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44 Cards in this Set
- Front
- Back
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magnification
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Object appears larger than it is
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Resolution/resolving power
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ability to distinguish between adjacent objects
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limit of resolution
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actual measurement of how far apart two points must be for the microscope to view them as being separate
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Field of view
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Portion of sample viewed at given time
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bright-field
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routine work
best resolution ~0.2µm bright background, objects dark (exception: negative stain) |
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Compound microscope
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object magnified twice (2 sets of lenses)
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scanning objective
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40X
4x objective lens x 10x ocular |
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low power objective
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100x
10x objective lens x 10x ocular |
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high power objective
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400x
40x objective x 10x ocular |
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oil immersion
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1000x
100x objective x 10x ocular |
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Why is oil required for 100x objective but not the other objectives?
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Improves the resolution--channels light from slide into objective lens
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Coccus
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Spherical
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Bacillus
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rod-shaped
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vibrio
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crescent
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Spirillum
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Spiral
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Spirochaete
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tight spiral
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Cell arrangement for cocci
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1 to many planes
Diplococci (2 cocci) Streptococci (chain) tetrad (four/1 plane) sarcinae (cube/2 planes) staphylococcus (cluster) |
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Cell arrangement for bacilli
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diplobacilli (2 bacilli/1 plane)
Streptobacilli (chain/1 plane) Coccobacillus (shortened bacilli) |
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What two activities are performed before and after lab?
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Wash hands and disinfect lab table
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Aseptic technique
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without microbes
label flame loop take test tube of inoculum, grasp cap with pinkie of loop hand and remove flame tube mouth insert loop into sample and remove flame open mouth of tube and replace cap take test tube of sterile media and grasp cap with pinkie of loop hand and remove flame mouth of tube insert loop into tube and inoculate flame mouth of tube and replace cap flame your loop |
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Why are plates incubated upside down?
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to prevent condensation buildup within the plate
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What temperature do we typically incubate bacterial cultures at?
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37 degrees Celsius
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What temperature is room temperature?
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~24 degrees Celsius
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Why do we maintain our stock cultures at room temperature rather than 37 degrees Celsius?
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If kept at incubating temperature, the bacteria would grow and die off more quickly. Lowering the temp slows the growth, which will allow them to grow for a longer period
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TSA/TSB
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TSA slant -- agar slant in test tube
TSB broth -- nutrient broth in test tube |
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nosocomial infection
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infections that result from treatment in a hospital or other health care facility
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turbidity
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cloudiness or haziness of a fluid caused by individual particles generally not seen by the naked eye
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Smear preparation
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place a small drop of water on slide
aseptically add bacteria to water allow to air dry heat fix smear |
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simple stain
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staining cells with a colored dye to make them more visible
Crystal Violet (purple), Safranin (yellow), or Methylene Blue (blue) |
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Negative Stain
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Uses a dye solution in which the chromogen is acidic and carries a negative charge. The negative charge on the bacterial surface repels the negatively charged chromogen, so the cell remains unstained against a colored background.
Nigrosin used--purple. Add a drop to slide, add bacteria, spread with clean slide, allow to dry, view. |
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Gram stain
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type of differential stain in which a decolorization step occurs between the aplication of two basic stains
Primary stain: crystal violet Iodine added as a mordant to enhance crystal violet staining Decolorize by alcohol or acetone (gram negative are decolorized, whereas gram positive are not) Gram negative stains then colorized by a counterstain Safranin |
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acid-fast stain
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type of differential stain
Mycolic acid present in certain cell walls gives them a higher affinity for the primary stain and resistance to decolorization by an acid alcohol solution. Two methods, Ziehl-Neelson and Kinyoun. Method: Kinyoun carolfuchsin stains cells Rinse stain with alcohol Counterstain with meth. blue, rinse |
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Endospore stain
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Stain with malachite green
decolorize with water--removes stain from cells, but not spores within capsule safranin for counterstain colors capsule |
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Endospore can ID which genera, and what can they cause?
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Bacillus, Clsotridium
Bacillus can cause anthrax (b. anthracis) Clostridium can cause tetanus (c. tetani), botulism (c. batulinum), gas gangrene (c. perfringens) and pseudomembranous colitis (c. difficile) |
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Acid-Fast can ID which genera?
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Mycobacterium
Can cause leprosy (m. leprae) and tuberculosis (m. tuberculosis) |
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Staphylococcus aureus
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Purple clusters of cocci--gram positive
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Escherichia coli
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Gram negative
pink bacillus, coccobacillus |
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Bacillus subtilis
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Gram positive
purple bacilli |
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rhodospirillium rubrum
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Gram negative
pink spirals |
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Viable count
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counts live cells, since it counts the number of colonies that grow to form colonies
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Why are samples typically diluted before plated?
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To make the necessary calculations, you need isolated colonies, so you have to dilute the number of cells present in the sample.
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Why are samples diluted serially, rather than in one step?
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because of the ratio of dilution, you would need a container which holds nearly 10million milliliters of water to directly dilute.
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Pour plate
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mix cells with media that contains agar which hasn't solidified yet. Then pour mixture into sterile petri plate. Cells grow and form colonies in, on, and under agar.
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Calculations for Quantification of bacteria
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Colony forming units/Total dilution factor
If 225 colonies grew on a 10^-7 plate, then the concentration of bacterial cells in your original sample = 225 x 10^7 cells/mL Dilutions increase by ^-2 per dilution: 10^-2, 10^-4, 10^-6, etc. |
