The Kingdom Fungi.
a. parasites - obtaining nutrients from a living host and ultimately harming that host. An example of another parasite is mistletoe, parasitizing mesquite trees or catclaws.
b. mutualistic symbionts - obtaining their nutrients from a living host while providing some benefit to that host. An example \would be lichens: an algal-fungal partnership. The fungi that lie in association with algae, obtain sugars and other compounds from the photosynthetic forms and, in return, provide water and minerals to the algae.
c. saprobes - obtaining nutrients from nonliving organic material or the remains and by-products of organisms. The mycelium surrounding a dead fly on a windowpane or the fungi that cause rot in wood are examples of this saprophytic mode of nutrition.
1. The absorptive lifestyle of fungi is intimately associated with 2 important characteristics: production of spores and hypha (mycelial growth).
2. A spore is a tiny, usually haploid, cell that disperses the fungus to new habitats, usually by floating thru the air. The production of many tiny spores increases the chance that at least a few will fall onto a suitable food source, germinate, and start absorbing food, and then growing into a thread-like hypha.
a. the hyphae, which develops right after spore germination, puts out powerful enzymes needed to digest food for the fungus.
b. at the same time, mycotoxins, fungal by-products poisonous to animals, or antibiotics, metabolites that inhibit growth of microbes, may also permeate the substrate.
c. the purpose of these products is apparently to discourage potential competitors from getting more than their share of available food.
3. Hypha – thread-like structure of very fine, colorless threads, that makes up the body of a fungus. They are usually hidden from view – deep within the soil, assorted food sources, rotting matter, wood, decaying animals – and remains undetected until it develops one or more fruiting bodies containing reproductive spores. The fruiting body is usually the only indication that a fungus is present. Hyphae grow until resembling a tangled mass of threads. The body of a fungus, made up of many hyphae, is called a mycelium.
4. The mycelium is well-suited to absorbing food. It has a high surface-volume ration permitting the surface exposed to the external food source to absorb enough food to nourish the enclosed body of cytoplasm.
Parasitic fungi absorb nutrients from the body fluids of its host, and parasites of plants may produce specialized hyphae called haustoria that penetrate a plant’s cell wall and lie against the plasma membrane, where they can both absorb food.
Mushroom body plan
1. cap - apical surface; on edible fungi usu. rounded and smooth. Poisonous pp. May have warts (patches of fungal tissue that can’t be removed without tearing the cap surface).
2. gills - flat-sided, blade-like radial structures on the underside of the cap, covered with microscopic basidia, which holds the mushroom’s spores. Gills are important in identifying mushrooms: density of gills, color of gills, whether they bruise of injure easily, etc.
3. stalk - typically a cylindrical structure that lifts the cap above the soil surface, like a stem or shoot in seed-bearing plant.
4. veil - a layer of fungal tissue that covers all or part of some immature mushrooms.
Divisions of the Kingdom Fungi
1. Fungi are divided into true fungi and slime molds.
2. The kingdom consists of 7 divisions, 5 divisions in true fungi, 2 divisions in slime molds.
3. I’d like to confine my talk to 2 divisions: Ascomycota (ca. 30,000 spp.) and Basidiomycota (ca. 25,000 spp.)
Ascomycota (Ascomycetes or sac fungi) asci = sac
1. Largest class of fungi
2. Included within the 30,000 or so spp. are the unicellular yeasts, as well as many multicellular forms.
3. In some species, the hyphae have been organized into definite, often fleshy bodies; in others, hyphae form cottony growths of indefinite extent.
4. They reproduce asexually by budding conidiospores, and by fragmentation.
a. the characteristic reproductive structures are sacs, or asci, formed at the ends of specialized hyphae.
5. They may be parasites or saprophytes.
6. Importance to humans
a. cause many familiar diseases of economic plants: peach leaf curl, Dutch elm disease, chestnut blight. Produces the largest number of plant diseases.
b. industrial uses - manufacture of alcoholic beverages, cheese, the “raising” of bread dough,
c. food spoilage
d. human food: truffles and morels
e. decay of dead organisms and their wastes
f. commercial production of organic chemicals
g. production of antibiotics.
7. Common representatives
a. Yeasts - one-celled, non-filamentous. Reproduces chiefly by budding, less frequently by ascospores. Important in brewing and baking. Secretes a number of enzymes which convert glucose to alcohol and CO2.
b. Cup fungi - hyphae organized into fleshy, cup-shaped ascocarps, inside of which the asci are formed. Chiefly saprophytes in rich soil, decaying wood, etc.
c. Powdery mildews - parasites, chiefly on leaves of green plants (euonymous, roses, lilac). Forms whitish patches of hyphae on leaves.
d. Blue and green molds - saprophytes on old leather, jellies, spoiling fruit, potatoes, etc. Hyphae form indefinite growths, producing conidiospores and ascospores in large numbers. Penicillium is a common blue mold, Aspergillus produces blue or black spores. Some Penicillia are important in cheese manufacture and production of penicillin.
Basidiomycota (Basidiomycetes): mushrooms, bracket fungi, smuts.
1. The most familiar basidiomycetes are the mushrooms.
a. In these fungi, a well-fed mycelium forms an underground mass of hyphae that differentiates into a bulbous base, a stalk, and a knob-like cap.
b. Some mornings after a rain we awake to find that the hyphae composing that stalk have swelled with moisture and elongated, carrying the cap above ground.
c. The cap opens like an umbrella after the rain has ceased, and numerous basidia along the edges of the gills or pores beneath the cap prepare to lose their spores. (the gills or pores on the underside of a mushroom increase the surface area where spores can be formed and discharged).
2. Bracket fungi, bird’s nest fungi, coral fungi are also fruiting bodies of basidiomycetes; they are often found on rotting wood.
Importance to humans
1. Edible species - some mushrooms and puffballs
2. Plant diseases - rusts, smuts
3. Facilitates the rotting of wood
4. Causes decay of dead organisms and the wastes of other organisms.
1. Smut fungi - parasites on cereal grains, especially damaging to oats, corn, and wheat. (Formaldehyde treatment of seeds kills smut spores). Black-colored spores.
2. Rust fungi - causes serious diseases on oats, wheat, and rye. Called rust because of reddish spores formed on the surface of diseased tissues.
3. Gill fungi - mushrooms. Mycelium grows saprophytically undeground or in decaying wood, and peridically forms fleshy sporophores (mushrooms) of characteristic size and shape. A mushroom consists of a stalk and an umbrella-ahaped cap, on underside of which are radiating gills, which bear basidia and numerous basidiospores
4. Puffballs - spherical, pear-shaped. Basidiospores borne internally. The covering ruptures or has a pore for escape of spores. Most puffballs are edible when young. Mostly saprophytic.
1. Lichens are associations of certain algae (blue-greens and greens) with fungi (chiefly sac fungi: ascomycetes) in a state of symbiosis (mutual benefit). An obvious reproductive structure visible on many lichens is a cup-shaped ascocarp typical of certain ascomycetes.
2. The association of fungi and algae are so complete that lichens are given scientific names as if they were a single organism. There about 18,000 spp. of lichen. (The algae in 90% of these species are comprised of only 3 genera).
3.The fungi obtain food from the photosynthetic algal cells, and absorbs and retain water and minerals, some of which the algae use in the process of photosynthesis.
a. the physical mass of fungus protects algae from ultra violet radiation of the sun.
4. Algae comprises about 5-10% of the lichen, fungi about 90%.
5. Lichens are common on rocks, tree bark, fence posts, etc, and are able to colonize some of the most inhospitable habitats on earth. They can survive in extremely cold areas (high mountain tops, the arctic), and may be the only plant form surviving some of these areas providing vitally important sources of food for some animals. In arctic, caribou and reindeer feed on lichen (reindeer moss), the dominant vegetation in some areas. Hot deserts, bare rock.
6. Three types of lichen:
a. Foliose - flat, leafy or thallus lichens.
b. Crustose - thin, hard crusts, especially common on rocks.
c. Fruticose (shrublike) - erect, branched growths.
7. Lichens have incredibly slow growth rates: a few millimeters each year. Great longevity, some believed to be 4,555 years old.
8. Sensitive to air pollution, especially sulfur dioxide: the disappearance of certain lichen species may be a means of measuring the extent of air pollution within an area.
a. Lichen absorb water and minerals from rainwater and directly from the atmosphere over their entire surface.
b. This makes them extremely sensitive to atmospheric pollution.
c. As a result, there are few lichen in or near industrialized centers and towns.
9. Extracts from certain lichen have been used medicinally as antibiotics.
10. Many lichens are brightly colored and Native peoples used them as sources of dyes. They contain alum (potassium aluminum sulfate), a mordant used since antiquity. (mordant = do not impart their color immediately, as direct dyes do. Fibers must be treated with a chemical agent, a mordant. The mordant fixes the dye to the fabric).
11. Ancient Egyptians used lichen as packing material for mummies.
Mycorrhizae: root-fungal partnership (literally: fungus root)
1. Many fungi grow associated with plant roots in a symbiosis called mycorrhiza. In fact, there are estimates that 90% of all vascular plants posses fungi in mutualistic associations with their roots.
2. The plant furnishes the fungus with sugars and amino acids (products of photosynthesis), while the fungus aids in the absorption in minerals and water form the soil. Fungal hyphae are highly branched and extends thru a relatively large volume of soil.
4. Their ecological role and importance in forestry and agriculture have become clearer with revegetation efforts. Some mycorrhizae are necessary for transplants of trees.
When pine trees were introduced into new areas, as in Puerto Rico and
5. Even when a species may grow without mycorrhizae, the same species with mycorrhizae may be more tolerant of pollution, need less fertilizer, or grow in marginal soils.
a. Acid rain, caused by industrial pollution, promotes 2 changes in the soil unfavorable to plants: leaching (washing away) of required nutrients, making them unavailable to plants; and increased solubility of toxic materials such as zinc, copper, aluminum, and manganese. The appropriate mycorrhizal fungus can absorb nutrients from depleted soil water and make them available to the plant. It is also known that mycorrhiza can protect a plant from toxic substances in the soil, such as slagheaps of mines.
6. (From Oliver Sacks', Oaxaca Journal): Most of the world's plants - more than 90% of the known species - are connected by a vast subterranean network of fungal filaments, in a symbiotic association that goes back to the very origin of land plants, 400 million years ago. these fungal filaments are essential for the plants' well-being, acting as living conduits for the transmission of water and essential minerals (and perhaps organic compounds as well) not only between the plants and fungi but from plant to plant. Without this fragile gossamer-like net of fungal filaments the towering redwoods, oaks, pines, and eucalyptus of our forests would collapse during hard times. And so too would much of agriculture, for thee fungal filaments often provide links between very different species - between legumes and cereals, for instance, or between alders and pine. thus nitrogen-rich legumes and alders do not merely enrich the soil as they die and decompose, but can directly donate, thru the fungal network, a good portion of their nitrogen to nearby plants. United by these multifarious underground channels (and also by the chemicals they secrete in the air to signal sexual readiness or news of predator attack, etc.) plants are not as solitary as one might imagine, but form complex interactive, mutually supportive communities.
Role of fungi in the environment
1. Decomposers (Nature’s recyclers: the degradation of organic material and the recycling of its nutrients).As decomposers, the fungi are vitally important members to the plant and animal kingdoms. When a dead leaf drifts to the forest floor or an animal dies of disease, fungal and bacterial spores floating in the air have already settled on it. These spores quickly germinate and begin to break down the dead organism, releasing small organic molecules that can be used as food, as well as minerals that may be absorbed by the decomposer or by nearby plants.
2. Fungi, together with bacteria, are responsible for most of the recycling which returns dead material to the soil in a form in which it can be reused. Without fungi, these recycling activities would be seriously reduced. We would effectively be lost under piles, many meters thick, of dead plant and animal remains.
3. The fungi which make our bread and fruit go moldy are only recycling organic matter, even tho in this case we would probably prefer it didn’t happen. Fungal damage can be responsible for large losses of stored food, particularly food which contains any moisture. Dry grains can usually be stored successfully, but the minute they become damp, molds are likely to render them inedible.
4. Bioremediation of toxic materials – use of microorganisms to reclaim soil and water that have become contaminated with hazardous materials.
a. Inexpensive compared with conventional physical or chemical methods of decontamination.
b. Typically performed on-site, requiring only the addition of nutrients in the soil to stimulate the growth of microorganisms in the immediate environment.
c. Some of the bracket fungi (they can degrade lignin and cellulose) have been proposed as bio-remediators in the pulp and paper industry to reduce the use of hazardous chemicals.
5. Many fungi tolerate extreme acidity: acid foods pickles and jam (fruit is acid) are safe from attack by bacteria but not by fungi. Their ability to absorb water from damp air permits fungi (unlike bacteria) to grow in environments where there is no liquid water. Bacteria survive anaerobic conditions better than fungi: altho yeasts can survive anaerobic conditions using fermentation, no fungus can grow and reproduce in the absence of oxygen.
Fungi for food
1. Fungi are eaten directly as a type of vegetable or used as a fermentative agent to convert foods into alternative forms.
2. Human being have long known that most fermented foods keep better than food from which they are made. This was a compelling motive for producing beer, wine, cheeses, sauerkraut, pickles, yoghurt, and bread before refrigerators were invented. Fermented foods are also often more nutritious, flavorful, less apt to spoil, and digestible than their raw counterparts. (protein values are often enhanced in fermented foods thru the enzymatic release of amino acids, and many of the microbial agents synthesize vitamins, further improving nutritional quality).
3. In east Asian countries, soybeans mixed with cereals have been fermented by various bacteria and fungi to yield an impressive array of flavoring agents and protein sources such as tofu, soy sauce, miso, tempeh
a. good soy sauce (shoyu) is made by fermenting boiled soybeans and wheat with the ascomycete Aspergillus oryzae for about a year. Chinese invented this thousands of years ago; it added flavor and vital amino acids, produced by fungus and bacteria, to a low-protein diet of rice. (Most soy sauce is made by hydrolyzing soybeans with hydrochloric acid).
4. Edible mushrooms
a. The most commonly eaten mushrooms are the basidiomycetes. The basidiocarp (fruiting body) is the part that is eaten. The 2 popular exceptions are the morels and truffles, fruiting bodies of ascomycetes.
Agaricus bisporus (button or field mushroom) is the mushroom most often
purchased in grocery stores in
c. Shiitake is cultivated on oak logs or synthetic logs created from sawdust and other organic materials, and placed in the forest. In addition to eating shiitakes, the Japanese also use it medicinally: it is prescribed in cancer therapy for its anti-tumor action as well as counteracting undesirable effects of conventional chemotherapy. Shiitake tea, made from soaking the dried mushrooms in boiling water, is claimed to boost the immune system, lower blood cholesterol, and promote weight loss.
d. Nutritionally, fresh mushrooms have a high water content (85-92% of fresh wt.). Complete source of protein, with appreciable amts of Vit C, D, and some Bs. Naturally low in calories, high in fiber.
e. Saccharomyces cerevisiae (yeast fungus) used in fermentation process in production of beer, wine, spirits, and bread.
g. Blue mould, Penicillium, is used in the ripening process to prepare specialty cheeses such as blue cheese, Roquefort, Gorgonzola, Camembert, and Brie.
1. There is no simple or universal way to distinguish an edible from a poisonous mushroom without precisely identifying the species.
2. Latin saying “If you awaken in the morning after an evening meal of wild mushrooms, you know they were good ones”
3. Mushrooms of the genus Amanita should be avoided. They account for most of the fatal accidents of mushroom poisoning.
4. Before picking any of the gilled mushrooms to eat, examine the specimen to rule out the presence of a saclike cup, or volva, around the base of the stalk.
5. Beware also of an annulus or ring on the stalk.
Types of mushroom poisoning:
1. Gastrointestinal – nausea, vomiting, diarrhea; symptoms terminate rapidly and normal health returns in one or two days.
2. Cerebral – exhilaration, staggering gait, weird disturbance of vision; normalcy returns soon.
3. Blood-dissolving - abdominal distress with ensuing jaundice; blood transfusion needed. About 200 recorded deaths.
4. Nerve-affecting – early gastrointestinal symptoms, followed by hallucinations; lethal cases rare because mushrooms must be eaten.
5. Choleriform – gastrointestinal reactions rapidly develop accompanied by violent pains; rapid loss of strength with cardiac muscle damage and coma before death; death rate 60% or more depending on amount eaten. E.g. Amanita.
Note: in some members of Amanita, both volva and annulus are prominent structures that aid in identification, but either one or both of these structures may weather away. Amanita virosa (the destroying angel) and A. phalloides (the death cap) are the most notorious killers of the Amanita group.
Chemical defenses of fungi
Fungal toxins fall into two groupings: mycotoxins (formed by the hyphae of common molds growing under a variety of conditions) and mushroom toxins (formed in the fleshy fruiting bodies of some fungi).
1. Mycotoxins are commonly produced by fungi growing in contaminated foods.
2. These toxins have profound direct chronic and acute effects on humans and livestock when contaminated foods are eaten. In addition to direct toxic effects, mycotoxins are among the most potent known carcinogens.
3. The fungal contaminant, Aspergillus flavus, has given rise to the toxin aflatoxin, a toxic and carcinogenic toxin, that is found contaminating peanut butter and grain products.
4. The ascomycete Claviceps purpurea infects the flowers of rye and other cereals and produces a structure called an ergot (dark sclerotia or hardened mycelial masses: looks like the spur on a rooster’s leg) where a seed would normally be found in the head of the grain.
5. Because of the way the sclerotia are lodged in the seed head, it is easy for them to get mixed in with good grain during the harvest. If not culled in the field or in storage, the sclerotia would be ground into flour and eventually find their way into foods eaten by people and livestock.
Humans may be poisoned
by ergots when they eat bread made from infected rye, and ergotism,
also known as St. Anthony’s Fire, caused the
death of thousands in medieval
1. LSD was first synthesized by the Swiss chemist Albert Hofmann in 1938. LSD is a very potent psychoactive drug.
2. It affects the midbrain activity by interfering with the action of the neurotransmitter serotonin. In small amounts LSD mimics the action of the neurotransmitter, but in larger amounts it is antagonistic to the action of serotonin.
3. The hallucinations and changes in perception are due to the disruptions in the normal pathways of sensory stimulation.
4. LSD also produces increased blood pressure, respiration, and perspiration, often accompanied by heart palpitations.
b. Ergotism was known as “sacred fire” because of the burning sensation common in the extremities of afflicted individuals. Later, it was associated with St. Anthony, a 4th century Christian monk who was thought to have power over fire.
c. Ergot was also used medically: for centuries midwives employed ergot to induce abortions and aid in childbirth because it caused uterine contractions and hastened birth.
d. Today the purified alkaloid ergometrine is used medicinally to reduce postpartum bleeding.
e. The alkaloid ergotamine is an effective treatment for migraine. By constricting the diameter of the cranial arteries, the pulsating pressure and resulting headaches are relieved.
f. Fields of rye are deliberately inoculated with spores of Claviceps purpurea to produce the ergot needed for the pharmaceutical industry.
1. Other species of the genus Amanita are known for their psychoactive properties.
a. Amanita muscaria (fly agaric) has a long history of use as an intoxicant. Its orange-red cap and white scales make it easily identifiable. The common name arises because flies are attracted to the mushroom and then killed (or stunned) from its insecticidal properties.
b. It contains ibotenic acid. Many of its symptoms are similar to alcohol intoxication, but may progress into epileptic-type seizures.
This mushroom may have
been used in ancient
Some tribal peoples in
Psilocybe, or the sacred mushroom to the indigenous tribes of
a. The major toxic compounds in this mushroom are the alkaloids, psilocybin and psilocin (in the body psilocybin is converted to psilocyn, the biologically active element).
b. Psilocyn is structurally similar to the neurotransmitter serotonin and, like LSD, interferes with the action of this substance in the brain. Hallucinations usually begin within 30-60 minutes of ingestion and last for several hours.
The toxins produced by Claviceps, Amanita, Psilocybe, and the notorious poisons of some of the other mushrooms, protect these fungi from predators and parasites.
Fungi, like many of the plants we’ve already discussed, produce a wide array of secondary compounds, and thousands of these compounds from fungi have been studied. Included in this group are alkaloids, as well as other compounds that may serve as antibiotics or toxins.
1. These are compounds that are toxic to microorganisms.
2. In the natural environment, these substances give the producing organisms an advantage over competing microorganisms for available resources.
3. Antibiotics have been one of the recent mainstays of the pharmaceutical industry and one of the primary weapons for fighting bacterial infections.
1. Penicillin is a by-product of certain Penicillium spp. of fungi from the Ascomycota.
2. The antibiotic works by blocking cell wall synthesis in the bacterium, and results in the death of the bacterial cell by lysis (disintegration or dissolution).
3. It is particularly effective because, unlike other know therapeutic agents, penicillin suppresses bacterial growth without being toxic to animals or humans.
4. The discovery of Penicillium was made by Alexander Fleming, a British physician, in 1928.
a. He found that the mold had contaminated some of his bacterial cultures, and killed the culture of Staphylococcus aureus bacteria growing in a petri dish.
b. Altho initially attracting little attention, the beginnings of WWII led to the investigations of naturally occurring antibacterial compounds, and Fleming’s work (of 11 years earlier) came under the attention of 2 scientists from the Oxford U.
c. Penicillium was then analyzed and its bacteria-destroying properties were demonstrated and confirmed in laboratory test tubes.
5. The success of Penicillium notatum led to further investigations for more high-yielding sources for the drug, now known as penicillin.
a. Penicillium chrysogenum was found on a contaminated cantaloupe, and the isolated fungus was found to produce 200 times more penicillin than Fleming’s isolate.
b. Soon after the war, the pharmaceutical industry developed chemically altered versions of the penicillin molecule. These modified penicillins provided for greater stability, broader antibacterial activity, and also oral administration of the drug, which would then permit home use of antibiotics.
c. Through further induce mutations of P. chrysogenum, the antibiotic now produces 10,000 times more penicillin than Fleming’s original isolate.
6. Drawbacks to penicillin
a. Penicillin was over-prescribed by both physicians and veterinarians, and the antibiotics were routinely incorporated into animal feed for use in feedlots: this widespread use led to the evolution of penicillin-resistant bacteria. (Some bacteria spp. can reproduce every 20 minutes, so the evolution of new strains may be considerably faster than for other organisms).
b. A small percentage of the population is allergic to penicillin, often resulting in severe or even fatal anaphylactic reactions. (anaphylaxis is a rapid and dramatic allergic reaction that may result in death thru airway obstruction or irreversible vascular collapse). Several hundred people die each year from anaphylaxis due to penicillin allergy.
(Other spp of Penicillium are widespread indoor contaminants, some are found on moldy fruits and vegetables, others are the source of the moldy smell from the basement, wt carpets, or old shoes.
Some fungi which parasitize caterpillars have also been traditionally used as medicines. The Chinese have used a particular caterpillar fungus as a tonic for hundreds of years. Certain chemical compounds isolated from the fungus may prove to be useful for treating certain types of cancer.
The shelf-like, woody, reishi mushroom (Ganoderma lucidum) is the Taoist “elixir of life”.
It is associated with longevity and spiritual energy.
It is said to improve circulation, reduce cholesterol, lower blood pressure, boost immune system, and has anti-tumor properties.
Cordyceps - the fungus attaches itself to an insect’s exoskeleton as it wanders past. It then secretes a chemical that burns a hole in the insect’s armor. Next, Cordyceps inserts itself into the insect body and proceeds to devour all of the hosts nonvital organs, all the while preventing the insect from dying of infection by secreting an antibiotic and a fungicide (as well as an insecticide to deter other predators). Once the nonvital organs are consumed, the fungus eats part of the insect’s brain, causing the insect to ascend to the top of a tall tree in the forest. There, Cordyceps devours the rest of the bug’s brain. At that point the fungus can release its spores a hundred feet above the forest floor.
Chagas’disease is a leading cause of death in some of the drier
Chinese Olympic runners attribute their record-breaking performances in recent Olympics to a special diet including Cordyceps. Ancient Chinese have employed Cordyceps for everything from impotence to backache; in the early 1700s, it was worth more than 4 x its weight in silver. Recent clinical studies have confirmed its effectiveness in treating loss of sexual drive among the elderly, making Cordyceps a fungal version of Viagra.
The Swiss pharmaceutical giant, Sandoz, has isolated a compound in Cordyceps (NIM-811) that chemically resembles cyclosporin (the immuno-suppressant drug) in terms of its molecular structure but does not suppress the immune system. However, it exhibits anti-HIV activity. Like ATZ (azidothymidine), it interferes with the virus’ ability to replicate. However, it disrupts the virus’ reproduction at a different stage in the pathogen’s reproductive cycle than does AZT. Used together, then, they may exhibit a synergistic level of inhibition.
Inkcap mushroom - yields coprine which, when mixed with alcohol induces nausea. This
has been given to alcoholics to dissuade them from drinking. (Remember