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archive2.zipMicrobial Motility VR.docx
BIO2073: Microbiology Lab
Microbial Motility
1. Explain how cilia differ from flagella.
2. From the microbial motility playlist (https://youtube.com/playlist?list=PLdq8zMg9wvgdmkNK16mDscUpC2EcGWPR5) pick 5 videos to view and record your observations below. Note that some of the information you are looking for may be found in the description box for each video on YouTube.
a. What species did you observe?
b. Does the organism appear to be motile? If so, describe any motion you observed. (For example, was the motion fast or slow, all in one direction or in multiple directions, smooth/gliding, erratic, etc.). Be sure to include whether the organism uses flagella, cilia, or pseudopodia as a form of movement.
3. Explain the pros and cons of using a wet mount versus a hanging drop.
4. Explain how Brownian motion differs from true motility. (Refer to your textbook if needed.)
5. In the video entitled “Bacterial flagellar motility,” (from user “microfetish” – 5th video on the playlist), the bacterium in the center of the image was spinning around in circles. What caused this? (Hint: check the video’s description box!)
Bonus! Do you think it would be better to use a fresh culture or an older culture when doing this experiment? Explain your answer.
Smears and simple stains individual.docx
BIO2073: Microbiology Lab
Smears and Simple Stains: Individual Assignment
1. List 3 bacterial characteristics that can be determined using a simple stain. (1 pt)
2. Explain how a basic stain allows us to visualize our microbes. Be sure to address the chemistry of the reaction. (You may want to refer to your lab text for a refresher on how basic stains work.) (2 pts)
3. Explain how a negative stain differs from a basic stain. (1 pt)
4. Explain how you would heat fix a slide. (1 pt)
5. List two effects of heat-fixing a slide. (1 pt)
6. List 3 commonly used basic stains. (1 pt)
7. List 2 commonly used negative stains. (1 pt)
8. What would happen if you did not leave the stain on your sample long enough? (1 pt)
9. What would happen if you did not heat-fix your sample prior to staining? (1 pt)
Bonus! Why might a negative stain, which does not heat fix the bacterial sample, be a better choice for viewing some microbes? (1 pt)
Gram Stains Individual Activity.docx
BIO2073- Microbiology Lab
Gram Stains Individual Activity
1. What makes a differential stain different from a simple stain?
2. What purpose does iodine serve in the Gram stain reaction?
3. Imagine you made the following mistakes when performing your Gram stain. Indicate whether your cells would appear to be G+, G-, or colorless (NC), at the end of the procedure, assuming you followed all other steps. Then provide a brief rationale for why you would get this result.
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Mistake |
Result (G+/G-/NC) |
Rationale |
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You didn’t counterstain with safranin. |
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You skipped the decolorizing step. |
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You forgot to add the iodine. |
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You used safranin as your primary stain and crystal violet as your counter stain. |
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4. Describe how the structure of the Gram+ cell wall differs from that of a Gram- cell wall, and how that leads to the different results we see in the Gram stain reaction.
Bonus! If you were to stain one of your own eukaryotic cells using the Gram stain method, would you expect the result to be positive or negative? Explain your answer. (Note: while Gram staining is used to characterize bacteria, you should still be able to predict what color your own cells would be using the Gram stain method, based on the structure of the cell. Think about how the cell structure of your cells compares to that of G+ and G- bacteria.)
Heat Lab OL.docx
BIO2073- Microbiology lab
Summer Quarter 2020
Lab Report: Heat as a method of control
1. What was the objective of this lab exercise?
2. Use the following table to document your data. For each plate that you look at, be sure to indicate the species, and the temperature used. Then, for each time point, evaluate the relative amount of growth in each section using a scale from 0-4 where 0 = No growth 4= heaviest growth
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Organism |
63°C |
72°C |
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0 sec |
30 sec |
1 min |
2 mins |
5 mins |
15mins |
0 sec |
30 sec |
1 min |
2 mins |
15 mins |
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3. Why was it important to plate out a sample at 0 seconds, prior to exposing the culture to heat?
4. In general, was 63°C or 72°C more effective at killing the microbes? Does this align with the results you expected? Why or why not?
4. Both “young” (less than 24 hours) and “old” (several weeks) cultures of B. subtilis were used in this experiment. Why do you think this was done? Hint: what do you know about the Bacillus genus and their survival mechanisms? Why use Bacillus and not old/young E.coli for example?
6. The thermal death time and the term death point are two different ways to describe a microbe’s sensitivity to heat. Which of these two measurements were we evaluating in this experiment? Explain your answer.
7. Give an example of a non-laboratory use of each of the following methods to control microbial growth:
a. Incineration:
b. Pasteurization:
c. Autoclaving:
Bonus! The species Geobacillus stearothermophilus is often used as an indicator species to test the effectiveness of autoclaving. Why do you think this species is used instead of E. coli or B. subtilis?
Acid Fast individual report OL.docx
BIO2073: Microbiology Lab
Acid-Fast Staining: Individual Activity
1. Explain how the cell wall of an acid-fast bacterium is unique compared to most other bacteria.
2. The acid-fast staining procedure often uses heat when applying the primary stain. Explain how heat helps the staining process.
3. Refer to Figure 3.60 in your textbook. Mycobacterium tuberculosis is often seen in clumps when viewed under the microscope. How is this different than the clusters viewed with microbes like Staphylococci?
4. Mycobacteria and Nocardia species are acid-fast genera that include human pathogens. Pick one pathogen from one of these genera and provide the following information:
a. Full species name: ____________________
b. Associated disease: ___________________
c. Symptoms/Signs: _____________________
d. Prevention/Treatment: ________________
Bonus! If you were to isolate a random, unknown organism from the environment, which staining method would be better to start with: Gram staining or Acid fast staining? Explain your answer.
