Labs 1-3 Flashcards
After using crystal violet to visualize endospores in the bacterium Bacillus subtilis, a student observes dark purple rods. These rods can be described as _________.
a reproductive structures
b structures very resistant to heat
c metabolically active vegetative cells
d covered in mycolic acid
c metabolically active vegetative cells
Which of the objective lenses on the compound light microscope must always be used with immersion oil, and why?
100x objective lens. Oil is used because less light is available, so need to minimize refraction. Increases numerical aperture for better viewing power.
When looking at a specimen using the high-dry objective lens the total magnification is what?
400x
Both E. coli and S. cerevisiae use flagella for motility. True or false?
False.
A. niger distinguishes itself from S. cerevisiae, since it is an eukaryote. True or false?
False. Both S. cerevisiae and A. niger are fungi. Fungi are eukaryotic organisms, while bacteria are prokaryotic.
What is parafocality?
Changing the objective lens and still maintaining focus
In introductory microbiology, acidic dyes are more commonly used than basic dyes.
True or false?
False.
When you inoculate your TSA plate what is the right way to handle the lid of the plate to avoid contamination?
Partially open the lid of the plate and continue to hold it in this way while you streak
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.
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.
Acidic dyes are not often used to stain bacteria since __________.
- ) the dyes cause the cells to break-down
- ) slides made will need to be viewed using an electron microscope
- ) the dyes have the same negative charge as bacterial cells
- ) they are caustic and dangerous to use in a teaching lab
3.) the dyes have the same negative charge as bacterial cells
To calculate the concentration of cells (CFU/ml) in a starter culture we need to know the __________.
- ) incubation temperature.
- ) name of the growth media.
- ) size of the inoculum.
- ) number of colonies on countable plates.
- ) Dilution factions.
- ) number of colonies on countable plates.
5. ) Dilution factions.
When Gram staining a smear, what should you do immediately after rinsing a slide with acetone alcohol?
Rinse slide with water, then cover smear with safranin.
If you fail to heat fix a smear prior to gram staining, what is likely to occur?
The smear may wash off of the slide during staining.
