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ULM Micro Lab Midterm (Ch. 1-9)

Terms in this set (55)

Why would a viable count or serial dilution technique be used?
to count the number of live bacteria in a culture when there are too many cells in a culture
When microorganisms accidentally get into your culture, the culture is said to be...
contaminated
How do you label your work?
your name, date, and specimen (write label on the bottom of the petri plate)
Characteristics of a Colony
Form, Elevation, and Margin
Negative stain
a simple stain that stains the background but leaves the bacteria unstained (Capsule stain)
Heat fixing...
expands the cell wall & allows for the stain to set in
Why do mother cells not pick up a malachite green stain during endospore staining?
b/c of their tough protein coats made of keratin, they are highly resistant
Transient flora
species of microorganisms that reside on the skin surface and are easily removed
Resident (or normal) flora
species of microorganisms that live naturally and permanently in various areas of our body
General purpose media
used to grow a wide variety of microorganisms (Nutrient agar)
Enriched media
contains extra nutrients needed by some bacteria
Selective media
inhibits growth of some bacteria
Differential media
makes it easy to distinguish colonies of different microbes on the same plate
Simple stain
staining a bacteria using a single stain
Differential stain
the use of multiple stains to distinguish between different bacteria
Gram-negative cell wall
has three layers consisting of a cytoplasmic membrane, thin peptidoglycan layer, and an outer cell membrane
Gram-positive cell wall
has many layers of peptidoglycan (thick) and teichoic acids
Gram Stain Mechanism:
helps distinguish between different organisms
1. Crystal Violet (primary stain)
2. Iodine (mordant)
3. Ethyl Alcohol (decolorizer)
4. Safranin (counterstain)
Once the counterstain (Safranin) sets on a bacteria, how can you tell whether the bacteria is gram-negative or gram-positive?
gram-negative bacteria will appear red/pink; gram-positive bacteria will appear purple
Process of making a "smear":
-Place a drop of water onto a clean glass slide
-Flame your loop, pick up a small amount of culture, and mix it into the drop of water, spreading it
-Flame the loop again & allow the smear to air-dry
What is the main function of the bacterial endospore?
to ensure the survival of a bacteria through periods/centuries of environmental stress
What is one function of the bacterial capsule?
acts as a virulence factor b/c it enhances the ability of bacteria to cause disease
What colors are the endospores after endospore staining? The mother cell?
the endospores are a dark blue/green color; the mother cells are pinkish
How would opsonins affect the pathogenicity of a capsule?
they would lessen the chance for the bacterial cell to cause diseasse
Capsule Stain Mechanism:
helps see the capsule as a light halo around the bacteria cell by staining the background
1. Congo Red (primary stain)
2. Acid Alcohol (decolorizer)
3. Carbol Fuchsin (counterstain)
How can any stain be observed under a microscope?
with oil immersion (100x)
Differences between terminal, central, and subterminal spores:
terminal- at the end of the cell
central- in the middle of the cell
subterminal- between the middle and the end of the cell
Difference between endospore and fungal spore:
fungal spores promote reproduction (can make many spores); bacterial endospores don't promote reproduction (one cell makes one endospore)
Are spores involved in bacterial reproduction?
Nah
Scanning lens
shortest objective, magnification of 4x
Low power objective
10x
High dry objective
40x
Oil immersion lens
100x
Compound microscope
has two magnifying lenses
1. Ocular- eyepiece lens (usually 10x)
2. Objective- nosepiece lenses (commonly 4x, 10x, 40x, and 100x)
What is the purpose of mordant?
causes a stain to become more tightly bound to the cell
Sterile
incapable of reproducing
Synthetic medium
one whose composition can be changed according to the requirement of the microbes to be grown
How does handwashing effect nosocomial infections?
it lessens the possibility of contamination and the presence of bacteria
Streak Plate
performed by spreading an inoculum of bacteria across the surface of an agar plate in such a way as to produce isolated colonies
Pour Plate
made by inoculating melted agar with bacteria then pouring the agar into an empty Petri plate to harden
Plate Count Technique:
dilution= volume of sample/ volume of sample + dilutent
Proper Aseptic Technique:
1. Protect yourself and others by not allowing the culture you are working with to escape
2. Prevent unwanted outside microorganisms from contaminating your culture or your patient
Endospore Staining Mechanism:
helps visualize bacterial endospore
1. Malachite Green (primary stain)
2. Heat (mordant)
3. Safranin (counterstain)
What effect does the presence of a capsule have on pathogenicity?
it allows certain species of bacteria to escape the bodies defenses and produce infection
The amount of light that passes through is called...
transmittance
Cocci
spherical shaped bacteria
Tetrad
a group of four bacteria
Streptococci
chains of cocci
Bacillis
rod shaped bacteria
Staphylococci
clusters of bacteria
What regulates the amount of light that reaches the slide?
the diaphragm
The ability of a microscope to remain relatively in focus when changing from one objective to another is called...
parfocal
Bacterial cell wall molecule that allows gram staining is called...
peptidoglycan
For example, if your objective lens is set to 40x, what is the total magnification?
400x
Spirochetes
flexible helicoidal bacteria
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