The fungus Penicillium produces a compound that blocks peptidoglycan assembly. Why is a fungus trying to kill bacteria?

Question

A.  Fungi eat bacteria.
B.  Fungi and bacteria are both decomposers and compete for resources.
C.  The compound produced by the fungus is used for nitrogen fixation, the antibacterial properties are accidental.
D.  The fungal compound is produced in response to a bacterial invasion of the fungal hyphae.

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 fungi? 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.  Fungi and bacteria are both decomposers and compete for resources.

Clarify Question
· What is the key concept addressed by the question?
        o You have a petri dish covered in bacteria, which form a translucent white coating on the dish. You then place pieces of Penicillium in the dish. 24 hours later, there is a clear ring around each of the pieces of Penicilium because all the bacteria within 2 millimeters of the fungus are dead. Why does Penicilium produce a chemical that is toxic to bacteria?
· What type of thinking is required?
        o This is an “evaluate” question, so use your knowledge about fungi and bacteria to evaluate the relative merit of each hypothesis. Remember, a hypothesis is an educated guess, so you should be able to back up your choice with facts.
 
Gather Content
· What do you already know about fungi? How does it relate to the question?
        o Fungi occur in a variety of environments, including soil and water. They can be multicellular or unicellular. Multicellular fungi have bodies made of hyphae, which are long strands one cell wide and many cells long. No fungi are autotrophs; they all need to consume other organisms to get energy. Some are decomposers, consuming material from dead organisms. Others are predators or parasites. One predatory fungus creates traps for nematodes. When the nematode gets stuck in the trap, the fungus sends hyphae into the nematode’s body and digests the nematode from the inside out.
· What other information is related to the question? Which information is most useful?
        o As decomposers, fungi are very important for carbon cycling. They can digest wood, which is very difficult. Which nutrient cycles are bacteria involved in?
  Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Each of the options provides a valid hypothesis as to why Penicilium produces a toxin that kills bacteria. You need to determine which option is the best hypothesis. Which evidence supports each hypothesis. Which evidence argues against each hypothesis?
 
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 hypothesize why Penicilium produces a toxin that kills bacteria. Answering the question depended on your ability to judge which option was the best hypothesis.
        o If you got the correct answer, well done!
        o If you got an incorrect answer, where did the process break down?
            · Fungi could eat bacteria, but they generally consume things that are larger. There isn’t much evidence against this hypothesis, but there isn’t much in favor of it either.
            · We know that bacteria and fungi compete for resources, so a fungus that kills neighboring bacteria would have access to more resources. This hypothesis had the best evidence in favor and the least evidence opposed to it.
            · There is no evidence that fungi participate in nitrogen cycling.
            · The toxin could be produced in response to an attack of pathogenic bacteria, but there is no evidence to support this hypothesis. Penicilium produces the toxin when exposed to any bacteria, not just pathogenic bacteria.