Fungi - Introduction to the Fungi, Ecological Impacts of Fungi, and Phylogenetic Relationships of FungiMichael Cheng, Samir Raman, and Chris “Fun Guy” Zhu

Absorptive nutrition enables fungi to live as decomposers and symbionts Fungi must obtain food

through absorption. Saprobic fungi absorb

nutrients from nonliving organic material.

Fungi that absorb from live hosts are parasitic fungi.

Organisms such as lichen are mutualistic fungi because the algae and fungi work together.

Variation in lichen growth forms.

Extensive surface area and rapid growth adapt fungi for absorptive nutrition

FIGURE 31.1 – Fungal mycelia (p.575)

Fungi allow ribosomes to flow from cell to cell through the septa.

Much like early fly embryo, coenocytic fungi have many nuclei in the cytoplasm with no cell walls.

FIGURE 31.2 – Characteristics of fungal hyphae (p.575).

10 cubic centimeters can contain 1 km hyphae.

Parasitic fungi differ from other fungi because they have haustoria in place of hyphae.

FIGURE 31.2 – Characteristics of fungal hyphae (p.575).

Fungi reproduce by releasing spores that are produced either sexually or asexually When the

environment favors rapid growth, fungi will reproduce asexually by producing spores.

Fungal hyphae and spores are haploid.

Mycelia may become diploid due to the fusion of hyphae.

FIGURE 31.3 – Generalized life cycle of fungi (p.576).

Syngamy – sexual union of cells from two individuals in kargogamy (fuse nuclei) and plasmogamy (fuse cytoplasm)

This process produces dikaryon, which are two nuclei

Ecosystems depend on fungi as decomposers and symbionts Wood rotting fungi became a dominant

group of organisms about 250 million years ago during the mass extinctions that occurred at the end of the Permian era.

Fungi and bacteria are principal decomposers that supply the ecosystem with essential inorganic nutrients.

Their invasive hyphae hydrolyze polymers within the lining of the cell wall.

During the Revolutionary War the British lost more ships to fungal rot than to enemy attack!

Some fungi are pathogens

Athlete’s Foot, a yeast infection (EWW!) and many lung infections are all due to fungus.

The Dutch elm disease changed the landscape of the Northeast when logs that carried the fungus from Europe were shipped to the US during WWI.

Some fungi such as Aspergillus contaminate grain by secreting compounds called aflatoxins, which are carcinogenic.

Some fungi such as lysergic acid (a main component of LSD) are strong hallucinogens…trust me.

Many animals, including humans, eat fungi

Many plants and animals (including humans!) consume a variety of fungi

The most common example is the mushroom. The most prized mushroom is the truffle, which is renowned for its great taste and versatility

Mushrooms often emit odors through their spores to attract animals to eat them.

Jeremy Clarkson of Top Gear with an expensive fungus.

Fungi and animals probably evolved from a common protistan ancestor Molecular evidence

supports that the four fungal divisions are monophyletic.

The occurrence of flagella in the chytrids indicates that fungi and animals have a common ancestor.

Fungi and animals probably evolved from aquatic flagellated organisms.

Comparisons of several proteins and ribosomal RNA indicate that fungi are more closely related to animals than to plants.