gene transfer in prokaryotes?
- Conjugation - bacterial mating
- Transformation - bacteria take up naked DNA
- Transduction - viral transfer of DNA
