Microbiology Lab Exam # 1 Questions
and Answers 100% Pass
Considering the cultures used to inoculate each medium in this exercise, how many
different microbial types should you expect to see in/on each medium? (1.4) - ✔✔You
should only have 1 if using good sterile technique. A successful aseptic transfer will
have only micrococcus lutes growth- this would be a pure culture
You were asked to describe differences in appearance of growth in each culture, if
present. In which medium was this the most difficult to determine? What made it
difficult? (1.4) - ✔✔More difficult to see in broth because you can only see if growth
occurred on the top or bottom etc. Better in slant because you can observe different
growth patterns.
Which medium was most difficult for you to transfer from? Which medium was most
difficult for you to inoculate? Why? (1.4) - ✔✔Most people don't like working with
slants (solid)
If you got growth on sterile NA and NB slant rubes, why? (1.4) - ✔✔Possible
contamination include not heating the loop to orange-hot, not holding the open tubes
on an angle, and/or placing the cap on the table surface during the process.
Katelyn Whitman, All Rights Reserved © 2025 1
,Did you notice a difference in density (turbidity) of growth in NB tubes inoculated from
NB and NA slants? Possible reasons?( 1.4) - ✔✔Generally, more cells are transferred
from growth on a solid medium than from a broth culture. Therefore, broth cultures
made from growth on a solid medium will show greater turbidity than those inoculated
from a broth culture.
Did you notice a difference in density of growth on NA slants inoculated from NA
slants and NB? (1.4) - ✔✔Generally there will be denser growth on the slant inoculated
from the NA slant, because more cells are transferred from solid medium than broth.
Pure culture (1.4) - ✔✔When a culture ( a medium that contains living microbes)
contains a single species.
Broths (1.4) - ✔✔A medium used to grow microbes when fresh cultures or large
numbers of cells are required. Used for ID.
Agar Slant (1.4) - ✔✔A type of medium used to grow stock cultures that can be
refrigerated after incubation and maintained for several weeks.
Plated Media (1.4) - ✔✔A type of medium used for obtaining isolation of species,
differential testing, and quantifying bacterial densities.
Inoculating loops (1.4) - ✔✔An instrument used to inoculate a medium.
Inoculation (1.4) - ✔✔To introduce (cells or organisms) into a culture medium.
Katelyn Whitman, All Rights Reserved © 2025 2
,Using a pencil, draw a quadrant streak (1.5) - ✔✔Should look like this. You should also
rotate a little less than 90 Degrees each streak, and heat the loop so you can get good
results. Also, let the loop cool!!
Mixed Culture (1.5) - ✔✔A microbial culture consisting of two or more species.
What is generally the first step in identifying a microbial organism? (1.5) - ✔✔Obtaining
isolations of Individual colonies. The technique we used in class was the isolation
technique- the streak plate. Cells that have been sufficiently isolated will grow into
colonies, consisting only of the original cell type.
Colonies (1.5) - ✔✔Individual microbial cell type. They can also form from a pair, chain,
or cluster of cells.
Colony Forming Unit (CFU) (1.5) - ✔✔A more correct description of the colony origin
Zigzag Inoculation (1.5) - ✔✔A type of inoculation pattern used to when the sample
does not have a high enough cell density.
Quadrant streak technique: (1.5)
- how much space should you try to use?
- describe what each of the quadrants should look like
Katelyn Whitman, All Rights Reserved © 2025 3
, - describe order - ✔✔- maximize the space used
- Q1: confluent growth (colonies overlapping), max growth
- Q2: less growth, some separation
- Q3: even less growth
- Q4: isolated colonies
- flame, only go to culture once at the beginning, Q1, flame, Q2, flame, Q3, flame, Q4,
flame
Quadrant plate questions: (1.5)
- What if no overlap?
- too much overlap?
- plate with white and yellow colonies is what type of plate? - ✔✔- no overlap --> no
isolation
- too much overlap --> too much confluent growth
Katelyn Whitman, All Rights Reserved © 2025 4
and Answers 100% Pass
Considering the cultures used to inoculate each medium in this exercise, how many
different microbial types should you expect to see in/on each medium? (1.4) - ✔✔You
should only have 1 if using good sterile technique. A successful aseptic transfer will
have only micrococcus lutes growth- this would be a pure culture
You were asked to describe differences in appearance of growth in each culture, if
present. In which medium was this the most difficult to determine? What made it
difficult? (1.4) - ✔✔More difficult to see in broth because you can only see if growth
occurred on the top or bottom etc. Better in slant because you can observe different
growth patterns.
Which medium was most difficult for you to transfer from? Which medium was most
difficult for you to inoculate? Why? (1.4) - ✔✔Most people don't like working with
slants (solid)
If you got growth on sterile NA and NB slant rubes, why? (1.4) - ✔✔Possible
contamination include not heating the loop to orange-hot, not holding the open tubes
on an angle, and/or placing the cap on the table surface during the process.
Katelyn Whitman, All Rights Reserved © 2025 1
,Did you notice a difference in density (turbidity) of growth in NB tubes inoculated from
NB and NA slants? Possible reasons?( 1.4) - ✔✔Generally, more cells are transferred
from growth on a solid medium than from a broth culture. Therefore, broth cultures
made from growth on a solid medium will show greater turbidity than those inoculated
from a broth culture.
Did you notice a difference in density of growth on NA slants inoculated from NA
slants and NB? (1.4) - ✔✔Generally there will be denser growth on the slant inoculated
from the NA slant, because more cells are transferred from solid medium than broth.
Pure culture (1.4) - ✔✔When a culture ( a medium that contains living microbes)
contains a single species.
Broths (1.4) - ✔✔A medium used to grow microbes when fresh cultures or large
numbers of cells are required. Used for ID.
Agar Slant (1.4) - ✔✔A type of medium used to grow stock cultures that can be
refrigerated after incubation and maintained for several weeks.
Plated Media (1.4) - ✔✔A type of medium used for obtaining isolation of species,
differential testing, and quantifying bacterial densities.
Inoculating loops (1.4) - ✔✔An instrument used to inoculate a medium.
Inoculation (1.4) - ✔✔To introduce (cells or organisms) into a culture medium.
Katelyn Whitman, All Rights Reserved © 2025 2
,Using a pencil, draw a quadrant streak (1.5) - ✔✔Should look like this. You should also
rotate a little less than 90 Degrees each streak, and heat the loop so you can get good
results. Also, let the loop cool!!
Mixed Culture (1.5) - ✔✔A microbial culture consisting of two or more species.
What is generally the first step in identifying a microbial organism? (1.5) - ✔✔Obtaining
isolations of Individual colonies. The technique we used in class was the isolation
technique- the streak plate. Cells that have been sufficiently isolated will grow into
colonies, consisting only of the original cell type.
Colonies (1.5) - ✔✔Individual microbial cell type. They can also form from a pair, chain,
or cluster of cells.
Colony Forming Unit (CFU) (1.5) - ✔✔A more correct description of the colony origin
Zigzag Inoculation (1.5) - ✔✔A type of inoculation pattern used to when the sample
does not have a high enough cell density.
Quadrant streak technique: (1.5)
- how much space should you try to use?
- describe what each of the quadrants should look like
Katelyn Whitman, All Rights Reserved © 2025 3
, - describe order - ✔✔- maximize the space used
- Q1: confluent growth (colonies overlapping), max growth
- Q2: less growth, some separation
- Q3: even less growth
- Q4: isolated colonies
- flame, only go to culture once at the beginning, Q1, flame, Q2, flame, Q3, flame, Q4,
flame
Quadrant plate questions: (1.5)
- What if no overlap?
- too much overlap?
- plate with white and yellow colonies is what type of plate? - ✔✔- no overlap --> no
isolation
- too much overlap --> too much confluent growth
Katelyn Whitman, All Rights Reserved © 2025 4
