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Here are Nine Safe Practices for the Microbiology Laboratory that you should follow
when working with microorganisms (James, 2008):
Treat all microorganisms as potential pathogens. While the majority of
microorganisms are not pathogenic to humans and have never been shown to
cause illness, under unusual circumstances a few microorganisms that are not
normally pathogenic can act as pathogens. Treat all microorganisms—
especially unknown cultures—as if they were pathogenic. A student who has a
compromised immune system or has had a recent extended illness should talk
with his or her instructor before working in the microbiology laboratory.
Sterilize equipment and materials. All materials, media, tubes, plates, loops,
needles, pipettes, and other items used for culturing microorganisms should
be sterilized by autoclaving. Otherwise, use commercially sterilized products.
Understand the operation and safe use of all equipment and materials needed
for the laboratory.
Disinfect work areas before and after use. Use a disinfectant, such as a 10%
bleach or 70% ethanol solution, to wipe down benches and work areas both
before and after working with cultures. Also be aware of the possible dangers
of the disinfectant, as 70% ethanol can catch fire around open flame or high
heat sources. Bleach, if spilled, can ruin your clothing. Either alcohol or bleach
can be dangerous if splashed in the eyes. You should know where the nearest
eyewash station and sink are located.
Wash your hands. Use a disinfectant soap to wash your hands before and after
working with microorganisms. Non-disinfectant soap will remove surface
bacteria and can be used if disinfectant soap is not available. Gloves may be
worn as extra protection.
Do not eat or drink in the lab, nor store food in areas where
microorganisms are stored. Never eat or drink in the laboratory while
working with microorganisms. Keep your fingers out of your mouth, and wash
your hands before and after the laboratory activity. Cover any cuts on your
hands with a bandage. Gloves may be worn as extra protection.
Label everything clearly. All cultures, chemicals, disinfectants, and media
should be clearly and securely labeled with their names and dates. If they are
hazardous, label them with proper warning and hazard information.
Autoclave or disinfect all waste material. All items to be discarded after a
class, such as culture tubes, culture plates, swabs, toothpicks, wipes,
disposable transfer needles, and gloves, should be placed in a biohazard
autoclave bag and autoclaved 30 to 40 minutes at 121° C at 20 pounds of
pressure. If no autoclave is available and you are not working with
pathogens, the materials can be covered with a 10% bleach solution and
allowed to soak for at least 1 to 2 hours.
Clean up spills with care. Cover any spills or broken culture tubes with a 70%
ethanol or 10% bleach solution; then cover with paper towels. After allowing the spill
to sit with the disinfectant for a short time, carefully clean up and place the materials
in a biohazard autoclave bag to be autoclaved. Wash the area again with
disinfectant. Never pick up glass fragments with your fingers or stick your fingers
into the culture itself; instead, use a brush and dustpan. If working with animal or
plant pathogens, keep the area clear and notify your instructor.
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Lab report:
A visual diagram: using 3 of your most interesting petri dishes, draw and colour a
visual representation of the growth in your dish. Include the location it was
swabbed from.
Dish 1:
Location:
Dish 2
Location:
Dish 3
Location:
What Can Grow on a Nutrient Agar Plate?
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Bacteria: Each distinct circular colony should represent an individual
bacterial cell or group that has divided repeatedly. Being kept in one place,
the resulting cells have accumulated to form a visible patch. Most bacterial
colonies appear white, cream, or yellow in color, and fairly circular in shape
Yeasts: Yeast colonies generally look similar to bacterial colonies. Some
species, such as Candida, can grow as white patches with a glossy surface.
Molds: Molds are actually fungi, and they often appear whitish grey, with
fuzzy edges. They usually turn into a different color, from the center
outwards.
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Bacteria grow tremendously fast when supplied with an abundance of nutrients.
Different types of bacteria will produce different-looking colonies, some colonies
may be colored, some colonies are circular in shape, and others are irregular. The
characteristics of a colony (shape, size, pigmentation, etc.) are termed the colony
morphology. Colony morphology is a way scientists can identify bacteria. In fact
there is a book called Bergey's Manual of Determinative Bacteriology (commonly
termed Bergey's Manual) that describes the majority of bacterial species identified
by scientists so far. This manual provides descriptions for the colony morphologies
of each bacterial species.
Although bacterial and fungi colonies have many characteristics and some can be
rare, there are a few basic elements that you can identify for all colonies:(1)
Form - What is the basic shape of the colony? For example, circular, filamentous, etc.
Elevation - What is the cross sectional shape of the colony? Turn the Petri dish on
end.
Margin - What is the magnified shape of the edge of the colony?
Surface - How does the surface of the colony appear? For example, smooth,
glistening, rough, dull (opposite of glistening), rugose (wrinkled), etc.
Opacity - For example, transparent (clear), opaque, translucent (almost clear, but
distorted vision, like looking through frosted glass), iridescent (changing colors in
reflected light), etc.
Chromogenesis (pigmentation) - For example, white, red, purple, etc.
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In each Dish describe the how the colonies are arranged based on the previous
diagrams and list whether it contains Bacteria, Fungi, or Mold
DISH 1:
Form
Elevation
Margin
Surface
Opacity
Chromogenesis
B, F, M ?
DISH 2:
Form
Elevation
Margin
Surface
Opacity
Chromogenesis
B, F, M?
DISH 3:
Form
Elevation
Margin
Surface
Opacity
Chromogenesis
B, F, M:
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Microscopic viewing of a your dish:
1. Select your most interesting dish to view with a microscope.
2. Select one person to be in charge of handling the open petri dish. This person
must wear gloves at all times.
3. Have them create a slide of one of your colonies. Using tooth pics, carefull remove
a small amount of the chosen colony, and apply it to a slide. Add a drop of water and
a slide cover.
4. Quickly replace the cover of the petri dish and return it to the zip lock bag.
5. Have each member of your group view the slide and make a sketch.
6. Please put the slide and cover into the garbage and everyone in your group should
sterilize their hands.
*** IF ANYONE IN YOUR GROUP IS PRONE TO RESPIRATORY ILLNESS OR HAS A
WEAKENED IMMUNE SYSTEM HAVE THEM SIT THIS LAB OUT!
1. Discussion Questions: Which of your sample locations produced the greatest
variety of micro organisms? Why do you think that is?
2. Which sample produced the fewest results? Why do you think that is?
3. What happened to your control group? Explain the results
What steps do you need to take in order to be able to positively identify your micro
organisms?
4. How could you have modified this lab to increase the results (IE: Either the
variety of micro organisms or the quantity of a single organism found in the dish)
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5. What conclusions could you draw from this lab that you could share with others
to help prevent the spread of micro organisms.
6. Create a “Public Health” handout promoting safety and prevention of micro
organisms. Use the gross factor. Your target audience is Elementary and Middle
school.