1. Chapter 12
The Eukaryotes: Fungi

2. Mitochondrion degenerates
The Three-Domain System
Eukarya
Origin of mitochondria
Fungi
Animals
Bacteria
Origin of chloroplasts
Amebae
Mitochondria
Slime molds
Archaea
Cyanobacteria
Plants
Ciliates
Extreme
halophiles
Proteobacteria
Green
algae
Chloroplasts
Methanogens
Dinoflagellates
Hyperthermophiles
Diatoms
Gram-positive
bacteria
Euglenozoa
Thermotoga
Giardia
Horizontal gene transfer
occurred within the
community of early cells.
Mitochondrion degenerates
Nucleoplasm grows larger

3. Domain Eukarya –Kingdom Fungi Yeasts, Molds and Mushrooms
Eukaryotic
First classified as plants, fungi are now considered different enough from plants to be placed in a separate kingdom
Though the appearance of many fungi may resemble plants, they are probably more closely related to animals.

4. Mycology is the study of fungi
Unicellular (yeasts) and multicellular.
Fungi come in a wide variety of sizes and forms.
Cell wall - chitin, glucans, mannans.
Chemoheterotrophic – saprophytes and parasites
Absorptive - Fungi secrete exoenzymes into the environment , than absorb the digested nutrients.
Can metabolize complex carbohydrates
Many fungi absorb nutrients directly from the soil.
Many others feed on dead and decaying organisms (decomposers), and therefore have an important role in the recycling of nutrients in natural systems.
Others feed on living organisms.
Aerobic or facultative anaerobic.
Nonmotile
Have asexual and sexual reproductive cycles
Develop from spores or hyphal fragments
Resistant to osmotic pressure
Preferred growing at pH 5
Many have great economic importance.

5. Morphological groups of Fungi
1. The single-celled fungi are yeasts
2. The multicellular fungi are molds
3. Dimorphism
Grow as molds in vitro on artificial culture medium, but as yeasts in vivo in infected tissue.

6. 1. Yeasts Unicellular fungi (nonfilamentous) Can use oxygen
Capable of facultative anaerobic growth
Asaxual reproduction - mitosis
Fission yeasts divide symmetrically
daughter cells separated by formation of a septa in the center (fission)
Budding yeasts divide asymmetrically
protuberance(bud)
elongates
parent cell’s nucleus divides
one nuclei migrate to the bud
cell wall material is then laid down between the bud and parent cell
the bud eventually breaks away
If fails to separate - pseudohyphae
Sexual reproduction - meiosis
Form zygote
Form spores
Figure 12.3

7. 2. Multicellular Fungi
The fungal thallus (body) consists of hyphae ( long filaments of cells joined together)
A mass of hyphae is called mycelium.
A hypha is a tubular structure that grows by elongation.
Septate hyphae - contain cross-walls (septa)
Coenocytic hyphae - contain no septa (long, continuous cells with many nuclei)
Table 12.1

8. Mold mycelium Vegetative hyphae The portion that obtain nutrients
Fungal hyphae have a small volume but
large surface area, enhancing the fungal absorptive capacity
Aerial hyphae
The portion concerned with reproduction
Produce spores
Figure 12.2

9. 3. Dimorphic fungi
Pathogenic dimorphic fungi are yeast like at 37°C and mold like at 25°C
Figure 12.4

10. Fungal Life Cycle Asexual reproduction (haploid cells)
Sexual reproduction (diploid zygote)

11. Asexual reproduction Binary fission - fission yeast Budding – yeast
By fragmentation (mold hyphae)
Asexual spores (molds)
Formed by individual fungi through mitosis ( exact copy of the parent)
Formed on the ends of aerial hyphae of one organism

12. Asexual spores 1. Sporangiospore – spores are enclosed in a sac
2. Conidiospore - no sac
Arthrospore
fragmentation of septate hypha
Blastoconidium
buds coming off the parent cell
Condida
produced in chain
Chlamydospore
enlargement within the hypha segment
Figure 12.1

13. Sexual reproduction
Sexual spores– form after the fission of two haploid nuclei from opposite mating type cells of the same species
Plasmogamy
Haploid donor cell (+) nucleus penetrates cytoplasm of recipient cell (–)
Karyogamy
(+ ) and (–) nuclei fuse Zygote (2N)
Meiosis
Diploid nucleus produces haploid nuclei (sexual spores) (N)
Sexual spores produced by fungi characterize the phyla

14. Sexual spores 1. Zygospore
Fusion of haploid cells produces one zygospore
2. Ascospore
Formed in a sac (ascus)
3. Basidiospore
Formed externally on a pedestal (basidium)
Figure 12.6

15. Zygomycota Conjugation fungi Type of hyphae - Coenocytic
Asexual spores - Sporangiospores
Sexual spores- zygospores.
Rhizopus nigricans,
Common bread mold –
Mucor
a genus of about 40 species molds commonly found in soil and on plant surfaces, as well as in rotten vegetable matter (Opportunistic, systemic mycoses)

16. The Life Cycle of a Zygomycota
Figure 12.6

17. Ascomycota Type of hyphae - Septate Asexual spores - Conidiospores.
Sexual spores – Ascospores (in a sac - sac fungi)
Opportunistic pathogens
Aspergillus (black house mold) -opportunistic, systemic mycosis
Blastomyces dermatitidis, Histoplasma capsulatum (systemic mycoses)
Microsporum, Trichophyton (cutaneous mycoses)
Saccharomyces (bread and beer yeast)
Soy sauce production – fermenting soy beans

18. The Life Cycle of an Ascomycota
Yeast comes in two mating types—"a" and “α” (alpha) - haploid
Or as slightly larger diploid cell that carries both "a" and “α”
Spore formation
Under high stress conditions, haploid cells will generally die;
When diploid cell runs out of food, undergo sporulation - entering sexual reproduction (meiosis) and producing a variety of haploid spores of the two different mating types,
Spores remain enclosed in a tough shell until times improve.
Then these spores burst forth and start looking for mates of the opposite type; as soon as they find a suitable mate, they fuse (conjugate) together.
Saccharomyces life cycle

19. Basidiomycota Type of hyphae - Septate.
Asexual spores - Conidiospores.
Sexual spores - Basidiospores
Cryptococcus neoformans (systematic mycosis)
often found in soil which has been contaminated by bird excrements
lung infection
fungal meningitis

20. The Life Cycle of a Basidiomycota
Figure 12.8

21. Anamorphic fungi
Teleomorphic fungi - Produce sexual and asexual spores.
Anamorphic fungi - Produce asexual spores only.
rRNA sequencing places most in Ascomycota, a few are Basidiomycota
Penicillium (green fruit mold)
Sporothrix (subcutaneous mycosis)
Stachybotrys, Coccidioides, Pneumocystis (systemic mycoses)
Candida albicans (Cutaneous mycoses)

22. Fungi Identification Physical appearance Colony characteristics
Reproductive spores
Fungi differ from bacteria:
Like acidic environments (pH 5)
Resistant to osmotic pressure
Grow in low moisture
Require less nitrogen
Can metabolize complex carbohydrates
Table 12.1

23. Lichens
Mutualistic combination of Fungus and a Photosynthesizing partner
Fungus provides holdfast
Photosynthesizing partner - Alga or Cyanobacteria -, produces and secretes carbohydrates
Lichens colonize habitats that are unsuitable for either the alga or the fungus alone.
Lichens may be classified on the basis of morphology as crustose, foliose, or fruticose.
Lichens are used for their pigments and as air quality indicators.

24. Economic Effects of Fungi
Ecological Role: decomposing organic matter; indispensable in nutrient cycling and exchange
Some human and plant pathogens
Some spoil food
Biothechnology
Food and beverage production
Antibiotics
Vaccine production
Biological control of pests - entomopathogenic fungi

25. Fungal Diseases (mycoses)
Fungal infections classified on the degree of tissue involvement and mode of entry into the host:
Superficial mycoses - localized to the skin, the hair, and the nails.
Cutaneous mycoses (dermatomycoses) - affect hair, skin, nails
Subcutaneous mycoses - beneath the skin
Systemic mycoses - deep within body
Opportunistic mycoses - caused by normal microbiota or fungi that are normally not pathogenic

26. Learning objectives List the defining characteristics of fungi.
Differentiate between sexual and asexual reproduction, and describe each of these processes in fungi.
List the defining characteristics of the three phyla of fungi
Identify beneficial and harmful effects of fungi.
Describe the roles of the fungus and the alga in a lichen.