1.  The fungi are one of the 4 eukaryotic kingdoms

2.   Characteristics of fungi

• Heterotrophs
  • take in food molecules by absorption
  • grow on and through their food and secrete digestive enzymes - external digestion

• Most are multicellular, but there are some single-celled types as well (yeasts).


• Cell walls contain chitin

• Chitin is a polymer similar to cellulose but contains nitrogen
• Molecular structure of chitin
• Chitin is also an important component of arthropod exoskeletons
  
  
• Multicellular types usually have branching filamentous form
  • these filaments are called hyphae
    • some fungi have partitions between cells
      • partitions often are not complete, so cytoplasm flows between cells
    • in some cases cells are coenocytic (meaning no partitions )
  • a mass of hyphae = mycelium
  • filamentous form gives large surface area for absorption
• the large reproductive structures of some fungi (e.g. mushrooms) are made up of masses of fused filaments.
  
  
• Fungi have several cell types
  • most fungi are haploid most of the time
  • diploid stages are produced during sexual reproduction prior to meiosis
    • sometimes the diploid period is brief
  • in some types, dikaryotic stages preceed the diploid stages
    • dikaryotic cells have separate nuclei from fusion of two haploid cells (but the nuclei have not fused yet)
      
      
• Reproduction often involves production of spores
  • tiny structures - carried by wind
    • protective covering - resistant to environmental extremes
    • important for dispersal
  • depending on the fungus, spores may be
    • sexually produced
    • asexually produced
    • or both
      
      

3. Fungal lifestyles in brief (will be discussed further later)

• Decomposers - along with bacteria, fungi are the most important decomposers
  • cellulose
  • lignin - virtually the only organisms that break this down!
  • many other substances as well
    
• Mutualisms (symbiotic relationships with benefits to both partners)
  • mycorrhizae
  • lichens
  • endophytes
  • etc
    
• Pathogens/Parasites
  

4. There are four major fungal groups

 

5. Life cycles of the different groups

Zygomycota - e.g. bread mold

 

Ascomycota - e.g. morels and cup fungi

Some members of the Ascomycota are single-celled - yeasts

 

Basidiomycota - e.g. mushrooms, puffballs, shelf fungi, etc

 

Chytridiomycota - mostly aquatic

• similar to the very first fungi
  • (see: nice overview of the chytrids)
• diverse lifestyles - decomposers, pathogens, etc
• one type is an important pathogen of frogs and other amphibians

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6. More about fungal lifestyles, interactions with other organisms, and human uses:

Lichens - Symbiotic relationships between lichens and algae

• Ascomycota together with either green algae (Chlorophyta) or blue-green algae (cyanobacteria)

• Lichens can grow where neither the fungus nor the algae could otherwise grow on their own.
• the fungus provides physical support, attachment to a surface, and some protection from dessication, and it absorbs water and mineral nutrients from environment.
• the alga does photosynthesis

A lichen is composed of two different species from different kingdoms, but

• there are distinct types of lichens that are found repeatedly
• these have been given scientific names as though they are distinct species (but they really are combinations of two separate species)!
• lichens typically produce distinct reproductive structures that neither partner would produce on their own.
  • these contain both fungus and algae
  • these allow a lichen to disperse as a unit (with both partners together) and colonize new places

Here is an informative page with LOTS more information on lichens (skim and look at photos and diagrams, or read completely if the topic intrigues you)

Lots of photos of lichens can be found here

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Mycorrhizae - associations between fungi and plant roots.

• Either Acscomycota, Basidiomycota, or Zygomycota
• MOST plants form associations with mycorrhizal fungi
  • Some plants MUST have proper fungi to associate with or they will not grow!

• Mutualism - a form of symbiosis where both members of association benefit
  • fungus provides huge surface area for more effective uptake of nutrients and water
  • plant provides fungus with organic compounds (e.g. sugar - energy and carbon source for fungal growth).

• Some mycorrhizal fungi mostly just form a sheath around roots (and perhaps penetrating inbetween root cells, others penetrate root cells:

Here is an informative page with LOTS more information on mycorrhizae (skim, look at photos and diagrams, etc).

Many of the mushrooms you find in forests are from mycorrhizae.

Mycorrhizae often link plants together underground!

• really cool diagram can be found near the bottom of this informative web page

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Parasites/pathogens

There are numerous fungi that parasitize other organisms

• Human diseases - e.g. athletes foot, ringworm, etc

• Diseases of amphibians - e.g. the chytrids discussed above

• Plant diseases - e.g. powdery mildew, fusarium wilt, wheat rust , white pine blister rust, cedar apple rust
  • For much more on wheat rust read this article
  • fungi parasitizing plants sometimes have complex life cycles involving multiple hosts, e.g. white pine blister rust life cycle , cedar apple rust life cycle
• etc.....

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Carnivorous fungi - some soil fungi capture and digest nematode worms!

• for example: Arthrobotrys: photos

Videos:

 

And a video discussing research on behavior that helps nematodes escape from these fungi

 

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World's largest organism? - some say it is the fungus Armillaria

Information

This fungus produces thick root-like structures (called rhizomorphs) that grow out through soil in search of new trees! photo

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And finally, "fungi" that are not actually fungi...... the Oomycota (water molds, downy mildews, etc). Information

• Formerly thought to be fungi
  • Look like fungi
  • Grow and behave much like fungi
• But are filamentous protists, most closely related to the brown algae and diatoms!
• Varied lifestyles
  • Some are decomposers
  • Some are plant parasites (downy mildews)
  • Sometimes causes disease in fish - e.g. Saprolegnia and others