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Microbiology 211 Lab > Quiz 2 > Flashcards

Quiz 2 Flashcards

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1
Q

What is the purpose of the gram stain?

A

The gram stain helps us differentiate between gram + and gram - bacteria. It is the first step in identifying an unknown bacteria

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2
Q

What is the first step in the gram stain procedure? What is happening chemically?

A

The first step involves the primary stain, which is done with crystal violet. The crystal violet dyes all forms of bacteria because it is a cationic substance reacting with an anionic exterior of bacteria.

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3
Q

What is the second step in the gram stain procedure? What is happening chemically?

A

The second step is the mordant and it is iodine. The iodine creates a crystal complex which allows the crystal violet to stick properly to the cell wall

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4
Q

What is the third step in the gram stain procedure? What is happening chemically?

A

The third step is decolorize and it is done with ethanol. The alcohol does not allow gram - to retain crystal violet and will dissolve the color. In gram + nothing will happen

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5
Q

What is the fourth step in the gram stain procedure? What is happening chemically?

A

The fourth step involves a counterstain and it is done with safranin. Since it is lighter than violet, it will not affect the gram + bacteria that have crystal violet. Since gram - bacteria are decolorized from previous stain, it will stain them pink/red

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6
Q

What is the difference between gram +and gram - bacterial cell walls?

A

Gram + have an inner cell membrane and a thick peptidoglycan layer
Gram - have an inner cell membrane, thin peptidoglycan layer, and an outer cell membrane

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7
Q

What would happen if iodine was left out of the procedure?

A

Since iodine allows crystal violet to bind to cells, skipping this step will not allow us to see a clear difference between gram + and gram -

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8
Q

What would happen if ethanol was left out of the procedure?

A

Since alcohol usually dissolves lipids (outer layer of gram -), skipping this step will not allow gram - bacteria to turn pink since they will not be decolorized

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9
Q

What would happen if safranin was left out?

A

Since safranin helps stain gram - cells, skipping this step will not allow us to see them. We would only observe gram + bacteria

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10
Q

What happens if we perform a gram stain on cultures that are old?

A

It could give us false results and we could see a mixture of pink and purple for all types of bacteria (regardless of gram -/+

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11
Q

What is the purpose of the acid fast stain?

A

The Acid-fast stain is used to identify Mycobacterium species based on the detection of the mycolic acid layer

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12
Q

What is the main pathogen associated with the presence of mycolic acid? What disease does it cause in us?

A

Mycobacterium Tuberculosis, causes TB in us

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13
Q

What is the first step in acid fast staining?

A

We first stain with Carbolfushion (KF) for 4 minutes

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14
Q

What is the second step in acid fast staining?

A

The second step is Decolorizer, which is Acid Alcohol for up to 30 seconds.

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15
Q

What is the third step in acid fast staining?

A

Counterstaining with Methylene blue for 30 seconds

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16
Q

What is the interpretation of acid fast stain?

A

Dark red/pink rods: positive…mycolic acid present

Blue rods: negative… no mycolic acid present

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17
Q

What is an endospore?

A

It is a specialized cell structure that keeps bacteria alive during extreme environmental conditions

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18
Q

What substances do we use for an endospore stain?

A

Malachite green and Safranin

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19
Q

What is an example of capsules (aka slime layers)?

A

Bio films

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20
Q

What is nosocomial?

A

A hospital acquired infection

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21
Q

What is a vegetative state for bacteria?

A

Basically, bacteria without spores. When a bacteria becomes “active” again (feeding, reproducing, excreting, etc), after being an endospore, we can describe it as a vegetative state.

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22
Q

What is a bacterial capsule?

A

A bacterial capsule can be referred to as glycocalyx. Within glycocalyx, we have different types of capsules that benefit bacteria in many ways. In most cases, a capsule will help bacteria be protected from an outside environment, thus making it a virulence factor.

23
Q

Why is capsule staining also called negative staining?

A

Because the capsule itself is not stained. Instead the background and bacteria are stained but the capsule is left free from stain.

24
Q

What substances do we use to stain capsules?

A

We use congo red and maneval’s stain

25
Q

What is the purpose of a streak plate?

A

In order to isolate bacteria from mixed culture and create a pure culture.

26
Q

How does a T streak work?

A

We want to dilute the bacteria into different section so the bacteria is streaked across the surface of the agar in order to grow single colonies.

27
Q

What are transient microbes?

A

These are skin contaminants that are temporarily present but maybe pathogenic

28
Q

What are residential microbes?

A

These are permanent, normal contaminants of humans, usually not pathogenic.

29
Q

Name 4 types of microbes in our normal flora

A

Corynebacterium diphtheriae
Staphylococcus aureus
Micrococcus luteus
Staphylococcus epidermidis

30
Q

What do endospores encapsulate?

A

DNA and cell components

31
Q

What is quality control?

A

In order to make sure we are being accurate, we have to include quality control slides to make sure our reagents are working correctly.

32
Q

What is a plate count?

A

A technique used to determine the number of bacteria in an unknown sample

33
Q

How is bacterial plate count important to the food industry?

A

It will determine quality of food

34
Q

What is the number for kilo?

A

1000

35
Q

What is the number for milli?

A

-1000

36
Q

What is the base unit?

A

10

37
Q

What is a micro unit?

A

10^-6

38
Q

What is a nano unit?

A

10^-9

39
Q

What is a diluent?

A

the fluid used to dilute the concentrated sample

ex: water

40
Q

What is an aliquot?

A

The smaller volume that is taken from a bigger sample

ex: e.coli

41
Q

What volume do we use P1000 for? What colored tip?

A

200-1000 microliters.. blue tip

42
Q

What volume do we use P200 for? What colored tip?

A

20-200 microliters.. yellow tip

43
Q

We use P1000 in lab to place ______ in centrifuge.

A

water

44
Q

We use P200 in lab to place ______ in centrifuge

A

e. coli

45
Q

Why do we have to spread plate?

A

To evenly spread liquid culture onto an agar plate

46
Q

Why do we have to test bacterial growth characteristics?

A

So that we know which specific environmental conditions the microbes succeed in

47
Q

What is a strict aerobe?

A

A microbe that cannot exist without oxygen, it requires it to grow

48
Q

What is a strict anaerobe?

A

A microbe that cannot exist with oxygen presence. Oxygen would be toxic

49
Q

What is facultative anaerobe?

A

A microbe that can grow in both the presence or absence of oxygen

50
Q

What is a thioglycolate medium?

A

a medium that may be used in two ways: to grow microorganisms under anaerobic conditions, and to test for the oxygen requirement of a bacterium. It is a differential medium that allows one to differentiate among species according to their oxygen requirements.

51
Q

What temperature is mesophile best in?

A

10-48 C

52
Q

What temperature is psychrophile best in?

A

-8 - 18 C

53
Q

What temperature is thermophile best in?

A

40-70 C

Microbiology 211 Lab (5 decks)

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