Download Prescott`s Microbiology, 9th Edition Chapter 26 –The Fungi

Prescott’s Microbiology, 9th Edition
Chapter 26 –The Fungi (Eumycota)
GUIDELINES FOR ANSWERING THE MICRO INQUIRY QUESTIONS
Figure 26.1 Compare the nodes and branches that lead to the monophyletic taxa Basidiomycota
and Ascomycota. How do they differ from those leading to Zygomycota and Chytridiomycota?
What can be concluded from this?
Both Zygomycota and Chytridiomycota are located at multiple nodes, while Basidiomycota and
Ascomycota are at only one node. Thus suggests the former two are paraphyletic (multiple
origins), while the latter are monophyletic (derived from one common ancestor each).
Figure 26.6 What is the function of the chytrid rhizoids?
Chytrid rhizoids penetrate substrates and are involved in nutrient acquisition.
Figure 26.8 Why do you think neither arbuscular mycorrhizae nor ectomycorrhizae enter the
host cell cytoplasm?
Arubscular mycorrhizae and ectomycorrhizae are in mutualistic relationships with their host
plants. If they penetrated the cytoplasm this would be an invasive and stressful to the plant and
would establish a parasitic relationship. Damage to the host would decrease host fitness, and
almost certainly the symbiotic fungi’s fitness as well.
Figure 26.10 What determines when a yeast cell can no longer bud?
Budding leaves a scar on the cell wall of the mother cell, which inhibits future budding at that
location. Once the entire cell wall is covered by scars, no budding can occur. Some process at
that point triggers cell senescence.
Figure 26.12 In what ways is the life cycle of filamentous ascomycetes similar to that of the
zygomycete shown in figure 26.7? How do the two life cycles differ?
The life cycles of ascomycetes and zygomycetes are similar in that they both undergo
germination with mating of negative and positive strains resulting in fertilization, karyogamy,
and meiosis. In ascomycetes, fertilization results in the formation of ascocarps whereas
zygomycetes form zygosporangium. Ascomycetes also have an additional mitosis step after
meiosis.
Figure 26.17 What adaptations do you think Ustilago has evolved that has led to its
pathogenicity? Contrast this with mycorrhizae.
Unlike mycorrhizae, Ustilago must penetrate the plant cells. Ustilago must undergo appressoria
formation in order to trigger the host to form the tumors that the fungus proliferates in.
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