Lab 2 Flashcards
Why do electron microscopes have better resolution than light microscopes?
1) They have higher magnification.
2) They have larger lenses.
3) They use electrons rather than light.
4) They use magnetic rather than glass lenses.
3) They use electrons rather than light.
Remember that electrons have a much smaller wavelength (approximately 11,000 times smaller) than light waves.
When using the _________, the specimen will appear brightly illuminated on a dark background.
1) brightfield microscope
2) darkfield microscope
3) phase-contrast microscope
4) Transmission electron microscope
2) darkfield microscope
Exercise 2 of your lab manual discusses the darkfield microscope.
Which of the following microbes that you will either use or observe this lab period are bacteria?
THERE IS MORE THAN ONE ANSWER TO THIS QUESTION. CLICK ALL CORRECT ANSWERS.
1) Saccharomyces cerevisiae
2) Proteus vulgaris
3) Aspergillus niger
4) Escherichia coli
2) Proteus vulgaris
4) Escherichia coli
Both S. cerevisiae and A. niger are fungi. Fungi are eukaryotic organisms, while bacteria are prokaryotic.
Most fungi is described as hyphal. Hyphae form mats of growth known as
1) spores.
2) mycelia.
3) yeast.
4) colonies.
2) mycelia
On a plate of solid medium, mycelia will look like “hairy” or “furry” growth sticking up from the surface of the medium.
Colonies of yeast and bacteria growing on a plate of medium may look similar. How might you tell them apart?
1) You can distinguish between them by microscopic examination.
2) The yeast colonies growing on the plate look smaller to the naked eye.
3) Bacterial colonies should be more colorful than yeast colonies.
4) Yeast colonies will look “fuzzy” due to the hyphal growth.
1) You can distinguish between them by microscopic examination.
When you examine yeast cells microscopically, they will typically be much larger than bacterial cells. You also should see nuclei in yeast cells and budding (a form of reproduction), but not in bacteria.
If you look at a sample from hay infusion and see larger microbes moving with clearly visible cilia or flagella, the microbes must be
1) prokaryotic
2) eukaryotic
3) yeast
4) fungi
2) eukaryotic
Bacteria do not have cilia and the flagella that are visible under a light microscope. Thus, any organisms with visible cilia or flagella must be eukaroytic. However, not all eukaryotic cells are motile. Fungi (hyphal and yeast forms) are non-motile and so have neither cilia nor flagella.
When making a wet mount from a colony on a plate culture, you should
1) use the whole colony in order to get enough sample.
2) use about half the colony for best results.
3) take samples from two different colonies.
4) lightly touch the colony, so there will not be too many bacteria to view.
4) lightly touch the colony, so there will not be too many bacteria to view.
Refer to the appendix for directions of how to make a wet mount aseptically from a plate culture. You will view a video of making a wet mount from a BROTH culture during lab. Making the mount from a plate is very similar except you must place a small drop of water on your slide, before you transfer culture from the plate. Please ask your TA, if you have questions about this procedure.
What part of your inoculating loop should you dip into the alcohol prior to igniting it in the flame of your burner?
1) just the round loop at the end
2) the entire length of the wire including the round loop
3) the handle
4) In Microbiology 4000, no part of the inoculating loop should be dipped in alcohol
4) In Microbiology 4000, no part of the inoculating loop should be dipped in alcohol
Which of the following is an advantage of a light microscope over an electron microscope?
1) Light scopes have higher magnification.
2) Light scopes have higher resolution.
3) Light scopes can be used to trace processes at the molecular level.
4) Light scopes can be used to observe motility and living specimens.
4) Light scopes can be used to observe motility and living specimens.
Because organisms are killed during preparation for viewing with electron microscopes, these scopes can not be used to determine motility.
How are the dark field microscope and the fluorescence microscope alike?
1) Both use a mercury vapor lamp
2) Both have a phase-shifting element
3) Both have a resolution of about 0.04 nm
4) Both use a paraboloid condenser
4) Both use a paraboloid condenser
Which of the following microbes that you will use in this lab period are fungi?
THERE IS MORE THAN ONE ANSWER TO THIS QUESTION. CLICK ALL CORRECT ANSWERS.
1) Saccharomyces cerevisiae
2) Proteus vulgaris
3) Aspergillus niger
4) Escherichia coli
1) Saccharomyces cerevisiae
3) Aspergillus niger
S. cerevisiae is a yeast form of fungi while A. niger is a hyphal form.
You will look at fungi with two different types of morphologies in this lab. What are these two morphologies?
1) hyphal and mycelial forms
2) spores and hyphal forms
3) hyphal and yeast forms
4) colonial and spore forms
3) hyphal and yeast forms
Hyphal forms of fungi will grow as mycelia on a plate of culture and look “hairy” in appearance. Yeasts will form colonies on a plate that look somewhat similar to bacterial colonies, but can easily be distinguished from bacteria microscopically.
Which of the following would be a way to microscopically distinguish bacteria from yeast?
1) yeast cells should be much larger than bacterial cells
2) yeast should appear as “fuzzy” hyphae on the plate
3) nuclei should be visible in bacteria but not in yeast
1) yeast cells should be much larger than bacterial cells
Because they are eukaryotic, yeast cells typically will be much larger than prokaryotic bacterial cells.
If you look at a sample from hay infusion and see very small microbes moving but no cilia or flagella are visible, the microbes are most likely
1) prokaryotic
2) eukaryotic
3) yeast
4) fungi
1) prokaryotic
Prokaryotic organisms (bacteria) do not have cilia and flagella that are visible under a light microscope. They are also much smaller than eukaryotic organisms. Thus, any tiny organisms moving without visible cilia or flagella are likely to be prokaroytic. Cilia and flagella of eukaryotic organisms should be visible under a light microscope.
When taking a sample from a broth culture, why should you vortex the tube?
1) to mix oxygen into the culture
2) to resuspend the organisms
3) to separate the organisms from the broth
4) to sterilize the tube
2) to resuspend the organisms
Refer to the appendix for directions for how to make a wet mount aseptically. You will view a video of this procedure during lab (also available on Carmen), please watch it carefully and ask your TA if you have questions about this procedure.
