Lecture 19: Fungi

Question 1

Fungal usages for humans

Answer 1

•Food
-Bread, some cheeses, alcoholic beverages
•Important drugs
-Antibiotics—Penicillin, cephalosporin
-Cyclosporin—an anti-rejection drug

Question 2

Dangers of fungi

Answer 2

-Some are parasitic in animals
-Some cause important diseases in plants

Question 3

Fungi beneficial roles

Answer 3

•Decompose dead organisms-recycle nutrients
•90% of plants form mycorrhizae
-Fungal associations with roots helps absorb water and minerals

Question 4

Fungi 5 phyla

Answer 4

•Chytrids
•Zygomycetes
•Glomeromycetes
•Ascomycetes
•Basidiomycetes

Question 5

Penicillin discovery

Answer 5

Sir Alexander Fleming in 1929

Question 6

Fungi types

Answer 6

•Yeast
-Small round single cells
•Molds
-long branched filaments called hyphae
•Some fungi are dimorphic
-can grow as both yeast-like cells and mold-like cells

Question 7

Yeasts

Answer 7

•unicellular fungi
•Many are Ascomycetes
•Most reproduce by budding
•include the common model yeast: Saccharomyces cerevisiae (aka Brewer’s yeast or baker’s yeast

Question 8

Lee Hartwell

Answer 8

Won Nobel Prize in 2001 for studies using budding yeast (Saccharomyces cerevisiae

Question 9

Paul Nurse

Answer 9

Nobel prize in 2001
-Cell cycle studies in S. Pombe (co-awarded with Lee Hartwell)

Question 10

Fungal division types

Answer 10

•Division by budding and fission
•Dendritic colony morphology
•Repeated, simultaneous multi-budding
•Meristematic division, filamentation, and cellularization

Question 11

Fungi quality

Answer 11

•Fungi are often heterotrophs
-Feed on preformed organic material
•Fungi digest THEN ingest
•Fungi produce hydrolysis enzymes that are secreted and break-up organic material
•Digested food absorbed
•Many fungi are saprobes
-Get nutrients from dead organisms

Question 12

Saprobes

Answer 12

Use non-living material
Important scavengers

Question 13

Parasites

Answer 13

Use organic material from living hosts, harming them in some way

Question 14

Mutualists/Symbionts

Answer 14

Fungi that live in association with the host without harming it (and often helping it).

Question 15

Molds

Answer 15

•Molds are filamentous fungi
•Cells may contain more than one nucleus, sometimes 100:
-A single filament is known as a hypha: a nucleated tube containing cytoplasm
•Some grow below the surface
-Largest organism on Earth may be Armillaria -Spreads over 1000s of acres and several feet deep.

Question 16

Common molds

Answer 16

-Rhizopus
-Aspergillus

Question 17

Spores

Answer 17

Aerial hypha form conidia: asexual spores

Question 18

Mushrooms

Answer 18

•Basidiomycetes
-Filamentous fungi that form fruiting bodies
•Sexual spores

Question 19

Sexual spores

Answer 19

(Basidiospores) on the underside on the cap of the mushroom. Spores dispersed by wind.

Question 20

Mycorrhizae

Answer 20

•’Fungal-root’
•Rootz of most terrestrial plants are mycorrhizal
•Mycorrhizal fungi get their carbon from root secretions and inorganic minerals from the soil
•Mycorrhizal plants get more nutrients from the soil due to greater surface area from fungal filamentous cells

Question 21

Mycorrhizae phyla

Answer 21

•Zyomycetes
•Glomeromycetes
•Ascomycetes
•Basidiomycetes

Question 22

Mycorrhizal interaction

Answer 22

-Ectomycorrhiza and endomycorrhiza
•Fungus provides inorganic materials for plant (N and Pi)
•Plant provides organic materials (C based) for fungus
Mutualistic interaction

Question 23

Truffles

Answer 23

Truffles are ectomycorrhizal fungi and are therefore usually found in close association with the roots of trees

Question 24

Plant fungal pathogens

Answer 24

•Dutch elm disease
•Corn smut
•Rice blast

Question 25

Magnaporthe oryzae

Answer 25

Causes rice blast, the most serious disease of cultivated rice

Question 26

Chytrids

Answer 26

Infect frogs, causes loss in amphibian biodiversity
Accelerated spread due to climate change

Question 27

P. destructans

Answer 27

An ascomycetous fungus associated with bat “White-Nose syndrome” (WNS)
-An emerging disease of hibernating bats

Question 28

Human pathogenic fungi

Answer 28

•Most serious ‘mycoses’ are not contagious
-do not spread by person to person contact
-Result from exposure to environmental sources
•Dermatophytes are contagious
-Live in dead layers in the skin
-ex. Ringworm
•Only 4 know fungi are true human pathogens (most are opportunistic)
•Dimorphic depending on temperature

Question 29

Candidiasis

Answer 29

•Candida is part of normal microbial flora on skin and mucous membranes
-Normal part of GI tract in most people
-A pathobiont—lives in association with outer organisms but don’t derive their nutrition from them
•Causes both mucosal infections (oral thrush, yeast infections) and bloodstream infections (typically in immuno-compromised individuals, target macrophages)

Question 30

Biofilms and candida infections

Answer 30

•Yeast cells attach to the surface
•Grow up several layers of cells
• Switch to form hyphae and extracellular matrix formed
•Dispersal to new sites

Question 31

Why are biofilms drug resistant?

Answer 31

•Physical barriers to the drug
•Non-dividing cells/persister cells that are more resistant to the drug
• Cells in biofilms can activate responses that decrease drug efficiency
(E.g., unregulate effluent drug transporters)

Question 32

Candida albicans produces a toxin

Answer 32

Ece1 is a secreted peptide (“candidalysin”) that generates pores in host cells

Candidalysin allows candida to colonize the gut

Question 33

Did fungi end the reign of the dinosaurs?

Answer 33

Mammals are more resistant to fungal infections due to higher body temperature, this out-survived the dinosaurs when fungi began to flourish