Examples of questions at different Bloom’s levels1:
Prepared by Samantha Elliott
St. Mary's College of Maryland
St. Mary's City, MD
Level 1 (knowledge):
Which of the following is the correct order of the steps of a Gram stain?
A.
B.
C.
D.
E.
Safranin  Iodine  Alcohol  Crystal violet
Crystal violet  Iodine  Alcohol  Safranin
Iodine  Crystal violet  Alcohol  Safranin
Alcohol  Safranin  Iodine  Crystal violet
Crystal violet  Iodine  Safranin  Alcohol
Author’s comments: This question tests the ability of student to recall the steps of a Gram stain. There is
no higher order thinking other than memorization. Depending upon the specific reagents used in the
classroom, instructors can substitute more specific terms for “Iodine” and “Alcohol.”
Level 2 (comprehension):
Which step of the Gram stain dissolves lipids within the cell wall?
A.
B.
C.
D.
E.
Crystal violet
Iodine
Alcohol
Safranin
Water
Author’s comments: This question tests the ability of students to comprehend the purpose of different
steps in the Gram stain. While it is still lower-level cognition, more thought than simple memorization is
required. Depending upon the specific reagents used in the classroom, instructors can substitute more
specific terms for “Iodine” and “Alcohol.”
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Based upon the Blooming Biology Tool from Crowe et al. (2008) CBE-Life Sci Ed vol 7: 368-381
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Level 3 (application):
Scientists engineer a Gram-positive bacterium to express a polysaccharide-rich outer capsule. What
effect would this have on a Gram stain of this engineered organism?
A.
B.
C.
D.
E.
It would still stain as a Gram-positive bacterium.
It would stain as a Gram-negative bacterium.
It would become a Gram-indeterminate bacterium.
It would become a Gram-variable bacterium.
Cannot tell from the information provided.
Author’s comments: This is a classic perturbation of the system, testing the ability of students to
understand what happens to a Gram stain when you add in a polysaccharide capsule. Note that
application questions can require either lower- or higher-order cognitive skills. For purposes of CTQB, we
accept any level 3 or higher question.
Level 4 (analysis):
Your microbiology class is characterizing a single unknown bacterium. Each member of the class
performs three independent Gram stain replicates on the culture, and adds their results to the table
below. Which of the following is the best conclusion about your aggregate data?
Name
John
Sue
Mary
Liz
Steve
Age of
cultures
10-12 hours
12-14 hours
12 hours
12-24 hours
24-36 hours
Cell Morphology
Gram stain results
Rod, in chains
Rod, in chains
Rod, in chains
Rod, in chains
Rod, in chains
Gram positive, Gram positive, Gram positive
Gram positive, Gram positive, Gram positive
Gram positive, Gram negative, Gram positive
Gram positive, Gram negative, Gram negative
Gram negative, Gram negative, Gram negative
A. Fresh staining solutions should be made and the Gram staining performed again.
B. The unknown bacterium is Gram positive. Changes in cell wall structure cause older cultures
to stain differently.
C. The unknown bacterium is Gram negative. Newer cultures have incomplete cell walls which
cause them to stain differently.
D. The unknown bacterium is Gram indeterminate.
E. Students should practice their Gram staining technique on known bacteria before trying this
experiment again.
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Author’s comments: This question requires students to interpret data and select the best outcome. The
primary concept tested here is that age of culture plays a huge role in the outcome of a Gram stain.
Newer cultures are better indicators of Gram type than older cultures.
Level 5 (synthesis):
Author’s comments: Not possible for multiple choice questions. Synthesis requires the creation of
something new. On multiple choice questions, students choose from a series of answers, rather than
synthesizing a new answer.
Level 6 (evaluation):
As your final project in lab, you and your classmates are tasked with identifying a single, unknown
organism in your Microbiology class. One of your friends asks you to check over her work to see if it
makes sense. She hypothesizes that she has identified a gut-associated bacterium based upon the
results in the table below. Based upon these results, choose the best answer in regards to your friend’s
hypothesis.
Gram stain
negative
A.
B.
C.
D.
E.
Cell
morphology
short rod
Motility?
Spores?
yes
no
Lactose
fermentation
positive
Oxygen
requirements
facultative
anaerobe
Her hypothesis is correct. It’s definitely a gut-associated organism.
Her hypothesis may be correct. She should run a coagulase test to be sure.
Her hypothesis may be correct. She should grow the organism on MacConkey agar to be sure.
Her hypothesis is incorrect. It’s definitely a soil-associated organism.
Her hypothesis is incorrect. She should run more tests to identify the organism.
Author’s notes: This question not only requires data interpretation, but the use of this information to
support a specific hypothesis, making it an evaluative item. Enteric organisms can grow in the presence
of bile salts, which are present in MacConkey agar. Because this organism is already identified as a
Gram-negative bacterium, MacConkey agar is an appropriate choice because it selects for growth of only
Gram-negative bacteria. MacConkey agar would be inappropriate for a Gram-positive enteric organism,
such as Enterococcus species. A bile esculin test would be more appropriate for those organisms.
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Table 1. Characteristics of multiple choice questions according to the Blooming Biology Tool (Crowe et
BLOOM’S LEVEL
CHARACTERISTICS OF MULTIPLE CHOICE
QUESTIONS
Recall of information
No significant distractors
Understanding of concept or terms
Includes significant distractors to test student
misconceptions
Knowledge
Comprehension
Application
Prediction of most likely outcome
New situation or perturbation of system
Analysis
Data interpretation and selection of best
conclusion
Synthesis
Evaluation
Not applicable
Assessment of information relative to support of
an argument
al. 2008. CBE-Life Sci Ed vol 7: 368-381). Rows in grey are Bloom’s levels not appropriate for submission
to CTQB.
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