Vibrio cholerae lives in water and gets toxin genes from a virus by phage conversion. The toxin kills the intestinal epithelial cells in the human host, resulting in massive diarrhea. Untreated cholera has about a 50% mortality rate. How do the bacteria benefit?
A. Diarrhea helps the bacteria to spread from person to person.
B. Killing humans provides nutrients for the bacteria.
C. They don’t -- humans are not the main host and their symptoms are maladaptive for the bacteria.
D. The bacteria reproduce faster in a dead human.
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 cholera?
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?
A. Diarrhea helps the bacteria to spread from person to person.
Clarify Question
· What is the key concept addressed by the question?
o This question addresses cholera.
· What type of thinking is required?
o This question is asking you to weigh and judge evidence, or evaluate, to choose the best of the possible answers.
Gather Content
· What do you already know about cholera?
o Cholera is a devastating disease caused by the bacterium Vibrio cholerae.
o The bacterium usually exists in a harmless form, but a second, disease-causing form also occurs.
o A lysogenic phage introduces into the host bacterial cell a gene that codes for the cholera toxin.
o The toxin gene is expressed along with the other host genes, thereby converting the benign bacterium to a disease-causing agent.
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
o Does killing humans provide nutrients for the bacteria, or do they reproduce faster in a dead human? No, they require a living host.
o Are the symptoms of cholera maladaptive for the bacteria? No. As a water-borne disease, the diarrhea is essential for the bacteria and virus to spread from host to host.
o Does diarrhea help the bacteria to spread from person to person? Yes. The symptom is adaptive for the bacteria to help them spread.
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 The question required you to weigh and judge evidence, or evaluate, to choose the best of the possible answers.
o Did you recognize that diarrhea is adaptive for the bacteria and virus, because it spreads them to a new host?
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