Week 4: Quantitation of microorganisms

Question 1

what is a serial dilution?

Answer 1

a stepwise dilution of a substance in solution

Question 2

.1 part / 10 parts total = (2) ?

Answer 2

1/100 ; 10^-2 dilution

Question 3

describe a 10^-2 dilution

Answer 3

1/100

Question 4

PFU/ml = ?

Answer 4

(# of plaques/plate) x (factor for volume plated to make volume to 1 ml) x (dilution factor)

Question 5

CFU/ml = ?

Answer 5

(# of colonies/plate) x (factor for volume plated to make volume to 1 ml) x (dilution factor)

Question 6

calculate the titer for 50 plaques if i plated out 0.1 ml of a 10^-5 diluted phage suspension

Answer 6

50 x 10 x 10^5 = 5 x 10^7 PFU/ml

Question 7

what is a bacteriophage?

Answer 7

a virus that infects bacteria

Question 8

what is a lytic phage?

Answer 8

phage infects and then lyses the host cell to escape

Question 9

what is a temperate phage

Answer 9

phage can choose between a lytic infection or incorporating into the host genome (lysogeny)

Question 10

what are plaques?

Answer 10

a visible structure formed by phages when they infect a bacterial culture on solid medium, like a bacterial colony