Quiz 5 (Simple Stain) – Flashcards
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Under which of the following conditions would you be most likely to prepare (and use) a smear?
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Staining bacterial cells to observe under the microscope.
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When making a bacterial smear on a slide, you should first dilute the bacteria in water if
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the bacteria has been grown as a solid culture, such as on a plate or a slant.
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You're preparing a smear from a broth culture. You've labeled a clean slide. You've flamed the inoculating loop and let it cool. What's your next step?
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Flick the culture tube.
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Smear preparation from a slant culture differs from smear preparation from a broth culture in what way?
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Bacteria from a slant culture must be mixed with a loopful of water.
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A student properly flames her loop but then forgets to let it cool. Instead, she immediately inserts the hot loop into her broth culture. What is the most important issue associated with this mistake?
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The hot loop may create aerosols when it touches the culture.
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Which of the following describes a proper fixation technique?
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Pass the slide two or three times through a flame.
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After making your bacterial smear, you should allow your organism to COMPLETELY dry. You cannot overdry your smear, but you can ruin your stain prep by not drying it enough. What will happen if the cells still have water in them when you heat fix the cells?
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They will explode like popcorn.
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Heat fixing kills the cells. Where should the slides be desposed of?
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"Broken Glass" crock
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What is the purpose of applying a stain to a bacterial smear?
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To provide contrast between the organism and the background.
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Since bacterial cells are generally transparent, it is very helpful to stain bacteria to provide contrast. Which of the following does staining not allow you to determine?
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Metabolism
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What is the charge on the surface of most bacterial cells?
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Negative
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What is the definition of a basic stain?
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Stain with a positively charged chromogen
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Which is not an example of a basic (postively charged) stain?
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Congo Red
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After the bacterial smear has been stained and rinsed, what should happen next?
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Blot the slide gently by placing it in the tablet of bibulous paper. Do not rub. Use care to not break the slide.
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What magnification should you observe your bacteria under?
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1000X (oil immersion objective X ocular), but start with the lowest magnification and work your way up to this. ONLY apply the oil between viewing at 400X and 1000X!!!
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Which of the following is not an example of a morphology (shape)?
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tetrad
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Which of the following describes an arrangement of a cube-shaped packet of 8 cocci?
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sarcina
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Look at the examples of morphologies in your lab textbook. How would you describe an ovoid cell which is no more than twice as long as it is wide?
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Coccus
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How would you describe cells that have uniform diameters and varying lengths, but the lengths are always at least twice the diameter?
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Bacilli
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Which arrangement is the result of random planes of division?
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Staphylococcus
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Which arrangement is NOT the result of a single plane of division?
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Tetrad
