Transcript Unit 2 Seminar

SC246 Microbiology
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General questions about the class~
Discussion Board
Participate throughout the week
Respond to at least 2 classmates posts
1. Give 3 examples of safety procedures you
should always follow in the microbiology lab.
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Microorganisms are normally present in the environment and many kinds are carried on
and in the human body. However, the varieties and concentrations of microorganisms
found in a microbiology laboratory are such that special precautions must be taken for the
safety of the student and those around him or her.
Everyone must wear a lab coat or lab apron while in the laboratory.
Do not work with an uncovered open cut. Bandages and plastic gloves are
available if needed.
Upon entering the lab, and after finishing, wash down your bench space with the
disinfectant provided.
Keep all sources of possible contamination out of your mouth--hands, pencils,
laboratory ware, other items. Do not smoke or eat in the laboratory.
Discard contaminated equipment such as pipettes into the disinfectant
tray provided on the bench. Petri dishes, test tubes, and similar items should be
placed in the large plastic containers provided. Pipettes are disposed of tip side
down.
Closed-toed shoes must be worn at all times in the laboratory.
Observe aseptic technique at all times when dealing with microbial cultures. Wash
hands with soap and water or disinfectant before leaving the laboratory.
2. Why do you stain cells before observing them
under the microscope? Name some common
shapes and arrangements observed when
viewing bacteria under a microscope.
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Average size: 0.2 -1.0 µm  2 - 8 µm
Basic shapes: cocci, rods, spiral
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Unusual shapes
Star-shaped Stella
 Square Haloarcula
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Figure 4.5
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Pairs: diplococci,
diplobacilli
Clusters:
staphylococci
Chains:
streptococci,
streptobacilli
Questions from text
3. In a Gram stain, one
step could be
omitted and still
allow
differentiation
between gram
positive and gram
negative cells.
What is that one
step?
3. In a Gram stain, one
step could be omitted
and still allow
differentiation
between gram
positive and gram
negative cells. What is
that one step?
The counterstain!
4. Assume that you are
viewing a Gram-stained
sample of vaginal
discharge. Large (10um)
nucleated red cells are
coated with small (0.5
um X 1.5 um) blue cells
on their surfaces. What
is the most likely
explanation for the red
cells and blue cells?
5. A sputum sample from Calle, a 30-year-old
Asian elephant, was smeared onto a slide and
air dried. The smear was fixed, covered with
carbolfuchin, and heated for 5 minutes. After
washing with water, acid alcohol was placed
on the smear for 30 seconds. Finally, the smear
was stained with methylene blue for 30
seconds, washed with water, and dried. On
examination at 1000X, the zoo veterinarian saw
red rods on the slide. What infection to the
results suggest? (Calle was treated and
recovered.)
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Acid fast bacteria
have mycolic acid in
their cell wall
Mycolic acid is a waxy
material which makes
acid-fast bacteria
resistant to the Gram
stain procedure
Acid fast bacteria
include the genus
Mycobacterium
members can cause
TB or leprosy
Photo credit: http://commons.wikimedia.org/wiki/File:Mycobacterium_tuberculosis_Ziehl-Neelsen_stain_02.jpg
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Discuss 2 other examples of staining
techniques, and when they are used.
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Negative staining
is useful for
capsules.
Heat is required to
drive a stain into
endospores.
Flagella staining
requires a
mordant to make
the flagella wide
enough to see.
Figure 3.13
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Tortora, G., Funke, B., & Case, C. (2007).
Microbiology: An Introduction (8th ed.). San
Francisco, CA: Pearson.