Lab Basics
What are two things you should do every time you come to lab?
Put on lab coat
Wash hands
Disinfect table
You are studying a bacterium under a microscope on 100X objective magnification and are having a difficult time with your microscopy since the distance between two points needed for them to be distinguished as two points is relatively large. What would be the best course of action?
A. Add a stain to the bacteria
B. Add a drop of immersion oil
C. Remake the slide with a better smear
D. Give up, the microscope is too old
B.
Of the following, choose all that CAN survive in the presence of oxygen?
Obligate aerobe
Facultative anaerobe
Aerotolerant anaerobe
Obligate anaerobe
Obligate aerobe, facultative anaerobe, aerotolerant anaerobe
True or false: you need to add a culture of microorganisms to make yogurt?
True
How should you ALWAYS label a plate?
Aseptic technique involves:
Flaming loops before and after each microbe transfer
Flaming loops only before each microbe transfer
Flaming loops only after each microbe transfer
Using antiseptics as the only form of microbe control
1.
Staining for which structure requires you to place the stained slide over a can of boiling water?
A. Cell wall
B. Lipopolysaccharides
C. Endospore
D. Plasma membrane
C.
What is the temperature survival range for:
Psychrophile
Mesophile
Thermophile
Mesophile: 20-45 C
Thermophile: >45 C
What is the name of the type of enzyme that allows some microbes to break down red blood cells?
Hemolysin
What is the color of G+ and G- bacteria under a microscope?
G+ is purple, G- is red
Where in the room do each of these items go after use?
Glass tubes
Used glass slides
Used plates
Tubes = rack by the whiteboard
Slides = glass waste
Plates = biohazard waste
G- : 2 membranes, Lipopolysaccharides (LPS), thin peptidoglycan
G+: One membrane, Thick peptidoglycan, Techoic acids
Which metabolic test causes the color of the medium to change from red to yellow due to the formation of acid?
Carbohydrate fermentation
What is the appearance of a colony that is:
Alpha hemolytic
Beta hemolytic
Gamma hemolytic
Alpha: Greenish
Beta: Clear ring
Gamma: Whitish
How do you calculate viral titer?
number colonies divided by dilution times volume of sample
A scientist is interested in studying a newly discovered species of microbe. The bacteria is picky, and glucose must be provided on the media for the bacteria to feed. The scientist prepares media supplemented with glucose, but with an otherwise unknown and imprecise composition.
Which describes the media in the experiment?
A. Non-synthetic media
B. Selective media
C. Enriched media
D. A and B
E. A and C
E
In some of your staining experiments, you "heat fixed" the bacteria to the slide. What purpose does this have?
Adheres the bacteria to slide better
In your own words, explain the starch test:
What is the indicator?
What enzyme is it testing for?
What is a + and a - result?
Testing for presence of amylase, which degrades starch
Iodine is indicator, which complexes with starch
+ result is clear ring on plate, - result is no clear ring
What is the difference between the lytic and lysogenic viral life cycles?
Lytic = rapid replication of cell components and assembly of viral progeny
Lysogenic = integration into host chromosome, dormant stage
What is a positive result in a fermentation test? Including if you use durham tubes?
Positive result for acid = color change red -> yellow
"Bubble" in top of durham tube = gas production
Describe in your own words the streak plate method, and explain how the pour plate method is used to achieve the same goal?
Streak plate = isolate individual colonies by spreading a culture out over an agar plate
Pour plate = similar in attempting to isolate pure colonies, achieves this by diluting colonies out in molten agar then plating
In a traditional gram staining experiment, crystal violet is added to a mixture of gram-positive and gram-negative bacteria, followed by a decolorizer and a safranin counterstain. Purple gram-positive bacteria are then distinguishable from red gram-negative bacteria under a microscope. In a particular run of this experiment, a researcher forgets to add the decolorizer. Predict how this mistake would change the outcome of the experiment.
All bacteria (G+ and G-) appear purple
You are a nurse in an infusion clinic, where a patient requires fluid for hydration. You task the nursing student working with you to assist in setting up the infusion, but notice they bring pure water into the room instead of the 0.9% isotonic saline you had asked for. What is the problem with using pure water instead of saline?
A. Pure water will be hypotonic relative to red blood cells, causing them to shrink
B. Pure water will be hypertonic to red blood cells, causing them to shrink
C. Pure water will by hypotonic to red blood cells, causing them to swell and burst
D. Pure water will be hypertonic to red blood cells, causing them to swell and burst
C.
If an individual makes both anti-A and anti-B antibodies, what is their blood type?
A. A
B. B
C. AB
D. O
D.
Show how to use a micropipet!
Correctness judged by Chris in real time