STRAIGHTERLINE MICROBIOLOGY LAB
BIO250L LABS 1 2 3 4 5 6 7 8 EXAMINATION
TEST 2026 PRACTICE QUESTIONS AND
RELIABLE ANSWERS GRADED A+
⩥ Which agent seemed to be least effective at removing microbes from
the fingertips? Answer: Hibiclens was the least effective at removing
microbes because about 3 different types of bacteria grew on my plate.
⩥ What other variables besides the cleansing agent might be responsible
for any differences noted between fingers or students? Answer: Some
other variables that may be responsible for any differences are the
bacteria that was on our fingertips before, where i rubbed the bottom of
my shoe, the duration of hand washing, and the action of scrubbing my
palm.
⩥ Did you or any other students notice some microbes persisting more
than others after washing? Answer: Yes, some factors that may have
contributed are how long i washed my hands, how long it was in the
hand washing agent, and how vigorously i scrubbed my palm.
⩥ What media was most difficult to transfer from? Which media was
most difficult to inoculate; For me specifically. Answer: I didn't think
that any of the mediums were difficult to transfer from. If i had to say
one, i would say the plate was most difficult just because you have to
,stay very still to make sure you don't puncture the plate. The Slants were
more difficult to inoculate because i was worried about puncturing the
slant.
⩥ When preparing a bacterial smear for staining, why is it important to
AIR DRY the slides before heat fixing? Answer: To prevent boiling
during the heat fix, that would damage the cells.
⩥ To observe the SHAPE of individual bacterial cells typically requires
total magnification of: Answer: 1000x
⩥ The total magnification of a microscope with 10X ocular lens and
40X objective lens would be: Answer: 400x
⩥ In scientific practice, experimental control samples (positive and
negative controls) are: Answer: Fundamental and required.
⩥ You failed to achieve isolation from your streak plate. What might
have gone wrong? Answer: 1. You forgot to flame your loop between
quadrants.
2. You dipped your loop back in the bacteria, before going to the next
quadrant.
3. You placed your plate in the incubator with the lid up and
condensation caused the bacteria to spread.
, ⩥ A single colony on a plate is typically composed of: Answer: A visible
mass of cells that originated from one cell undergoing many rounds of
replication.
⩥ If you were performing a Gram stain and accidentally performed the
decolorization step using water rather than 95% ethanol, what would
your negative control look like (under the microscope, after completion
of the entire Gram-Stain procedure)? Answer: Purple
⩥ Microbiologists perform a differential stain in order to: Answer: Help
to visualize any differences between cells or parts of a cell.
⩥ After the Gram stain procedure, the cells must be examined under the
microscope - cells from your Gram positive control should appear:
Answer: Purple
⩥ Gran Negative cells appear _____ after the gram stain procedure.
Answer: Clear, After safrinin; Pink
⩥ When should you wear gloves in the microbiology laboratory?
Answer: 1. When working with a live bacterial specimen.
2. When working with chemicals or reagents that you are not familiar
with.
BIO250L LABS 1 2 3 4 5 6 7 8 EXAMINATION
TEST 2026 PRACTICE QUESTIONS AND
RELIABLE ANSWERS GRADED A+
⩥ Which agent seemed to be least effective at removing microbes from
the fingertips? Answer: Hibiclens was the least effective at removing
microbes because about 3 different types of bacteria grew on my plate.
⩥ What other variables besides the cleansing agent might be responsible
for any differences noted between fingers or students? Answer: Some
other variables that may be responsible for any differences are the
bacteria that was on our fingertips before, where i rubbed the bottom of
my shoe, the duration of hand washing, and the action of scrubbing my
palm.
⩥ Did you or any other students notice some microbes persisting more
than others after washing? Answer: Yes, some factors that may have
contributed are how long i washed my hands, how long it was in the
hand washing agent, and how vigorously i scrubbed my palm.
⩥ What media was most difficult to transfer from? Which media was
most difficult to inoculate; For me specifically. Answer: I didn't think
that any of the mediums were difficult to transfer from. If i had to say
one, i would say the plate was most difficult just because you have to
,stay very still to make sure you don't puncture the plate. The Slants were
more difficult to inoculate because i was worried about puncturing the
slant.
⩥ When preparing a bacterial smear for staining, why is it important to
AIR DRY the slides before heat fixing? Answer: To prevent boiling
during the heat fix, that would damage the cells.
⩥ To observe the SHAPE of individual bacterial cells typically requires
total magnification of: Answer: 1000x
⩥ The total magnification of a microscope with 10X ocular lens and
40X objective lens would be: Answer: 400x
⩥ In scientific practice, experimental control samples (positive and
negative controls) are: Answer: Fundamental and required.
⩥ You failed to achieve isolation from your streak plate. What might
have gone wrong? Answer: 1. You forgot to flame your loop between
quadrants.
2. You dipped your loop back in the bacteria, before going to the next
quadrant.
3. You placed your plate in the incubator with the lid up and
condensation caused the bacteria to spread.
, ⩥ A single colony on a plate is typically composed of: Answer: A visible
mass of cells that originated from one cell undergoing many rounds of
replication.
⩥ If you were performing a Gram stain and accidentally performed the
decolorization step using water rather than 95% ethanol, what would
your negative control look like (under the microscope, after completion
of the entire Gram-Stain procedure)? Answer: Purple
⩥ Microbiologists perform a differential stain in order to: Answer: Help
to visualize any differences between cells or parts of a cell.
⩥ After the Gram stain procedure, the cells must be examined under the
microscope - cells from your Gram positive control should appear:
Answer: Purple
⩥ Gran Negative cells appear _____ after the gram stain procedure.
Answer: Clear, After safrinin; Pink
⩥ When should you wear gloves in the microbiology laboratory?
Answer: 1. When working with a live bacterial specimen.
2. When working with chemicals or reagents that you are not familiar
with.
