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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Explain Why do acidic dyes not stain bacterial cells?
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
bacteria. Some bacteria stain purple (retaining the crystal violet) while others stain pink (from the
counter-stain safranin).
a) What is the biological molecule that is present in these bacteria that produces different results
between Gram-positive and Gram-negative bacteria (be specific!) AND
b) What is the difference between Gram-positive and Gram-negative bacteria that creates the
different staining patterns (purple vs. pink)?
(2-3 sentences max)
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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- Which of the following technique is FALSE in microscopy? Osmium tetroxide can be used as a fixative as well as a negative stain in transmission electron microscopy. Two proteins; each tagged with their individual primary antibody followed by one protein with rhodamine conjugated secondary antibody and the other with fluorescein-conjugated secondary antibody can be visualized simultaneously using a fluorescence microscope. The emission spectrum of Rhodamine is 580 nm The emission spectrum of Fluorescein is 521 nm O An objective lens with 100X magnification and projection lens with 10X magnification is going to produce a 1000X total magnification. Phase contrast and differential interference contrast (DIC) do not require staining.arrow_forwardSeveral 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_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
- 1)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_forwardBoth 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_forward
- You accidentally switch the Crystal violet and Safranin steps during your Gram stain. When you look under the microscope, what color will a Gram positive bacteria, like Staphylococcus aureus, be? Red/Pink Purple colorlessarrow_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_forwardstains are attracted to the negatively charged surface of bacterial cells.arrow_forward
- a. 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_forwardYou accidentally switch the Crystal violet and Safranin steps during your Gram stain. When you look under the microscope, what color will a Gram positive bacteria, like Staphylococcus aureus, be? a)red/pink b)purple c)colorlessarrow_forwardWhy are bacterial cells generally stained for microscopic viewing?arrow_forward
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