Laboratory Experiments in Microbiology (12th Edition) (What's New in Microbiology)
12th Edition
ISBN: 9780134605203
Author: Ted R. Johnson, Christine L. Case
Publisher: PEARSON
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Chapter 7, Problem 3CT
Human cells can be stained with crystal violet and safranin, so why can’t human cells be
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Different stains have different affinities for different organisms or different parts of organisms. Elaborate on this statement using the Hematoxylin and Eosin staining as an example.
In lab, we used the Gram stain to differentiate between Gram-positive and Gram-negative
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counter-stain safranin).
a) What is the biological molecule that is present in these bacteria that produces different results
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b) What is the difference between Gram-positive and Gram-negative bacteria that creates the
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Explain Why do acidic dyes not stain bacterial cells?
Chapter 7 Solutions
Laboratory Experiments in Microbiology (12th Edition) (What's New in Microbiology)
Ch. 7 - Why do gram-positive cells more than 24 hours old...Ch. 7 - Can iodine be added before the primary stain in a...Ch. 7 - Prob. 3QCh. 7 - Which step can you omit without affecting...Ch. 7 - Suppose you performed a Gram stain on a sample...Ch. 7 - Prob. 2CTCh. 7 - Human cells can be stained with crystal violet and...Ch. 7 - Considering that it isnt possible to identity...
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- Several students argued about why Gram-positive cells stain purple with the Gram stain whereas Gram-negative cells stain pink. Which explanation is correct? Multiple Choice Alcohol dehydrates peptidoglycan; the thick layer of dehydrated peptidoglycan in Gram-negative cells prevents the crystal violet from being washed out Safranin stains lipopolysaccharide, and because only Gram-negative cells have lipopolysaccharide, those cells look pink. Safranin stains lipopolysaccharide, and because only Gram-negative cells have lipopolysaccharide, those cells look pink. Alcohol dehydrates peptidoglycan; the thick layer of dehydrated peptidoglycan in Gram-positive cells prevents the crystal violet from being washed out. Crystal violet specifically stains peptidoglycan, and because Gram-positive cells have a thicker peptidoglycan layer those cells look purple. Alcohol destroys lipopolysaccharide in Gram-negative cell walls, allowing safranin to enter the cells and staining them pink.arrow_forward1)What is the natural color of cytoplasm? How is it related to our need to stain bacterial cells? 2) Which of the following is the main goal when staining a culture? A) improve contrast B) identify bacteria C) Visualize bacterial structuresarrow_forwardAs part of an experiment where absorbance values are measured using a spectrophotometer, you are taking readings of your sample every 20 minutes. The non-motile microbe you're testing has a generation time of roughly 20 minutes at an incubation temperature right around room temperature. Things start out fine, with the expected results — as time goes by at the correct incubation temperature, absorbance starts to rise as the medium starts to become more cloudy with growing microorganisms. But roughly 2 hours into the process, you notice that the absorbance levels flatten out, and then start to decrease unexpectedly. What is most likely taking place in your experiment?arrow_forward
- Both crystal violet and safranin are basic stains and may be used to do simple stains on Gram positive and negative cells. This being the case, explain how they end up staining Gram positive and gram negative cells differently.arrow_forwardArchaea with cell walls consisting of a thick, homogeneous layer of complex polysaccharides often retain crystal violet dye when stained using the Gram-staining procedure. Suggest a reason for this staining reaction.arrow_forwardThe bacterial cells in the image below were stained with a high concentration of carbolfuschin for an extended period of time (5 minutes) while the slide was heated. The slide was decolorized with a mixture of acid and alcohol. The slide was then counter-stained with methylene blue. What kind of stain does this describe?arrow_forward
- stains are attracted to the negatively charged surface of bacterial cells.arrow_forwarda. What can you observe in viewing your stained bacterial slide under the microscope if you fixed a lot of bacterial colonies in your slide during smear preparation? b. What can you observe in viewing your stained bacterial slide under the microscope if you heat fixed your slide in a much longer exposure to heat?arrow_forwardWhy are bacterial cells generally stained for microscopic viewing?arrow_forward
- Why is it important to perform a gram stain for any type of bacteria? After performing the gram stain method what would be the next step? (Think in terms of the real-world situation) Explain.arrow_forwardThe acid fast bacterium, Mycobacterium smegmatis, is relatively safe for students to work with because of its thin cell wall. If a gram stain is to be performed on this particular microbe, it often takes the gram stain reaction. Why?arrow_forwardWhy does UV light have to be directly exposed and waved around an object that needs to be disinfected and not waved around a bag with the items that need to be disinfected inside of it?arrow_forward
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