Chapter 29

opisthokont

-Fungi are assigned to the opisthokont clade -the common ancestor of all plants, fungi, and animals was an ancient flagellate protist -opisthokonts includes the choanoflagellates, the animals, and the fungi -amoebozoa (a group of amoebas), fungi, animals, and a few protists, including the choanofla- gellates (a group of flagellate protists), form a monophyletic "supergroup," the UNIKONTS -Within this supergroup, the clade opisthokonts includes the choanoflagellates, the animals, and the fungi -genetic and structural similarities support this -Like animals, fungi have platelike cristae in their mitochondria -another key characteristic of this clade is that flagellate cells propel themselves with a single posterior flagellum. -systematists now view fungi as more closely related to animals than to plants.

bioremediation

-Fungi are used in bioremediation and to biologically control pests -Some fungi can biodegrade pesticides, herbicides, coal tars, and petroleum -Fungi convert these products into carbon dioxide -These fungi can be used along with certain bacteria to decon- taminate farm land and to clean up oil spills. -species of microsporidia—for the biological control of pathogens and insect pests -In some cases, they interfere with reproduction in their insect host. -microsporidia may pose a threat to beneficial insects. For example, a microsporidian has been implicated as one factor in the die-off of honeybee colonies.

zygomycetes life cycle

-Like most fungi, most zygomycetes reproduce both asexually and sexually. 1) Spores germinate and produce haploid mycelia. 2a) In asexual reproduction, certain hyphae form sporangia in which clusters of black, asexual, haploid spores develop. When released, they give rise to new hyphae. 2b) Hyphae of (+) and (−) mating types grow toward one another. 3) When (+) and (−) hyphae meet, they form gametangia. PLASMOGAMY 4) Plasmogamy occurs as gametangia fuse. KARYOGAMY 5) Karyogamy occurs with nuclei fusing to form diploid zygote. 6) Zygospore develops from zygote; it is encased by thick-walled, black zygosporangium. MEIOSIS 7) Meiosis occurs, and zygospore germinates; hypha develops sporangium at its tip.

fairy rings

-Many basidiomycetes produce "fairy rings" in lawns and forests -A fairy ring may first appear as a dark green ring surrounding an inner brown circle -The size of the ring ranges from a few centimeters to more than 15 m (about 51 ft) in diameter. -The green ring consists of grass, well nourished by the nutrients released as the fungi decompose organic material. -Grass dies, producing the inner brown circle, because the mass of mycelia decreases the movement of water into the area. As the fungi grow out- ward, the circle widens. -The rings grow a few centimeters to more than a meter per year -After rainfall or irrigation, a ring of mushrooms may appear just outside the green circle.

asexually

-Many fungi reproduce asexually -Yeasts reproduce asexually, primarily by forming buds that pinch off from the parent cell -multicellular fungi also reproduce asexually -Spores are produced by mitosis and then released into the air or water

asexual and sexual reproduction

-Most fungi can reproduce both asexually (which allows rapid proliferation) and sexually (which produces new genotypes). 1) Spores germinate and form mycelia by mitosis 2) Mycelia of two different mating types fuse at their tips, and plasmogamy (fusion of cytoplasm) occurs. PLASMOGAMY 3) (dikaryotic) Dikaryotic (n + n) mycelium develops KARYOGAMY 4) (diploid stage) Karyogamy (fusion of nuclei) occurs, forming a diploid (2n) zygote nucleus. MEIOSIS 5) Meiosis results in four genetically different haploid (n) nuclei. Spores develop around nuclei. 6) Spores are released. 7) (asexual reproduction) Large numbers of haploid (n) spores are produced by mitosis. 8) (asexual reproduction) Spore germinates and forms mycelium by mitosis

spores

-Most fungi reproduce by means of microscopic spores -reproductive cells that can develop into new organism -spores are nonmotile -They are dispersed by wind, water, or animals. -air we breathe is filled with hundreds of thousands of fungal spores -When a spore germinates, it gives rise to a hypha, which then develops into a mycelium -spore-> hypha-> mycelium -spores are produces either sexually or asexually -asexual: many new individuals, but little genetic variability -sexual: involves meiosis and generates new genotypes -usually produced on specialized aerial hyphae or in fruiting structures

sexually

-Most fungi reproduce sexually -Most fungi (but not all) reproduce both asexually and sexually -Many fungal species reproduce sexually when they come into contact with other mating types. -most fungal cells contain haploid nuclei.

mycology

-Mushrooms, morels, and truffles, delights of the gourmet, sharea recent common ancestry with baker's yeast, the black mold that forms on stale bread, and the mildew that collects on damp shower curtains -the study of fungi, is concerned with all these diverse life-forms.

thallus

-The term thallus describes the simple body plan of certain algae, fungi, and plants. -The thallus may have slender extensions, called rhizoids, that anchor it to a food source and absorb food -Many chytrids have a microscopic body form consisting of a rounded, coenocytic thallus and branched rhizoids that superficially resemble roots. -The rhizoids may anchor the chytrid thallus and absorb predigested food.

karyogamy

-This cell gives rise by mitosis to other cells with 2 nuclei (from plasmogamy) -At some point the two haploid nuclei fuse. -This process, called karyogamy, results in a cell containing a diploid nucleus known as a zygote nucleus -the zygote nucleus is the only diploid nucleus.

zygomycetes

-Zygomycetes reproduce sexually by forming zygospores -zygomycetes (phylum Zygomycota) -these appear most closely related to chytrids -zygomycetes are NOT a monophyletic group -Most zygomycetes are decomposers that live in the soil on decaying plant or animal matter -The stalked sporangia, which are 5 to 10 mm tall, act like shotguns and force- fully discharge sporangia (the black tips) away from the dung onto nearby grass. Pilobolus. -Some zygomycetes form a type of symbiotic association (mycorrhizal relationship) with plant roots -A few species cause disease in plants and animals, including humans. -zygomycetes produce sexual spores, called zygospores. -The zygospores are typically pro- duced in spore sacs called zygosporangia -The hyphae in zygomycetes are coenocytic; that is, they lack regularly spaced septa. However, septa do form to separate the hyphae from reproductive structures. -most familiar zygomycete is the black bread mold, Rhizopus stolonifer, a decomposer that breaks down bread and other foods -Bread becomes moldy when a spore falls on it and then germinates and grows into a myce- lium. Hyphae penetrate the bread and absorb nutrients. -Eventually, certain hyphae grow upward and develop sporangia at their tips. Clusters of more than 50,000 black asexual spores can develop within each sporangium. -The spores are released when the delicate sporangium ruptures. The spores give the black bread mold its characteristic color.

mutualism

-a mutualistic symbiotic association: both partners benefit. Example: mycorrhizal relationship -if a plant grows in phosphate-deficient soil or has a limited root system, its growth is enhanced by having a fungal partner -for those that have rich soil then they won't need fungal partner and the fungus may be a parasite. -For example, some fungi release alkaloids that protect the plants from herbi- vores and pathogens. Plants also exchange nutrients with one another through fungi that connect them. -mycorrhizal fungi was discovered about 400 my old. this suggests that when plants moved onto the land, their fungal partners moved with them -fungal partners may have been critical for early vascular plants to colonize the land because the fungal hyphae may have provided plants with water and minerals before their own root systems evolved.

chitin

-a polymer that consists of subunits of a nitrogen- containing sugar -Fungi have cell walls that contain chitin -fungal cells are enclosed by cell walls during at least some stage in their life cycle. -the cell wall consists of complex carbohydrates, including chitin, -Chitin is also a component of the external skeletons of insects and other arthropods. -It is resistant to breakdown by most microorganisms.

fungal body structure

-yeast are unicellular -most fungi are multicellular and have bodies made of haploid hyphae -hyphae: are long, branched filaments -septate hyphae divided into separate cells by cell walls (Septa) -coenocytic hyphae lack septa -hyphae grow by mitosis fro single haploid spore to form mycelium fungal body structure

Asci

Each ascus contains eight ascospores. Asci line the inner portion of the ascocarp.

primary mycelium

Hyphae of a primary mycelium consist of monokaryotic cells.

bacteria

Interestingly, researchers have shown that some mycorrhizal fungi harbor bacteria in their cytoplasm. Although the role of the bacteria is not yet clear, their presence suggests that they may be members of a three-way partnership: fungus, plant, and bacteria.

growth forms of lichen

Lichens typically exhibit one of three different growth forms -Crustose lichens are flat and grow tightly against their substrate (the surface they are growing on). -Foliose lichens are also flat, but they have leaflike lobes and are not as tightly pressed to the substrate. -Fruticose lichens grow erect and have many branches.

ascocarp

The ascocarp (fruiting body) of the common brown cup (Peziza badio-confusa). This ascocarp is shaped like a saucer or bowl and is 3 to 10 cm (1 to 4 in.) wide. It is found on damp soil in woods throughout North Americ

ascomycetes

ascomycetes produce ascospores inside asci that line the insides of ascocarps

basidia

basidia are comparable in function to the asci of ascomycetes -Each basidium is an enlarged hyphal cell that undergoes meiosis to form four basidiospores -Note that basidiospores develop on the OUTSIDE of a basidium, whereas ascospores develop WITHIN an ascus.

basidiomycetes

basidiomycetes produce basidiospores that hang outside basidia on the gills of basidiocarps/mushrooms

drugs

drugs -penicillium notatum (mold) produces penicillin -statins (lower cholesterol) -cyclosporine (immunosuppressant for transplants)

plasmogamy

hyphae/cytoplasm fusion

lichens

lichens -symbiosis b/n fungus (usually ascomycete) and photoautotroph (cyobacteria or green algae) -photoautotroph provides organic nutrients to fungus -fungus may provide water and minerals to phototroph -grow in almost all terrestrial environments -on exposed rocks, leaves, and tree bark. secrete acids that break up rocks to from soil

karyogamy

nuclei fusion

meiosis

spores produced by meiosis in sexual reproduction

mitosis

spores produced by mitosis in asexual reproduction

Deuteromycetes

-25,000 species have been assigned to a group called deuteromycetes (phylum Deuteromycota). It was a polyphyletic group (members did not share a recent common ancestor) lumped together simply as a matter of convenience. -fungi were classified as deuteromycetes if no sexual stage had been observed for them at any point during their life cycle. -some of those fungi have lost the ability to reproduce sexually whereas other reproduce sexually only rarely -Most fungi classified as deuteromycetes reproduce only by means of asexual spores. the asexual stage is still identified as a deuteromycete -Most of the deuteromycetes have been reassigned to phylum Ascomycota, and a few have been reassigned to phylum Basidiomycota.

major groups of fungi

-5 major groups of fungi -some groups not monophyletic. Chytrids, zygomycetes -most species ascomycetes or basidiomycetes. sister taxa based on spectate hyphae and prolonged dikaryotic stage. all other fungi have coenocytic hyphae and brief dikaryotic stage.

lichen

-A lichen consists of one or more fungi and a photoautotroph -Although a lichen looks like a single organism, it is actually a compound organism, a combination of one or more fungi and a photoautotroph -Fossils suggest that fungi developed symbiotic partnerships with photoautotrophs before the evolution of vascular plants. -photoautotrophic component of a lichen is a green alga, a cyanobacterium, or both -The fungus is typically an ascomycete, although a basidiomycete is the fungal part- ner in some tropical lichens -The photoautotroph grows more rapidly when separated, whereas the fungus grows more slowly and requires many complex carbohydrates. neither resembles a lichen in appearance when grown separately -photoautotroph and fungus can be sometimes reassembled as a lichen thallus, but only if they are placed in a culture medium under conditions that cannot support either of them independently. -not really a case of mutualism but one of controlled parasitism of the photoautotroph by the fungus. -phtoautortoph does phtosytnehsis producing carbon compounds for both members of lichen it is unclear how the p.a benefits some say it get water, nutrients, and protection from desiccation from the fungus

more on lichens

-Able to tolerate extremes of temperature and moisture, lichens grow in almost all terrestrial environments except polluted cities. -exist farther north than any plants of the arctic region and are equally at home in the steaming equatorial rain forest -grow on tree bark, leaves, and exposed rock surfaces, from solidified lava to tombstones -form soil from rock by releasing minerals. when lichens die they are become part of the soil -Reindeer mosses of the arctic region are lichens, not mosses -some produce colored pigments -orchil, is used to dye wool; another, litmus, is widely used in chemistry laboratories as an acid-base (pH) indicator -vary greatly in size, some are almost invisible -they grow slowly; the radius of a lichen may increase by less than 1 mm each year. -absorb minerals from the air, rainwater, and the surface on which they grow -cannot excrete the elements they absorb this is a reason why they are sensitive to toxic compounds -lichens could be used to measure air purity. Today, reduction in lichen growth is used as a sensitive indicator of air pollution, particularly from sulfur dioxide. -The return of lichens to an area indicates an improvement in air quality.

mycelium

-As hyphae grow they form a tangled mass or tissue like network, called a mycelium -Fungi that form mycelia are commonly called molds. cobweb-like mold sometimes seen on bread is the mycelium of a fungus. -What is not seen is the extensive mycelium that grows into the bread. -some fungi can alternate between a yeast phase and a phase in which they produce hyphae, based on the environment

life cycle of ascomycetes

-Ascomycetes produce asexual spores called conidia and sexual spores called ascospores. 1)Haploid myceliaof opposite mating types both produce coenocytic sexual hyphae. PLASMOGAMY 2)Plasmogamy occurs as hyphae of the two mating types fuse and nuclei are exchanged. 3) Dikaryotic hyphae form and produce asci. 4) Hyphae form an ascocarp. KARYOGAMY 5) Karyogamy occurs in each ascus. Two haploid nuclei fuse, forming a diploid zygote nucleus. MEIOSIS 6) Meiosis occurs, forming four haploid nuclei. 7) Mitosis produces eight haploid nuclei. 8) Each nucleus becomes incorporated into an ascospore. 9) When released, ascospores germinate and form new haploid mycelia. 10) In asexual reproduction, hyphae produce haploid conidia that can develop into new mycelia.

Basidiomycota

-(basidiomycetes or club fungi) Mushrooms, bracket fungi, puffballs, rusts, smuts -Asexual Reproduction: Uncommon -Sexual Reproduction: Basidiospores develop on club-shaped basidia -Other Key Characters: Have a dikaryotic stage; many form mycorrhizae with tree roots Basidiomycota

Chytridiomycota

-(chytrids or chytridiomycetes) Allomyces -Asexual Reproduction: Flagellate, diploid zoospores produced by mitosis in zoosporangia -Sexual Reproduction: Flagellate, haploid gametes in some species -Other Key Characters: Haploid zoospores produced in resting sporangia; form haploid thallus Chytridiomycota

conidiophores

-(from the Greek, meaning "dust-bearers") -are specialized hyphae that produce asexual spores called conidia -The arrange- ment of conidia on conidiophores varies from species to species.

Glomeromycota

-(glomeromycetes) -Asexual Reproduction: Large, multinucleate blastospores -Sexual Reproduction: Has not been observed -Other Key Characters: Form arbuscular mycorrhizae with plant roots Glomeromycota

Zygomycota

-(zygomycetes) Black bread moldMicrosporidia are classified with the zygomycetes. -Asexual Reproduction: Haploid spores produced in sporangia -Sexual Reproduction: Zygospores develop in zygosporangia. -Other Key Characters: Important decomposers; some are insect parasites.Microsporidia are opportunistic pathogens that infect animals. Zygomycota

soredia

-Lichens reproduce mainly by asexual means, usually by fragmentation, a process in which special dispersal units of the lichen, called soredia break off and, if they land on a suitable surface, establish themselves as new lichens. -contain cells of both partners. -In some lichens the fungus produces ascospores, which may be dispersed by wind and find an appropriate algal partner only by chance

ascomycetes

-sac/ cup fungi -decomposers, pathogens, lichens, and mycorrhizae -yeast, food molds, mildews, morels, truffles -sexual reproduction -after plasmogamy, dikaryotic fruiting body (ascocarp) produced -ascocarp: lined with saclike asci -karyogamy occurs In each ascus and form diploid zygote nucleus that undergrounds meiosis to produced ascospores

gametangia

(cont of zygomycetes) but only one word -When hyphae of opposite mating types grow in close proximity, they signal one another with pheromones. -In response to these chemical signals, the tips of the hyphae come together and form gametangia, which serve as gametes -Plasmogamy occurs as the gametangia fuse. Then karyogamy occurs as the (+) and (-) nuclei fuse to form the diploid zygote nucleus. The zygote develops into a zygospore. Zygospores are encased in a thick protective zygosporangium -The zygospore may lie dormant for several months. It can survive desiccation and extreme temperatures. -Meiosis probably occurs at or just before germination of the zygospore. -once zygospore is germinated an aerial hypha develops with a sporangium at the tip. Mitosis within the sporangium produces haploid spores. -These spores may be all (+) spores, all (-) spores, or a mixture of (+) and (-) spores. When released, the spores germinate to form new hyphae. -Only the zygote and zygospore of a black bread mold are diploid; all the hyphae and the asexual spores are haploid.

Ascomycota

-(ascomycetes) Yeasts, powdery mildews, molds, morels, truffles -Asexual Reproduction: Conidia pinch off from conidiophores. -Sexual Reproduction: Ascospores develop in asci -Other Key Characters: Have a dikaryotic stage; form important symbiotic relationships as lichens and mycorrhizae Ascomycota

ascomycetes

-Ascomycetes reproduce sexually by forming ascospores -Ascomycetes (phylum Ascomycota) -diverse ascomycetes include most yeasts; the powdery mildews; most of the blue-green, pink, and brown molds that cause food to spoil; decomposer cup fungi; and the edible morels and truffles. -ascomycetes affect humans more than any other group -used to flavor cheeses, to bake break (yeast), and to ferment alcohol. -some are used to produce antibiotics -have been useful models for cellular processes, including protein synthesis -many fungi in tis group form mycorrhizae with tree roots, and about 40% join with green algae or cyanobacteria to form lichens. -ascomycetes cause most fungal diseases of plants and animals, including humans. Example: the dutch elm disease, ergot disease on rye, powdery mildew on fruits and ornamental plants, and chestnut blight -sometimes referred to as sac fungi because their sexual spores are produced in microscopic sacs called ASCI (sing., ascus) -Their hyphae usually have septa, but these cross walls have pores so that cytoplasm is continuous from one cell compartment to another. -ascomycetes asexual reproduction involves production of spores called conidia, which form at the tips of certain specialized hyphae known as conidiophores. production through this way is a means of rapidly propagating new mycelia when environment is favorable -Conidia occur in various shapes, sizes, and colors in different species. The color of the conidia produces the characteristic blue-green, pink, brown, or other tints of many of these molds. -resemble paintbrushes. Note the conidia pinching off from the tips of the "brushes." Conidia are asexual reproductive cells produced by ascomycetes and some basidiomycetes. Biologists use the arrangement of conidia on conidiophores to identify species of these fungi. -Some species of ascomycetes are heterothallic. (means that an individual fungal hypha mates only with a hypha of a different mating type) -Others are homothallic (they are self-fertile and have the ability to mate with themselves) -in both homo- and heterothallic, sexual reproduction takes place after two gametangia come together and their cytoplasm mingles.

basidiomycete reproduction

-Asexual reproduction is less common in basidiomycetes than in other groups, so we will focus here on sexual reproduction -We begin with two compatible primary mycelia -When in the course of its growth a hypha of a primary myce- lium encounters a compatible monokaryotic hypha, typically of a different mating type, the two hyphae fuse (plasmogamy) -the two haploid nuclei remain sepa- rate within each cell. -a SECONDARY MYCELIUM with dikaryotic hyphae, in which each cell contains two haploid nuclei, is produced. The n + n hyphae of the secondary myce- lium grow rapidly and extensively. -when environment is favorable the hyphae form compact masses, called buttons, along the myce- lium. -each button grows into a fruiting body (mushroom/basdidiocarp) -each basidiocarp has a cap and the cap consist of perpendicular plates called GILLS that radiate from the stalk to the edge of the cap -kayogmy takes place within the young basidia on the gills of the mushroom. -The haploid nuclei fuse in the dikaryotic cells, forming diploid zygote nuclei. they are the only diploid cells that form -Meiosis then takes place, forming four haploid nuclei with different genotypes. -These nuclei move to the outer edge of the basidium. Finger- like extensions of the basidium develop, into which the nuclei and some cytoplasm move; each of these extensions becomes a basidiospore. -A septum forms that separates the basidiospore from the rest of the basidium by a delicate stalk that breaks when the basidiospore is forcibly discharged. Each basidio- spore can germinate and give rise to a primary mycelium.

ectomycorrhizal fungi

-At least 5000 species of ascomycetes and basidiomycetes also form mycorrhizal connections, but their hyphae coat the plant root rather than penetrate its cells. -These species are referred to as ectomycorrhizal fungi.

basidiomycetes life cycle

-Basidiomycetes produce sexual basidiospores on the gills of basidiocarps (fruiting bodies). -Asexual reproduction is uncommon in this group. 1) Basidiospores germinate and form primary mycelia. 2) Plasmogamy of primary mycelia occurs with the fusion of two (n) hyphae of different mating types. PLASMOGAMY 3) Fast-growing secondary mycelium is produced, composed of dikaryotic (n + n) hyphae. 4) Basidiocarps periodically develop from secondary mycelium. KARYOGAMY 5) Basidia form along gills of basidiocarps. In each basidium karyogamy occurs, producing a zygote nucleus. MEIOSIS 6) Meoisis occurs, producing four haploid nuclei that become basidiospores. 7) Basidiospores forming

basidiomycetes

-Basidiomycetes reproduce sexually by forming basidiospores -basidiomycetes (phylum Basid- iomycota) -include the largest most familiar of the fungi: the mushrooms, bracket fungi, and puffballs -basidiomycetes are decomposers that obtain nutrients by break- ing down organic matter. -cause dry rot in buildings, economic loss -some basidiomycetes form mycorrhizae, others infect important crops. A few cause human disease -sometimes called club fungi: they have club-shaped basidia -Each individual fungus produces millions of basidio- spores, and each basidiospore has the potential to give rise to a new primary mycelium -The mycelium of a basidiomy- cete, such as the commonly cultivated mushroom Agaricus brunnescens, consists of a mass of white, branching, threadlike hyphae that live mostly underground -septa are perforated and allow cytoplasmic streaming between cells

chytrids

-Chytrids have flagellate spores -the chytrids, also known as chytridiomycetes (phylum Chytridiomycota) -approximately 1000 species of chytridiomycetes are members of kingdom Fungi. perviously thought to be fungus like protist or similar to water molds but they are NOT. -Like fungi, their cell walls con- tain chitin, and molecular comparisons, particularly of DNA and RNA sequences, have provided compelling evidence that chytrids are indeed fungi. -chytrids are NOT a monophyletic group, and they may be divided into four clades. -Chytrids are small, relatively simple fungi that inhabit ponds and damp soil. a few have been found in salt water -Most chytrids are decomposers that degrade organic matter. -a few species cause disease in plants and animals. one has been found responsible for declining amphibian populations. -Infected frogs have been identified in many parts of the world -chytrids are unicellular -or composed of a few cells that form a simple body, called a THALLUS -the only fungi that have flagellate cells. Their spores bear a single, posterior flagellum. -no sexual reproduction -Species that do reproduce sexually have flagellate gametes. -produce branched, coenocytic mycelia -allomyces, a common chytrid has an alternation of generations. -chytrids were probably the earliest fungal group to evolve -chytrids have a flagellate cells other fungal groups apparently lost the ability to produce motile cells, perhaps during the transition from aquatic to terrestrial habitats.

fungi evolution

-Fossil evidence has not been very helpful to systematists studying evolutionary relationships among fungal groups -most fossilized fungi recovered to date is microscopic. Example: fungal spores in amber (more than 225 my old), hyphae associated with cyanobacteria or algae (are more than 550 my old) -a few large mushrooms have been found -fungi have been classified mainly by the characteristics of their sexual spores and fruiting bodies -comparative DNA and RNA sequences, have helped clarify relationships among fungal groups

coenocytes

-some fungi are coenocytes, which lack septa. -In these species nuclear division is not followed by cytoplasmic division. -As a result, a coenocytic fungus is one elongated, multinucleated, giant cell

plant diseases

-Fungi cause many important plant diseases -Fungi are more destructive to plants than any other disease- causing organism. -responsible for about 70% of all major crop diseases -All plants are apparently susceptible to some fungal infec- tion. -A plant often becomes infected after hyphae enter through stomata (pores) in the leaf or stem or through wounds in the plant body -the fungus may produce cutinase, an enzyme that dissolves the waxy cuticle that covers the surface of leaves and stems. After dissolving the cuticle, the fungus easily invades the plant tissues. -As the mycelium grows, it may stay mainly between the plant cells, or it may penetrate the cells -Ascomycetes cause serious plant diseases, including powdery mildew, chestnut blight, Dutch elm disease, apple scab, wilt on potatoes, and brown rot, which attacks cherries, peaches, plums, and apricot -Basidiomycetes cause smuts and rusts that attack corn, wheat, oats, and other grains -basidiomycete Puccinia graminis, which causes black stem rust of wheat, have complex life cycles that involve two or more different host plants and the production of several kinds of spores. Its spread may lead to widespread food shortages.

pheromones

-Fungi communicate chemically by secreting signaling molecules called pheromones -The pheromone binds with a compatible receptor on a different mating type -Example: in the zygomycetes, a pheromone induces the formation of specialized aerial hyphae. Another pheromone causes the tips of aerial hyphae of opposite mating types to grow toward each other and fuse prior to sexual reproduction

symbiotic relationship

-Fungi form symbiotic relationships with some animals -animals do not have enzymes necessary to digest cellulose and lignin, and cattle and other grazing animals cannot by themselves get the nutrients they need from the plants they eat. -Their survival depends on fungi that inhabit their guts. fungi have the enzymes that break down these organic compounds -the fungi benefit by living in a nutrient rich environment -Leaf-cutting ants bring leaves to their fungi and protect them from com- petitors and predators The ants also disperse the fungi to new locations. In exchange, the fungi digest the leaves, providing nutrients for the ants. -This symbiosis can involve other organ- isms. The farmed fungi can be infested by fungal parasites. In response, the ants culture bacteria (actinomycetes) that produce antibiotics to control these parasites. -these relationships are the product of 50 million years of coevolution

beverages and food

-Fungi provide beverages and food -yeasts to produce bread and alcoholic beverages -Yeasts produce ethyl alcohol and carbon dioxide from glucose and other sugars by fermentation -yeast, genus Saccharomyces (ascomycetes) are used to produce wine, beer, and other fermented beverages -Wine is produced when yeasts ferment fruit sugar, and beer results when yeasts ferment sugar derived from starch in grains (usually barley). -Saccharomyces cerevisiae, referred to as baker's yeast, is used to bake bread, pizza, and other wheat products. carbon dioxide produced by yeast becomes trapped in dough as bubbles, causing the dough to rise and giving leavened bread its light quality. Both the carbon dioxide and the alcohol produced by the yeast escape during baking. -Roquefort cheese. (The blue spots in Roquefort and certain other cheeses are masses of conidia.) Roquefort, Brie, Gorgonzola, and Camembert is produced by species of Penicillium. -Aspergillus tamarii and certain other fungi are used to pro- duce traditional soy sauce by fermenting soybeans with the fungi for at least three months. adds vital amino acids from both the soybeans and the fungi themselves, which, in some parts of the world, supplement a low-protein rice diet. -mushroom Agaricus brunnescens is the principal fungal species grown extensively for food -Morels, which superficially resem- ble mushrooms, and truffles, which produce underground fruiting bodies, are ascomycetes -Truffles are now cultivated as mycorrhizal fungi on the roots of tree seedlings. -most poisonous mushrooms belong to the genus Amanita -The sacred mushrooms of the Aztecs—Conocybe and Psilocybe—are still used in religious ceremonies by native peoples of Central America for their hallucinogenic properties. -psilocybin is responsible for the trances and visions experienced by those who eat these mushrooms.

mycorrhizae

-Glomeromycetes are symbionts that form intracellular associations with the roots of most trees and herbaceous plants. -These symbiotic associations between the hyphae of certain fungi and the roots of plants are called mycorrhizae (from Greek words meaning "fungus roots") -Glomeromycetes extend their hyphae through the cell walls of root cells but often may not penetrate the plasma membrane. -As each hypha pushes forward, the plasma membrane of the root cell surrounds it. -Thus, the hyphae can be thought of as fingers pushing into a glove formed by the plasma membrane. -Because they penetrate the cell wall, these fungi are referred to as endomycorrhizal fungi. -mycorrhizal relationships the roots supply the fungus with sugars, amino acids, and other organic substances -mycorrhizal fungus decomposes organic material in the soil and also benefits the plant by extending the reach of its roots. -slen- der mycelia are far thinner than roots and can extend into narrow spaces, absorbing nutrients that the plant could not capture on its own -the plant can also take in more nutrient minerals such as phosphorus and nitrogen b/c of this relationship

glomeromycetes

-Glomeromycetes have a symbiotic relationship with plant roots -Glomeromycetes (phylum Glomeromycota) have coenocytic (no septa) hyphae -reproduce asexually with large, multinucleate spores called blastospores. Sexual reproduction has not been documented -previously considered zygomycetes but molecular data helped determine that they form a separate monophyletic group.

monokaryotic

-Hyphae that contain only one nucleus per cell are described as monokaryotic.

dikaryotic

-Hyphae that contain two genetically distinct, sexually compatible nuclei within each cell are described as dikaryotic -This condition is referred to as n + n rather than 2n because there are two separate haploid nuclei -The presence of a dikaryotic stage is an important defining char- acter of the ascomycetes and basidiomycetes.

septa

-In most fungi hyphae are divided by cross walls, called septa, into individual cells containing one or more nuclei -The septa of many fungi are perforated by a pore that may be large enough to permit organelles to flow from cell to cell.

plasmogamy

-In sexual reproduction the hyphae of two genetically compatible mating types come together, and their cytoplasm fuses, a process called plasmogamy. -the resulting cell has two haploid nuclei, one from each fungus. -This cell gives rise by mitosis to other cells with 2 nuclei

2 largest phyla

-In the two largest fungal phyla, the ascomycetes and basidiomycetes plasmogamy occurs (hyphae fuse) -but karyogamy (fusion of the two different nuclei) does not follow immediately -For a time, the nuclei remain separate within the fungal cytoplasm.

mycorrhizae

-Mycorrhizae are symbiotic associations between fungi and plant roots -Mycorrhizae occur in about 80% of plants (and more than 90% of all plant families) -glomeromycetes, mycorrhizal fungi decompose organic mate- rial in the soil and increase the surface area of a plant's roots so that the plant can absorb more water and mineral nutrients. In exchange, the roots supply the fungus with organic nutrients. -signaling molecules from the plant root cells stimulate fungal cells to shift to a presymbiotic growth phase in which their energy metabolism increases and their hyphae branch. fungal cells then signal the root cells, activating a signaling pathway that activates gene expression in the root cells. -orchids do not grow unless an appropriate fungus lives with them. Similarly, many forest trees, such as pines, cedars, decline and eventually die b/c lack the appropriate mycorrhizal fungi. When forest soil containing the appropriate fungi is added they quickly resume normal growth -Growth of the plants that formed mycorrhizal associations was significantly enhanced. -Mycorrhizal fungi connect plants, allowing nutrient transfer among them. -Mycorrhizal fungi also release chemi- cals that protect the plant against herbivores and pathogens. -Mycorrhizae improve the soil by decreasing water loss and erosion -mycorrhizae can modify toxic heavy metals, such as cadmium, so that plants cannot absorb them. (solution for pollution)

haustoria

-Parasitic fungi often produce special hyphal branches called haustoria that penetrate the host cells and obtain nourishment from the cytoplasm.

budding

-Phylum Ascomycota includes more than 300 species of unicellular yeasts -Asexual reproduction of yeasts is mainly by budding; in this process, a small protuberance (bud) grows and eventually separates from the parent cell. Each bud can grow into a new yeast cell. -Yeasts reproduce sexually by forming ascospores. During sexual reproduction, two haploid yeasts fuse, forming a diploid zygote. The zygote undergoes meiosis, and the resulting haploid nuclei are incorporated into ascospores. -These spores remain enclosed for a time within the original cell wall, which corre- sponds to an ascus.

medicine

-Saccharomyces cerevisiae has served as a model eukaryotic cell. It was the first eukaryote whose genome was sequenced. -used S. cerevisiae to study molecular genetics, including how genes regulate cell division -used to study the mechanism of action of antifungal drugs and resistance to these drugs. -Aspergillus nidulans, an opportunistic pathogen of humans, to study mitosis and other cell processes. the genetics of microtubules. -genes that have been cloned in yeast are those for insulin, human growth hormone, and molecules important in immune function -Alexander Fleming, penicillin, produced by the mold Penicillium notatum, is still among the most widely used and effective antibiotics -cephalosporin antibiotics (produced by Cephalosporium), statins (used to lower blood cholesterol levels), and cyclosporine (used to sup- press immune responses in patients who receive organ trans- plants). -Fumagillin, a chemical produced by the ascomycete Aspergillus fumigatus, inhibits the formation of new blood vessels. an anticancer agent. treat diseases caused by microsporidia. -ascomycete Claviceps purpurea infects the flowers of rye plants and other cereals, toxic for animals but ergot compounds are now used clinically in small quantities as drugs to induce labor, to stop uterine bleeding, to treat high blood pressure, and to relieve one type of migraine headache.

heterothallic

-Sexual reproduction in the black bread mold occurs when the hyphae of two different mating types, designated plus (+) and minus (-), grow into contact with one another. -The bread mold is heterothallic, meaning that an individual fungal hypha mates only with a hypha of a different mating type. -only between a member of a (+) strain and one of a (-) strain, not between members of two (+) strains or members of two (-) strains -not appropriate to refer to them as "male" and "female".

diseases

-Some fungi cause diseases in humans and other animals -Certain ascomycetes cause superficial infections in which only the skin, hair, or nails are infected. -Ringworm, athlete's foot, and jock itch are examples of superficial fungal infections. -Many pathogenic fungi are opportunists that cause infec- tions only when the body's immune system is compromised such as in patients infected with HIV. Cancer patients and organ transplant recipients who are given medication to suppress their immune systems are also at risk -Candida is an ascomycete that inhabits the human mouth and vagina -scomycete Aspergillus fumigatus is usually harmless but causes aspergillosis in people with lowered immune function. fungus can invade the lungs, heart, brain, kidneys, and other vital organs and cause death. -Histoplasmosis, for example, is a lung infection caused by inhaling spores of a fungus common in soil contaminated with bird feces. -Fungi contribute to sick-building syndrome, a situation in which occupants of a building experience acute adverse health effects linked to the time they spend in a given building. When conditions are moist, molds can grow on carpets, leather, cloth, wood, insulation, and food. Mold spores, fragments, and aerosol mold products make their way into the air, and people are exposed through inhalation as well as by skin contact. Exposure to molds and their toxins has been linked to depressed immune function, irritation of the throat and respiratory passageways, infection, and toxicity. -mold exposure are reactions that range from mild to severe illnesses, including hay fever, sinusitis, asthma, and dermatitis.

mycotoxins

-Some fungi produce poisonous compounds collectively called mycotoxins -A few species of Aspergillus, for example, pro- duce potent mycotoxins called aflatoxins that harm the liver and are known carcinogens. -aflatoxin-producing fungi commonly grow include peanuts, pecans, corn, and other grains. -Other foods that may contain traces of aflatoxins include animal products such as milk, eggs, and meat (from animals that consumed feed contaminated by aflatoxin).

sporangia

-Structures in which spores are produced are called sporangia

fruiting bodies

-The aerial hyphae of some fungi produce spores in large, complex reproductive structures, referred to as fruiting bodies -The familiar part of a mushroom is a large fruiting body -We do not normally see the bulk of the fungus, a nearly invisible mycelium buried out of sight in the rotting material or soil on which it grows

hyphae

-The body consists of long, branched, threadlike filaments called hyphae -a mass of threadlike filaments called hyphae. -The hyphae penetrate the food to obtain nourishment and produce a mass of hyphae called the mycelium. -specialized hyphae grow from the mycelium, giving rise to erect stalks with fruiting bodies (sporangia) at their tops -Hyphae consist of tubular cell walls surrounding the plasma membranes of the fungal cells -hyphae are an adaptation to the fungal mode of nutrition -Growth occurs at the tips of the hyphae; as the hyphae elongate, the fungus grows into and infiltrates food sources. -ungus absorbs nutrients through its very large surface area.

Chytrids life cycle

-alternation of generations (common in plants, but rare in fungi), spending part of its life as a multicellular haploid (n) thallus and part as a multicellular diploid (2n) thallus. The haploid and diploid thalli are similar in appearance. -At the tips of its branches, the haploid thallus bears two types of sporangia, structures in which gametes form by mitosis. -Each sporangium produces a different type of flagellate gamete. Each type of gamete secretes a pheromone that attracts the other type -The two gametes fuse, and plasmogamy and karyog- amy occur, resulting in a motile zygote. Each zygote can develop into a diploid thallus. -The thallus bears two kinds of spore cases: zoosporangia and resting sporangia. Zoosporangia produce flag- ellate diploid zoospores that develop into new diploid thalli. -Meiosis occurs within resting sporangia, producing haploid zoospores. Each zoospore has the potential to develop into a haploid thallus. - -Life cycle of the chytrid Allomyces arbuscula -Chytrids have flagellate reproductive cells. 1) Haploid zoospore grows into haploid thallus 2) Haploid thallus produces two types of gametes by mitosis. 3) Gametes fuse, and their nuclei fuse, producing flagellate zygote PLASMOGAMY AND KARYOGAMY 4) Zygote germinates and develops into diploid thallus. 5a) Meiosis occurs in resting sporangia. 5b) Zoosporangia produce flagellate diploid zoospores by mitosis. Zoospores give rise to new diploid thalli. 6) Haploid zoospores are produced by meiosis.

animal pathogens

-animal fungal pathogens -in animals some ascomycetes cause superficial infections: ringworm, athletes foot, jock itch, yeast infections of mouth, throat, or vagina caused by candida when immune system is compromised -others cause internal infections, especially of lungs -histoplasmosis: lung infection caused by inhaled spores present in soil contaminated with bird/bat feces. childhood asthma -fungal based biopesticides often include fungus that parasitizes insects (crop pests) -others include fungus that forms protective barrier around plant roots. animal pathogens

fungi

-are eukaryotes -cells contain membrane-enclosed nuclei, mitochondria, and other membranous organelles -optimum pH for most fungal species is about 5.6, but various fungi can tolerate and grow in environments where the pH ranges from 2 to 9 -fungi are less sensitive to high osmotic pressures than are bacteria. -can grow in concentrated salt solutions or in sugar solutions such as jelly, which discourage or prevent bacterial growth -can survive a wide variety of temperature range (in fridge sometimes) -Most fungi are multicellular.

basidiomycetes

-club fungi -decomposers, pathogens, and mycorrhizae: mushrooms, bracket (shelf) fungi -sexual reproduction -after plasmogamy, dikaryotic fruiting body (basidiocarp) produced. -club shaped basidia develop along gills of basidiocarp -karyogamy occurs in each basidium and forms diploid zygote nucleus that undergoes meiosis to produce basidiospores -asexual reproduction rare

chytrids

-decomposers in damp soil and ponds -pathogenic chyrtrid responsible for declining amphibian populations -unicellular or simple multicellular -spores posses single, posterior flagellum. Only fungal group to retain this ancestral character

mycobiome

-fungal component of microbiome. Human typically have 9-23 fungal strains in/on body -includes beneficial species but also some known to cause disease -disease causing fungi typically kept in check by other fungi and bacteria -newly discovered yeast superbug (candida auris) spreads from person to person: causes deadly blood infection. -fungal infections typically opportunistic; not spread from person to person like viral or bacterial infections mycobiome

fungi food

-fungi absorb food from the environment -fungi are heterotrophs -they depend on preformed carbon molecules produced by other organisms -fungi do not digest their food, they infiltrate a food source and secrete digestive enzymes onto it. digestion takes place outside the body -when complex molecules are broken down into smaller compounds the fungi absorbs the predigested food into its body -fungi are efficient at absorbing nutrients and growing -rapidly converts nutrients into new cell material -if there is excessive food available they will store it as lipid droplets or glycogen fungi food

ecological importance

-fungi are free-living decomposers, chemoheterotrophs that absorb nutrients from organic wastes and dead organisms -fungal decomposers degrade cellulose and lignin, the main components of plant cell walls -fungi release water, carbon (as CO2), and mineral components of organic compounds, and these elements are recycled. without this decomposition, essential nutrients would remain locked up in animal carcasses, feces, branches, logs, and leaves. they would not be able to be used by new generations and life would die. -fungi form form important symbiotic relationships with ani- mals, plants, bacteria, and protists -3 way symbiotic relationship with fungus, grass and a virus. example: Yellowstone where fungi infects roots on grass and when infected with a specific virus the fungus is heat tolerant and converts heat tolerance to the grass.

fungi

-fungi are unikonts and opisthokonts -synapomorphy: single posterior flagellate cells. sister taxon to choanoflagellates and animals -oldest fossils approximately 550 mya -most fungi are terrestrial decomposers -prevalent in moist habitats. require moisture to grow. Approximately 100,000 described species -chemoheterotrophs that use external digestion. grow into food source, secrete digestive enzyme onto food, and absorb digested nutrients. -cell wall of chitin (polysaccharide)

fungal diversity

-fungi have cell walls and vacuoles and are sessile; that is, they cannot move around from place to place. -many types of fungi inhabit the soil. -fungal cell walls do not contain cellulose. -they contain chitin, a polysaccharide found in insect skeletons. -fungi are heterotrophs -slime molds and water molds were formerly classified as fungi but are now included among the protists fungal diversity

fungi reproduction

-fungi reproduce by spores. -spores produced in sporangia. specialized aerial hyphae or complex fruiting bodies. dispersed by wind, water, or animals -many fungi reproduce asexually. yeast reproduce by budding. ascomycetes and some basidiomycetes produce specialized hyphae (conidiophores) that produce asexual spores (conidia) by mitosis. fungi reproduction

yeast

-the simplest fungi -are unicellular with a round or oval shape -widely distributed in the soil; on leaves, fruits, and cured meats; and on and in our bodies -Yeasts are unicellular fungi -Yeasts can reproduce asexually by budding -budding, a form of asexual reproduction.

fungi

-grow best in moist habitats, but they are found universally wherever organic material is available -require moisture to grow -in a dry environment...fungi survive by going into a resting stage or by producing spores that resist desiccation (drying out) -Some fungi grow to enormous size, some covers more than 1500 acres -Like prokaryotes, most fungi are decomposers that obtain nutrients and energy from dead organic matter. -they break down the organic compounds found in dead organisms, leaves, garbage, sewage, and other waste. -When they decompose organic compounds, carbon and other elements are released into the environment, where they are recycled. -terrestrial plants have fungal partners that live in close association with their roots. -fungi live symbiotically with algae and cyanobacteria as lichens -Others are parasites and pathogens that cause disease in animals or plants -Most fungi are multicellular.

glomeromycetes

-live entirely underground and form endomycorrhizae -extend hyphae into cell walls of plant root cells

homothallic

-means that they are self-fertile and have the ability to mate with themselves.

food/beverage

-morels, truffles, mushrooms -blue cheese, brie, and Gorgonzola made by adding penicillium to cheese curds -yeast used to make bread and alcohol -produced ethyl alcohol and CO2 during fermentation -saccharomyces cerveisiae (bakers yeast) is model eukaryotic organism. first eukaryotic genome sequenced

zygomycetes

-most are decomposers in soil or on decaying plants/ animals -example: black bread mold

decomposers

-most fungi are decomposers -absorb nutrients from organic wastes and dead organisms, and recycle elements back to ecosystem. Many degrade cellulose and lignin -symbiotic relationships -gut symbionts: in herbivore digestive tracts -the fungi break down plant material -herbivores provide food and habitat -some ants "farm" fungi. ants feed on fungi, and disperse and provide food for fungi -mycorrhizae

sexual reproduction in fungi

-most fungi reproduce sexually 1. hyphae from genetically different mycelia come together 2. plasmogamy (fusion of cytoplasm) occurs. fused cell has two separate haploid nuclei=dikaryotic (n+n) 3. in ascomycetes and basidiomycetes, dikaryotic cell divided by mitosis to form other dikaryotic cells 4. karyogamy occurs. fusion of two haploid nuclei to form diploid nucleus: zygote nucleus 5. zygote nucli(us) undergo meiosis, each producing four genetically distinct haploid spores 6. spores released and germinate into new mycelium by mitosis. -HAPLOID dominant life cycle -fruiting bodies releasing spores

Endomycrorrhizae

-most widespread endomycorrhizae are called arbuscular mycorrhizae because the hyphae inside the root cells form branched, tree-shaped structures known as ARBUSCULES -The arbuscules are the sites of nutrient exchange between the plant and the fungus. Arbuscular mycorrhizae live entirely underground. -This mycelium has grown into a plant root. Its hyphae branch between the cells of the root. Hyphae have penetrated through the cell walls of two root cells and have branched extensively to form arbuscules. The tip of one hypha between root cells has enlarged and serves as a vesicle that stores food. The tip of a hypha in the soil has enlarged, forming a spore -glomeromycetes form endomycorrhizal connections; they infiltrate the cells of plant roots.

fungal groupings

-mycologists assign fungi to five main groups: Chytridiomycota, Zygomycota, Glomeromycota, Ascomycota, and Basidiomycota -some consider these groups to be a phylum. however some of these groups are NOT monophyletic -About 95% of all named fungi have been assigned to phyla Ascomycota and Basidiomycota. these phyla are considered sister taxa b/c they share a more recent common ancestor with each other than either form with any other group -Fungi of phyla Ascomycota and Basidiomycota have septate hyphae and a dikaryotic stage during the sexual part of their life cycle

impact of fungi

-owerful digestive enzymes that fungi use can also be used with great efficiency to reduce wood, fiber, and food to their basic components. -basidiomycetes have enzymes that break down the lignin (organic compound, 2nd most abundant, 1st is cellulose) in wood. -fungi cause incalculable damage to stored goods and building materials each year. Bracket fungi, for example, cause enormous losses by decaying wood, both in living trees and in stored lumber. -Some fungi cause serious diseases in animals and plants, yet fungi also contribute to our quality of life. -People eat them and grow them to make various medications, such as penicillin -use them to make certain industrial chemicals and for bioremediation -fungus has been discovered that synthesizes 55 hydrocarbons, may be able to use the genes of this fungus to engineer other microorganisms to produce fuel more efficiently. -About 50 g (2 oz) of this mushroom can kill an adult man. The destroying angel, which is 7.5 to 20 cm (3 to 8 in.) tall, is found in grass or near trees throughout North America.

plant pathogens

-plant fungal pathogens -most plant diseases caused by fungi -hyphae or spores enter stomata, cuticle, or damaged region -ascomycetes: powdery mildew, chestnut blight, brown rot on fruits, dutch elm disease -basidiomycetes: smuts and rusts on corn and grains plant pathogens

Ascomycete Reproduction

-plasmogamy takes place as hyphae of two different mating types come together and fuse -this fused structure, pairs of haploid nuclei, one from each parent hypha, associate but do not fuse -New hyphae, with dikaryotic cells, develop from the fused structure. -The hyphae branch repeatedly until the hyphal tips reach the site where asci will be produced. -As the many sac-shaped asci develop, each con- taining two dissimilar nuclei (one from each parent), they are surrounded by intertwining haploid (monokaryotic) hyphae. -These hyphae help make a fruiting body known as an ASCOCARP -Karyogamy occurs in each ascus. The two nuclei fuse and form a diploid zygote nucleus. -The zygote nucleus then under- goes meiosis to form four haploid nuclei with different genotypes. -One mitotic division of each of the four nuclei usually follows, resulting in eight haploid nuclei. -Each haploid nucleus becomes incorporated into a thick-walled ASCOSPORE; thus, there are typically eight haploid ascospores within the ascus -ascospores are usually released through a pore, slit, or hinged lid at the tip of the ascus. Air currents carry individual ascospores, often for long distances. If one lands in a suitable location, it germinates and forms a new mycelium -The fungus can reproduce asexually by producing conidia that can develop into new mycelia.