Introduction to the Fungi

Basic phylogeny

How many fungi do you see??

There is only one fungus. In this picture. Most of it is underground. Each of the mushrooms you see is a “fruiting body” (like a flower) that the mushroom uses to reproduce.

Hyphae = the “bricks” from which the mushroom is built

Most fungi are filamentous because the main body is composed of thread-like filaments called hyphae which form the mycelium.

Example of a “humungous fungus”

• Armillaria bulbosa – a mushroom producing wood decomposer

• Covers at least 38 acres in a forest in Michigan

• Estimated to weigh 100 tons (size of a blue whale)

• Estimated to be at least 1500 yrs old

Kingdom Fungi

• Eukaryotic heterotrophs with external digestion– Most are saprotrophs:

digest decaying material– Important for recycling

nutrients• Range from a single cell

(yeast) to mushrooms whose mycelia cover hundreds of acres

• Chitinous cell walls

Chitin and Cellulose

• Chitin – polymer of glucosamide• Cellulose – polymer of glucose

Fungi Importance

• Food production (cheese, bread, etc.)

• Industrial enzymes (bioremediation)

• Plant growth hormones

• Antibiotics (penicillin)

• Recycling nutrients

• Mycorrhizae – fungi hyphae in close association with plant roots; increases absorption of water and nutrients

• Lichens = symbiosis between fungi and algae

PenicilliumWWI, bacterial infections killed more soldiers than bullets.

1928 Dr. Andrew Fleming working at St. Mary’s Hospital in London noticed that mold growing on staph bacterial culture plates had killed the pathogen

zone of dead bacteria

Penicillin kills bacteria by interfering with their ability to synthesize cell wall.

Mycorrhizae• “myco” = fungus and “rhiza” = root

• Symbiotic association between plant roots and fungi

• Several different types of association (defined by structure of fungus:plant interface)

Advantages to plant• Fungi are better than plants at acquiring

mineral nutrition (P,K, N) from the soil.

• Fungi improve a plant’s access to water

Because fungi– can access greater soil volume– can break molecules down into useable forms

Fungi can access more of the soil because

1. Hyphae are smaller than plant roots

Hyphae are 1/500th the diameter of a plant root hair

Root Hair

hyphae

Fungi are better at acquiring nutrients because

2. Fungi have digestive enzymes that plants do not (remember absorptive nutrition)

– Can turn inorganic phosphorus and nitrogen into forms usable by plants

Because fungi secrete their enzymes outside of their cells (into the soil) they can use “dangerous” enzymes which produce too many free radicals to use inside cells

and fungi expand the surface area available for nutrient uptake

Some fungi are predators!

• They catch and digest other organisms (like nematodes)

But still absorptive nutrition! Just have to catch it first…

Negative impacts of fungi• Fungi can infect plants and animals, including

humans. (athletes foot, ringworm)• In plants, masses of spores cause discolouration of

the leaves so infections often called smuts, rusts, spots and other names describing the symptoms.

Eyespot of wheatTarspot of sycamore Leaf rust of daisy

Fungus = mycobiontAlgae = photobiont

Controlled parasitism??

Lichen are among the “pioneer species” which create soil in areas that have only rocks (such as a lava field).

Can withstand areas of drought and extreme temperature; slow growth.

They absorb nutrients from the air and from rainfall so lichen are good indicators of air quality.

Lichens: fungi/algae symbiosis

Absorptive nutrition makes lichens good indicators of air quality