Microbio Lab 11 Flashcards
What are viruses composed of?
RNA or DNA, but never both
And a protein coat
What are viruses that infect bacterial cells?
They’re called bacteriophages, or phages
What is the lytic cycle?
Involves virulent phages that cause lysis and death of the host cell. Virus assumes control of cell metabolism and uses the cell’s metabolic machinery to manufacture phage components
What is the lysogenic Cycle?
Involves temperature phages, which can either lyse the host or integrate their DNA into host cell DNA and alter the genetics of the host cell.
Virus - Step One
Adsorpption: Phage is absorbed to specific receptor site on the bacterial cell surface. This is Time Zero
Virus - Step Two
Phage DNA enters cell to initiate Eclipse Stage. Bacterial DNA is degraded within minutes
Virus - Step Three
Phage capdis, tails, and phage DNA begin to appear within 12 minutes as phage reorients cell metabolism to its own fabrication process
Virus - Step Four
Components of phage are assembled into mature infective virions
Virus - Step Five
Cell wall opens due to enzymatic action to release mature virons. Burst size is the number of units released b cell. Total time: 40 minutes
Bacteriophages Definition
Viruses that infect bacterial cells. Called a “Bacterial Eater”
What are Bacteriophages also known as?
Obligate Intracellular Parasites; Meaning they must invade host cell in order to replicate and reproduce.
What is a Capsid?
Viruses are composed of a single kind of nucleic acid molecule encased in a protein coat that protects the nucleic acid.
Viruses also exhibit..
specificity for their host.
What is a nucleocapsid?
A phage that contains a capsid made of nucleic acid and protein
What is a Sheath?
The nucleocapsid is attached to this protein sheath that is contractile and contains a hollow tube in its center
What is a single virus or phage particle called?
A viron
Receptors in gram-negative bacteria?
Pili and Lipopoplysaccharides
Receptors in Gram-Positive bacteria?
Teichoic Acids
What is a Lytic Infection?
When phages such as T phages produce a reaction in E. Coli.
Productive Infection?
When new phages are made and released from the cell.
Ecilpse Period
During this time, no mature virus can be detected by assay procedures
Self-Assembly
Once all the parts are synthesized, they come together to form mature phage particles
Lysogenic Phage?
The bacteriophages infect a bacterial cell, the phage genome can integrate into host DNA to become a stable genetic element in the host cell genome. Everytime the cell replicates, so does this virus.
Lysogens?
Bacterial cells that have temperate phage DNA integrated into their DNA.
PRophage or Provirus?
The integrated phage genome.
Burst Size
One phage particle infecting a single host cell can produce as many as 200 virions
Confluent Lawn
In a soft agar, phages will infect the cells causing them to undergo lysis and form clear areas int he confluent lawn called plaques.
Plaque-Forming Units
Like CFUs, they can be counted to determine the number of viral particles in a suspension of phage
