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Biology 15 - General Microbiology > Lab Exam 3 Gram + > Flashcards

Lab Exam 3 Gram + Flashcards

1
Q

Gram + test

You should memorzie a few potential species used for these tests.

A
  • Aureus (Used in MSA)
  • Epidermidis (Used in MSA)
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1
Q

Gram + test

What two genera were used for these tests?

A
  1. Staphylococcus
  2. Streptococcus
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2
Q

Gram + test

What does a positive result of the Selective and Differential test look like?
What does a negative result of the Selective and Differential test look like?

Think of the MSA plate and what color it is when it’s a positive result.

A

A positive result for the S&D test will result in a yellow color change. (Staphylococcus aureus)
A negative result for the S&D test will result in the plate remaining red. (Staphylococcus epidermidis)

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3
Q

Gram + test

What does a positive result look like when testing for coagulase production when using Vogel-Johnson agar? What does a negative result look like?

Think of the color of colonies that should show on the plate.

HINT: There are two tests; coagulase and mannitol fermentation

A
  • Positive for coagulase = Black colonies
  • Negative for coagulase = No black colonies
  • Positive for Mannitol fermentation = Yellow zones around colonies
  • Negative for Mannitol fermentation = No yellow ; plate remains red
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4
Q

Gram + test

What does a positive result look like for hemolysin production when using Blood Agar? What does a negative result look like?

A
  • Positive result: Red dissapearing from underneath the colonies (clearance zones). Known as Beta pattern.
  • Negative result: Plate remains fully red, meaning there is no hemolysin. Known as a Gamma Pattern.
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5
Q

Gram + test

Is urea a product or reactant for this test?

A

Urea is a reactant for the urease test.

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6
Q

Gram + test

What are the two products of the enzyme urease? Know how to write out the molecular formula of each of these products.

A

The two products are ammonia (NH3) and carbon dioxide (CO2).

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7
Q

Gram + test

Which product of urease changes the pH of the sample tube?

A

Ammonia changes the pH of the sample tube.

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8
Q

Gram + test

Will a tube that is positive for urease activity become more acidic or more alkaline?

A

A tube positive for urease activity will become more alkaline.

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9
Q

Gram + test

What is the weak acid/weak base pair that is produced by urease activity?

A

Ammonium hydroxide (NH4OH).

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10
Q

Gram + test

Which pH indicator is used in a urea agar slant?

A

Phenol red

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11
Q

Gram + test

What color is a tube that is positive for urease activity?

A

Pink

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12
Q

Gram + test

What is the name of the toxin that destroys red blood cells?

A

Hemolysin (exotoxin)

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13
Q

Gram + test

What would a positive blood agar test result look like?

A

Clearance zones around bacterial colonies, indicating hemolysis.

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14
Q

Gram + test

Which two Greek letters are used to describe a positive test result for Blood Agar?

A

Alpha (α) and beta (β).

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15
Q

Gram + test

Which Greek letter is used to describe a negative test result?

A

Gamma (γ).

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16
Q

Gram + test

What type of agar is used to screen for antibiotic sensitivity of our unknown?

A

TSA

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17
Q

Gram + test

Which plating technique is used to prepare this plate for antibiotic resistance?

A

Lawn plate technique

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18
Q

Gram + test

How does novobiocin inhibit bacterial growth?

A

By interfering with DNA replication.

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19
Q

Gram + test

What would a positive test result for resistance look like?

A

No death zone

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20
Q

Gram + test

What would a negative test result for resistance look like?

A

A death zone greater than 4mm

21
Q

Gram + test

Which form of metabolism (from chapter 5 in your lecture book) utilizes nitrate salt as a final electron acceptor?

A

Anaerobic respiration

22
Q

Gram + test

Is nitrate an oxidized or a reduced salt?

A

Nitrate is an oxidized salt

23
Q

Gram + test

What is the molecular formula of nitrate?

A

NO3-

24
Q

Gram + test

What is the is reduction process showing nitrate being reduced to ammonia?

A
  • NO3- —> NO2- —>N2O(g) —>N2 —> NH3
  • Nitrate reduced to Nitrite (red color change), Nitrite reduced to Nitrous oxide, Nitrous oxide reduced to nitrogen gas (bubbles form in durham tube), Nitrogen gas reduced to ammonia.
25
Q

Gram + test

In the anaerobic respiration / nitrate test, which reduced products are gases?

A

Nitric oxide (NO) and nitrous oxide (N2O) are gases.

26
Q

Gram + test

Which color is produced by a positive nitrite test?

A

Red

27
Q

Gram + test

Is a positive nitrite test a positive or negative result for nitrate reduction?

A

A positive nitrite test indicates nitrate reduction.

28
Q

Gram + test

What is the function of a Durham tube?

A

It traps gas in the nitrate broth.

29
Q

Gram + test

Is the presence of bubbles in the Durham tube positive or negative for nitrate reduction?

A

Positive; bubbles indicate gas production.

30
Q

Gram + test

What would the results look like for an organism that did not use the nitrate?

A

No color change, no gas production

31
Q

Gram + test

Gelatin is what type of biological molecule?

A

Protein

32
Q

Gram + test

What is the name of the enzyme that hydrolyzes gelatin?

A

Protease

33
Q

Gram + test

How did we inoculate the gelatin agar so that it could be incubated?

A

Using needle

34
Q

Gram + test

If we were to analyze the tubes for gelatin hydrolysis directly after removing the cultures from the incubator, our results would be incorrect. What do we need to do before analyzing the results of our hydrolysis test?

A

Chill the tubes to solidify the gel

35
Q

Gram + test

Briefly describe the appearance of a tube that is positive for gelatin hydrolysis.

A

The medium remains liquid after chilling.

36
Q

Gram + test

A
37
Q

Gram + test

What are the 2 Vogel Johnson Agar test are and the results of these tests?

A
  1. Testing for Coagulase
  2. Testing for mannitol fermentation
    Positive result for coagulase = black colonies
    Positive result for mannitol fermentation = yellow zones around colonies
    Negative result = no black or yellow
38
Q

Gram + test

How are black colonies formed as a positive result from the Vogel-Johnson agar test?

A

Tellurite gets reduced into bellurium.

39
Q

Gram + test

What concentration of NaCl is used in our hypertonic broth?

A

6.5% saline solution

40
Q

Gram + test

Which pH indicator is present in the saline broth?

NaCl test

A

Bromocrosal Purple

41
Q

Gram + test

What color is the broth before it is inoculated in the NaCl test?

NaCl saline test

A

Purple

42
Q

Gram + test

How does bacterial growth affect the pH of the saline broth?

A

Decreases pH making it more acidic

43
Q

Gram + test

What is expected with a positive test result in the NaCl saline test?

A
  1. Broth becomes cloudy
  2. Broth changes to yellow-brown
44
Q

Gram + test

What does BEA stand for?

A

Bile Esculin Agar

45
Q

Gram + test

Which two ingredients in a BEA plate act to select against the growth of most microbes?

A

1.) Bile
2.) Azide

46
Q

Gram + test

What is the substrate in the BEA plate?

A

Esculin

47
Q

Gram + test

What are the two products of degradation? Which of these products reacts with iron ions?

BEA test

A

Two products of degradation:
1.) Glucose
2.) Esculetin
Esculetin reacts with iron ions

48
Q

Gram + test

What color is produced by a positive test result?

BEA test

A

Black splotches

49
Q
A

Biology 15 - General Microbiology (29 decks)

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