1. Chapter 26
The Fungi (Eumycota)

2. Overview on Fungi
are found wherever moisture, the appropriate temperature and suitable organic nutrients are present
exist primarily as filamentous hyphae
mycelium = a mass of hyphae
fungi secrete exoenzymes to digest insoluble matter, then absorb the solubilized nutrients
have two reproductive structures
sporangia form asexual spores
gametangia form sexual gametes

3. True fungi fungus (pl., fungi) eucaryotic spore-bearing
chemoorganoheterotrophs with absorptive metabolism
reproduce sexually and asexually
belong to kingdom Fungi (Eumycota) within domain Eucarya

4. Some terms fungus mycology mycologists mycotoxicology mycoses
eucaryotic organisms that are spore-bearing, have absorptive nutrition, lack chlorophyll and reproduce sexually and asexually
mycology
study of fungi
mycologists
scientists who study fungi
mycotoxicology
study of fungal toxins and their effects
mycoses
diseases caused by fungi

5. Distribution primarily terrestrial
few aquatic species
many are pathogenic in plants or animals
some form associations
mycorrhizae – associations with plant roots
lichens – associations with algae or cyanobacteria

6. Importance beneficial impact detrimental impact decomposers
industrial fermentations
fermented foods and beverages
steroids, antibiotics and other drugs
research
model eucaryotic organisms
detrimental impact
major cause of plant diseases
cause of many animal, including human, diseases

7. Table 26.1

8. Structure thallus body or vegetative structure of a fungus
cell walls usually composed of chitin
polysaccharide consisting of N-acetyl glucosamine residues

9. Yeasts unicellular fungi reproduce asexually, often by budding
reproduce sexually by formation of spores

10. For clarity, the plasma membrane has been drawn separated from the cell wall. In a living cell the plasma membrane adheres tightly to the cell wall.
Figure 26.4

11. Molds filamentous fungi hyphae (s., hypha) mycelium (pl. mycelia)
the filaments of a mold
may be coenocytic (no cross walls) or have septa (cross walls)
mycelium (pl. mycelia)
bundles or tangled masses of hyphae

12. Figure 26.5

13. Figure 26.6

14. diagrammatic representation of hyphal tip
Figure 26.7

15. Table 26.2

16. Dimorphism some fungi change from yeast form (Y) to mold form (M)
YM shift
in animals, Y in host and M outside host
in plants, M in host and Y outside host

17. Nutrition and Metabolism
most are saprophytes
obtain nutrients from dead organic material
secrete hydrolytic enzymes
chemoorganoheterotrophs
glycogen in primary storage polysaccharide
most are aerobic
some are facultative anaerobes
obligate anaerobic fungi are found in rumen of cattle

18. Reproduction asexual reproduction sexual reproduction
transverse fission
budding
spore production
sexual reproduction
involves union of compatible nuclei followed by formation of sexual spores (zygospores, ascospores, or basidiospores)

19. Figure 26.8

20. Sexual reproduction zygote formation several mechanisms
fusion of gametes
fusion of gametangia
gamete-producing bodies
fusion of hyphae

21. Sexual reproduction + and – Pheromones - proteins
Two different strains
+ and –
Pheromones - proteins
Attract negative strain – mate
+ and - fuse to make zygote
Differentiates into a sexual spore
Environmental conditions
Nutrient depletion

22. Zygomycota zygomycetes
form coenocytic hyphae containing numerous haploid nuclei
most are saprophytes
a few are plant and animal parasites
some of industrial importance
foods, antibiotics and other drugs, meat tenderizer, and food coloring

24. Reproduction in Fungi Figure 26.10
A drawing of the generalized life cycle for fungi showing the alternation of haploid and diploid stages. Some fungal species do not pass through the dikaryotic stage. The asexual (haploid) stage is used to produce spores that aid in the dissemination of the species. The sexual (diploid) stage involves the formation of spores that survive adverse environmental conditions (e.g., cold, dryness, heat).
Figure 26.10
Rhizopus nigricans – common bread mold

25. Ascomycota ascomycetes (sac fungi) considerable human impact
during sexual reproduction produce ascus (pl., asci) containing haploid ascospores
considerable human impact
food spoilage and plant diseases
edible mushrooms, and food and beverage production
research
can be filamentous or yeast form
filamentous forms have septate hyphae and asexual reproduction by conidiospores

26. Figure 26.13

28. Life cycle of ascomycetes
Life cycle of ascomycetes. Sexual reproduction involves the formation of asci and ascospores. With the ascus, karyogamy is followed by meiosis to produce the ascospores. This figure shows sexual reproduction and ascocarp morphology of a cup fungus.
Figure (a)

29. Life cycle of ascomycetes
Life cycle of ascomycetes. Sexual reproduction involves the formation of asci and ascospores. With the ascus, karyogamy is followed by meiosis to produce the ascospores. This figure shows sexual reproduction and ascocarp morphology of a cup fungus.
Figure (b)

30. Basidiomycota basidiomycetes (club fungi) human impact
during sexual reproduction form basidium
human impact
decomposers
edible mushrooms
pathogens of humans, other animals, and plants
e.g., Cryptococcus neoformans – cryptococcosis
systemic infection, primarily of lungs and central nervous system

32. Figure 26.15

33. Glomeromycota considered zygomycetes by some
major importance as endomycorrhizal symbionts of vascular plants
form intracellular associations within roots of almost all herbaceous plants and tropical trees
Fungi delivers soil nutrients
Plant provides carbohydrates

34. Claviceps purpurea Grows on grains – rye Toxin – ergot Ergotism
Hallucination
Constriction of the capillaries – gangrene
Middle ages

35. Figure 24.10
Hard mass of hypha
Ergot of Rye