Bacteriophages

Question 1

What are bacteriophages ?

Answer 1

Viruses of bacteria and archaea

Question 2

What is the most abundant bacteriophage?

Answer 2

Tailed phages which has dsDNA

( phages can be ss, ds, RNA or DNA

Question 3

How do bacteriophages infect bacteria with differing Gram staining results ?

Answer 3

Phages only infect limited number of gram positive but many gram negative

Question 4

What are bacteriophages made of ?

Answer 4

• genetic material
• capsid to protect and enclose DNA/RNA
• Tails (long, contractile, non-contractile and short
• adsorption apparatus (first step of injection, baseplate, tail fibres, tip)

Question 5

How is a bacteriophage absorbed into the host?

Answer 5

1. phage in contact with r, reversible adsorption (weak)
2. Walks along surface to find place to absorb irreversible (strong)
3. DNA ejection into cell (sometimes aided by proteins which degrade inner membrane (lysosomes)

Question 6

What increases the chance of finding bacteria ?

Answer 6

Rigid body

Question 7

How is DNA injected into the cell ?

Answer 7

• tail ejection (contractile)
• long flexible ejection
• short tail injection (looks like screw)

Question 8

What do temperate phages do?

Answer 8

make decisions between lysis or lysogenic cycle
Known as phage lamba
Communicate using small molecules

Question 9

What is general and specialised transduction ?

Answer 9

General = antibiotic resistance 
Specialised = phage pulls DNA and brings part of the host with it

Question 10

What is an eclipse period?

Answer 10

Before lysis all elements replicated

Question 11

What is the latent period?

Answer 11

time for phage to release progeny

Question 12

What is burst size?

Answer 12

number of progeny produced in cycle

Question 13

What is the bacteriophage life cycle ?

Answer 13

1. hack host machinery for rep and protein synthesis
2. DNA packing + vision assembly
3. cell burst (lysis)