Quiz 2 Flashcards
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Using a microscope adjust the light intensity by moving the______________ until the image has the best _________ against the back ground.
Diaphragm lever, contrast
Oil immersion is used on which objective?
100X
Should the diaphragm be fully open or fully closed during oil immersion?
Open
Always move objective lens and stage towards or away from each other to prevent damage to the lens
Away
What is used to clean the oil from the objective?
Lint free Lens paper
If the light intensity is too high the ________ between the microbes and the _________ will suffer
Contrast, background
As magnification increases the light must ______
increase
Can kimwipes be used in the lens?
No
Reasons oil immersion lens is not working
Not enough oil, Air bubbles, not enough bacteria, didn’t centre, upside down slide, fine focus turned too far,
Why air dry the film?
to prevent washing off during staining, and denature bacterial enzymes that could digest the cell wall.
Preparing a smear - Add ___% methanol for ___min
95%, 1
thick smear will make it difficult to
observe cell shape, arrangement, and size - thick smears may not be completely decolorized in a differential stain.
staining times for 1. carbolfuchsin, 2. crystal violet, 3. methylene blue, 4. safranin in a simple stain?
- 5-10 sec
- 20-30 sec
- at least 1 min
- at least 1 min
gram stain - which stain first for how long
crystal violet for 20 secs
gran stain - which stain second for how long
Gram’s iodine - 1 min
Gram stain - decolorize with?
95% ethanol or ethanol/acetone
gram stain - which stain is 3rd? for how long?
Safranin - 1min
if gram’s iodine is pale yellow
it’s old and lost it’s potency
if culture used to prepare smear is over 18hours some gram- _____ bacteria will appear gram _______
positive, negative
if too much decolorizing agent is applied
too much crystal violet/iodine complex will wash out from gram positive cell walls
Why is negative stain beneficial in some cases
some cells are difficult to stain with basic dyes
some cells are fragile and easily distorted by heat-fixation
Negative stain - if nigrosin is pushed not pulled the film will not be_______
uniform
Preparing a capsule - on top of the fixed nigrosin cover with
safranin or crystal violet
Capsule stain is to view
capsules or slime layers
What stain can stain an endospore with heat?
Malachite Green
Endospores are generated by a few ______ of Gram_______ bacteria
genera, positive
the size of a microorganism is measured in
micrometers uM
a calibrated ruler on a glass disk is placed in an ocular lens and is called?
Ocular micrometer
engraved lines on the a calibrated ruler is _______aprt
10 uM
Gram-Positive finishes as what colour
purple
Gram-Negative finishes as what colour
safranin
