Chapter 31

Question 1

Defining Kingdom Fungi

Answer 1

Eukaryotic absorptive heterotrophs, secrete enzymes to digest and absorb nutrients (outside of cell body). Most multicellular, a few unicellular (yeast). Reproduce sexually or asexually by spores. Contain cell wall of chitin. Unusual mitosis.
460-600 MYA

Question 2

Monophyletic phyla and Paraphyletic phylum

Answer 2

Blastocladiomycota
Neocallismastigamycota
Chytridiomycota
Glomeromycota
Basidiomycota
Ascomycota
Paraphyletic: Zygomycota (Microsporidia sometimes included)

Question 3

Body of fungi

Answer 3

Unicellular or filamentous masses (threadlike form called mycelia)
Body plan - mass of connected tiny filaments called hyphae (Hypha), single cells joined end to end surround by a cell wall.
Hypha - long filament of fungal cells
Mycelium (Mycelia) - Mass of hyphae (mass of filamentous threads

Question 4

Hyphae organization

Answer 4

Some continuous. Others are divided by septa. Cytoplasm flows throughout hyphae, allows rapid growth under good conditions.

Question 5

Cell walls

Answer 5

Chitin - polysaccharide, same material as exoskeletons of arthropods. Internal end wall (when present) Septum (septa)

Question 6

Dikaryotic cell
Monokaryotic cell
Heterokaryotic
Homokaryotic

Answer 6

Dikaryotic - Fungal cells that contain 2 or more nuclei. Both genomes transcribed.
Monokaryotic - 1 nucleus in cells.
Heterokaryotic - nuclei from genetically distinct individuals
Homokaryotic - Nuclei are genetically similar to one another.

Question 7

Unusual Mitosis

Answer 7

Mitosis not followed by cell division. Eukaryotes - Replication and segregation of genetic material and division of cytoplasm, cell is unit of division, does not happen in fungi.
Nuclei are “units of division” not cells: nuclear envelopes do NOT breakdown, spindle fibers form within nucleus, cytokinesis does not occur. Centrioles are absent, except Chytrids

Question 8

Reproduction
Sexual

Answer 8

Asexual and sexual. Sexual - Fusion of two haploid hyphae of compatible mating types (+ and -). Some fungi fusion immediately results in a diploid cell. Others have a dikaryon strange (1n+1n) before parental nuclei from diploid nucleus. May form mushroom or puffball. Two haploid nuclei fuse to form a zygote that divides by meiosis to produce haploid spores

Question 9

Spores

Answer 9

Most common means of reproduction among fungi. May form from sexual or asexual processes. Most are dispersed by wind, small size suspended in air for a long time and can spread over long distances.

Question 10

Asexual

Answer 10

Spore production in sporangia in enclosed sac. Conidia - spores in chains.
Haploid spores from mitosis

Question 11

Nutrition fungi

Answer 11

Obtain food by secreting digestive enzymes into surroundings then absorb the organic molecules produced by this external digestion. Fungi can break down cellulose and lignin (plant cell wall). Decompose wood (glucose) Some carnivorous (nematodes)

Question 12

Ecology

Answer 12

Fungi together with bacteria are principal decomposers in biosphere. Make material available to other organisms such as breakdown lignin, releases carbon, nitrogen and phosphorus. Many are difficult or impossible to culture in the lab. Can study environmental DNA, which reveals organisms prevent without having to culture them.

Question 13

Interactions with other species fungi

Answer 13

Symbioses - Obligate (essential for fungus survival) and facultative (Nonessential)
1 Pathogen - harms host by causing disease
b Parasites - cause harm to host (do not cause disease.)
2 Commensal - Relationships benefit one partner but does not harm the other
3 Mutualistic - relationship that benefits both partners.

Question 14

Endophytic fungi

Answer 14

Live in the intercellular spaces inside plants. Some parasitic, some commensal and some mutualistic (could change depending on environment) Some fungi protect their hosts from herbivores by producing toxins. Italian rye grass is more resistant to aphid feeding in the presence of endophytes

Question 15

Lichens general info and three types

Answer 15

Cyanobacteria or green algae (photosynthesis organism). Symbiotic association between a fungus and a photosynthetic partner. Most are mutualistic (some parasitic). Ascomycetes are found in most of 15,000 lichen spp.
Fruticose lichen - short gray stalks (coral like)
Foliose lichen (usually trees, leafy looking)
Crustose lichen (Scale like)

Question 16

Lichen Biology

Answer 16

Fungi in lichens are unable to grow normally without partner. Fungi protect their partners from strong light and desiccation. Lichens have invaded the harshest of habitats. Striking colors play a role in protecting photosynthetic partner. Sensitive to pollutants. Bioindicator of air quality

Question 17

Mycorrhizae

Answer 17

Mutualistic relationships between fungi and plants. Found on the roots of about 90% of all known vascular plant families.
Functions as extension of root system. Increase soil contact and absorption. Two principal types - ectomycorrhizae and arbuscular mycorrhizae

Question 18

Arbuscular mycorrhizae

Answer 18

Most common 80% of all plant spp. and also bryophytes. Fungal partners are glomeromycetes. No aboveground fruiting structures. Potentially capable of increasing crop yields with lower phosphate and energy inputs. Hyphae penetrate the outer cells of root cell wall but not plant membranes, don’t penetrate cell membrane.

Question 19

Ectomycorrhizae

Answer 19

Most hosts are forest trees (pines, oaks etc). Fungal partners are mostly basidomycetes. At least 5000 spp of fungi involved in this relationship. Hyphae surround and weave around cell but do not penetrate the root cells.

Question 20

Animal mutual symbioses

Answer 20

Ruminant animals host neocallimastigamycete fungi in their gut to help break down cellulose.
Leaf cutter ants have domesticated fungi that they keep underground. Mutualistic

Question 21

Fungal parasites, pathogens, and diseases

Answer 21

Mycoses - direct contact (skin and nails)
Mycotoxins - ingested toxin produced by fungi
Fungi secrete mycotoxins making food unpalatable, carcinogenic, or poisonous. Aspergillus flavus-aflatoxin.
Ustilago maydis - corn smut
Athlete’s foot, ring worm.
Batrachochytrium dendrobatidis - amphibian decline
Fungal diseases difficult to treat due to phylogenetic relationship between fungi and animals

Question 22

Phylum Basidiomycota

Answer 22

Club fungi (sexual reproductive structure). Most familiar. Include mushrooms, toadstools, puffballs, and shelf fungi. Rusts and smut pathogen.
Karyogamy (the final step in the process of fusing together of two haploid eukaryotic cells) occurs within basidia (club, above ground for spore dispersal). Only diploid cell in life cycle. Meiosis follows. Four haploid products are incorporated into basidiospores.
Spore germination leads to the production of monokaryotic hyphae and monokaryotic mycelium (primary mycelium). Different mating types of monokaryotic hyphae may fuse resulting in dikaryotic or secondary mycelium.
Basidiocarps (mushroom) are formed entirely of secondary mycelium.

Question 23

Phylum Ascomycota

Answer 23

Sac fungi. Contains about 75% of known fungi. Bread yeasts, common molds, cup fungi, truffles, and morels. Serious plant pathogens - cause of chestnut blight and DED.
Penicillin producing fungi, genus Penicillium
Named Ascus - microscopic sac like reproductive structure.
Karyogamy occurs within asci. Only diploid nucleus of life cycle. Asci differentiate in ascocarp. Meiosis and mitosis follow producing 8 haploid nuclei that become walled ascospores.
Asexual reproduction is very common. Conidia formed at the ends of modified hyphae called conidiophores. Allow for rapid colonization of a new food source. Hyphae are divided by perforated septa, allows cytoplasm to flow length of hypha. Perforations may be blocked in unfavorable conditions

Question 24

Yeast

Answer 24

Ascomycetes phylum. Asexual, budding or cell fission
Ferments carbohydrates. Break down glucose into ethanol and CO2. Model in genetic research. First eukaryote to be manipulated extensively and first to have genome sequenced.

Question 25

Phylum Glomeromycota

Answer 25

Tiny group of fungi 200 spp alive. Form intracellular associations (obligate symbiosis) with plant roots called arbuscular mycorrhizae. Cannot survive without plant host. No evidence of sexual reproduction. No septa in hyphae

Question 26

Phylum Zygomycota

Answer 26

Incredibly diverse 1,000 spp. Not monophyletic- still under research. Common bread molds, a few human, animal and plant pathogens.
Sexual reproduction. Fusion of gametangia. Haploid nuclei fuse to form diploid zygote nuclei- karyogamy. Develops into zygosporangium in which zygospore develops. Meiosis occurs during germination of zygospore and releases haploid spores.
Asexual reproduction more common, sporangiophores have sporangia that release haploid spores

Question 27

Phylum Chytridiomycota

Answer 27

Little pot - structure that releases zoospores to environment.
Aquatic flagellated fungi. Closely related to ancestral fungi. Have motile zoospores. Flagellated and asexual. Z
Ex. Batrachochytrium dendrobatidis - amphibians.

Question 28

Phylum Blastocladiomycetes

Answer 28

Unflagellated zoospores. Allomyces example. Water molds. Haplodiplontic life cycle. Parasite of another fungi. Alternation of generations.

Question 28

Phylum Neocallimastigomycota

Answer 28

Digest plant biomass in mammalian herbivore rumens (cellulose and lignin). Mammals depend on fungi for sufficient calories. Greatly reduced mitochondria lack cristae (hydrogenesomes produce ATP).
Zoospores have multiple flagella. Horizontal gene transfer brought cellulase gene from bacteria into their genome.

Question 28

Microsporidia

Answer 28

Obligate, intracellular animal parasites (crustaceans, insects, amphibians). Some immunocompromised humans, but generally not. Long though to be protists. Lack mitochondria, have genes related to it. Do not undergo aerobic respiration.
Ex. Encephalitozoon cuniculi - Commonly cause disease in immunosuppressed pts. Infect hosts with their spores, which contain a polar tube. Infects intestinal and neuronal cells, leading to diarrhea and neurodegenerative disease.