Ch. 3 Observing Microbes Through The Microscope Flashcards
mm (millimeter)
- 1 × 10^-3 m
* 1,000 of a meter
mcm (micrometer)
1 x 10^-6 m
1 millionth of a meter
nm (nanometer)
1 x 10^-9 m
1 billionth of a meter
What is the average size of a bacterium?
3 mcm
What is the highest magnification of a binocular Compound Light Microscope?
1000x
What magnification do you go to when observing bacteria?
Highest (1000x)
Bacteria are considered to be what type of cell?
Unicellular
When light from a microscope scatters, what does it do to your image?
• Compromises the image quality
What is refraction?
• Bending/scattering of light, includes air (higher the refractive index the more it bends)
What is the purpose of using pure mineral oil?
Causes the refractive index to lower, therefore causing less light to scatter (has a lower refractive index than air)
What’s resolution?
• Clarity and sharpness
What’s contrast?
Range of light and dark values in an image (the greater the range of light/dark values the higher the contrast)
Bright field
- The entire field of view is (lit up) illuminated uniformly
- Ex. paramecium
- Pellicle somewhat distinguishable
- Less distinguished between the inner and outer boarder
- Can see cilia
- Can’t observe nucleus
Dark field
Uses a special condenser with an opaque disk that blocks light from entering the objective lens directly.
- No cilia observed - Vacuoles & nucleus can be seen - Illuminated pellicle but the boarders a fuzzy - Stain introduces and increases contrast - Examine live microorganisms that are either invisible in the ordinary light microscope. Cannot be stained by standard methods
What are the different types of light illumination from the compound light microscope?
- Bright field
- Dark field
- Phase contrast
What are the two types of compound lens?
- Objective
- Highest magnification 100x (oil immersion lens)
- Light scatters bc it hits the small air space
- 4 diff magnification
- Highest magnification 100x (oil immersion lens)
- Ocular
- Fixed magnification @ 10x
What is the resolution limit?
- 0.2 mcm
* Amount of distance btwn two objects before they look like they’re touching
What are the two most common types of electron microscopy (EM)?
- Transmission
* Scanning
What color does each stain for the Gram Stain?
- Gram positive = purple
* Gram negative = pink
Name the two types of helminths?
• Worm & Flukes
What can you focus the electron beams and change their direction with?
Electromagnets
Where is fluorescence generated for the EM?
By the flow of electrons
Give examples of photosynthetic microbes?
Algae & Cyanobacteria
Phase Contrast
- Condenser containing an annular (ring-shaped) diaphragm
- Can observe sharpness and graininess of the internal structures of the cytoplasm
- More defined vacuoles
- Better resolution in the cytoplasm than in the dark field
Clear distinction of the inner and outer pellicle
What does staining introduce?
Contrast
Phase Contrast
- Condenser containing an annular (ring-shaped) diaphragm
- Can observe sharpness and graininess of the internal structures of the cytoplasm
- More defined vacuoles
- Better resolution in the cytoplasm than in the dark field
Clear distinction of the inner and outer pellicle
What does staining introduce?
Contrast
