1. Decomposers, Mutualists, and Killers
Fungi
Decomposers,
Mutualists,
and
Killers

2. Fungi Fungi (most) degrade dead organic matter
form nutritional partnerships with most vascular plants & some algae
are pathogens of some plants & animals

3. parasitic fungi Figure 31.1

4. Fungi Fungi are absorptive heterotrophs saprobic mutalistic parasitic
predatory (rarely)

5. predatory fungus Figure 31.5

6. fungal hyphae Figure 31.3

7. Fungi Fungal growth forms yeasts are unicellular
most fungi produce multinucleate hyphae
high surface area for absorption
coenocytic or septate
chitinous cell walls
mycelia are massed hyphae

8. c o n i d I a Figure 31.12

9. budding yeast Figure 31.2

10. Fungi Fungal reproduction asexual reproduction
sporangia - chambers producing haploid spores
conidia - naked spores on hyphal tips
binary fission or budding
fragmentation

11. Fungi Fungal reproduction sexual reproduction
between haploid hyphae of different mating types
fusion of haploid hyphae (plasmogamy) produces dikaryotic (n+n) hyphae (heterokaryon)
dikaryotic nuclei eventually fuse (karyogamy) to produce zygote
meiosis produces haploid spore nuclei

12. Fungi Phylogeny four phyla differ in presence of septa in hyphae
sexual reproductive structures
methods of sexual spore formation
DNA sequencing agrees that the four phyla are monophyletic

13. Fungi
Phylogeny
deuteromycetes are fungi without sexual reproductive data
a polyphyletic “holding category”
new techniques are assigning deuteromycetes to the four phyla

14. fungal phylogeny Figure 31-6

15. fungal classification Table 31.1

16. Fungi Phylum Chytridiomycota earliest diverging fungal group aquatic
parasitic or saprobic (rarely mutualistic)
unicellular or mycelial
haploid or diploid, none dikaryotic

17. Fungi Phylum Chytridiomycota reproduction in Allomyces
haploid zoospore germinates to produce haploid body
haploid body produces male and female gametangia
gametangia produce haploid gametes
[flagellated gametes and zoospores is a unique (ancestral?) character]

18. Fungi Phylum Chytridiomycota reproduction in Allomyces
pheromone attracts male gamete to female
fusion of gamete nuclei produces zygote
zygote grows into diploid body
diploid body produces many diploid zoospores
diploid zoospores produce more diploid bodies

19. Fungi Phylum Chytridiomycota reproduction in Allomyces
diploid bodies produce resting sporangia
meiosis within resting sporangia produces haploid zoospores
alternation of generations

20. Allomyces sp. gametangia forming haploid gametes Figure 31.7

21. Fungi Phylum Zygomycota mostly coenocytic haploid except zygote
entirely nonmotile
some participate in mycorrhizal association with plants
familiar example: Rhizopus stolonifer

22. Pilobolus sp. sporangiophores topped with sporangia Figure 31.8

23. sporangium shedding spores Figure 31.9

24. Fungi Phylum Zygomycota reproduction
asexual spores are produced on stalked sporangiophores bearing single or multiple sporangia
sexual reproduction occurs between hyphae of different mating types

25. Fungi Phylum Zygomycota reproduction sexual reproduction
pheromones cause hyphae to grow toward each other
gametangia are produced and fuse into a zygosporangium
gametes (1n) fuse into a zygote (2n)

26. Fungi Phylum Zygomycota reproduction sexual reproduction
meiosis produces zygospores (1n) inside the resistant zygosporangium
after dormancy, zygosporangium releases zygospores
zygospores germinate to produce haploid hyphae

27. Zygomycete life cycle Figure 31.9

28. Fungi Phylum Ascomycota large diverse group (~30,000 spp.)
saprobes, parasites, mutualistic symbionts
hyphae segmented by porous septa
produce sexual spores in asci (sacs)

29. Fungi Phylum Ascomycota two major subgroups Hemiascomycetes
mostly unicellular (yeasts) or microscopically multicellular
asexual reproduction by fission or budding

30. Fungi Phylum Ascomycota Hemiascomycetes sexual reproduction
fusion of haploid cells of different mating types
[+/- mitotic population growth]
meiosis produces four haploid nuclei
[+/- mitosis to produce eight]
ascospores in the original cell = ascus

31. Fungi Phylum Ascomycota Hemiascomycetes
familiar example = Saccharomyces cerevisiae (baker’s, brewer’s yeast)

32. Fungi Phylum Ascomycota Euascomycetes mycelia of septate hyphae
multicellular sexual fruiting bodies: ascocarps
asexual reproduction by conidia

33. Fungi Phylum Ascomycota Euascomycetes sexual reproduction
mating structures form on two compatible mating types
haploid nuclei from the “male” enter the female mating structure
the dikaryotic mating structure produces ascogenous hyphae

34. Fungi Phylum Ascomycota Euascomycetes sexual reproduction
tips of n+n hyphae form asci
in asci, haploid nuclei fuse
meiosis produces four haploid nuclei
[+/- mitosis to form 8 haploid nuclei]
spores are formed and released

35. characteristic ascomycete reproductive sacs Figure 31.10

36. Ascomycete life cycle Figure 31.13

37. Fungi Phylum Ascomycota Euascomycetes familiar examples
Neurospora crassa bread mold used by Beadle and Tatum
brightly colored cup fungi
morels & truffels
Penecillium spp.
Aspergillus spp.

38. Figure 31.11

39. Fungi Phylum Basidiomycota large diverse group (~25,000 spp.)
saprobes, parasites, mutualistic symbionts
produce sexual spores on basidia

40. Fungi Phylum Basidiomycota familiar examples puffballs bracket fungi
mushrooms and toadstools, edible and toxic
bird’s nest fungi
jelly fungi
smut and rust fungi

41. Basidiomycetes Figure 31.14

42. Fungi Phylum Basidiomycota sexual reproduction
basidiospores germinate to produce haploid, septate hyphae
hyphae of different mating types fuse to form dikaryotic hyphae
dikaryotic hyphae eventually produce a characteristic basidiocarp

43. Fungi Phylum Basidiomycota sexual reproduction
basidiocarp bears surfaces covered with basidia
two nuclei in n+n basdium fuse to form 2n zygote
meiosis produces four basidiospores
basidiospores are displayed on tip of basidium and released

44. basidiomycete life cycle Figure 31.15

45. Fungi Fungal Mutualisms with plants mycorrhizae
endomycorrhizal fungi are within the root
ectomycorrhizal fungi are outside the root
fungal symbiont enhances absorption of water and some nutrients by photosymbiont
photosymbiont provides carbohydrate to fungal symbiont

46. Fungi Fungal mutualisms with plants lichens (~13,500 spp.)
partnerships between fungi and green algae or cyanobacterium
fungal symbionts are usually ascomycetes
lichen are classified as distinct organisms
among the hardiest organisms

47. Fungi Fungal mutualisms with plants lichens
critical primary producers in arctic ecosystems
fungal symbiont provides mineral nutrients
photosymbiont provides fixed carbon
among the most environmentally sensitive organisms

48. Fungi Fungal mutualisms with plants lichens three general growth forms
crustose - crust-like
foliose - “leafy”
fruticose - “shrubby”

49. crustose, foliose, fruticose lichens Figure 31.17

50. Fungi Fungal mutualisms with plants lichens reproduction
fragmentation of thallus
some fungal symbionts produce ascospores or basidiospores

51. Fungi Fungal mutualisms with plants lichens reproduction
fragmentation of thallus
some fungal symbionts produce ascospores or basidiospores
soredia

52. reproduction by soredia Figure 31-18