FungusFungus

Chapter 31Chapter 31

What you need to know!What you need to know!

The characteristics of fungiThe characteristics of fungi Important ecological roles of fungi in Important ecological roles of fungi in

mycorrhizal associations, and as decomposers mycorrhizal associations, and as decomposers and parasitic plant pathogensand parasitic plant pathogens

Kingdom FungiKingdom Fungi Phylum: Myxomycota (slime molds)Phylum: Myxomycota (slime molds) Phylum: Eumycota (true fungi)Phylum: Eumycota (true fungi)

class: Phycomycetesclass: Phycomycetes class: Glomeromycetesclass: Glomeromycetes class: Ascomycetesclass: Ascomycetes class: Basidiomycetesclass: Basidiomycetes

Domain EukaryaDomain Eukarya

Fungi are eukaryotes and most are Fungi are eukaryotes and most are multicellular.multicellular.

Fungi are heterotrophicFungi are heterotrophic Animals (not plants) are the closest Animals (not plants) are the closest

relatives of fungi.relatives of fungi.

CharacteristicsCharacteristics

One of the two major decomposers in the One of the two major decomposers in the environment: fungi (bacteria is the other)environment: fungi (bacteria is the other)

decompose dead organisms (fallen leaves, feces, decompose dead organisms (fallen leaves, feces, dead bodies, other organic materials)dead bodies, other organic materials)

Recycles vital chemical elements back to the Recycles vital chemical elements back to the environment environment

Many plants depend on mutualistic fungi that help Many plants depend on mutualistic fungi that help their roots absorb minerals and water from the soil.their roots absorb minerals and water from the soil.

Humans cultivate fungi to produce antibiotics and Humans cultivate fungi to produce antibiotics and other drugs, to make bread rise (yeast), and to other drugs, to make bread rise (yeast), and to ferment beer and wine (yeast).ferment beer and wine (yeast).

Role in the EnvironmentRole in the Environment

Fungi acquire their nutrients by absorption.Fungi acquire their nutrients by absorption. Exoenzymes, powerful hydrolytic enzymes secreted by Exoenzymes, powerful hydrolytic enzymes secreted by

the fungus, digest food outside its body to simpler the fungus, digest food outside its body to simpler compounds that the fungus can absorb and use.compounds that the fungus can absorb and use.

Some exoenzymes attack the digestive system (toxic to Some exoenzymes attack the digestive system (toxic to humans)humans)

They absorb small organic molecules from the They absorb small organic molecules from the surrounding medium.surrounding medium.

Some fungi can digest lignin (wood) growing in forestsSome fungi can digest lignin (wood) growing in forests Some contain chemicals that act as hallucinogensSome contain chemicals that act as hallucinogens

Decomposers and SymbiotsDecomposers and Symbiots

Extensive surface area and rapid growth adapt Extensive surface area and rapid growth adapt fungi for absorptive nutritionfungi for absorptive nutrition

The vegetative bodies of most fungi are The vegetative bodies of most fungi are constructed of tiny filaments constructed of tiny filaments called hyphae called hyphae that form an that form an interwoven interwoven mat called a mat called a mycelium.mycelium.

StructureStructure

Fungal mycelia can be huge, but they usually Fungal mycelia can be huge, but they usually escape notice because they are subterranean.escape notice because they are subterranean. One giant individual of Armillaria ostoyae in One giant individual of Armillaria ostoyae in

Oregon is 3.4 miles in diameter and covers 2,200 Oregon is 3.4 miles in diameter and covers 2,200 acres of forest, acres of forest,

It is at least 2,400 years old, and weighs hundreds It is at least 2,400 years old, and weighs hundreds of tons.of tons.

Fungal hyphae have cell walls.Fungal hyphae have cell walls. These are built mainly of chitin, a strong but These are built mainly of chitin, a strong but

flexible nitrogen-containing polysaccharide, flexible nitrogen-containing polysaccharide, identical to that found in arthropods.identical to that found in arthropods.

StructureStructure

Most fungi are multicellular with hyphae divided into Most fungi are multicellular with hyphae divided into cells by cross walls, or septa.cells by cross walls, or septa. These generally have pores large enough for ribosomes, These generally have pores large enough for ribosomes,

mitochondria, and even nuclei to flow from cell to cell.mitochondria, and even nuclei to flow from cell to cell. Fungi that lack septa (coenocytic fungi) consist of a Fungi that lack septa (coenocytic fungi) consist of a

continuous cytoplasmic mass with hundreds or continuous cytoplasmic mass with hundreds or thousands of nuclei.thousands of nuclei.

This results from This results from repeated nuclear repeated nuclear division without division without cytoplasmic cytoplasmic division.division.

StructureStructure

Parasitic fungi usually have some hyphae modified Parasitic fungi usually have some hyphae modified as haustoria, nutrient-absorbing hyphal tips that as haustoria, nutrient-absorbing hyphal tips that penetrate the tissues of their host.penetrate the tissues of their host.

Some fungi even have hyphae adapted for preying Some fungi even have hyphae adapted for preying on animals.on animals.

Parasitic FungiParasitic Fungi

Fungi reproduce by releasing spores (n) that are Fungi reproduce by releasing spores (n) that are produced either sexually or asexually.produced either sexually or asexually.

Distributed by wind, waterDistributed by wind, water The nuclei of fungal hyphae and spores of most The nuclei of fungal hyphae and spores of most

species are haploid, except for transient diploid species are haploid, except for transient diploid stages that form during sexual life cycles.stages that form during sexual life cycles.

However, some mycelia become genetically However, some mycelia become genetically heterogeneous –heterokaryotic mycelium- heterogeneous –heterokaryotic mycelium- through the fusion of two hyphae that have through the fusion of two hyphae that have genetically different nuclei (sordaria)genetically different nuclei (sordaria)

ReproductionReproduction

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

In many fungi with sexual life cycles, karyogamy, In many fungi with sexual life cycles, karyogamy, fusion of haploid nuclei contributed by two parents fusion of haploid nuclei contributed by two parents (sordaria), occurs well after plasmogamy, (sordaria), occurs well after plasmogamy, cytoplasmic fusion by the two parents.cytoplasmic fusion by the two parents.

Fig. 31.3

ReproductionReproduction

Phylum: Phylum: Myxomycophyta (slime Myxomycophyta (slime

molds)molds) Sometimes placed with Sometimes placed with

protistsprotists Enormous single cells Enormous single cells

with thousands of nucleiwith thousands of nuclei They swarm together They swarm together

and build fruiting bodies and build fruiting bodies for reproduction using for reproduction using chemical markerschemical markers

Black bread moldBlack bread mold Penicillium Penicillium

Class: Phycomycetes-MoldsClass: Phycomycetes-Molds

GlomeromycetesGlomeromycetes

Symbiotic root Symbiotic root fungifungi - -MycorrhizaeMycorrhizae

Lichens: Lichens: algae + algae + fungi bodyfungi body

Class: Ascomycota – Sac FungiClass: Ascomycota – Sac Fungi Yeast, truffles, sordaria, Yeast, truffles, sordaria,

and ringwormand ringworm Ergots on wheat – highly Ergots on wheat – highly

toxic toxic Contains Lysergic acid: Contains Lysergic acid:

40,000 died in 944 in an 40,000 died in 944 in an Epidemic in EuropeEpidemic in Europe

Class: Basidiomycota-(mushrooms)Class: Basidiomycota-(mushrooms) Mushrooms, shrooms, shelf fungi, puffballs, Mushrooms, shrooms, shelf fungi, puffballs,

etc.etc. May be edible or toxicMay be edible or toxic

Depends on the enzymes they haveDepends on the enzymes they have