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BIOL 2P98 > Ch 2 & 3: Microscopy & Laboratory culture of microorganisms > Flashcards

Ch 2 & 3: Microscopy & Laboratory culture of microorganisms Flashcards

1
Q

what are microscopes are used for

A

magnify an image and increase resolution

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2
Q

What is resolution

A

ability to distinguish 2 adjacent objects as distinct + separate

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3
Q

Whats the benefit of better resolution

A

more detail

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4
Q

What is the resolution of the human eye

A

~100 um

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5
Q

what lense does compound light microscope have

A

2 lenses - objective + ocular

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6
Q

in compound light microscope, where is the light source focus

A

focused on the specimen by a condenser

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7
Q

what does resolution depend on

A

wavelength and light gathering ability of the lens

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8
Q

what does immersion oil do

A

increase light that enters the lens

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9
Q

how do you find total magnification

A

objective magnification x ocular magnification

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10
Q

what is a bright field microscope

A

range of techniques used for illumination of samples in light microscopes

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11
Q

Why are staining dyes used

A

to increase contrast for bright-field microscope

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12
Q

what is the charge of most dyes

A

positive charges - theyre basic in nature

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13
Q

how do staining dyes work

A

dyes are positively charged, they bind to negatively charged cell components (nucliec acids, proteins etc)

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14
Q

what is a differential stain

A

stain different kinds of cells different colors

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15
Q

most common differential stain

A

gram stain

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16
Q

gram stain divided bacteria into what groups

A

gram-positive (purple)
Gram - negative (pink)

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17
Q

what do gram stains happen

A

due to differences in cell wall structures

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18
Q

where are acid fast stains used

A

used to identify acid fast organisms

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19
Q

What does mycolic acid do

A

attaches to cell wall surface, producing wax like hydrophobic coating

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20
Q

What color is the initial stain and counterstain

A

red and bluw

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21
Q

what does initial stain do

A

penetrates and is retained by mycolic acid (red) , the other cells destain and take up the blue counterstain

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22
Q

what is the best resolution with light microscope

A

~0.2uM

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23
Q

how are specimens visualized in a bright field microscope

A

slight differences in contrast between them and the surroundings

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24
Q

Can we see bacterial in a bright-field miscroscope

A

Typically difficult to see bacterial cells, unless the organisms are pigmented

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25
Q

some examples of staining dyes

A

methylene blue, crystal violet, safranin

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26
Q

What is a gram stain positive bacteria

A

thick cell wall

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27
Q

what does gram stain negative bacteria

A

thin cell wall

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28
Q

Types of light microscopy

A

phase contrast and dark field

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29
Q

In phase contrast microscope, how do different materials show light

A

by different amount

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30
Q

In phase contrast microscope, what is used to increase contrast between background and specimen

A

phase ring amplifier

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31
Q

In phase contrast microscope, what is the contrast like

A

dark cells on light background

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32
Q

in dark field microscope, how does light reach specimen

A

central portion of light beam is blocked, light only reaches from the sides

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33
Q

in dark field microscope, what is the contrast like

A

light cells on a dark background

34
Q

in dark field microscope, what light reaches the lens

A

only light scattered by the specimen

35
Q

what is fluorescence

A

emission of light of one colour after absorbing light of another colour

36
Q

why does fluorescence occur

A

Occurs due to excitation of electrons to a high-energy state

37
Q

when will cells fluorescence

A

due to naturally fluorescent substances

38
Q

examples naturally fluorescent substances

A

Chlorophyll emits red fluorescence

39
Q

if cells don’t have naturally occurring fluorescent dye, how can they get dyed

A

by getting stained with a fluorescent dye. Egm DAPI binds with DNA and emits blue light

40
Q

How does a differential interference contrast or DIC

A

uses a polarizer and prism to generate 2 distinct beams of light that pass through the specimen then are recombines

41
Q

How does differential interface contrast (DIC) make cells appear

A

3d appearemce

42
Q

How does confocal scanning laser micrscopy work

A

using a computerized microscope coupled with a laser source to generate a 3D image

43
Q

How does the computer in confocal scanning laser micrscope focus on specimen

A

can focus on single layers

44
Q

how can different layers be viewed in confocal scanning laser micrscopy

A

they can be compiled to construct to 3D image

45
Q

in confocal scanning laser micrscopy, how can you observe cells in different layers

A

in bacterial biolfilm

46
Q

in confocal scanning laser microscopy, what is the resolution improved to

A

0.1 micrometeres

47
Q

How does the electron microscope work

A

uses electrons instead of visible light (photons) to image cells and cell structures

48
Q

what has shorter wavelengths, electrons or photons

A

electrons

49
Q

what is the signficance of the length of wavelength and image resolution

A

shorter wavelength = better resolution

50
Q

Can electrons penetrate

A

yes, but they are poor at it

51
Q

How can you use an electron microscope to view the internal cell structures

A

you would need thin sections of the cell because a single cell is too thick

52
Q

what are the 2 types of electron microscopes

A
  1. Transmission
  2. Scanning
53
Q

How does the transmission electron microscope work

A

electron beam passes through ultrathin tissues sections of cell or very small specimens

54
Q

In transmission electron microscope , what are samples first stained with

A

high atomic weight stains

55
Q

Why is high atomic weight stain used in transmission electron microscope

A

allows electrons to pass more freely in areas that bind less. they absorb energy from the electron beam

56
Q

what is the resolution of transmission electron microscope

A

0.2 nm

57
Q

what is the fold improvement of transmission electron microscope

A

1000

58
Q

How does the scanning electron microscope work

A

electron beam scans back and forth and the scattered electrons are collected and projected onto a monitor to produce an imag

59
Q

What color are the images in electron microscope

A

black/white but fake colour can be added

60
Q

how do you prep a specimen for electron microscope

A

coat it with thin film of heavy metal

61
Q

what can you view of the object with electron microscope

A

the surface

62
Q

what is required to culture microbes in lab

A

all nutrients required for growth

63
Q

what are nutrienta

A

compounds of chem elements that can be used by the cell to support growth and metabolism

64
Q

In what amounts are macronutrients needed

A

large

65
Q

in what amounts are micronutrients needed

A

small

66
Q

what are the essential elements

A

CHONPSSe
Carbon, hydrogen, oxygen, nitrogen, phosphate, sulfur selenium

67
Q

What is culture media

A

nutrient solution used to grow microorgs in labs

68
Q

what is a defined media

A

contains precise amounts of pure chemicals in distilled water where the exact composition is known

69
Q

What are complex media made from

A

digests of microbial, animals or plants

70
Q

in complex media, is the nutrient composition known

A

yes but not precisely

71
Q

what are some examples of digests of microbes/animals/planst

A

casein - milk protein, beef extract, tryptic soy broth, yeast extract etc

72
Q

what is selective media

A

contains compounds that inhibit the growth of some microorgs but not others

73
Q

what is differential media

A

contains compounds or additives that allow microorgs to be distinguised by the appearance of colony or surrounding media

74
Q

what are enriched media used for

A

nutritionally demanding microbes

75
Q

what do enriched media contain

A

complex media plus additives like serums or blood

76
Q

examples of enriched media

A

chocolate agar and blood agar

77
Q

what does the blood agar distinguish between

A

hemolytic and non hemolytic bacteria

78
Q

how do you prepare a culture media before use

A

by sterilizing it. by heating in an autoclave

79
Q

how are liquid culture media solidified

A

by adding 1-2% agar and poured into sterile petri plates

80
Q

what does a solid media do to the cells

A

immobilizes cells, allowing them to grow and form isolated masses called coloniess

81
Q

what are colonies

A

isolated masses

BIOL 2P98 (8 decks)

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