MIP 302 exam with Answers to Questions
where do you write your name and section number on the plate? why?✔✔on the
bottom so that the plate can still be identified even if it is separated from the lid
Why is broth not used as an isolation medium?✔✔the different types of bacteria that
grew cannot be separated or identified
would you use a TSA slant as an isolation medium?✔✔no, the slant does not allow
enough surface area for growth or enough access
why is it important that the TSA slant be inoculated with a pure bacterial culture,
instead of a mixed culture?✔✔pure bacterial cultures must be used in order to
properly identify the identity of the bacteria in the sample
Gram stain procedure✔✔1: primary stain - crystal violet (purple)
2: mordant- grams iodine (binds to crystal violet, still purple)
3: decolorizer- alcohol/acetone mixture (removed iodine from gram negative, gram + is
purple, gram - is colorless)
4: counterstain - safranin (turns gram - cells pink)
gram + appear what color✔✔purple
gram - appear what color✔✔pink
acid-fast staining procedure✔✔1: primary stain - carbon fuchsin + heat (all cells hot
pink/red)
, 2: decolorized- acid alcohol mix (acid-fast + are pink, acid-fast - are colorless)
3: secondary stain - methylene blue (acid-fast - are blue)
endospores stain what color✔✔green
vegetative cells stain what color✔✔pink
acid-fast + appear what color✔✔pink/red
acid-fast - appear what color✔✔blue
endospore staining procedure✔✔1: primary stain - malachite green + heat (all green
at this point)
2: decolorizer - water (washes off excess stain out of vegetative cells, endospores =
green, vegetative cell = colorless)
3: secondary stain - safranin (endospores = green, vegetative cells = pink)
why do gram positive cells stain purple, and gram negative cells stain pink?✔✔gram +
cells stain purple because they have a thick peptidoglycan layer that is too thick for the
decolorizer to remove the grams iodine, whereas gram - cells have a thin ppg that allow
for the removal of the mordant and for them to stain pink
what objective lens do you use to determine the gram stain reaction and the
morphology of bacteria?✔✔using the 100x objective lens allows for the gram stain
reaction and bacterial morphology to be determined
What is total magnification you use to determine the gram stain and bacteria
morphology?✔✔10x (ocular lens) x 100x (objective lens) = 1000x total magnification
where do you write your name and section number on the plate? why?✔✔on the
bottom so that the plate can still be identified even if it is separated from the lid
Why is broth not used as an isolation medium?✔✔the different types of bacteria that
grew cannot be separated or identified
would you use a TSA slant as an isolation medium?✔✔no, the slant does not allow
enough surface area for growth or enough access
why is it important that the TSA slant be inoculated with a pure bacterial culture,
instead of a mixed culture?✔✔pure bacterial cultures must be used in order to
properly identify the identity of the bacteria in the sample
Gram stain procedure✔✔1: primary stain - crystal violet (purple)
2: mordant- grams iodine (binds to crystal violet, still purple)
3: decolorizer- alcohol/acetone mixture (removed iodine from gram negative, gram + is
purple, gram - is colorless)
4: counterstain - safranin (turns gram - cells pink)
gram + appear what color✔✔purple
gram - appear what color✔✔pink
acid-fast staining procedure✔✔1: primary stain - carbon fuchsin + heat (all cells hot
pink/red)
, 2: decolorized- acid alcohol mix (acid-fast + are pink, acid-fast - are colorless)
3: secondary stain - methylene blue (acid-fast - are blue)
endospores stain what color✔✔green
vegetative cells stain what color✔✔pink
acid-fast + appear what color✔✔pink/red
acid-fast - appear what color✔✔blue
endospore staining procedure✔✔1: primary stain - malachite green + heat (all green
at this point)
2: decolorizer - water (washes off excess stain out of vegetative cells, endospores =
green, vegetative cell = colorless)
3: secondary stain - safranin (endospores = green, vegetative cells = pink)
why do gram positive cells stain purple, and gram negative cells stain pink?✔✔gram +
cells stain purple because they have a thick peptidoglycan layer that is too thick for the
decolorizer to remove the grams iodine, whereas gram - cells have a thin ppg that allow
for the removal of the mordant and for them to stain pink
what objective lens do you use to determine the gram stain reaction and the
morphology of bacteria?✔✔using the 100x objective lens allows for the gram stain
reaction and bacterial morphology to be determined
What is total magnification you use to determine the gram stain and bacteria
morphology?✔✔10x (ocular lens) x 100x (objective lens) = 1000x total magnification
