If the label on a slide reads Gram-positive bacillus, what would a students expect to see?

Question

A.  Pink helical cells
B.  Purple rod shaped cells
C.  Red spherical cells
D.  Blue coiled cells

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
 
Gather Content
· What do you already know about Gram staining? How does it relate to the question?
· What other information is related to the question? Which information is most useful?

  Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?

  Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
 

Answer 1

B.  Purple rod shaped cells

Clarify Question
· What is the key concept addressed by the question?
        o If you had a slide of a gram-positive bacillus bacterium that was stained using the Gram staining process, what would it look like?
· What type of thinking is required?
        o This question is an “apply” question. You need to combine your knowledge from two different areas (Gram staining and bacterial shapes) to answer the question.
 
Gather Content
· What do you already know about Gram staining? How does it relate to the question?
        o During gram staining, you use crystal violet and iodine, which stay under the peptidoglycan layer of gram-positive cells. In gram-negative cells, there are pores between sections of the peptidoglycan layer, which allow the crystal violet and iodine to escape.
        o You then use saffranin, which stains all of the cells. The gram-positive cells are already purple, so their color does not change much. The gram-negative cells change from clear to pink.
· What other information is related to the question? Which information is most useful?
        o Bacteria can be round, rod-shaped, or spiral-shaped. They can also be in chains, pairs, or clusters. What vocabulary terms describe each of these shapes and arrangements? Try looking up bacillus, coccus, spirochete, diplo, and strepto.

  Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o First, figure out which color the bacteria should be. Then figure out what shape the bacteria should be. For an option to be correct, both parts of the answer need to be correct.

  Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o This question asked you to determine what a gram-positive bacillus would look like.
        o If you got the correct answer, great job!
        o If you got an incorrect answer, where did you get stuck?
            · Gram-positive bacteria are purple after a gram staining procedure. Bacilli are rod-shaped. Cocci are round, and spirochetes are spiral-shaped.