Fungi

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Fungi

• Multicellular, heterotrophic - decomposers,
  parasites, and symbionts
• Feed mainly through absorption which requires
  extensive surface area
• Can reproduce either sexually or asexually
• Composed of 4 phyla Chytridomycota, Zygomycota,
  Ascomycota, and Basidiomycota
• Some are pathogenic, many are commercially
  important
• Fungi and animals evolved from a common ancestor

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Structure of a Fungus

• Composed of many filaments called hypha to form
  the mycelium
• Septa form crosswalls between individual cells
• Cell wall is formed of chitin
• Some fungi are aseptate and therefore coenocytic
• Fungi are nonmotile - they extend themselves
  through growth

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Specialization of Fungi

• Most fungi spend most of their energy and
  resources on adding hyphal length
• Some have haustoria which enable penetration of
  host
• Some have adapted in order to trap prey in
  constricting hoops

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Fungal Reproduction

• Fungi are often heterokaryotic, which means the
  nuclei within the body are often a mix of haploid
  or dikaryotic
• Karyogamy can form a transient diploid state
  which then undergoes meiosis
• Spores are then formed asexually or sexually

• Zygotic life cycle with dominant haploid state
• Plasmogamy can create a dikaryotic state through
  fusion of cytoplasm only
• Fungi can be genotypically and phenotypically
  heterogeneous

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The delay between plasmogamy and karyogamy may
take days, years, even decades . . .
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Chytridiomycota

• Aquatic saprobes and parasites
• Flagellated zoospores seem to exclude them from
  Kingdom Fungi
• Molecular evidence supports their placement as
  the most primitive fungus

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Chytrids as Fungi

• Chitinous walls
• Absorption for nutrition
• Some are unicellular, but most form coenocytic
  hyphae
• Enzymes of metabolic pathways resemble those of
  fungi

Chytrids are flagellated and display a life cycle
with alternation of generation.
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Zygomycota

• Terrestrial - soil or decaying materials
• Mutualistic mycorrhizae are associated with
  plants
• coenocytic with septa only in reproductive
  structures
• Enters sexual reproductive phase when environment
  is harsh
• Formation of a zygosporangium in sexual
  reproduction

Pilobolus can aim sporangium at light and fire 2
meters away.
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Sexual and Asexual Reproduction in Zygomycota
Rhizopus
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Ascomycota

• Known as sac fungi
• Saprobes and plant pathogens
• Lichens are mutualistic association with algae
• Form mycorrhizae with plants or live in mesophyll
  where they release insect repellent

Ascomycota can be unicellular yeast or elaborate
truffles, cups and morels.
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Ascomycetes extend their heterokaryotic stage
during ascocarp formation
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Basidiomycota

• Puff balls, shelf fungi, and rusts (club fungus)
• Long lived dikaryotic mycelia
• Plant and wood decomposers
• Rusts and smuts are plant parasites
• Little asexual reproduction

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Basidiomycetes reproduce sexually
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Fairy rings . . .

• . . . will magically appear overnight.

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Deuteromycota

• Fungi imperfecti
• Show no sexual reproduction
• Some molds and yeast fall into this category
• When a sexual reproductive cycle discovered, they
  are reclassified

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Fungi can be useful to us . . .

• Saccharomyces is often used as bakers yeast or
  brewers yeast
• Yeast will reproduce asexually through budding or
  cell division, living in fluid or moist habitats
• Some yeast are ascomycetes, some are
  basidiomycetes, and some are deuteromycetes

Penicillium produce antibiotics such as
penicillin. Other medications include lovastatin
to lower cholesterol, and cyclosporine to
suppress the immune system.
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. . . plants, algae , and cyanobacteria.

• Mycorrhizae are fungal associations with plant
  roots to increase area for absorption in exchange
  for nutrients.
• Lichen are fungal associations with filamentous
  green algae or cyanobacteria
• Often ascomycetes with some basidiomycetes
• Can reproduce through producing soredia
  (fragmentation)

Plant growth is often stunted without the
presence of mycorrhizae.
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Likin the Lichens . . . .

• Lichen are pioneers
• Can exploit harsh environments
• Fungi provide water retention, minerals,
  increased gas exchange, shielding from sunlight,
  protection from consumers, and housing.
• Algae or cyanobacteria provide nitrogen through
  fixation, and leak out carbohydrates.

Crustose lichen remain closely associated with
the ground. Foliose lichen are lobed and
resemble leaves. Fruticose lichen stand up from
the ground and may branch out.
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Hatin the mold . . .

• Rhizopus is commonly found on food
• Mold is a rapidly growing, asexually reproducing
  saprobe or parasite
• Often belonging to zygomycota or ascomycota, mold
  only refers to its asexual state.
• What you see on the food is the sporangia or
  conidia.

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. . . Not to mention diseases.

• General term for fungal infection is mycosis
• Ringworm and athletes foot are caused by fungi
• Candida is a normal human inhabitant, but can be
  an opportunistic pathogen
• Aspergillus contaminate grains and peanuts with
  carcinogenic aflatoxins
• Claviceps causes ergot in rye, which can in turn
  cause gangrene, nerve spasms, burning, and
  hallucinations in humans.

Plants are often targets for fungi. The Dutch elm
disease, American chestnut blight, wheat rust,
and ergot on rye are all examples of fungal
attacks.
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But lets go back to the good stuff . . .

• Carbon dioxide provided to raise bread
• Some cheeses derive their unique flavor from
  fungi
• Fermentation gives us the ethyl alcohol in wine,
  beer and other fermented beverages.
• Mushrooms for salads,etc.
• Soy sauce . . .
• very important !!!!

Depending on the sugar source yeast receive, it
can produce wine, beer, or other ales ciders.
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. . . But dont forget the bad !!!

• Edible and poisonous mushrooms are similar in
  appearance
• Amanita virousa destroying angel and Amanita
  phalloides death capare extremely toxic
• About 50g of mushroom will kill a grown man in 5
  -10 days. Even if diagnosed, prognosis is not
  good for survival.
• Filtration systems of the body are among the
  first to fail.
• Just dont mess with mother nature ! ! ! ! !