Lab Practical

Question 1

What type of medium is SF broth/ BPB?

Answer 1

Selective

Question 2

What is SF Broth/BPBused for?

Answer 2

detection and differentiation of enterococci from other cocci

Question 3

Positive SF broth/BPB and what it means

Answer 3

Yellow
glucose fermentation

Question 4

Negative SF Broth/BPB and what it means

Answer 4

purple
does not ferment

Question 5

What does BPB contain that inhibits aerobic respiration?

Answer 5

sodium azide
Inhibits electron transfer

Question 6

What type of medium is MacConkey agar?

Answer 6

selective and differential

Question 7

What does MacConkey select for?

Answer 7

Gram-negative: selects against Gram-positive organisms

Question 8

What does growth mean on MacConkey agar?

Answer 8

organism is Gram-negative

Question 9

How is MacConkey agar differential?

Answer 9

differential for lactose fermentation

Question 10

What does pink MacConkeyy mean?

Answer 10

positive for lactose fermentation
acidic

Question 11

What does orange MacConkey mean?

Answer 11

negative for lactose fermentation
neutral

Question 12

Purpose of Na+ Glucose plates?

Answer 12

serves as a control
any organisms will grow on it

Question 13

What kind of medium is tryptic soy broth?

Answer 13

complex liquid media

Question 14

Positive TSB tube

Answer 14

turbidity/cloudy
this means there is growth

Question 15

negative TSB tube

Answer 15

clear

Question 16

What does amylase do?

Answer 16

enzyme that catalyzes starch hydrolysis

Question 17

How to test for amylase

Answer 17

Starch plate flooded with Gram’s iodine

Question 18

Amylase positive

Answer 18

reddish/amber zone surrounding the colonies
- due to a lack of starch

Question 19

Amylase negative

Answer 19

Dark color surrounding growth

Question 20

What does Caseinase do?

Answer 20

enzyme that hydrolyzes milk proteins (Casein)

Question 21

How to test for caseinase?

Answer 21

casein plate

Question 22

Caseinase positive

Answer 22

clear zone surrounding growth
- due to hydrolysis of casein

Question 23

Casein negative

Answer 23

no clear zone surrounding growth
because there is no hydrolysis of casein

Question 24

What does gelatinase do?

Answer 24

enzyme that hydrolyzes gelatin

Question 25

How to test for gelatinase?

Answer 25

cooling of gelatin tubes

Question 26

Gelatinase positive

Answer 26

gelatin tubes remain liquid
- because gelatin was hydrolyzed

Question 27

Gelatinase negative

Answer 27

gelatine tubes remain solid

Question 28

What does catalase do?

Answer 28

Protects cell from hydrogen peroxide by producing water and oxygen

Question 29

How to test for catalase?

Answer 29

put colony sample onto filter paper squares and add 3% hydrogen peroxide

Question 30

Catalase positive

Answer 30

sample bubbles immediately after adding a drop of hydrogen peroxide

Question 31

Catalase negative

Answer 31

sample does not bubble after adding hydrogen peroxide

Question 32

what does oxidase do?

Answer 32

oxidase activity indicates presence of cytochrome c (component of ETC)

Question 33

How to test for oxidase?

Answer 33

Put colony sample onto parafilm and add drop of oxidase reagent

Question 34

oxidase positive

Answer 34

turns blue

Question 35

Oxidase negative

Answer 35

remains clear