Microbiology: an Introduction Chapter 3 Study Deck

What microscope would be best to observe a stained bacterial smear
Compound light microscope
What microscope would be best to observe unstained bacterial cells, the cells are small and no detail is needed?
Darkfield microscope
What microscope would be best to observe unstained living tissue when it is desirable to see some intracellular detail?
Phase-contrast microscope
What microscope would be best to observe a sample that emits light when illuminated with ultraviolet light?
Fluorescence microscope
What microscope would be best to observe intracellular detail of a cell that is 1µm long?
Electron microscope
What microscope would be best to observe unstained live cells in which intracellular structures are shown in color?
Differential interference contrast microscope
The standard unit of length is?
the meter
Microorganisms are measure in?
Micrometers, µm (10-6m) or Nanometers, nm (10-9m)
A simple microscope has how many lenses?
A compound lens has how many lenses?
The most common microscope used in microbiology is?
The compound light microscope.
How is the total magnification of an object as seen through a microscope measured?
By multiplying the magnification of the objective lens by the magnification of the ocular lens.
What kind of light is used with a compound microscope?
Visible light
The maximum resolving power (the ability to distinguish two points) of a compound light microscope is? Maximum magnification?
0.2 µm/2000x
Why are specimens stained?
To increase the difference between the refractive indexes of the specimen and the medium
Why is immersion oil used?
Immersion oil is used with an oil immersion lens to reduce light loss between the slide and the lens
How is a stained smear best observed?
Brightfield illumination
What is the best way to observe unstained cells?
Darkfield, phase contrast, or DIC microscopy
What is seen in a darkfield microscope?
A light silhouette of an organism against a dark background
When is a darkfield microscope best?
For detecting the presence of extremely small organisms
How does a phase-contrast microscope work?
It brings direct or reflected or diffracted light rays together (in phase) to form an image of the specimen on the ocular lens
What is a phase-contrast microscope best for?
It allows detailed observation of living organisms
What kind of image does a Differential Interference Contrast microscope provide?
A colored three-dimensional image
What is a Differential Interference Contrast microscope best for?
It allows detailed observation of living organisms
How does a fluorescence microscope work?
The specimen is first stained with fluorochromes and then view through a compound microscope using ultraviolet light.
How do specimens look through a fluorescence microscope?
Objects appear bright against a dark background. (like a velvet painting)
What is the primary use of a fluorescence microscope?
In a diagnostic procedure called flourescent-antibody (FA) technique or immunoflourescence.
How does confocal microscopy work?
A specimen is stained with a flourescent dye and illuminated with short-wavelength light. Then the two and three-dimensional images are process by computer for the complete picture
How does two photon microscopy work?
Specimens are stained with a flourescent dye and then illuminated with long-wavelength light.
How does a scanning acoustic(SAM) microscope work?
The interpretation of sound waves through a specimen
What is a scanning acoustic microscope used for?
To study living cells attached to the surfaces such as cancer cells, artery plaque, and biofilms.
What is staining?
Coloring a microorganism with a dye to make some stuctures more visible
What is fixing?
Using heat or alcohol to kill and attach mocirorganisms to a slide
What is a smear?
A thins film of material used for microscopic examination
What kind of stain is used for bacteria?
The colored positive ions of a basic dye will stain bacterial cells
What is used to stain the background of a bacterial smear?
The colored negative ions of an acidic dye will stain the background of a bacterial smear
What is a simple stain?
An aqueous or alcohol solution of a single basic dyes.
Why is a simple stain used?
To make cellular shapes and arrangements visible
What might be used to improve a simple stain?
A mordant might be used to improving the bond between the stain and the specimen
What are differential stains, such as Gram and acid-fast stains used for?
They are used to differentiate bacteria according to their reactions to the stains
What stains are used in the Gram Staining Procedure?
Crystal Violet - Primary
Iodine - Mordant
Alcohol - decolorizer
Fuchsin - Secondary
How are the results of a Gram Staining read?
Gram + retain the purple coloring of the CV after the decolorizing, while the Gram - do not but appear but turn pink from the Fuchsin.
How are the results of an Acid-Fast Staing read?
Acid-fast microbes,such and members of the genera Mycobacterium and Nocardia, retain carbolfuchsin after acid-alcohol decolorization and appear red; non acid-fast microbes take up the methylene blue counterstain and appear blue.
What is the purpose of Negative Staining?
It is used to make microbial capsules visible. The endospore stain and the flagella stain are special stains that color only certain parts of the bacteria.