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Straigherline Culturing and Aseptic Technique Lab with Answers
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“Lab 2 Culturing & Aseptic Technique BIO250L”Student Name XXXXX
Access Code (located on the underside of the lid of your lab kit):XXXXX
“Pre-Lab Questions”
1. Proper aseptic technique is crucial to ensuring growth of pure bacterial colonies. What is one
experimental way you can test your practices to confirm that you are using proper aseptic
technique?
One way you can use proper aseptic technique is by making sure that the media is
covered, by holding the lid so there is no contamination and making it less exposed to
air.
2. In a laboratory setting, what are three ways you can properly sterilize culturing equipment?
a. UV Radiation or chemical solvents
b. Dry heat ex:(flame or electronic sterilizer)
c. Wet heat (autoclave)
3. For each inoculation tool, give one scenario in which use of that tool would be appropriate.
Inoculation Loops: useful for transferring microbes from one plate to another
Sterile Cotton Swabs: used when beginning a culture plate
Inoculation Needles: used to collect microbes, transfer to other containers, it can also
be used to inoculate in stab tubes.
Sterile Plate Spreaders: used to spread microbial colonies.
4. Why don’t microorganisms in cultures exhibit constant exponential growth? What are some
steps you could take to extend the lifespan of a microbial culture?
When cultures are exposed to oxygen, they do not have much nutrients or room to grow.
Microorganisms cannot exhibit exponential growth. To expand the lifespan, is by giving
more nutrients to the medium, or moving the bacteria to a bigger plate for it to grow.
5. Using a textbook or a reputable online source, describe how lab cultures are maintained in a
continual pattern of growth. Focus particularly on those used in biotechnology, such as E. coli,
which is used to make human insulin.
Bacterial production of a substance such as E.coli are manipulated to produce chemicals
so that they are easily harvested for use in medicine. The continuous growth pattern is
maintained by devices like chemostat.
, “Lab 2 Culturing & Aseptic Technique BIO250L”
6. Which of these has a constant growth pattern: an open system or a closed system?
Open system has a constant growth pattern.
7. A human patient represents what kind of system for bacterial infections?
Open system .
8. You’re a physician trying to isolate bacterial colonies from the human gut in attempt to diagnose
a gastrointestinal infection. You streak your sample on a growth media containing glucose, amino
acids, and salts that contain both sulfur and phosphorous with a pH of 7. You incubate the plates
in aerobic conditions at 37 ˚C for three days, at which point you can see clear bacterial colonies
forming on the plate. Would you feel confident in stating that you had successfully cultured all
the bacteria from your gut sample? Why or why not?
No, I would not feel confident in stating that I had successfully cultured all the bacteria
from the cut sample. Because I would only know by seeing the aerobes on the cultures. I
wouldn’t be able to take into consideration the anaerobic bacteria since it will not grow in
this experiment.
“EXPERIMENT 1: Agar Plate Preparation and Bacterial Inoculation
Data Tables
Table 1: Experiment 1 Colony Growth
Growth
Plate Number Source
(Color, Amount, Shape, etc.)
Curled, orange, rounds
Rhizoid, large, Irregular, lobate,
1 Shoe yellow, some raised. A lot of
different colonies. = ++++ a lot of
growth patterns
White, umbonate, punctiform
2 Floor
+++ moderate growth
undulate (wavy) white, flat
3 Wall
++ moderate growth
4 Control Nothing
small, white, punctiform
5 Airborne Contamination
+ small growth
Post-Lab Questions
1. Do some research and try to identify one to three types of microbes cultured on your plates.
Using any resources available to you (i.e., a textbook or internet sources such as the CDC
website), look up what bacteria are usually found on the areas from which you obtained your
samples and the morphological characteristics of their colonies. Describe what morphological
traits (i.e., size, shape, arrangement, color, margin, etc.) led to your hypothesized species
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