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HLSC 124 - Microbiology for Health Professionals > Chapter 3 - Observing Microorganisms Through a Microscope > Flashcards

Chapter 3 - Observing Microorganisms Through a Microscope Flashcards

1
Q

Ocular Lens/Eyepiece

A

-remagnifies the image formed by the objective lens
-the part you look through

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2
Q

Body Tube

A

-transmits the image from the objective lens the the ocular lens

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3
Q

Objective Lenses

A

-primary lenses that magnify the specimen
-the rotating piece with different magnifications

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4
Q

Stage

A

-holds the microscope slide in position

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5
Q

Condenser

A

-located underneath the stage
-focuses light through the specimen

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6
Q

Diaphragm

A

-controls amount of light entering the condenser

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7
Q

Illuminator

A

-light source

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8
Q

Total Magnification

A

-calculated by multiplying the objective lens magnification by the ocular lens magnification

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9
Q

Resolution (aka resolving power)

A

-ability of lenses to distinguish fine detail and structure

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10
Q

Refractive Index

A

-a measure of the light-bending ability of a medium

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11
Q

Electron Microscope

A

-beam of elections is used instead of light
-resolving power is greater

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12
Q

Staining

A

-colouring the microorganisms with a dye that emphasizes certain structures
-the structures must be fixed (attached) to the slide

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13
Q

Stain Composition

A

-salts composed of a positive and negative ion

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14
Q

Smear

A

-thin film containing the microorganism

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15
Q

Chromophore

A

-either the positive or negative ion that is coloured

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16
Q

Basic Dyes

A

-most common stain used in microbiology
-dyes in the cation (positive ion)

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17
Q

Acidic Dyes

A

-rarely used in microbiology
-dyes on the anion (negative ion)
-ie. Glycocalyx Satin

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18
Q

Why is basic dye more popular?

A

-bacteria are slightly negatively charged at pH 7
-the coloured cation in a basic dye is attracted to the negatively charged bacterial cell

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19
Q

Why is acidic dye less common?

A

-not attracted to most types of bacteria because the dyes negative ions are repelled by the negatively charged bacteria surface
-stain colours the background instead

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20
Q

Negative Staining

A

-preparing colourless bacteria against a coloured background
-valuable for observing cell shapes, sizes, and capsuls

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21
Q

Simple Stain

A

-aqueous or alcohol solution composed of one basic dye
-used to highlight the entire microorganism
-recognizes shape and structure
-too simple for healthcare

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22
Q

Mordant

A

-chemical added to the solution to intensify the stain
-makes it darker, hold the stain, or enlarge the specimen

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23
Q

2 Functions of a Mordant

A

1) Increased the affinity of a stain
2) Coat a structure (ie. flagellum)

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24
Q

Differential Stains

A

-react differently with different kinds of bacteria
-can be used distinguish them
-2 types: Gram stain and acid-fast stain

25
Q

Gram Stain

A

-developed by Hans Christian Gram
-classifies bacteria into two large groups: Gram-positive and gram-negative

26
Q

Gram Stain Procedure Step 1

A

-Primary stain
-Crystal violet
-smear is covered with this purple and colours all cells
-Results: both bacteria turn purple

27
Q

Gram Stain Procedure Step 2

A

-Mordant
-Iodine
-the purple dye is washed off and the smear is covered with iodine
-Results: both bacteria turn purple

28
Q

Gram Stain Procedure Step 3

A

-Decolourizing Agent
-Acetone alcohol
-the slide is washed with alcohol solution
-removed purple from the gram negative cells
-gram positive cells remain purple

29
Q

Gram Stain Procedure Step 4

A

-Counterstain
-Safranin (red)
-alcohol is rinsed off and the slide is stained with red dye
-smear is washed and examined
-Results: gram positive remains purple, gram-negative turns red/pink

30
Q

Gram-positive Bacteria

A

-retain the purple colour after alcohol has attempted to decolourize

31
Q

Gram-negative Bacteria

A

-bacteria that lose the purple colour after decolorization
-made visible after losing colour by Safranin

32
Q

What differs between gram-positive and gram-negative?

A

-because of structural differences in the cell walls
-affect the retention or escape of the crystal violet-iodine (CV-1) complex

33
Q

Gram-positive Bacteria explanation

A

-have a thicker peptidoglycan layer
-CV-1 complex is larger
-compound gets stuck and can’t be decolourized

34
Q

Gram-negative Bacteria explanation

A

-have a thinner peptidoglycan layer
-have a lipopolysaccharide layer in their cell wall
-alcohol wash disrupts outer lipopolysaccharide layer and CV-1 complex is washed out

35
Q

CV-1

A

-crystal violet or iodine alone are water soluble and drain out of the cell
-CV-1 is insoluble in water so it doesn’t easily leave the cell wall

36
Q

Antibiotics

A

-gram + easily killed by some antibiotics while gram - are more resistant since antibiotics can’t penetrate lipopolysaccharide layer

37
Q

Acid-Fast Stain

A

-binds strongly only to bacteria that have a waxy material (Mycolic acid) in their cell walls
-used to detected Mycobacterium tuberculosis and Mycobacterium leprae (leprosy)

38
Q

Acid-Fast Stain Procedure Step 1

A

-primary stain
-carbolfuchsin (red dye) applied to slide and heated for several minutes
-results: both cells appear red

39
Q

Heating Smears

A

-increases penetration and retention of the dye

40
Q

Acid-Fast Stain Procedure Step 2

A

-Decolorization
-acid-alcohol
-slide is cooled and washed with water
-acid-alcohol removes red stain from bacteria that are not acid-fast

41
Q

Why do acid fast keep their colour?

A

-carbolfuchsin is more soluble in the cell wall lips than in the acid-alcohol

42
Q

Why do non-acid fast lose their colour?

A

-cell wall lacks lipid components
-able to decolourize leaving cells colourless

43
Q

Acid-Fast Stain Procedure Step 3

A

-counterstain
-methylene blue
-smear is stained with blue dye
-non-acid-fast cells appear blue
-acid-fast remain red

44
Q

So which cells would be positive for TB/Leprosy?

A

-the red acid-fast cells would be positive for the pathogen
-the blue cells are just tissue cells

45
Q

Special Stains

A

-used to colour parts of microorganisms such as endospores, flagella, or capsules

46
Q

Capsule Stain (Negative Staining)

A

-determines the organisms virulence
-capsular materials are water soluble and may be dislodged during washing (makes this stain difficult)
-glycocalyx (acid stain)
-a quick stain

47
Q

Capsule

A

a gelatinous covering of a microorganism

48
Q

Virulence

A

-the degree to which a pathogen can cause disease

49
Q

Capsule Stain Procedure Step 1

A

-acidic stain
-colours the background (negative stain)
-uses India ink or nigrosin to colour background dark blue
-allows cells to shine through

50
Q

Capsule Stain Procedure Step 2

A

-Water wash
-negative results can occur from capsular materials washing away

51
Q

Capsule Stain Procedure Step 3

A

-simple stain
-Safranin (red dye)
-capsules don’t accept most dyes and thus appear as halos surrounding the red cells

52
Q

Endospore (spore) Staining

A

-7ish min stain
-require special stain cause simple dyes don’t penetrate endospores wall

53
Q

Endospore

A

-resistant, dormant structure formed within a cell that protects it from adverse environments

54
Q

Endospore Stain Procedure Step 1

A

-primary stain
-malachite green
-applied and heated for 5mins

55
Q

Endospore Stain Procedure Step 2

A

-water wash
-removes the green from all the cells parts except endospores

56
Q

Endospore Stain Procedure Step 3

A

-counterstain
-safranin
-stains portions of the cell other than endospores
-endospores appear green within the red cell

57
Q

Flagella Stain

A

-tedious and delicate procedure
-2 min stain
-flagella are delicate and can break off easily, resulting in a misdiagnosis

58
Q

Flagella

A

-structures of movement too small to be seen under light microscope without staining

59
Q

Flagella Stain Procedure

A

-carbolfuchsin (red) and a dark red mordant (potassium alum) are used to build up the flagella diameters until they become visible

HLSC 124 - Microbiology for Health Professionals (18 decks)

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