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Microbiology > Microscopy > Flashcards

Microscopy Flashcards

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Biology 101 flashcards
1
Q

Robert Hooke

A

was the first to describe microbes

  • first use of microscope - 1664
  • Illustrated the fruiting structures of molds
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2
Q

Who was the first to describe bacteria and described them as Wee Animacules?

A

Antoni van Leeuwenhoek

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3
Q

Ferdinand Cohn

A

Founded the field of bacteriology and discovered bacterial endospores

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4
Q

Light microscopes

A

used to look at intact cells under relatively low magnification

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5
Q

the ability to distinguish two adjacent objects as separate and distinct and is is determined by the wavelength of light used

A

Resolution

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6
Q

Limit of resolution for light microscope is about

A

0.2 μm

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7
Q

Why are specimens are visualized on bright-field scope?

A

because of differences in contrast (density) between them and surroundings

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8
Q

Two sets of lenses form the image

A

objective lens and ocular lens

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9
Q

Equation total magnification is a product of the magnification of the two sets of lenses

A

Objective magnification X ocular magnification

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10
Q

Maximum magnification is

A

1500X

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11
Q

An easy way to improve contrast

A

Staining

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12
Q

What is staining?

A

Dyes are organic compounds that have different affinities for specific cellular materials
Examples of common stains are methylene blue, safranin, and crystal violet

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13
Q

Recall how to stain

A

From lab/pcuicture

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14
Q

The Gram stain

A

differential stain and mostly used in lab.

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15
Q

Gram-positive bacteria appear ? and gram-negative bacteria appear ? after staining

A

+ purple

- red

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16
Q

Phase-Contrast Microscopy

A

Invented in 1936 by Frits Zernike

  • Phase ring amplifies differences in the refractive index of cell and surroundings
  • Improves the contrast of a sample without the use of a stain
  • Allows for the visualization of live samples
  • Resulting image is dark cells on a light background
17
Q

Dark-Field Microscopy

A

Light reaches the specimen from the sides

  • Light reaching the lens has been scattered by specimen
  • Image appears light on a dark background
  • Excellent for observing motility
18
Q

Fluorescence Microscopy

A

Used to visualize specimens that fluoresce

  • Emit light of one color when illuminated with another color of light
  • Cells fluoresce naturally (autofluorescence) or after they have been stained with a fluorescent dye like DAPI
  • Widely used in microbial ecology for enumerating bacteria in natural samples
19
Q

Differential Interference Contrast (DIC) Microscopy

A

Uses a polarizer to create two distinct beams of polarized light

  • Gives structures such as endospores, vacuoles, and granules a three-dimensional appearance
  • Structures not visible using bright-field microscopy are sometimes visible using DIC
20
Q

Atomic Force Microscopy (AFM)

A

A tiny stylus is placed close to a specimen The stylus measures weak repulsive forces between it and the specimenA computer generates an image based on the data received from the stylus

21
Q

Confocal Scanning Laser Microscopy (CSLM)

A

Uses a computerized microscope coupled with a laser source to generate a three-dimensional image

  • Computer can focus the laser on single layers of the specimen
  • Different layers can then be compiled for a three-dimensional image
  • Resolution is 0.1μm for CSLM
22
Q

Two types of electron microscopes

A

Transmission Electron Microscopes (TEM)

Scanning Electron Microscopes (SEM)

23
Q

Transmission Electron Microscopy (TEM)

A

electrons of the high voltage beam form the image of the specimen

  • Electromagnets function as lensesSystem operates in a vacuum
  • High magnification and resolution (0.2 nm)
  • Enables the visualization of structures at the molecular level
  • Specimen must be very thin (20 –60 nm) and be stained (permanganate or heavy metal salts
24
Q

Scanning Electron Microscopy (SEM)

A

produces images by detecting low energy secondary electrons which are emitted from the surface of the specimen due to excitation by the primary electron beam

  • Specimen is coated with a thin film of heavy metal (e.g., gold)
  • An electron beam scans the objectScattered electrons are collected by a detector and an image is produced
  • Even very large specimens can be observed
  • Magnification range of 15X – 100,000X

Microbiology (12 decks)

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