Kingdom Fungi

Introduction

High points - beer, other fermented beverages, leaven bread, antibiotics

Low points - athletes foot, jock itch, that pink stuff that grows on your shower curtain

Fungi are ubiquitous = present in air, water, soil and organisms, or on organism surfaces.

Fungi are very diverse (many different species) Vary in size from invisible yeasts, (only

several microns in diameter), to extremely large polypores, (may grow up to several meters in diameter).

Where are fungi found?

Classification

Once classified as plants Significant differences in structure,

life cycle and nutrition have earned them their own Kingdom

Fossils resembling fungi date back about 900 million years

~570 mya diverged from plants Became heterotrophic

Modern fungi evolved ~300 mya

What have mycologists found?

Botanists who study fungi have defined the members of this kingdom based on the following:

Decomposers Can break down almost

any organic compound including plastics

Human benefits = yeast (bread/wine/beer); penicillin (antibiotics); flavour; food items

Fungi Structures

Although diverse in species as well as in form, fungi share some common characteristics.

Fungi are eukaryotic organisms.

Compared to other eukaryotic plants or animals, fungi have relatively very small nuclei.

Distinctive fungal features

Fungi are heterotrophs. Fungi have several cell types. Some fungi have a dikaryon stage.

Two haploid cells coexisting in a single cell (dikaryon) before fusion to form nucleus (diploid)

Fungi have cell walls that include chitin. Fungi undergo nuclear mitosis.

During mitosis, the nuclear membrane does not breakdown, mitosis occurs in the nucleus

Fungi Nutrition

Fungi live heterotrophically as saprophytes, parasites or mutualists.

Fungi secrete digestive enzymes onto a food source nearby, dissolve it to smaller soluble molecules and then ingest them into cells.

How Fungi Obtain Nutrients

All fungi obtain food by secreting digestive enzymes and then absorbing the organic molecules produced (external digestion). extensive hyphae network provides

enormous surface area for absorption many fungi able to break

down cellulose in wood

Structures

The Body of a Fungus

Fungi exist mainly in the form of slender filaments (hyphae). long chains of cells joined

end-to-end divided by cross-walls (septa)rarely form complete

barriercytoplasm freely streams

in hyphae mycelium - mass of

connected hyphaegrows through and

penetrates substrate

Fungi Structures cont’d

Most fungi consist of hyphae, which may or may not have cross walls separating individual cells.

The hyphae combine to make up the fungal mycelium.

The Body of a Fungus

Fungi cell walls are formed of polysaccharides and chitin. not cellulose like those of plants gives strength and support to the fungi

cells. Mitosis is unique.

nuclear envelope does not break down and re-form

spindle apparatus formed within spindle plaques take place of centrioles

Classification

Four Major Groups of Fungi

Four major groups: Chytridiomycota Zygomycota Basidiomycota Ascomycota

Chytridiomycota

aquatic, flagellated fungi most closely related to ancestral fungi

Basidiomycota

Zygomycota (the conjugation fungi)

Ascomycota

Zygomycota

includes common bread molds produces temporarily dormant

zygosporangia sexual reproduction occurs by

fusion of gametangia asexual reproduction most common

hyphae produce clumps of erect stalks - sporangiophores

form sporangia

Zygomycota

Bread Mold

Division Zygomycota – Rhizopus stolonifer

Basidiomycota

Most familiar fungi (mushrooms, toadstools, puffballs, rusts, and smuts) named for characteristic sexual

reproductive structure, basidium Four haploid products of meiosis

incorporated into basidiospores Mycelium made up of monokaryotic

hyphae is called primary mycelium. fusion of different mating types forms

dikaryotic, secondary mycelium.

Basidiomycota

Mushroom parts

Cap (Pileus) - The top part of the mushroom.Cup (Volva) - A cup-shaped structure at the base of the mushroom. The

basal cup is the remnant of the button (the rounded, undeveloped mushroom before the fruiting body appears). Not all mushrooms have a cup.

Gills (Lamellae) - A series of radially arranged (from the center) flat surfaces located on the underside of the cap. Spores are made in the gills.

Mycelial threads - Root-like filaments that anchor the mushroom in the soli.

Ring (Annulus) - A skirt-like ring of tissue circling the stem of mature mushrooms. The ring is the remnant of the veil (the veil is the tissue that connects the stem and the cap before the gills are exposed and the fruiting body develops ). Not all mushrooms have a ring.

Scales - Rough patches of tissue on the surface of the cap (scales are remnants of the veil).

Stem (Stape) - The main support of the mushroom; it is topped by the cap. Not all mushrooms have a stem.

Ascomycota

Very large group including yeasts, common molds, and morels

Named for reproductive structure ascus haploid zygotic nucleus formed within asci differentiated with ascocarp

Asexual reproduction takes place in conidia spores at the end of conidiophores.

Ascomycota

Ascomycota

Yeasts unicellular - most reproduction is

asexual and takes place by cell fission or budding

ferment carbohydrates play a leading role in genetic research

Life cycle

How Fungi Reproduce

Differ from most animals and plants in that each compartment of hypha can contain one, two or more nuclei monokaryotic - each compartment has a

single nucleus dikaryotic - two distinct nuclei within

each hyphae compartment

How Fungi Reproduce

Possible for many nuclei to intermingle in common cytoplasm of fungal mycelium which can lack distinct cells heterokaryotic – dikaryotic or

multinucleate hypha has nuclei from genetically distinct individuals

homokaryotic – hyphae whose nuclei are genetically similar to one another

REPRODUCTION

Many fungi can reproduce both asexually and sexually.

Asexual Reproduction produces offspring that are

genetically identical to the parent, is most common when nutrients and water are abundant.

Sexual Reproduction occurs in fungi mostly when nutrients or water become scarce.

How Fungi Reproduce

Fungi reproduce sexually after two hyphae of opposite mating type fuse.

in some fungi fusion two haploid cells immediately results in diploid cell (2n)

basidiomycetes and ascomycetes have dikaryotic stage (1n + 1n) before parental nuclei fuse to form diploid nucleus

Reproduction

Spore production

How Fungi Reproduce

Spores most common means of reproduction may form from asexual or sexual

processes most often dispersed by wind but some

spread by insects or other small animals chytrids only group to retain ancestral

flagella and motile zoospores

Asexual Reproduction

Yeasts, which are unicellular and grow reproductively by some type of budding or fission, are an exception.

Fungi can reproduce sexually or asexually by producing spores that grow hyphae.

Fungi may also reproduce by fragmentation

Growth Hyphae increase length by Cellular Growth and Division

at the TIP.  As the hyphae grow, the size of the mycelium increase.

Fungi growth is rapid since all the hyphae in a mycelium share the same cytoplasm.

Septa may or may not divide the cytoplasm of the hypha.

Since materials can move quickly through the whole mycelium and are available to the growing hyphae, rapid growth occurs.

Ideal Growth Conditions:WarmDarkMoist

Growth cont’d

Several species of Fungi are able to change their form in response to change in their environment. For example, Histoplasma capsulatum, which

causes a severe disease in humans that can resemble tuberculosis, normally grows as mycelium on the ground, but when it invades a human, the increased temperature and available nutrients causes the fungus to grow unicellular like a Yeast.

This ability to change is called DIMORPHISM

(die-MOR-FIZ-uhm)

Ecology of Fungi

Mutualistic associations lichens - fungi and green algae mycorrhizae - fungi and plant roots

Mycorrhizae (fungi living symbiotically with plant roots)

Lichens (fungi living symbiotically with cyanobacteria)

Pioneer species Don’t require substrate

for Anchorage Nutrient supply

Can survive extreme environmental conditions

Temperature dryness

Lichens

Lichens are symbiotic associations between a fungus and a photosynthetic partner. usually ascomycetes

Specialized fungal hyphae penetrate photosynthetic cells and transfer nutrients to fungal partner.

Durable fungus, combined with photosynthetic properties, has enabled lichens to invade harsh climates.

extremely sensitive to pollutants

Mycorrhizae

Roots of about 90% of all kinds of vascular plants are involved in mutualistic symbiotic relationships (mycorrhizae). arbuscular mycorrhizae - fungal

hyphae penetrate outer cells of plant root

most common ectomycorrhizae - hyphae surround,

but do not penetrate, cell walls of roots

Mycorrhizae

Endophytes

Endophytic fungi live inside plants in the intercellular spaces. some may protect their hosts from

herbivores by producing chemical deterrents

Mutualistic Animal Symbioses

A range of mutualistic fungal-animal symbioses has been identified. Ruminants – fungi in gut – release

enzymes leaf-cutter ants – fungal gardens

Fungal Parasites and Pathogens

Chytridiomycosis - emergent infectious disease in amphibians chytrid Batrachochytrium dendrobatidis

Aflatoxins - carcinogenic compounds produced by strains of Aspergillus flavus grows on corn, peanuts, cotton seeds

Metabolic Pathways

Anaerobic fermentation provides flavor for wine and cheese.

Biochemical manufacturing of organic substances food pharmaceuticals

Yeasts break down carbon-containing products. bioremediation

Ecology of Fungi

Fungi and bacteria are the principal decomposers in the biosphere. mineral cycling

Fungi are virtually the only organisms capable of breaking down lignin.

Fungi often act as disease-causing organisms for both plants and animals. agricultural damage human health

Websites (resources)

http://www.sirinet.net/~jgjohnso/fungi.html

http://www.rogers.k12.ar.us/users/ehutches/2fungi.phtml

http://www.uwlax.edu/biology/volk/fungi3/sld001.htm

Summary Quiz

1. The body of a fungus is made of ___________________. 2. The cell wall of each hyphae contains _______________.3. Mushrooms and toadstools are types of _____________. 4. Fungi reproduce _____________________. 5. There are _____________________  divisions of fungi. 6. Fungi are _____________________. 7. Most fungi are _____________________. 8. Most fungi feed by _____________________. 9. Bread mold is a type of _____________________. 10. Division of fungi that includes yeast: ________________11. Division of fungi that includes mushrooms:

___________12. Division of fungi that does not have a sexual stage

known: ___________________________