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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 |
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