6.3: Bacteriophages Flashcards
What is the type of virus that infects bacteria?
bacteriophage (or phage)
True or False: Bacteriophages have a very common structure.
False. Bacteriophages have a very unique structure.
Bacteriophages possess an ___1___ capsid head group, containing the viral genome, and a ___2___ tail.
- icosahedral (20-sided polygon)
- helical
Attached to the Bacteriophages tail are ______—fibrous extensions or legs that aid in binding host cells.
tail fibers
What are the tail fibers of a Bacteriophage and what do they do?
They are fibrous extensions or legs that aid in binding host cells.
True or False: The particular structural arrangement of Bacteriophages have not been observed among viruses that infect either animals or plants.
True.
The phage virus does not ___1___ its capsid into the host cell. Instead, once the tail fibers have ___2___, the ___3___ penetrates the host cell wall and the viral genome is effectively injected through the hollow ___3___ and into the cytoplasm
- pass
- mediated binding
- helical tail
How does a Bacteriophage pass on its viral genome to the host cell?
Once the tail fibers have mediated binding, the helical tail penetrates the host cell wall and the viral genome is effectively injected through the hollow helical tail and into the cytoplasm
As viruses can only replicate within a host cell, researchers must ______ a virus with appropriate live cells.
co-culture
Relative to bacteriophages, there are two forms of replication:
lytic and lysogenic
How does a Lytic Bacteriophage replicate?
Lytic bacteriophages replicate within the host bacteria until it lyses, or ruptures, effectively destroying the host bacterial cell
The quantitative amount of virus present in the culture is referred to as the ______.
viral titer(viral Load)
Knowing the viral titer is what allows researchers to do what?
Carefully and effectively plan infectious experiments.
What happens when their is to much virus in the Viral Titer?
Too much virus will cause it to immediately overwhelm and kill the host cells.
What happens when their is to little virus in the Viral Titer?
Too little virus will take too long to generate detectable levels of newly produced virus.
What is a Lysogenic(or Template) Bacteriophage?
Lysogenic (or temperate) bacteriophages can exist in a non-replicative state such that its viral genome is integrated into the host genome.
Upon integration into the host genome, the phage is referred to as a ______.
prophage
As the host cell replicates its DNA, it also replicates the ______.
viral DNA
As the host cell replicates its DNA, it also replicates the viral DNA. However, the production of ___1___ via ___2___ and ___3___ is suppressed. Thus, the host cell may carry the phage DNA without risk of ___4___. However, under certain stress conditions, the prophage can reactivate, begin full replication of viral proteins, and re-enter a ___5___.
- viral proteins
- transcription
- translation
- lysis
- lytic replication cycle
True or False: Lytic cycle replication is easily detected in lab cultures.
True
During the initial inoculation of virus and bacteria, the media has a high degree of ______.
turbidity (cloudiness)
What is being presented in the picture?
Bacteriophage. (A) The structural elements of a bacteriophage are shown. An icosahedral head group is separated from the tail region by the collar, while the base plate (fixed at the end of the tail) and tail fibers are located at the conclusion of the helical sheath. (B) Viral DNA is injected into the host cell.
What is being presented in the picture?
Lytic and Lysogenic. The lytic life cycle begins with viral entry, and upon successful replication causes severe strain on the host cell to the point of rupture. However, if the viral genome is integrated into the host genome without actively replicating (dormancy) it is considered temperate. However, certain external stresses may cause reactivation of the viral, and the lysogenic cycle then becomes lytic.
What machine is used to determine the turbidity of a sample?
Spectrophotometer
What does the collar do in the complex structure of a bacteriophage?
It attaches the head to the rest of the body and helps it sense its environment.
Describe the sheath of a Complex Structure.
Is made of a contractile protein that produces a tube to move the Nucleic Acid from the capsid to the host cell.
Why is the baseplate important?
The baseplate is important for interacting with the host cell for actual infection.
What do the tail fibers initiate?
Initiate binding to receptors on the target cell
Lytic Bacteriophages are represented by the letter ___1___ followed by a ___2___
- “T”
- number
Bacteriophage. (A) The structural elements of a bacteriophage are shown. An icosahedral head group is separated from the tail region by the collar, while the base plate (fixed at the end of the tail) and tail fibers are located at the conclusion of the helical sheath. (B) Viral DNA is injected into the host cell.
Lytic and Lysogenic. The lytic life cycle begins with viral entry, and upon successful replication causes severe strain on the host cell to the point of rupture. However, if the viral genome is integrated into the host genome without actively replicating (dormancy) it is considered temperate. However, certain external stresses may cause reactivation of the viral, and the lysogenic cycle then becomes lytic.
What gives Bacteriophages their specificity?
The types of proteins they can interact with on the hosts cell surface.
The entry type of Bacteriophages is the third type of entry called ______ entry.
Direct
What is the protein called produced by Bacteriophages to lyse the host cell’s cell wall during the release phase of the Lytic Replication cycle?
Lysozyme
What are temperate Phages?
Phages that use the Lysogenic Replication Cycle.
What is Prophage?
Phage DNA integrated into host cell’s Genome
