The Fungi
Be the life of the party, fun-guys and fun-gals!
Overview
•	Study fungi at this time because they are heterotrophic, never autotrophic. 
–	Respiration only, no photosynthesis 
•	Fungi once thought of as degenerate plants
–	Closer to animals (degenerate animals?!)
•	Critically significant to life

•	Plants have life cycles that alternate between multicellular haploid and diploid generations (alternation of generations).  
•	Fungi are mostly haploid, sometimes with two nuclei per cell.
–	If the two nuclei are genetically different, this condition is called dikaryotic
Fungal Roles
•	Decomposition
–	Release C back to atmosphere and C cycle
–	Release nutrients back to plants that use them

•	Pathogens
–	Ergot spoils grain
–	Wheat rust
–	Athlete’s foot
–	Dutch elm disease
–	Corn smut
–	Apple scab
–	Candida (Thrush)

•	Production of food for animals
–	Mushroom-eating mice
–	Lichens of boreal regions
•	Food for humans
–	Wine and beer production 
–	Salad mushrooms
–	Cheese mold

•	Toxins and drugs
–	LSD
–	Psilocybin
•	Mycorrhizae

Fungal Vocabulary
•	Fungi are composed of tubular filaments called hyphae
–	in some groups cross walls may be lacking
•	A group of hyphae are a mycelium, a fungal “body”
•	A sporangium is a structure which produces spores

Mycelia
A Fungal Theme:

•	Many fungi are opportunists (“weedy”).  They specialize in colonizing new substrates.
•	In many, asexual reproduction prevails because it allows rapid colonization.
•	Many produce both asexually and sexually-derived spores
Key Fungal Groups in Lab
•	Zygomycota, Black bread mold (Rhizopus)
•	Ascomycota, Morel (Morchella)
•	Basidiomycota, Edible mushroom (Agaricus)

Hint:  The names of these phyla indicate the type of structure in which spores are produced.

e.g., Ascomycota: in an ascus
More vocabulary:
•	Plasmogamy:  fusion of the cytoplasma of two cells
•	Karyogamy: fusion of nuclei
Lichens
•	A symbiosis between an ascomycete fungus and a green alga (Chlorophyta) (most of the time)
•	Has evolved numerous times
•	Growth forms
–	fruiticose
–	foliose
–	crustose
•	Asexual reproduction: soredia

•	Common in severe habitats
–	Deserts, Arctic tundra
•	Sensitive to air pollution
–	Peppered moth example
•	Dehydration / rehydration governs metabolism

Mycorrhizae
•	Forms which penetrate plant cells, and those which surround plant cells
–	Endotrophic vs. ectotrophic
•	Most plants probably have this symbiosis
–	widespread in conifers, orchids

Zygomycota
Rhizopus (Zygomycota)
About the Zygomycetes
•	Hyphae lacking cross walls: coenocytic  (multinucleate cells)
•	Aggressive vegetative growth
–	stolons allow rapid colonization
–	rhizoids absorb substances
–	prolific production of haploid spores

Rhizopus (Zygomycetes)
•	Asexual spores
•	Sexual reproduction
–	fusion of hyphae to produce a resistant zygosporangium
–	zygospore inside undergoes meiosis
–	1n spores produced by sporangium arising from zygosporangium

Pilobolus: 
A unique zygomycete
Pilobolus
Ascomycota

About the Ascomycota
•	Largely filamentous, with perforated cell walls (septa) between cells
•	Conidia, haploid spores, produced at the ends of hyphae

•	Haploid spores produced in a sac, an ascus

•	Prominent examples:
–	Penicillium-- antibiotic and cheese mold
–	Dutch elm disease
–	Morels and truffles

Ascomycota Life Cycle
•	Dominantly haploid, many produce asexual spores
•	Hyphae of opposite sexual strain meet and fuse
•	A fruiting body is formed of haploid hypae of each strain, and dikaryotic hyphae from cell where fusion occurred

•	Dikaryotic hyphae line fruiting body
•	Nuclei fuse in dikaryotic hyphae
•	With cell, the nucleus undergoes meiosis, followed by mitosis
–	one 2n cell  four 1n cells  eight 1n cells
•	Eight nucleate cell becomes a sac called an ascus
•	Nuclei develop walls and become spores

Basidiomycota
About the Basidiomycota
•	Hyphae are always septate, but with perforations that have a donut shaped margin
•	Strongly haploid and dikaryotic phases  (no mixed phase as in Asco.)
•	Far fewer species have asexual reproduction

•	Produce spores on a basidium

•	Basidiomycota of note:
–	common mushrooms and toadstools
–	wheat rust
–	ergot and psilocybe
Basidiomycota Life Cycle
•	Nearly all reproduce sexually
•	Hyphae of opposite sexual strains meet and fuse, forming dikaryotic cells
•	Hyphae proliferate from the dikaryotic cells ONLY, producing a fruiting body

•	On or within fruiting body nuclei of some dikaryotic hyphae fuse (basidia)
•	Meiosis occurs with cells, forming four nuclei
•	Nuclei  migrate to end of basidium, and wall is pinched off around each nucleus, forming  four spores at end of basidium

Conidial Fungi
•	Imperfect fungi lack sexual reproduction
•	When a sexual phase is found, are often Ascomycota
–	Yeasts