1. Chapter 31
Fungi

2. Intro to Fungi Eukaryotes Most are multicellular
Were once thought to be plants
Recent molecular studies show that they are more closely related to animals than plants

3. Nutrition Heterotrophs that acquire nutrients by absorption
Small organic molecules are absorbed from surrounding medium
Digests food outside of body by secreting enzymes on the food
Exoenzymes: decompose complex molecules into more simple compounds

4. Nutrition Saprobes (decomposers) Parasites Mutualistic symbionts
Absorb nutrients from nonliving organic matter
Parasites
Absorb nutrients from living hosts
Some infect lungs of humans
Fungi cause 80% of plant disease
Mutualistic symbionts
Absorb nutrients from a host but provide functions beneficial to their partners
Aiding a plant in the uptake of minerals from the soil

6. Structure
Vegetative bodies are usually hidden around and within their food sources
Constructed of hyphae
Thin filaments that are composed of tubular walls surrounding plasma membranes and cytoplasm
Form an interwoven mat called mycelium
Feeding network of a fungus
Can be extremely large but hidden because it is subterranean

7. It is at least 2400 years old and hundreds of ton in weight
2000: found the mycelium of one individual fungus in Oregon that is 3.4 miles in diameter and spreads through 2200 acres
Equivalent to over 1600 football fields
It is at least 2400 years old and hundreds of ton in weight
One of Earth’s oldest and largest organisms

8. Structure Hyphae are divided into cells by cross-walls, or septa
Have pores large enough to allow ribosomes, mitochondria, and nuclei to flow from cell to cell
Cell walls made of chitin
Some don’t have septa
Coenocytic fungi consist of a continuous cytoplasmic mass with hundreds to thousands of nuclei
Resulted from the repeated division of nuclei without cytoplasmic division

9. Structure
Parasitic fungi have their hyphae modified as haustoria, which are tips that penetrate the tissues of the host plant
There are even fungi with hyphae that are adapted to feed on animals

10. Structure – Function Relationship
Filamentous structure of the mycelium provides an extensive surface area that assists the absorptive function of fungi
Mycelium can grow as much as a kilometer of hyphae each day as it branches out throughout a food source

11. Reproduction
Release spores that are produces either sexually or asexually
Amount of spores is tremendous
Puff balls can put out trillions of spores
Spores function as dispersal agents
Airborne spores of fungi have been found more than 100 miles above Earth

12. Heterokaryotic Stages
Nuclei of fungal hyphae and spores are haploid, except for transient diploid stages that form during sexual life cycles
Some mycelia become genetically heterogeneous through the fusion of two hyphae that have genetically different nuclei = heterokaryon
Different nuclei may stay separate or join in a “crossing over” occasion

13. Sexy Fungus
Plasmogamy: the fusion of the two parents’ cytoplasm when their mycelia come together
Karyogamy: fusion of the haploid nuclei contributed by the two parents
These stages may be separated by hours or even centuries
During interim, the hybrid exists as a heterokaryon

14. Diversity
More than 100,000 species are known, and there are estimated 1.5 million species worldwide
Fungi are broken down into four phyla:
Chytridiomycota
Zygomycota
Ascomycota
Basidiomycota

15. Chytridiomycota “Chytrids” are mainly aquatic
Some are saprobes, others parasitize protists, plants, and animals
Contributing to the worldwide decline of amphibians
Form coenocytic hyphae
Most primitive of fungi
Diverged earliest in the lineage of fungi

16. Chytridiomycota

17. Zygomycota 600 different species
Terrestrial and live in soil or on decaying organic matter
Mycorrhizae: mutualistic associations with the roots of plants
Hyphae are coenocytic
Ex: Black Bread Mold

18. Mycorrhizae

19. Black Bread Mold

20. Ascomycota 60,000 different species “Sac Fungi”
Marine, freshwater, and terrestrial
Include some of the most devastating plant pathogens
Live with algae to form lichens
Produce sexual spores in a saclike asci

21. Ascomycota

22. Basidiomycota 25,000 species “Club Fungus”
Include mushrooms
“Club Fungus”
Decomposers of wood and other plant material
Long-lived dikaryoric mycelium
Reproduces sexually by producing basidiocarps, which are the source of sexual spores

23. So…. When you eat mushrooms, you are eating Fungal Genitalia….

24. “Fairy Rings” A ring of mushrooms
Grass in center is stunted because the mycelium is using all the nutrients

25. Other Categories of Fungi
Molds
Yeasts
Lichens
Mycorrhizae

26. Molds Rapidly growing, asexually reproducing fungus
Saprobes or parasites
Mold is a mold if it is in the asexual stage
Later will turn into zygo, asco, or basidiomycotas
Imperfect Fungi
Have no sexual stages whatsoever

27. Yeasts
Unicellular fungi that inhabit liquid or moist habitats, including plant sap and animal tissues
“Bud” to reproduce
Raise bread and ferment alcohol
Metabolically active and release small CO2 bubbles or ferment sugars to alcohol
pH shift or immunodeficiency can lead to “yeast infections” where normal yeast populations have exponential growth

28. Yeast

29. Lichens Often mistaken for mosses or plants
Symbiotic association of millions of photosynthetic microorganisms held in a mesh of fungal hyphae
Algae provide fungus with food
Bacteria in lichens fix nitrogen and provide organic nitrogen
Fungus provides alga with a suitable environment for growth
Absorb nutrients from dust in the air or from rain

30. Lichens Important pioneers on newly cleared rock and soil surfaces
Burned forests and volcanic flows
Lichens make it possible for a succession of plants to grow
Can tolerate severe cold and desiccation
Reindeer moss
Can absorb more than ten times their weight in water

31. Lichens

32. Mycorrhizae “Fungus Roots”
Extensions greatly increase the absorptive surface of the plant roots
Exchange minerals accumulated from soil by the fungus for organic nutrients synthesized
Occur on almost all vascular plants
Show up as mushrooms at the base of trees

34. Ecological Impact Principal decomposers
Without them, carbon, nitrogen, and other elements would become ties up in organic matter
10-50% of world’s fruit harvest is lost each year due to fungus
During the Revolutionary War, British lost more ships to fungal rot than to enemy attack

35. Ecological Impact Pathogenic:
30% of fungus is parasitic, mainly on plants
Dutch Elm: Killed ALL American Chestnut trees
Some release toxins that are carcinogenic: Aspergillus
Ergot poisoning: gangrene, nervous spasms, hallucinations
One epidemic killed more than 40,000 people in France in 944 A.D.
One chemical from ergots is the raw material that LSD is made
Helpful in treating high blood pressure and stopping maternal bleeding after childbirth when given in small doses

36. Ecological Impact Mycosis: fungal infection Food Ringworm
Athletes foot
Histoplasmosis- causes tuberculosis-like symptoms
Opportunistic infections
Only capable of occurring because body is not in homeostasis or the immune response is lowered
Yeast infections
Food
Cheeses
Colas
Truffles
Use pigs to locate them because they give off a smell that mimics female pig pheromones

37. Evolution of Fungi
Oldest fossils of vascular plants have fungus on them
460 million years ago
Fungal ancestors were aquatic flagellated organisms
There is compelling evidence that animals and fungi diverged from a common protistan ancestor