Practical 2

Question 1

What is happening during the stationary phase of the bacterial growth curve?

Answer 1

dying = # growing; possibly limited/depletion of nutrients

Question 1

What do you look for in MSA?

Answer 1

If it grew, it’s halotolerant and does media change color

Question 1

What benefit does a bacterium receive from having the enzyme catalase?

Answer 1

Antioxidant. Can catalyze the conversion of hydrogen peroxide into water and oxygen. Serves useful functions like healthy immune response.

Question 3

What is blood agar and what does it test for?

Answer 3

TSA + sheep blood Tests for hemolase

Question 4

What is happening during the death phase of the bacterial growth curve?

Answer 4

Bacteria die (lack of nutrients, wrong temp, etc)

Question 5

What is happening during the log phase of the bacterial growth curve?

Answer 5

Bacteria are growing/multiplying as fast as they can (exponentially)

Question 6

MPK equation

Answer 6

1 - [(CFU of test/mL)/(CFU of control/mL)] x 100%

Question 8

How does UV radiation affect bacteria?

Answer 8

It’s a mutagen that damages DNA by forming thymine dimers

Question 9

What are a couple of limitations to UVGI?

Answer 9

Can’t go through most surfaces Destroys anything plastic

Question 10

How do you distinguish + from - results with TSA?

Answer 10

+ = bubbling - = no bubbles

Question 11

What’s a possible use for UVGI?

Answer 11

Sterilize surfaces

Question 12

What does TSA stand for and what does it test for?

Answer 12

Tryptic soy agar Tests for catalase

Question 13

What is happening during the lag phase of the bacterial growth curve?

Answer 13

Bacteria adapting to their conditions. They are maturing but not dividing. Preparing for division.

Question 13

What does TGA stand for and what does it test for?

Answer 13

Tellurite glycine agar Tests for coagulase

Question 13

How might a bacteria use the coagulase enzyme to increase its virulence?

Answer 13

Protects from host immunity. Takes our blood cells and coats itself to be unrecognized as intruder

Question 15

What type of media is MSA?

Answer 15

selective (for halotolerant bacteria) and differential (staph aureus (turns yellow), staph epidermis (stays pink))

Question 16

What are the possible results of blood agar?

Answer 16

Alpha = Some intact RBC remain near colony and blood agar looks slightly green or lighter red Beta = no blood cells, but halo around where cells were (transparent, yellow) Gamma = no change because no hemolysis

Question 18

What does MSA stand for and what does it test for?

Answer 18

Mannitol salt agar For halotolerance

Question 19

How do you distinguish + from - results with TGA?

Answer 19

+ = black colonies - = yellow/white

Question 20

What does UVGI stand for?

Answer 20

Ultraviolet Growth Inhibition

Question 21

What type of media is TGA?

Answer 21

selective (for gram +) and differential (for coagulase)