Lab Quiz 4

Question 1

What does zone of inhibition mean?

Answer 1

that a particular agent is microbicidal

Question 2

what are bacteriophages?

Answer 2

viruses that attack bacteria

Question 3

what is a plaque?

Answer 3

produces a clearing that can be view with the naked eye.

Question 4

what is PFU?

Answer 4

Plaque forming unit

Question 5

what is TNTC?

Answer 5

too numerous to count

Question 6

what is TFTC?

Answer 6

too few to count

Question 7

the number of plaque should fall between what numbers?

Answer 7

30-300

Question 8

how to calculate the number of pfu’s per mL?

Answer 8

multiplying the number of pfu’s on a plate times the dilution factor of the phage placed on that plate

Question 9

what time of phage are we using?

Answer 9

T2 or T4 coli-phage sample strain from E.coli

Question 10

what life cycle T2 or T4 use?

Answer 10

lytic cycle

Question 11

what is the lytic cycle?

Answer 11

1. The virus attaches to bacteria (host)\ (attachment)
2. The virus inserts its DNA into the bacteria (penatration)
3. The virus takes over the cell’s machinery (biosynthesis)
4. The virus reproduces itself and self-assembles.(Maturation)
5. The host cell is destroyed(release)

Question 12

why would you expect to find any streptomycin resistant mutants?

Answer 12

random chance

Question 13

what is the purpose of the streptomycin?

Answer 13

To reduce the development of drug-resistant bacteria and maintain the effectiveness of streptomycin and other antibacterial drugs (selects resistant bacteria)

Question 14

Does streptomycin induce mutations?

Answer 14

no

Question 15

what are Coliform bacteria?

Answer 15

gram negative
non-spore forming
Facultatively anaerobic rods that ferment lactose

Question 16

What are they used for?

Answer 16

enterics to indicate organisms for the possible presence other enteric pathogens such as Salmonella and Shigella.

Question 17

what is the most commonly used indicator organism?

Answer 17

E.coli

Question 18

potable water?

Answer 18

drinkable

Question 19

what is the recommended standards by the U.S. Public Health Service for drinking?

Answer 19

no more than 1 coliform per 100ml

Question 20

For total bacterial count?

Answer 20

no more than 100 bacteria/ml

Question 21

what are the advantages of filter method?

Answer 21

• relatively fast
• large volumes of water can be tested which would find relativity few contaminants (sensitive)
• accuracy, each colony represents a clone of a single bacterium; results reproducible and quantitative

Question 22

what are the disadvantages?

Answer 22

• turbidity clogs filter
• highly contaminated water must be diluted in order to obtain discrete
• countable colonies,

Question 23

What color is it for E.coli?

Answer 23

shiny green/gold

Question 24

what color for coliforms?

Answer 24

dark red/purple colonies

Question 25

what color for non-coliforms?

Answer 25

any other color

Question 26

How to calculate the number of coliforms?

Answer 26

divide the number of colonies counted by the mL of sample and multiply by 100 = #colonies/mLsample x 100

Question 27

Microbial Flora test: What are the result for Staphlococcus aureus, Staphylococcus epidermidis, and Staphylococcus saprophyticus in the Mannitol fermentation test?

Answer 27

Staphlococcus aureus= +, yellow agar, growth Staphylococcus epidermis= -, no yellow agar, growth Staphylococcus saprophyticus = -, no yellow agar, growth

Question 28

Microbial Flora test: What are the results for Staphylococcus aureus, Staphylococcus epidermis, and Staphylococcus saprophyticus in the Coagulase test?

Answer 28

Staphlococcus aureus = +, clot forms Staphylococcus epidermis = -, no clot Staphylococcus saprophyticus = -, no clot

Question 29

Microbial Flora test: What are the results for Staphylococcus aureus, Staphylococcus epidermis, and Staphylococcus saprophyticus in the Novobiocin Sensitivity test?

Answer 29

Staphylococcus aureus = susceptible (>=22mm zone) Staphylococcus epidermis = susceptible (>=22mm zone) Staphylococcus saprophyticus = resistant (<= 17mm zone)

Question 30

what causes cavities?

Answer 30

Lactobacilli and streptococci

Question 31

What does Lactobacilli and streptococci do?

Answer 31

ferment glucose to produce acids that erode tooth enamel and promote tooth decay leading to dental caries.

Question 32

What is pH of Snyder media?

Answer 32

4.8

Question 33

What bacteria and inhibit in Snyder media?

Answer 33

Lactobacilli and streptococci

Question 34

what type of media is this?

Answer 34

Snyder agar, contains 2% glucose and the pH indicator bromcresol green, tube agar