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 10, Problem 1CA
Assume you have performed a
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The number of bacterial cells in a culture broth is to be determined by a culture
technique.
Serial dilutions were performed and a 1 mL aliquot from each dilution was mixed with
warm molten agar and poured into a Petri dish. The numbers of bacterial colony
forming units (CFU) after overnight incubation are shown in the table below.
What is the number of colony forming units per mL of the culture broth? Choose only
the most appropriate plate for your calculation. Give your answer as the number only
(do not add text for the units). You may use scientific notation with the format
1.12e+6 (that is, 1.12 x 106 cfu/mL). (Note: Canvas will then display your answer a
whole number.)
Plate Dilution
Plate 1 10 dilution
Plate 2 10 dilution
-5
Plate 3 10 dilution
Plate 4 10 dilution
Plate 5 107 dilution
-8
Plate 6 100 dilution
*Too many to count
Number of colony forming units (CFU)
TMTC*
TMTC*
TMTC*
867
154
18
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?
A mixed culture is known to contain Gram negative bacilli and Gram positive cocci.
You perform a Gram stain of this mixed culture as a control while simultaneously Gram stainin
an unknown organism on the same slide (the same procedure you used in lab). The results,
observed under the 100x objective lens, are described below:
Results:
Control side: purple bacilli and purple cocci
Unknown side: purple bacilli
Using all the information given above, discuss the results of your unknown organism. Shoul
you be confident in this result?
Answer question A if you are confident, answer question B if you are not confident.
a. If you are confident in your results, why? Explain how the staining reagents produced the
described results.
b. If you are not confident, do you think an error was made in the Gram staining procedure? If
so, describe the error and explain how it impacted your results.
Chapter 10 Solutions
Laboratory Experiments in Microbiology (12th Edition) (What's New in Microbiology)
Ch. 10 - Which two stains done in this experiment are...Ch. 10 - Do all bacteria make endospores?Ch. 10 - What is the Gram reaction of acid-fast bacteria?Ch. 10 - Using Bergeys Manual and your text, place the...Ch. 10 - Which genera listed in the previous question...Ch. 10 - Assume you have performed a Gram stain on a sample...
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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, biology and related others by exploring similar questions and additional content below.Similar questions
- Based from the results obtained from Gram staining, explain why bacterial cells retained or changed their color. Briefly explain the principle behind the procedure. Cite advantages of differential staining method (Gram staining and endospore staining) over simple staining only. List other staining methods aside from those you performed in the laboratory. conclusion:arrow_forwardDescribe in detail all the steps needed to determine whether an Unknown bacteria has a Gram-positive or Gram-negative cell wall using the Gram stain. (You can describe the method presented in the Exercise 3-6 Gram stain videos or in the Lab Manual.) 1. Start by describing the method of transferring the bacteria onto the microscope slide, then describe heat-fixing the emulsion of the Unknown bacteria. (Do not describe all the steps needed to perform aseptic technique. Just say “Bacteria was added aseptically.”) 2. Describe the Gram stain in detail. (This description should include all the stains, how long the stain should set on slide, and Genus and species names of bacteria you are using as CONTROLS.)arrow_forwardUsing absorbance readings and a standard curve relating absorbance to cell number, you suspect that a bacterial culture contains 7.4 x 109 CFUs/ml. What dilution of this sample would give you a countable plate?arrow_forward
- Bacillus subtilis (Gram-positive) and Pseudomonas aeroginosa (Gram-negative) bacteria are heat-fixed on slide and subjected to Gram staining. What do you observe under the microscope when the following steps are skipped? Please explain.a. Staining with safraninb. Staining with Gram iodinec. Decolorizationarrow_forwardAssume you are observing the diatom pictured in Figure 1 using the 10X lens in a compound light microscope. You move to the 40X lens and then again to the 100X lens by only rotating the turret (remember that the lenses are parfocal), without making any other adjustments to the microscope. c) After making your adjustments, you notice that the midline of the diatom is in focus while the remainder is blurry. Explain, based on microscopy principles, why this has occurred Provide a description of the procedure to prepare an acidic stain of bacteria using Nigrosin as it would appear in the Methods section.arrow_forwardYou have spread 0.1ml of a 1x10-8 diluted bacterial culture sample on a Petridish and counted35 colonies. What was the cell density of your original culture (in cells/ml)? How many cellsdid you have in 100ml of that culture? DON’T FORGET TO ROUND!arrow_forward
- The above photograph (IMAGE ATTACHED) of a cheek smear was obtained using the high-power objective of a compound microscope. What is the size of the circled cheek cell in millimeters AND nanometers?arrow_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_forwardThe number of bacterial cells in a culture broth is to be determined by a culture technique. Serial dilutions were performed and a 0.1 mL aliquot from each dilution was spread onto Plate Count Agar (PCA). The number of bacterial colony forming units (CFU) after overnight incubation are shown as listed in the table below. What is the number of colony forming units per mL of the culture broth? Choose only the most appropriate plate for your calculation. Give your answer as the number only (do not add text for the units). You may use scientific notation with the format 1.12e+6 (that is, 1.12 x 106 cfu/mL). (Note: Canvas will then display your answer a whole number.) Plate Dilution Plate 1 10 dilution Plate 2 10 dilution Plate 3 107 dilution Plate 4 10 dilution Plate 5 107 dilution Plate 6 100 dilution *Too many to count Number of colony forming units (CFU) TMTC* 382 83 10 2 0arrow_forward
- The number of bacterial cells in a culture broth is to be determined by a culture technique. Serial dilutions were performed and a 0.1 mL aliquot from each dilution was spread onto Plate Count Agar (PCA). The number of bacterial colony forming units (CFU) after overnight incubation are shown as listed in the table below. What is the number of colony forming units per mL of the culture broth? Choose only the most appropriate plate for your calculation. Give your answer as the number only (do not add text for the units). You may use scientific notation with the format 1.12e+6 (that is, 1.12 x 106 cfu/mL). (Note: Canvas will then display your answer a whole number.) Plate 1 10 Plate 2 10 Plate 3 10 dilution dilution dilution Plate 4 10 dilution Plate 5 107 dilution Plate 6 10 dilution -6 *Too many to count Number of colony forming units (CFU) TMTC* TMTC* 840 28 19 1arrow_forwardFor a laboratory exercise of basic techniques in microbiology: Gram stain and Microscopy. What are the sources of error in performing Gram staining?arrow_forwardWhy 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_forward
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