Microbiology Lab exercise 14 -Fermentation

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1

Fermentation produces

acids
alcohols
gas

2

True or false. Nutrient agar there is no differentiation.

True

3

Carbohydrate fermentation procedure

Obtain 4 of each carbohydrate fermentation tubes:
glucose
sucrose
lactose

Obtain one each of the following: E. coli, E. aerogenes, A. faecalis, P. vulgaris
inoculate each set with each bacteria

4

Why is the durham tube upside down?

to detect gas production

5

carbohydrate fermentation media:

broths
uninoculated color: red
contains:
one peptone
durham tube
phenol red (pH indicator)

6

Phenol red is a pH indicator

yellow- positive for sugar fermentation pH lower
red- no change pH stayed same
pink/magenta- it couldn't metabolize the sugar and use for food so it metabolized the protein pH higher

7

The carbo. tube is full and no bubbles

positive for acid fermentation

8

Carbo tube has bubbles in durham tube

positive for gas fermentation

9

carbo tube has no change in color or gas production

negative for fermentation

10

Carbo tube is orange

Intermediate zone- (-) for fermentation

11

True or false. Bacteria can ferment a variety of carbohydrates through different pathways. No single bacterial species is capable of them all.

true

12

_______ it typically the starting point of carbohydrate fermentation.

pyruvic acid

13

True or false. Acids and/or gases may be produced as products of fermentation.

true

14

Fermentation ability depends on ______ and the ______ it produces.

bacteria
enzymes

15

Carbohydrate fermentation theory
positive for acid production

pH decreases
phenol red becomes yellow and turns media yellow

16

If positive for gas production in carbohydrate fermentation

media in durham tube is displaced
bubble forms within durham tube

17

Carbohydrate fermentation results:
yellow broth bubble in durham tube

positive for fermentation with gas and acid products

18

Carbohydrate fermentation results:
yellow broth no bubble in tube

positive for fermentation with acid products

19

Carbohydrate fermentation results:
red broth no bubble in tubes

no fermentation- no acid or gas production

20

Carbohydrate fermentation results:
pink broth no bubble in tube

protein catabolism: alkaline end product
no acid or gas

21

Carbohydrate fermentation results:
orange broth

negative for fermentation no gas or acid

22

MRVP results

red is positive for both tests

23

MRVP is _____ test and they are _____ and ______.

2
methol red
vogues proskauer

24

The methol red test is testing for?

mixed stable acids fermentation
it overcomes the buffer and changes the pH

25

The VP test is for?

to check for the production of acetoin

26

Methyl red test you add __ drops to the MRVP broth

5

27

In the methyl red test if the broth remains red than it is _____________.

positive for the production of mixed stable acids

28

The MRVP test contains:

glucose
protein
phosphate buffer (resists pH change)

29

In the methyl red test it is used to detect large amounts of ________.

mixed stable acids
acids are stable and overcome buffer
cause pH change

30

True or false. In the methyl red test the only true indication of a positive fermentation for mixed stable acids is ______.

red color

31

The VP test you add
12 drops of reagent 1 which is _________.
And 2-3 drops of reagent 2 which is __________.

a-napthol
KOH

32

In VP test after adding reagents put paraffin cover and shake vigorously and let stand for 30 mins
Results:

Light brown tea color (-) for acetoin production
Red or red band at top is positive for acetoin production

33

In the VP test it is the fermentation of ______ that produces acetoin.

glucose

34

Citrate test is done in a _______ and you ______ to inoculate the tube.

slant-green (solid) and you zig zag up to inoculate it

35

Citrate media is:

slant-solid media/green
One carbon source- sodium citrate (carbon)
One nutrient source monoammonium (nutrient)
Bromthymol blue- pH indicator
dipotassium phosphate
magnesium sulfate (cofactor for enzymes)
agar

36

The positive result of citrate is

green-----> blue

37

For the citrate test the bacteria need both ____ and ______.

carbon and energy

38

The citrate test tests the bacteria's ability to

obtain both carbon and energy

39

The citrate test allows differentiation between different members of Enterobacteriacea

enteric bacteria

40

If the citrate test is positive bacteria

produce citrate lyase
make ammonia from ammonium
increase the pH of agar
media turns a deep Prussian blue

41

Citrate test results:
blue even a small amount

positive
citrate is utilized

42

Citrate test results:
No color change; growth

citrate is utilized; positive

43

Citrate test results:
no color no growth

citrate not utilized
negative citrate test

44

KOH is

potassium hydroxide

45

a-napthol is used with KOH to detect

acetoin