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51 Cards in this Set
- Front
- Back
What type of microscope do we use in class and why is it called this?
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A bright-field, compound, and binocular microscope.
Bright-field: A dark image on a field of bright light Compound: a two-lens system Binocular: two ocular lenses |
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What is a compound microscope?
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A two-lens system:
1. The lens you look through: the ocular lens 2. The lens closest to the specimen: the objective lens |
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How do you calculate the total magnification?
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ocular X objective lens magnification
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What is the purpose of a simple stain?
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To identify bacterial size, shape, and arrangement.
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What is the purpose of a gram stain?
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To differentiate between cells containing a thick (Gram +, purple) or thin (Gran -, pink) peptidoglycan layer.
Also to identify the bacterial size, shape, and arrangement. |
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What is the purpose of a flagella stain?
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To identify presence and arrangement of flagella
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What is the purpose of an acid-fast stain?
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To differentiate between acid-fast and non-acid-fast bacteria
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What is the purpose of a capsule stain?
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To identify whether or not a bacterium produces a capsule
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What is the purpose of an endospore stain?
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To identify whether or not a bacterium produces and endospore.
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What is the procedure for a simple stain?
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1. Prepare heat-fixed bacterial smear
2. Add crystal violet, do not allow to dry on slide 3. Gently wash off with water 4. Blot dry |
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What is the procedure for a Gram stain?
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1. Heat fix bacterial smears
2. Apply crystal violate, do not allow to dry on slide 3. Gently wash with water 4. Apply Gram's iodine, do not allow to dry on slide (The mordant) 5. Gently rinse slide 6. Add alcohol to the slide and rock to spread (To decolorize gram negative cells) 7. Rinse slide 8. Apply safranin (the counterstain) 9. Rinse and blot dry |
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What is the procedure for a flagella stain?
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1. Mark a circle in the center of the slide using a marker
2. Put 2 drops of distilled water in circle 3. Transfer the colony to the water by lightly touching the surface of the water, and not touching the slide 4. Air dry- do not heat fix!! 5. Flood with Flagella stain and let sit 6. Rinse by running water over the slide in a dish 7. Air dry. Do not blot dry |
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What is the procedure for an acid-fast stain?
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1. Mark a circle on the slide
2. Transfer bacteria to slide 3. Add water to slide 4. Heat fix 5. Add carbolfuchsin KF stain, rinse 6. Add acid alcohol to decolorize, rinse immediately 7. Counterstain with methylene blue, rinse, blot dry |
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What is the procedure for a capsule stain?
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1. Place Nigrosin stain on slide
2. Apply 1-3 loopfulls of culture next to the drop 3. Mix the two, cover with a coverslip 4. Do not use heat! |
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What is the procedure for an endospore stain?
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1. Make a heat-fixed bacteria slide
2. Cover with paper towel, place slide in petri dish on heater 3. Add malachite green and steam (this cooks the dye into the endospore wall because it is very resistant to staining) 4. Rinse 5. Counterstain with safranin, rinse (the running water washes the green stain out of the vegetative cells and cause them to be colorless. The counterstain dyes them red) |
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What are
monotrichous amphitrichous lophotrichous and peritrichous flagella arrangements? |
Monotrichous- single flagellum
Amphitrichous- a flagellum on each end Lophotrichous- many flagellum located at the same spot Peritrichous- flagella projecting in all directions |
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What are two types of acid-fast bacteria?
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Mycobacterium (M. tuberculosis and M. leprae) and Nocardia
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How is an acid-fast stain different from a gram stain?
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Acid-fast bacteria have a waxy property (mycolic acid, or complex lipids) which make them resistant to the crystal violet dye used in a Gram stain. Heat or detergent softens these lipids and allows the stain to penetrate. Once stained the cells resist decolorization with acid alcohol.
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What is the purpose of a capsule?
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They exclude toxic materials, some hold water to prevent dessication, and most importantly they provide protection from things like being engulfed by eukaryotic cells such as macrophages.
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How does an endospore stain differ from a Gram stain?
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Spores have a tough covering made of keratin and are highly resistant to heat and staining, so malachite green is forced into the spores by heating the cells.
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What are two medically important bacteria which produce endospores?
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Bacillus and Clostridium: they can contaminate medical materials.
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If a microbiology lab technician left the safranin out of the Gram stain procedure, what would be the result?
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Gram-positive cells would be purple, and Gram-negative cells would be colorless
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What would you anticipate seeing if you accidentally switched crystal violet and safranin while performing a Gram stain?
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All bacteria would appear purple
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If you switched the mordant and the decolorizer in a Gram stain, what would the results be?
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All bacteria would appear pink
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What is the definition of these morphologies:
coccus bacillus spirillum |
Coccus: spherical shape
Bacillus: rod-shaped Spirillum: spiral shape |
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What is the definition of these arrangements:
Strepto- Staphylo- Random Diplo- Pallisading Tetrad Sarcina |
Strepto: two or more bacteria in a straight line
Staphylo: two or more bacteria bunched like grapes Random: random Diplo: two bacteria together Pallisading: rod shapes in a line next to each other/or a t Tetrad: four bacteria in a square shape Sarcina: bacteria in a cuboidal shape |
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What is the purpose of T-streaking?
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To streak a concentrated culture to obtain individual colonies/an isolation
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How is cfu/mL or bacteria/mL calculated?
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(# of colonies on plate X dilution factor)/mL of dilution plated
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What are the two reasons aseptic technique are used? What is involved in aseptic technique?
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1. protects our cultures from being contaminated with unwanted organisms
2. protects you and the environment around you from being contaminated with the microbes you are working with Aseptic technique involves flaming loops and test tube lids before and after use, and never putting loops or test tube lids down on the table (hold lids with your pinky) |
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What is the purpose of the carbohydrate fermentation tests? (glucose and lactose fermentation)
What is in the test tube? What does a bubble in the tube mean? No bubble in the tube? A yellow result? A red result? |
Tests for the ability to ferment sugar
There is phenol red pH indicator and sugar in the tube A bubble means gas production No bubble means no gas production A yellow result means an acidic pH and a positive result A red result means alkaline pH and a negative result |
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What is the purpose of a motility test, and how do you read the results?
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A motility test is looking for the ability of an organism to move through the medium. Growth throughout the medium beyond the prick indicates motility (left test tube in the picture)
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What is the purpose of a catalase test? How is the result read?
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A catalase test shows the breakdown of peroxide (H2O2) into H2O + O2-. A positive result is the presence of bubbles after adding peroxide to the culture.
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What is the purpose of a cytochrome oxidase test? How do you read the results?
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This test looks for cytochrome oxidase as the terminal step in the electron transport chain. A positive result is a purple/black color change. The disc contains the electron donor p-aminodimethylaniline monohydrochloride which when oxidized will appear purple.
(test may be performed slightly different than the picture shown, depending on your lab) |
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What is the purpose of an indole test? How are the results read?
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The indole test looks for the ability of an organism to produce tryptophanase. The reduction of tryptophan results in the formation of indole, pyruvic acid and ammonia. Kovac's reagent is added and red shows a positive result and yellow shows a negative result.
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What is the purpose of the methyl red test? How are the results read?
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The methyl red test is looking for the ability of an organism to use mixed acid fermentation which results in the formation of strong, stable acids. After the addition of methyl red pH indicator, red is a positive result, yellow is a negative result.
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What is the purpose of the Voges-Proskauer test? How are the results read?
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This test is looking for the ability of an organism to ferment pyruvic acid by butandiol pathway which results in formation of the neutral products acetoin and 2,3-butandiol. Barritt's A and B (alpha-napthol and 40% potassium hydroxide) are added, and a red ring is positive and a yellow ring is negative.
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What is the purpose of a citrate test? How are the results read?
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The citrate test is looking for the ability of organisms to use citrate as a sole carbon source. An increase of pH gives a positive result and a blue color. A negative result remains green.
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What is a thioglycolate test and how are the results read?
How do they grow in a gas pack, candle jar, and air? |
Thioglycolate is an oxygen scavenger that depletes oxygen in a medium. The medium is stabbed and the results can be:
Growth throughout the medium (facultative anaerobe) Only at the top of the medium (obligate aerobe) Only at the bottom of the tube (anaerobe) Gas pack: facultative: growth anaerobe: growth aerobe: no growth Candle Jar: facultative: growth anaerobe: no growth aerobe: no growth Air: facultative: growth anaerobe: no growth aerobe: growth |
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What is the difference between EMB (eosin methylene blue) selective and differential medium?
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Selective: contains aniline dyes that inhibit Gram+ organisms and selects for Gram- organisms (enteric organisms)
Differential: contains lactose and differentiates between lactose fermentors (purple or green metallic colonies) and non-fermentors (colorless) |
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What is mycology?
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Mycology is the study of fungi
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How to fungi reproduce?
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It can vary from simple asexual fission (yeasts) to complex reproductive styles. They reproduce by producing various types of spores (not to be confused with the endospores of bacteria)
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How are fungi classified?
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They are heterotrophic eukaryotes
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Are the following unicellular or multicellular?
Yeast Mold Mushrooms |
Yeast: unicellular
Mold: macroscopic and multicellular Mushrooms: multicellular |
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How do filaentous fungi propagate?
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They can propagate by either outward growth or fragmentation of existing hyphae
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What is a selective medium for fungi and why is it useful?
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Sabouraud dextrose agar is a selective medium for fungi. It contains acid which inhibits the growth of most bacteria and contains glucose to promote the growth of fungi.
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Define the following:
Psychrophile Mesophile Thermophile |
Psychrophile: can grow in extreme cold
Mesophile: can grow in middle temperatures Thermophile: can grow in extreme heat |
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Define the following:
Acidophile Neutrophile Alkalophile |
Acidophile: can grow in acidic environments
Neutrophile: can grow in neutral environments Alkalophile: can grow in alkaline environments |
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Define the following:
Halophile Halotolerant |
Halophile: organisms that live in high salt concentrations
Halotolerant: the ability to survive in a salty concentration |
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Define the following conditions in a cell:
Hypotonic Isotonic Hypertonic What do each of these do to a cell? |
Hypotonic: the molar concentration outside the cell is less than that inside the cell (cell expands)
Isotonic: the molar concentration outside the cell is the same of that inside the cell (normal cell) Hypertonic: the molar concentration inside the cell is greater than that outside the cell (cell shrinks) |
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What is the effect of UV radiation on bacteria?
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Slows or stops growth in most bacteria
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What is the Luisetti's test and how is it read?
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It is a differential medium which detects the presence of fluorescein-producing Pseudomonas species. A positive result will glow yellow-green when placed under a UV light.
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