FUNGI

Chapter 31

The Little Known Fungi

100,000 species known, 1.5 million unknown (estimate)

Some are single-celled (yeast), but most multicelled (mushrooms)

Found in every habitat Diverse, widespread, and essential for well-being Formerly classified as plants

Molecular data says more closely related to animals Mycologists are the scientists that study fungi

Nutrition

Heterotrophs, but absorb food instead of digest Secrete enzymes into environment to break

complex molecules into something more manageable

Enzymes also disrupt walls of plant cells for nourishment

Live as decomposers, parasites, or mutualisms' Fit into multiple niches Can digest wide range of food sources

Body Structure

Most grow as filaments and yeasts Yeast only growth is rare

Bodies form filamentous networks called hyphae Form a mycelium to

increase SA/volume ratio Proteins synthesized to

rapidly extend (not grow) hyphae Concentratie of energy

and resources to accomplish

Not motile, but can move hyphae

Specialized Hyphae

Some allow predation of living animals

Haustoria allow nutrient extraction or exchange

Mycorrhizae are mutually beneficial relationships between fungi and plants Improve mineral delivery to

plants in exchange for carbs

Ectomycorrhizal fungi: form a sheath of hyphae over plant roots and between plant cells

Arbuscular mycorrhizal fungi: extend hyphae through root cell walls and into plant

Sexual Reproduction

Hyphae release pheromones

Different mating types attract

Heterokaryon, nuclei don’t fuse right away

Dikaryotic, nuclei pair off and divide without fusing

Time to karyogamy varies

Usually only 2n stage

Final steps generate genetic variation

Asexual Reproduction

Varies widely among fungi (like sexual)

Produce haploid spores by mitosis Informally known as

molds if mycelia is visible

Grow rapidly and reproduce sexually if contacted by species of different mating type

Yeasts produce budding cells or spores via mitosis

Deuteromycetes reproduce asexually only

5 phyla recognized currently, but chytrids are likely paraphyletic

Study cycle diagrams for reproductive differences

Fungi Functional Groups

Chytridium globular fruiting bodies, one of the earliest to diverge

Mucor, grow into fruits and breads;may act as decomposers, parasites,or symbionts

Ecologically important; form mycorrhizal associations with plants

Sac fungi, common to water and land Aleuria aurantia

Decomposers and ectomycorrhizal fungi; fruiting bodies commonly called mushrooms

Phylum Chytridiomycota

Called chytrids and found in lakes and soil

Decomposers and pararsites of protists, other fungi, plants, or animals Live in sheep GI tracts to

help process plants Some form colonies with

hyphae, others as single cells

Only phyla with flagellated spores called zoospores

Phylum Zygomycetes

Reproduce by zygospores Sexually, formed in

zygosporagium Asexually, formed

atop sporangiophores Rhizopus stolonifer is

black bread mold Know the life cycle

Philobolus ‘aim’ and shoot sporangium

Resistant to freezing and drying

Phylum Glomeromycetes

Form arbuscular mycorrhizae Tips of hyphae push

into plant root cells and branch into treelike structures

Minerals to plant and organic compounds to fungi

Mutualistic partnership with 90% of all plant species

Phylum Ascomycetes

Reproduce sexually by spores in asci (sacs) and bear stages in ascocarps (fruiting bodies)

Reproduce asexually by conidiospores, spores formed at tips of hyphae called conidiophores

Include: morels and truffles Yeasts used in beer industry

Phylum Basidiomycetes

Includes mutualists that form mycorrhizae and plant parasites

Reproduce sexually by producing fruiting bodies called basidiocarps Produces 4 haploid

nuclei Asexual reproduction

is rare

Fungal Phylum Review

Decomposers

Any carbon containing substance can be consumed by some fungi

Important use in bioremediation Maintain essential inorganic nutrients for

plant growth Return nutrients to the soil

Mutualists

Fungus-Plant Ascomycetes benefit by producing toxins to deter

prey Fungus-Animal

Decomposers convert otherwise indigestible plant material

Lichens: symbiotic association with algae Algae contribute carbon compounds and fix nitrogen Fungi contribute suitable environments for growth Reproduce separately

Lichen: asexually via soredia, clusters of hyphae with algae

Pathogens Mostly on or in plants

Ascomycete Cryphonectria parasitica attacks chestnuts Basidiomycete Puccinia graminis causes black stem rust

on wheat Ascomycete Aspergillus contaminates improperly stored

grains and peanuts by secreting carcinogenic aflatoxins Mycosis are those that parasitize humans

Ascomycetes cause ringworm and athlete’s foot Coccidioidomycosis produces tuberculosis like

symptoms in lungs Candida albicans normal on moist epithelia, grow to

rapidly causes vaginal infections, diaper rash, and thrush

Practical Uses

Food Flavors of cheese Aspergillus used for

citric acid in cola Yeasts for breads, beer,

and wine Medicine

Antibiotic treatments Penicillium used to

produce penicillin Saccharomyces used to

study Parkinson’s and Huntington’s disease