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Microbiology 201 lab RUBENSTEIN IVY TECH (1)
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Microbiology 201 lab RUBENSTEIN IVY TECH (1)
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Microbiology 201 lab RUBENSTEIN IVYTECH
a gram negative organism will appear _______ when observed under a microscope. -
ANS-red or pink
clinical specimens will almost always be what type of culture? - ANS-mixed
coccus is what shape? - ANS-round
describe the structure of the gram positive cell wall - ANS-it would have a thick and
relatively rigid layer of peptidoglycan. the cytoplasmic membrane contains phospholipid
bilayer with proteins.
given the information below, do the steps to find the total number of bacteria in the
beaker:
petri dish size: 57cm^2
beaker: 500 ML
volume of effluent plated: 0.2ML
box 1: 14 colonies
box 2: 10 colonies
box 3: 11 colonies
box 4: 14 colonies
box 5: 13 colonies - ANS-total number of colonies: 14+10+11+14+13=62
62/5= 12.4
12.4X5cm^2= 706.8 colonies per plate
706.8/0.2ML= 3534 bacteria per ML
3534X500ML= 1,767,000 bacteria in 500 ML beaker
how can you tell whether a sample is gram positive or gram negative? - ANS-gram
positive is a PURPLE stain
gram negative is a PINK stain
how do you count the colonies on the petri dish if there seem to be >100? - ANS-you
would draw 5 1cm squares. you would then make a table(1-5 in each box)then count
the colonies in the squares and add them to the table. add up all the colonies and divide
by 5. once you find the average you would then multiply it by 57cm^2
, how do you determine the concentration of bacteria? (bacteria per ml) - ANS-take the
number of colonies on the petri dish and divide it by the amount of effluent volume
added (ex.410.4 colonies/plate X .4 ml)
how do you determine the total number of bacteria in the beaker? - ANS-take the
bacteria per ML and multiply it by 500 ml (size of beaker)
how do you do a T-Streak? - ANS-1. on petri dish, draw a T
2: follow the 1-3 steps on picture
how do you do an endospore stain? - ANS-schaffer fulton method
1. malachite green applied-bacteria smeared
2. heated until steaming
3. washed with water
4. safranin added
how do you do the Ziehl - Neelson method for acid fast stain? - ANS-1. smear covered
with carbolfuschin (red)
2. flamed until steam produced (shy of boiling)
3. stain rinsed
4. decolorizer (acid alcohol)
5. rinsed
6. loefflers methylene blue
how would you do a capsule or negative stain? - ANS-1. use acidic stain (congo red or
nigrosin)
2. basic stain (fuschin or methylene blue)
3. if worked, halo should appear
**bacteria is suspended in serum to adhere to surface instead of heat fixing
how would you ensure you keep your specimen sterile? - ANS-ensure you flame before
and after using/opening or dipping items. Keep items closed when not using and ensure
the flamed area doesn't touch anything
if the colonies on the petri dish are <100, what would be your next step? - ANS-you
would just count the colonies and that would be the total on the plate (DO NOT divide
by 5 or multiply by 57cm^2)
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