1. Fungal Diversity I. Introduction II. Fungal Phyla
Reading: Chap. 31
I. Introduction
A. What is a fungus?
B. What does a fungus do?
C. Basic fungal life cycle
D. Who cares about fungi?
II. Fungal Phyla
A. Overview
B-E. Life cycles of the phyla
III. Fungal mutualisms
A. Lichens
B. Mycorrhizae
Fungal Diversity
II. Ecological importance:
A. base of the food chain in aquatic ecosystems, both marine and freshwater; populations are controlled by seasonal climate shifts, predation, or nutrient limitation. Many very productive aquatic habitats - antarctic oceans, areas of upwelling off the Pacific coasts of N and S America are so because of abundant nutrients for phytoplankton. [Starr, fig. 37.3, OH 357]

2. Characteristics of Fungi
Non-motile eukaryotes lacking chlorophyll
Contain nucleus, mitochondria, 80S ribosomes
Plasma membrane contains ergosterol instead of cholesterol.
Cell wall is composed of chitin and various glucans, mannans, and complex polysaccharides
Larger than bacteria
Relatively simple nutritional requirements, wide range of growth rates
Form visible colonies in days to weeks
Unicellular or multicellular depending on the species

3. Molds Multicellular, tubular structures (hyphae)
Hyphae can be septate (regular crosswalls) or nonseptate (coenocytic) depending on the species (grow by apical extension)
Vegetative hyphae grow on or in media (absorb nutrients); form seen in tissue, few distinguishing features
Aerial hyphae contain structures for production of spores (asexual propagules); usually only seen in culture

4. Fungi
The parts:
Fig. 31.1
Cell walls - made of chitin. Same material that is in the external skeletons of arthropods - insects, arachnids, and crustaceans.

5. Molds - identification
Identification based on colony morphology (pigment, texture) and morphology of reproductive structures
Conidia - spores formed by budding (blastoconidia) or disarticulation of existing hypha (arthroconidia)
Sporangiospores - produced by free-cell formation within sporangium in nonseptate molds 1 1
Conidiopspores
Phialides
Vesicle
Conidiophore
Septate hyphae 3
sporangium
sporangiophore
Endospores
Nonseptate
hyphae
5. rhizoids 2 3 4 2 5 4 5

6. YEASTS Also yeasts - single-celled e.g., Saccharomyces cerevisiae
Candida albicans
31.15

7. Yeasts
Unicellular, 3-5 µm, reproduce by budding (blastoconidia formation) or fission
Identified by microscopic morphology (grow on cornmeal agar) and biochemical tests (sugar assimilation, enzymatic activity).
Molds and yeast are not exclusive forms, some species may exist in both yeast and mold forms (dimorphism).

8. Colonial Morphology of Fungi
Cryptococcus neoformans
Trichophyton tonsurans
Wangiella dermatitidis
Candida albicans
T. menta-grophytes
Aspergillus fumigatus

9. FUNGAL LIFE CYCLE
Asexual - budding or cell division
Sexual - fusion of 2 mating types spore formation

10. FUNGAL NUTRITION & ENVIRONMENT
Organic compounds needed for growth saprophytes as feed on dead organic matter
Adapted to: growth at pH growth on surfaces growth under high osmotic conditions growth at low water levels growth in low nitrogen environments growth on unusual nutrient sources

11. B. What does a fungus do? Absorptive heterotroph Such as: Mutualist
Parasite/pathogen
Mutualist
Detritivore

12. Also eat:
- wood in houses, boats, fences;
- food;
- other materials - cloth, paint, leather, waxes,
jet fuel, petroleum,
paper, wire insulation, photographic film,
- to name a few.
What do all of these materials have in common?
They are all C-based.

13. C. Basic fungal life cycle
2. Fertilization doesn’t happen all at once
Plasmogamy - fusion of cytoplasm
Karyogamy - fusion of nuclei (gametes)
heterokaryotic
dikaryotic
fig. 31.2

14. Classification of Fungi
Taxonomy is based on structural features of the teleomorph (sexual phase).
Zygomycota - includes all fungi with nonseptate hyphae
Ascomycota - includes most human pathogens
Basidiomycota - mainly saprobes or plant pathogens
Deuteromycota (fungi imperfecti)
Sexual phase unknown or doesn’t exist. Some can be assigned to above groups based on phylogenetic analysis.

15. B. Zygomycota 1. No dikaryotic growth
2. Both sexual and asexual sporangia

16. C. Ascomycota - Life cycle
1. Dikaryotic growth
2. Fruiting body: ascocarp
3. Fertile layer with asci
4. Eight ascospores per
ascus (sac)
5. Asexual reproduction
via conidia

17. D. Basidiomycota - Life cycle
1. Dikaryotic growth
2. Fruiting body: basidiocarp
3. Fertile layer on gills
with basidia (“clubs”)
4. Four spores per
basidium
5. Asexual reproduction
is rare

18. E. Deuteromycota - “fungi imperfecti”
1. Not a true phylum (not a natural group): polyphyletic
2. Fungi with no known sexual reproduction
3. Asexual reproduction by conidia

19. III. Fungal mutualisms Definitions:
Symbiosis - 2 organisms living together in intimate physical contact
Mutualism - both organisms benefit from the relationship
Parasitism - one benefits, one loses
Commensalism - one benefits, other not affected

20. A. Lichens 1. Partners a. Fungal partner - gives protection
- mostly Ascomycetes (~25,000 spp.)
- only found in lichens (not free-living)
b. Photosynthetic partner
- gives fixed carbon (sugars)
- green alga or cyanobacterium
- can be free-living

21. A. Lichens 2. Anatomy a. most of lichen body is fungal hyphae
b. photosynthetic partner in a distinct layer
c. sexual reproduction of fungal partner only
d. asexual reproduction: soredia, fragmentation
2. Anatomy
medulla

22. Figure 29.9a Ectomycorrhizal fungi (EMF) Root cells EMF Figure: 29.9a
Caption:
(a) Ectomycorrhizal fungi (EMF) form a dense network around the roots of plants. The combination of root and fungus is called a mycorrhiza. The drawing shows how the interaction works in EMF. Note that their hyphae penetrate the intercellular spaces of the root, but do not enter the cells themselves. 
EMF

23. A. Lichens
3. Morphology
fruticose
crustose
foliose

24. A. Lichens
4. Importance
a. rock weathering, soil formation in primary succession
- acid secretion
- trapping particulates
nitrogen fixation (cyanobacteria)
b. Indicators: susceptible to pollutants