Microbio Lab 11

Question 1

What are viruses composed of?

Answer 1

RNA or DNA, but never both

And a protein coat

Question 2

What are viruses that infect bacterial cells?

Answer 2

They’re called bacteriophages, or phages

Question 3

What is the lytic cycle?

Answer 3

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

Question 4

What is the lysogenic Cycle?

Answer 4

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.

Question 5

Virus - Step One

Answer 5

Adsorpption: Phage is absorbed to specific receptor site on the bacterial cell surface. This is Time Zero

Question 6

Virus - Step Two

Answer 6

Phage DNA enters cell to initiate Eclipse Stage. Bacterial DNA is degraded within minutes

Question 7

Virus - Step Three

Answer 7

Phage capdis, tails, and phage DNA begin to appear within 12 minutes as phage reorients cell metabolism to its own fabrication process

Question 8

Virus - Step Four

Answer 8

Components of phage are assembled into mature infective virions

Question 9

Virus - Step Five

Answer 9

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

Question 10

Bacteriophages Definition

Answer 10

Viruses that infect bacterial cells. Called a “Bacterial Eater”

Question 11

What are Bacteriophages also known as?

Answer 11

Obligate Intracellular Parasites; Meaning they must invade host cell in order to replicate and reproduce.

Question 12

What is a Capsid?

Answer 12

Viruses are composed of a single kind of nucleic acid molecule encased in a protein coat that protects the nucleic acid.

Question 13

Viruses also exhibit..

Answer 13

specificity for their host.

Question 14

What is a nucleocapsid?

Answer 14

A phage that contains a capsid made of nucleic acid and protein

Question 15

What is a Sheath?

Answer 15

The nucleocapsid is attached to this protein sheath that is contractile and contains a hollow tube in its center

Question 16

What is a single virus or phage particle called?

Answer 16

A viron

Question 17

Receptors in gram-negative bacteria?

Answer 17

Pili and Lipopoplysaccharides

Question 18

Receptors in Gram-Positive bacteria?

Answer 18

Teichoic Acids

Question 19

What is a Lytic Infection?

Answer 19

When phages such as T phages produce a reaction in E. Coli.

Question 20

Productive Infection?

Answer 20

When new phages are made and released from the cell.

Question 21

Ecilpse Period

Answer 21

During this time, no mature virus can be detected by assay procedures

Question 22

Self-Assembly

Answer 22

Once all the parts are synthesized, they come together to form mature phage particles

Question 23

Lysogenic Phage?

Answer 23

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.

Question 24

Lysogens?

Answer 24

Bacterial cells that have temperate phage DNA integrated into their DNA.

Question 25

PRophage or Provirus?

Answer 25

The integrated phage genome.

Question 26

Burst Size

Answer 26

One phage particle infecting a single host cell can produce as many as 200 virions

Question 27

Confluent Lawn

Answer 27

In a soft agar, phages will infect the cells causing them to undergo lysis and form clear areas int he confluent lawn called plaques.

Question 28

Plaque-Forming Units

Answer 28

Like CFUs, they can be counted to determine the number of viral particles in a suspension of phage