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Microbiology > Chapter 1 lecture 3 > Flashcards

Chapter 1 lecture 3 Flashcards

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Biology 101 flashcards
1
Q

Microscopy

A

microorganisms range in size from

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2
Q

microorganisms range in size from

Smallest=

A

nanometers (nm)

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3
Q

microorganisms range in size from
Largest=

A

protists (μm)

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4
Q

Colony is a ____ culture

A

pure culture

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5
Q

Magnification

A

ability to enlarge objects

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6
Q

Resolving power

A

ability to show detail

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7
Q

Magnification in most microscopes results from

A

an interaction between visible light waves and the curvature of a lens.

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8
Q

focal point

A

focus light rays at a specific
place

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9
Q

focal length

A

distance between center of
lens and focal point

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10
Q

strength of lens is related to the ____

A

the focal length

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11
Q

Refraction

A

bending of light when passing from one medium to another

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12
Q

Refractive index

A

measure of how greatly a substance slows the velocity of light

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13
Q

Direction and magnitude of bending is determined by

A

the refractive indices of the two media forming the interface (i.e., glass and air)

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14
Q

Glass has a _______ refractive index than air

A

higher

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15
Q

The Light Microscope Types

A

bright-field microscope
dark-field microscope
phase-contrast microscope
fluorescence microscope
confocal microscope

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16
Q

Modern microscopes are all _________ microscopes

A

compound (more than 1 lense)

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17
Q

The Bright-Field Microscope

A

Both stained and unstained

produces a dark image against a brighter background

has several objective lenses
parfocal microscopes

total magnification
- product of the magnifications of the ocular lenses and the objective lenses

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18
Q

Resolution

A

ability of lens to distinguish small objects that are close together

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19
Q

shorter wavelength –>

A

greater resolution

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20
Q

blue light 450 – 500 nm can not resolve structures smaller than ______

A

0.2 um

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21
Q

Numerical aperature

A

ability of the lens to gather light

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22
Q

Numerical aperture of lens ranges from

A

0.1 to 1.25

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23
Q

Shorter wavelength and larger numerical aperture will provide better ______

A

resolution

24
Q

Refractive index

A

how much a substance bends a light ray

25
Q

The refractive index of air is 1.00 if we increase this by using immersion oil, we can increase the ______________________

A

numerical aperture

26
Q

Why can smaller working distances give better resolution?

A

A smaller working distance can better separate close objects because the light spreads out more

27
Q

Immersion oil

A

Brings more light comes to the lense which increases numerical aperture

28
Q

working distance

A

distance between the surface of lens and the surface of cover glass or specimen when it is in sharp focus

29
Q

The Dark-Field Microscope

A

image is formed by light reflected or refracted by specimen

produces a bright image of the object against a dark background

used to observe living, unstained preparations

30
Q

How to do Dark Field Microscopy

A

Uses a hollow cone of light so that only light that has been reflected or refracted by the specimen enters the lens

31
Q

Examples of Dark-Field Microscopy

A

Treponema pallidum and Volvox

32
Q

The Phase-Contrast Microscope

A

Uses slight differences in refractive index and cell density

Uses a hollow cone of light

Cone of light passes through a specimen some is retarded (out of phase).

Light passes through phase plate brining it back into phase excellent way to observe unstained, living cells

33
Q

Examples of Phase-Contrast Microscopy

A

Pseudomonas sp., Amoeba, Paramecium

34
Q

The Differential Interference Contrast Microscope (DIC)

A

Similar to phase-contrast - creates image by detecting differences in refractive indices and thickness of different parts of specimen

Uses two beams of polarized light to create a 3D image of specimen

excellent way to observe living cells
- live, unstained cells appear brightly colored and three-dimensional

35
Q

Example of Differential Interference Contrast Microscopy

A

Amoeba proteus

36
Q

The Fluorescence Microscope

A

developed by O. Shimomuram, M. Chalfie, and R. Tsien
exposes specimen to ultraviolet, violet, or blue light
specimens usually stained with fluorochromes (fluorescent dyes)
shows a bright image of the object resulting from the fluorescent light emitted by the specimen
has applications in medical microbiology and microbial ecology studies

37
Q

Immuno-Fluorescence

A

antibody and fluorochrome combine

these then bind to the cell surface antigen molecules of a bacterial cell

38
Q

Cells stained with fluorescent dyes

A

Can identify living, dead, population size, and strain

39
Q

Confocal Microscopy

A

Uses lazer to focus on different depths of a sample, take photos of the depths to create a 3-D image

Specimen is usually fluorescently stained

Numerous applications including study of biofilms

40
Q

Preparation for optical microscopes requires

wet mounts and hanging drop mounts which allow

A

examination of characteristics of live cells: size, motility, shape, and arrangement

41
Q

Preparation and Staining of Specimens

A

Increases visibility of specimen.

Accentuates specific morphological features.

Preserves specimens.

42
Q

Fixation/ Smear Preparation

A

Preserves internal and external structures and fixes them in position.

Organisms usually killed and firmly attached to microscope slide.

43
Q

Heat fixation

A

Routinely used with bacteria and archaea.

Preserves overall morphology but not internal structures.

44
Q

Chemical fixation

A

Used with larger, more delicate organisms.

Protects fine cellular substructure and morphology.

45
Q

Basic dyes have ______ charges.

A

Positive

46
Q

Acid dyes have ______ charges

A

Negative

47
Q

Simple stains

A

A single stain is used.

Use can determine size, shape, and arrangement of bacteria.

Negative stain.

48
Q

Differential Staining

A

Divides microorganisms into groups based on their staining properties.

For example, Gram stain.

For example, acid-fast stain.

49
Q

Gram Staining

A

Most widely used differential staining procedure.

Divides bacteria into two groups, Gram-positive and Gram-negative, based on differences in cell wall structure.

50
Q

Acid-Fast Staining

A

Particularly useful for staining members of the genus Mycobacterium.

For example, Mycobacterium tuberculosis—causes tuberculosis.

For example, Mycobacterium leprae—causes leprosy.

High lipid content in cell walls (mycolic acid) is responsible for their staining characteristics.

51
Q

Capsule stain used to

A

visualize polysaccharide capsules surrounding bacteria

capsules may be colorless against a stained background

52
Q

Flagella staining uses a

A

Mordant applied to increase thickness of flagella

53
Q

Purple cells are gram ______

A

Positive

54
Q

Red cells are gram ______

A

Negative

55
Q

Endospore staining

A

To identify endospore which indicates which cells are producing them for survival purposes under stressful environments

Microbiology (17 decks)

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