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Microscopy
Microbiology
Question | Answer |
---|---|
Most common length units in microbiology are : | micrometer (µm) nanometer (nm) |
Compound light microscope uses: | Visible light |
Compound light microscope contains two lenses : | Ocular • 10X (most common) |
– Objective (in a revolver) | 4X, scanning • 10X, low-power • 40X, dry high-power • 100X, Oil-immersion high power |
4X | scanning |
10X | low power |
40X | dry high power |
100X | oil-immersion high power |
Magnification = | ocular 10 x times objective |
Resolution or (resolving power) | is the ability to distinguish fine detail between two points |
Resolution of brightfield microscope | 0.2um |
Human eye resolution | 0.2 mm |
• Resolution of electron microscope | 0.5nm |
– The shorter the wave length the______________. | the higher the resolution |
Long wevelength | light |
Short wevelength (electrons) | electrons |
field of vision for 4x | |
Long wevelength | light |
Short wevelength (electrons) | electrons |
Field of vision for 4x | 5 |
Field of vision for 10x | 2 |
Field of vision for 40x | 0.5 |
Field of vision for 100x | 0.2 |
Numerical aperture (NA) setting | Match NA of objective lens in use with NA of iris diaphragm in condenser |
Numerical aperture (NA) setting gives the specimen : | Better resolution and contrast |
Refraction is the: | the change in direction of a wave (light) due to a change in its transmission medium (air, glass, water, etc.) |
Without immersion oil | most light is refracted and lost |
Refractive index | Light-bending ability of a medium |
Electron beam is located on the | electron microscope |
The Light microscope 's highest magnification is : | 1000 x |
The Light microscope's Resolution is : | 0.2um |
The Light microscope's Radiation source is | Visible light |
The Light microscope's Lenses are: | Glass |
The electron's microscope's highest magnification is: | >100,000 |
The electron's microscope's resolution is | 0.5nm |
The electron's microscope's radiation source is | electrons |
The electron's microscope's lenses are: | electromagnet |
Preparation of bacterial specimens for brightfield microscopy include: | 1. Smear microorganisms onto slide 2. Fixing 3. Flood with stain 4. Washing 5. Drying 6. Microscope observation |
Smear | A thin film of a solution of microbes on a slide |
What are the most common heat-fixing? | Alcohol or heat |
What does heat-fixing do? | – Attaches microorganisms to slide – Kills microorganisms – Preserves structures with minimal distortion |
Chromophore is the positive ion • Chromophore attaches to negatively charged surfaces | Basic dyes |
Chromophore is the negative ion • Chromophore attaches to positively charged surfaces | Acidic dyes |
The colored ion is named the | chromophore |
Positive chromophore the dye: | penetrates the cell |
Negative Chromophore the dye: | does not penetrate the cell |
Basic (positive chromophore) typse of dyes are: | – Methylene blue – Fuchsin – Crystal violet – Safranin |
Acid dyes (negative chromophore) types of dyes are: | Nigrosin (China/India ink) – Eosin – Rose bengal |
Simple stains are rarely used and: | Highlight the entire microorganism Cell shape and Arrangement of cells |
Only one dye (basic) is used: | simple stain |
Differential Stains | Used to differentiate bacteria – Gram stain – Acid fast |
T/F Different bacteria respond differently to different stains | true |
Christian Gram | developed gram staining in 1884 |
not part of the original stain by Christian Gram) | Counterstain |
No lipid coat | gram positive |
Lipid coat present | gram negative |
Gram positive cells have a thick peptidoglycan coat that: | –Prevents CV-I complexes from exiting the cell |
Gram negative cells have a lipid coat and a thin peptidoglycan coat and | Alcohol disrupts the lipids, and the thin peptidoglycan coat does not stop CV-I complexes from exiting |
T/F Some bacteria stain poorly or not at all. | true. |
Why do older cultures of gram-positive bacteria give inconsistent results? | because of the degradation of peptidoglycans |
In acid fast staining Bacteria of the genus___________has a coat of waxy material. | Mycobacterium |
After staining with carbol-fuchsin (red), the red color persists after washing with | acid-alcohol (acid fast) |
Carbol-fuchsin is washed off from bacteria without the waxy coat (non-acid fast) | Red color disapears – Cell stained with a conunterstain, usually methylene blue |
What are the names of 3 type of special staining? | Negative staining, Endospore staining,Flagella staining |
Negative Staining: | – Stains background, not cell |
Endospore staining: | Heat to drive malachite green into endospore |
Flagella staining: | – Use of a mordant to widen flagella |