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microbiology 211 > Lab Practical 2 > Flashcards

Lab Practical 2 Flashcards

1
Q

what are the possible end products that you get from fermentation

A

acid
alcohol
gas–> never produced by itself, always with acid or alcohol

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2
Q

fermentation: what does it look like when you have a positive result for acid

A

ph becomes acidic, detected by phenol red

red at neutral ph and turns yellow as becomes acidic

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3
Q

fermentation: what does it look like whne you have a positive result for gas

A

tested in durham tube, if positive a bubble will form and the color will change

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4
Q

fermentation: what does it look like when you have a positive result for alcohol

A

the only way to tell if there is alcohol is if there is no acid produced, but there is gas produced

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5
Q

steps for fermentation experiment

A

E. coli, A. faecalis, S. pastorianus and 3 broth tubes consisting of lactose, glucose and sucrose.
transfer E. coli into glucose, sucrose, and lactose tubes
repeat for S. pastorianus and A. faecalis

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6
Q

reactions of catalase activity

A

2h2o2–>(catalase) 2h2o + o2(bubbles)

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7
Q

what can catalase differentiate between

A

enterococcus and staphylococcus

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8
Q

what is the purpose of oxidase test

A

determine between obligate aerobe (+) and facultative anaerobe (-)
determine if the organism can produce oxidase

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9
Q

what does a positive oxidase test look like

A

purple or pinkish color=obligate aerobe

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10
Q

steps for oxidase test

A
  1. oxidase test paper, wooden stick, oxidase reagent, e. coli, a. faecalis, p. aeruginosa
  2. add a drop of reagent to paper
  3. using wooden stick, transfer large amount of bacteria onto paper
  4. the result should occur within 20-30 seconds
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11
Q

nitrate reduction

A

no3–> no2–>nh3 or n2
reduced by nitrate/nitrite reductase
identify bacteria containing nitrate reductase

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12
Q

positive nitrate reduction test

A
  1. red color change = positive for nitrate reductase

2. no change= positive for nitrate reductase

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13
Q

steps of nitrate reduction

A
  1. e. coli, s. epidermis, p. aeruginosa, and 3 nitrate broth tubes
  2. transfer bacteria into each tube
  3. incubate fore 48 hours
  4. add nitrate a and b reagents
    if red=positive for nitrate reductase
    if no change move to 2
  5. add zinc
    if red=negative
    if no change=positive for nitrate reductase
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14
Q

what is the purpose of the durham tube in the carbohydrate fermentation broth

A

it can detect gas produced by a fermentation pathway

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15
Q

would an obligate anaerobe be positive for catalase? why?

A

no because they die in the presence of oxygen

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16
Q

what end product reacts with nitrate A and nitrate B reagents

A

NO2 because NO3 has been reduced

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17
Q

what is the function of zinc in the nitrate reduction test

A

reduce NO3 to NO2. if there is a color change the result is negative because there was NO3 still in there

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18
Q

starch hydrolysis

A

starch can be used for food by some bacteria however it is too big to get through the membrane. some bacteria produce an exoenzyme called alpha-amylase which breaks down starch allowing it to get into the membrane and used for food
test if alpha amylase is produced

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19
Q

starch hydrolysis reaction equation

A

starch–>(alpha amylase) dextrins, maltose, glucose

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20
Q

positive result of starch hydrolysis

A

clear around black line

black line indicates starch, clear indicates alpha amylase

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21
Q

steps of starch hydrolysis

A
  1. streak bacteria in straight line on plate

2. incubate for 24 hours then observe

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22
Q

casein hydrolysis

A

protease reduces casein to amino acid to use as a source of food for bacteria

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23
Q

positive casein hydrolysis test

A

bacteria will be clear against the opaque milky agar plate

indicates presence of protease

24
Q

gelatin hydrolysis

A

gelatin is broken down by gelatinase into amino acids to be used as a food source.

25
Q

why is gelatinase a virulence factor

A

because it breaks down connective tissue bc gelatin is connective tissue

26
Q

steps for gelatin hydrolysis

A

get gelatin tubes, stab 3/4th of the way down with needle with bacteria, incubate for 48 hours, then place in fridge

27
Q

positive gelatinase test

A

liquid after fridge = positive

solid=negative

28
Q

DNase test

A

DNase breaks down DNA into nucleic acid to transport across membrane as a food source

29
Q

positive DNase test

A

clear is positive

stays teal, negative

30
Q

why is DNase considered a virulence factor?

A

because it can degrade host DNA

31
Q

why are some bacteria able to grow on a milk plate even though they do not hydrolyze casein

A

they are able to metabolize other nutrients

32
Q

2 benefits of gelatinase produced by bacteria

A
  1. breaks down gelatin to be used as food

2. virulence factor bc breaks down connective tissue

33
Q

what 3 tesets are preformed with the sim tube

A

sulfide, indole, motility

34
Q

hydrogen sulfide test determines

A

if the microorganism can produce h2s

35
Q

sulfide test equationss

A

cysteine –cysteine desulfurase–> pyruvic acid + ammonia + h2s
or
thiosulfate–thiosulfate reductase–> sulfite h2s (anaerobic respiration)

36
Q

positive sulfide test

A

dark black line through the middle

37
Q

indole test determines

A

if indole is produced

38
Q

indole equation

A

tryptophan–tryptophanase–> pyruvic acid + ammonia + indole

39
Q

positive indole test

A

bright red on top is positive

40
Q

motility positive test

A

black strays away from line = positive

straight line = negative

41
Q

what does IMViC stand for

A

Indole, methyl red, voges-proskeur, citrate

42
Q

methyl red/ voges proskeur determines

A

if it is a mixed acid ferementer or butandediol fermenter

43
Q

methyl red tests will be positive if

A

its a mixed acid fermenter and turns red, at a ph of 4

44
Q

methyl red will be negative if

A

its a butanediol fermenter and turns yellow, ph of 6

45
Q

voges proskeur test will be positive if

A

its a butanediol fermenter and there is a red color

46
Q

voges proskeur will be negative if

A

its mixed acid fermeneter and there is an absence of red

47
Q

MRVP test steps

A

use mrvp broth tubes and an innoculating loop

place bacteria in tubes, incubate and observe

48
Q

citrate test determines if

A

microorganisms can use citrate as their sole carbon source

49
Q

citrate equation reaction

A

sodium citrate–citrate permease/citrase–> pyruvic acid = oxaloacetic acid = co2

50
Q

positive citrate test

A

blue

51
Q

steps for citrate test

A

use slant tube, transfer bacteria by smearing

52
Q

urease equation

A

urea + water –urease–> co2 + ammonia + water

53
Q

urease test determines

A

if produce urease enabling bacteria to use urea as a source of nitrogen

54
Q

positive urease test

A

bright red

55
Q

urea test steps

A

transfer bacteria and incubate. if turns red produces urease

microbiology 211 (6 decks)

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