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MCIM 224 > 2 Intro to the Bacteria, Microscopy & Staining > Flashcards

2 Intro to the Bacteria, Microscopy & Staining Flashcards

1
Q

Diff b/w eukaryotes and prokaryotes?

A

Eukaryote: Cells contain membrane-bound organelles

Prokaryote: Cells lack internal membrane-bound nucleus and other organelles

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2
Q

Name 5 microorganisms, and indicate whether they’re prokaryotic, eukaryotic, or neither.

A
  1. Bacteria (prokaryotic)
  2. Fungi (eukaryotic)
  3. Algae (eukaryotic)
  4. Parasites (eukaryotic)
  5. Viruses (neither)
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3
Q

Name the 3 Domains/Kingdoms of life.

A
  1. Eukarya (eukaryotic)
  2. Bacteria (prokaryotic)
  3. Archaea (prokaryotic)
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4
Q

Name two characteristics of archaea.

A
  1. Inhabit extreme envirs

2. Don’t cause human diseases

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5
Q

Earliest lifeforms on the Earth?

A

Bacteria

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6
Q

How are bacteria named?

A

They have binomial nomenclature:

  1. Genus
  2. Species
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7
Q

How do we name bacteria that have identical genus and species but are slightly different from each other?

A

By adding a “strain” name to their binomial name.

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8
Q

T or F: Bacteria are usually only referred to by their genus, species, and strain. Rarely do we consider their other taxonomic categories (e.g. their phylum, class, order, etc.)

A

T

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9
Q

What’s the value of bacterial taxonomy? (3)

A
  1. Consistency of communication
  2. Assess relatedness of diff bacteria
  3. For medical practice
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10
Q

T or F: All strains of E. Coli cause the same disease

A

F

Diff strains of a bacteria can cause completely diff diseases.

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11
Q

Up to what magnification can light microscopy reach?

A

1000x magnification

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12
Q

T or F: Light microscopy is sufficient for most routine bacterial observations.

A

T

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13
Q

Up to what magnification can electron microscopy reach?

A

200,000x

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14
Q

Main drawback of electron microscopes?

A

Expensive, thus limited use

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15
Q

2 advantages and 1 disadvantage of staining for light microscopy?

A

Advantage: Increase contrast of specimen
Advantage: Preserve specimen for future observation
Disadvantage: Staining kills microbe

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16
Q

What method can be used so that the microbe ISN’T killed in the process of preparing it for observation via light microscopy?

A

Hanging Drop method (aka “wet mount”)

17
Q

Disadvantage of wet mount?

A

Poor contrast

18
Q

Advantage of wet mount?

A

Observe microbe movement.

19
Q

Term for a coloured dye that binds to bacterial cells?

A

Stain

20
Q

What’re the three steps involved in staining bacteria?

A
  1. Smear layer of bacteria on glass slide
  2. Fix the smear by air drying + mild heating
  3. Flood fixed smear w/ dye and wash unbound dye away
21
Q

What step of staining kills the bacteria?

A

Air drying + heating the smeared slide

22
Q

What’re the 3 types of stains?

A
  1. Simple stain
  2. Differential stain
  3. Special stain
23
Q

Describe the simple stain.

A

a. A single dye is used
b. All bacteria appear as same colour
c. Cannot tell if diff species are present

24
Q

Name two types of differential stains.

A
  1. the Gram Stain

2. the Acid-Fast Stain

25
Q

Describe the steps of the Gram Stain (only the steps after heat-fixing the bacteria) (4)

A
  1. Flood heat-fixed smear w/ purple stain (all cells = purple)
  2. Add iodine (iodine allows stain to bind better; all cells are still purple)
  3. Decolourize cells w/ alcohol (Gram neg. cells become colourless)
  4. Counterstain w/ red dye (Gram neg. cells become red)
26
Q

What colour is a Gram positive cell?

A

Purple

27
Q

What colour is a Gram negative cell?

A

Red

28
Q

T or F: Most bacterial species are “acid-fast”

A

F

Most are, in fact, NOT acid-fast

29
Q

What’s the main difference b/w the acid-fast stain and the Gram stain?

A

The de-colourizing step - acid-fast stains use a harsher de-colourizing step (it uses acid-alcohol instead of alcohol)

30
Q

Give an example of a bacteria that is acid-fast.

A

Mycobacterium tuberculosis

31
Q

T or F: The dye of acid-fast bacteria are decolourized during the decolourizing step of acid-fast stains

A

F

Acid-fast bacteria are cannot be decolourized, and so remain the same colour (red) throughout the procedure

32
Q

What are special stains used for?

A

To see structures that’re not normally seen using light microscopy

33
Q

Give two structures that can observed using special stains.

A
  1. Spores

2. Flagella

34
Q

What is a “pure culture”?

A

A pop of bacteria consisting of only ONE species or strain.

All bacteria are genetically identical to one another.

35
Q

What method is used to get a pure culture of bacteria?

A

the “streak plate” method

36
Q

How can diff bacterial species be distinguished on an agar surface?

A

By “colony morphology”

MCIM 224 (25 decks)

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