Fungi Flashcards
What are fungi? Describe the kind of organisms they are (5)
1) Eukaryotic, heterotrophic, filamentous organisms which are mostly microscopic
2) Have vegetative hyphae and reproductive spores - they may reproduce sexually or asexually
3) Vegetative structures are usually haploid and take the form of filamentous hyphae, which form mycelial networks
4) asexual reproduction occurs via conidia (asexual spores)
5) Common and important in the environment as saprotrophs and parasites. Aren’t photosynthetic.
What kingdom do fungi belong to?
Kingdom fungi
How are fungi named?
With latin binomial nomenclature. Some fungi have separate names for their asexual and sexual morphs
Where can fungi be found in nature? (5)
Soil Water Air Plant material Extreme environments
Describe in more detail each of the 5 places where fungi are found in nature
Soil: the highest levels of fungi are found here, because of abundant moisture, nutrients, and protection from environmental extremes such as UV.
Plants: fungi can grow on stems, leaves, bark, flowers, and utilize the nutrients available after breaking down the tissues.
Air: plants are found in the air after spores spread from plants and soil and spread in the air
Water: some fungi are able to grow in the water and use the nutrients that are available there e.g. water molds
Extreme environments: very few fungi are found in extreme environments such as cold and freezing
What are the main phyla of fungi?
Phylum chytridiomycota (water moulds) Phylum Zygomycota (zygomycetes) Phylum Glomeromycota (the mycorrizhal fungi) Phylum ascomycota (ascomycetes) Phylum basidiomycota (basidiomycetes i.e. mushrooms) Phylum deuteromycota (asexual fungi with no sexual stage)
Spores may be … or …
Pigmented or hyaline
What conditions are needed by fungi for growth? (6)
Temperature: around 20 degrees C
Moisture: high humidity
Light: not required but grow better with it
pH: slightly acidic
Nutrients: varies, but nitrogen, micronutrients and vitamins
Oxygen
What kinds of media can fungi be grown on?
most nutrient agar media and in liquid broth cultures
Can be defined or undefined
What is undefined media?
media composed of inorganic chemical ingredients
What is defined media?
media composed of organic nutrient sources
Examples of media types
Russel’s defined media, potato dextrose, v8, lima bean, carrot
Describe the composition of the fungal cell wall
Structural components: Chitin microfibrils (beta 1-4 linked polymer of N-acetylglucosamine), chitosan (beta 1-4 linked polymer of glucosamine), Beta linked glucans
Gel-like components: mannoproteins which form a matrix throughout the all
When do fungi produce secondary metabolites?
After they complete mycellial growth and spore production. Once growth starts to slow down and there is an accumulation of other stalling products accumulate
What are examples of fungal secondary metabolites?
pigments (orange, red, yellow)
toxins (mycotoxins)
organic acids (citrix, oxalic)
melanin (brown, black)
Describe how fungi grow in nature
Most are saprophytic
Are heterotrophic
Some are symbionts of other organisms
What kinds of enzymes are produced by fungi?
Destroy cell walls: cellulase, ligninase, pectinase, semi-cellulase
Break down proteins: proteases
Destroy insects: chitinase
Infect humans: keratinase, lipase, protease, phospholipase
What are the types of fungal pathogens? (5)
Phytopathogens: infect plants Entomopathogens: infect insects Aquatic pathogens: infect frogs and fish Mycoparisites: infect other fungi Opportunistic pathogens: infect humans
What are the different fungal forms?
Mycellium, spores, rhizomorphs (thickened mycelium), oospores, sclerotia, chlamydospores
How long do mushroom spores last?
A few hours
How long do deuteromycotina spores live?
A few days
How long do mycelial strands and rhizomorphs live?
A few months
How long do sclerotia and oospores live?
A few months
Describe the two types of fungal reproduction
Asexual reproduction: produce conidia via mitosis
Sexual reproduction: produce zygospores, ascospores, basidiospores via meiosis. Requires the fusion of two strains of different mating or compatibility types
What is the nuclear condition at the various stages of the fungal life cycle?
Most fungi are haploid for most of their life cycle (Armillaria is diploid)
The diploid phase is short and is associated with heterokaryon (n+n) formation, karyogamy and zygote formation followed by meiosis to go back to being haploid. Hyphal fusion is required for zygotes to form.
Describe the life cycle of basidiomycetes
The predominant phase is the mycelium. When the sexual fruiting bodies (mushrooms) are formed, this initiates the sexual phase where karyogamy and meiosis occur
What are ways to recover fungi from the environment? (4)
From soil: tissue baiting method, soil dilution and plating on agar media.
From plant tissue: surface-sterilize and plate on agar media, sticky cards, trap plants
From air: volumetric sampling or aerial vehicles.
From humans: same as from plants
What are selective/semi-selective media?
Media that have been prepared so that only certain types of fungi will grow on them, e.g. by adding a fungicide or antibiotic
Discuss Sabourauds Dextrose Agar
Made of peptone, dextrose and sugar
High concentration of sugar and low pH select against bacteria and makes it selective for fungi
antibiotics such as chloramphenol, or penicillin and steptomycin inhibits bacterial multiplicatin
Saprophytic fungi inhibited by cycloheximide.
Describe the process of fungal identification through morphology
Morphological characteristics are the most important starting step for identifying to the genus level.
Species identification can be done using morphology such as colony morphology and pigmentation, spore size and shape and the presence or absence of unique fungal structures
What is a drawback of using morphological keys?
It is tedious and requires a wide range of specimens to ensure that all the morphological features are represented
Describe identification through DNA
polymerase chain reaction of specific regions of the fungal genome, obtaining the sequence of a specific part and comparing it to genbank to find a match. Phylogenetic anaylsis shows the relationships among the different species.
What is the only fungi that doesn’t have a fruiting stage?
Deuteromycota
What is the name of the asexual cycle of a fungus?
Anamorph
What is the name of the sexual cycle of a fungus?
Telomorph
Describe three good aspects of fungi nutrient cycling
Break down cellulose and lignin in trees to make the carbon more readily available to other organisms
Improtant part of composting, breaking down materials into useable matter
Break down animal carcasses and cadavers and secrete proteases
What are post-putrefaction fungi?
They break down the carcasses of animals and utilize proteins. They are often found on graves
What is the name of the fungi that can break down carcasses of animals and utilize proteins?
Post-putrefaction fungi
What are some examples of edible fungi?
Shiitake, oyster, lentulina etc.
What is corn smut?
A fungus that infects corn plants and causes galls to form on the cobs. Fungus name is Ustilago maydis
Discuss quorn mycoprotein
produced from the cultivation of fusarium venenatum indoors in fermentation vessels
What are some examples of fungi used in fermentation and food-making?
Tempeh (fermented soybeans)
Ripening and flavouring of cheeses using peniclillium species: they break down proteins and fats (proteolytic and lipolytic enzymes) and release amino acids and pepties. The strong flavours come from methyl ketones and lactones
What are some examples of fungal enzymes that have industrial uses?
Reduce pulp and other waste from paper. e.g. cellulase, hemicellulas
REduce agricultural wastes through composting
Enzymes are added to laundry detergents to break down food particles and remove stains
Used in biofuel production, e.g. fusarium on corn converts xylose to ethanol
Discuss the use of fungi to treat and modify fibers
Enzymes called catalylases are used to treat cotton and prepare it for the dying process.
By degrading surface fibres, many enzymes such as cellulases and xylenases are used to finish fabrics, stonewash jeans and tan learthers. Trichoderma partly digests the cotton fibres of jeans to give them a stonewashed look
Discuss ant-fungus mutualisms
Seen in some species of ants in the tropics. Ants cultivate fungus as a crop to eat. Sometimes they are dependent on each other for survival. e.g. leaf-cutter ant. Ants crush leaves, add saliva to inhibit bacteria, and cultivate fungi for food.
Discuss the decontamination of soils by fungi
Fungi can degrade pescicides, dies, hydrocarbons, pollutants, heavy metals
Requires P450 monooxygenase and oxygen
Describe fungi that attack insects
Entomopathogenic fungi are used to control insect populations. Examples are Beauvaria bassianae and Verticillium lecanii.
Penetrate the insect cuticle, secrete chitenases and grow inside th e insect, killing it and making spores to spread.
Require warm temperatures and high RH.
Discuss mycoparasitic fungi
Produce enzymes that destroy the cell wall of other fungi (chitenases and glucanases) and produce antibiotics.
Examples are trichodema, gliocladium and penicillium
Used as biocontrol agents to reduce plant diseases and commercial products are available
How do moulds end up in houses?
They are usually hyphomycete or ascomycete soil decomposers that occur naturally in the environment, but can end up in houses if building materials are wet.
Why do we do air quality assessments for moulds in houses?
Can indicate water leakage. Spores can have elevated levels inside compared to outside. They can cause illnesses including histoplasmosis, blastomycosis, coccidiomycosis, aspergillosis, zygomycosis etc. at high levels they can also cause sick building syndrome
What are examples of virulent and opportunistic infections caused by mould?
Virulent: histoplasmosis, blastomycocis, coccoidiomycosis
Opportunistic: aspergillosis, zygomycosis, candidiasis etc.
What is sick building syndrome?
when biogenic components of dust (mites, spoores etc. ) happen at problematic levels, they can cause people to get sick.
what are some examples of indoor fungi of interest?
Stachybotrys: trichotecines cause stachybotryotoxicosis
Chaetomium: causes allergic effects
Aspercillus, penicillium: Aspergillus fumigatus can cause Aspergillosis.
How are air quality assessments done?
Specialised pumps and samplign media are used. They are taken both inside and outside.
Casettes are cut open, mounted in Lactofuchsin and analysed.
Analyze transects up and down through the impact trace.
The aerospores are identified in this way.
What are some spores that are sampled for in agriculture?
Late blight: Phytophthora infestans
Cucurbit Downy Mildew: Pseudoperonospora cubensis
Define mushroom
a conspicuous fleshy sexual structure produced by fungi in the phyla ascomycota and masidiomycota.
It is a small structure produced by the larger fungal thallus.
Basidiomycetes are specialists in the degredation of…
Lignin
What are some secondary metabolites produced by mushrooms?
Hallucinogens: psilocybin from Psilocybe
Flavours
Medicinals: immunomodulatory compounds from Ganoderma lucidum
Poisons: amanitins from Amanita
What are some important factors to note when identifying mushrooms?
Date Weather Abundance Growth habit Substrate: type of wood, effects on wood. Type of dung, stage of decomposition, type of ground, Vegetation Size Colour Texture Odour and taste Veil Annulus Volva
What are some species of mushroom collected commercially in BC?
Morchella esculenta (yellow morel) Morchella elata (black morel) Cantharellus cibarus (Chantrelle) Boletus edulis (Porcini) Tricholoma magnivelare (matsutake) Sparrasis crispa
What species are white button mushrooms, crimini and portabello?
Agaricus bisporus
What species is oyeter mushrooms?
Pleurotus ostreatus
How are mushrooms cultivated?
Pure cultures are grown to large volumes as grain spawn
This spawn is used to inoculate larger volumes of bulk substrates
The substrates are colonized by the fungal thallus and fruited
Pure cultures can be started by mating spores or from tissue culture
Cells are replicated billions of times
Culturing is done under aseptic condition
The laminar flow bench blows HEPA filtered air accross the work surface
The pure culture is transferred to sterile grain and allowed to colonize the grain kernels. This is referred to as spawn
How are tissue cultures made?
Mushroom mycelium is aseptically removed from the mushroom and grown on agar media
What is spawn?
Grain kernals that have been colonized by a pure fungal culture. Used to inoculate sterile or pasteurized bulk substrates
What are some examples of bulk substrates?
Logs, sawdust, straw, compost, corn cobs etc.
What does it mean if a bulk substrate is “run”?
That it has been fully colonized
How ws lentinula edodes traditionally produced?
On logs under natural forest cover
What carcinogen is contained in Agaricus mushrooms?
Agaritine and 4-(hydroxymethyl)-benzenediazonium.
How does Agaricus bisporus behave in the wild?
It is a soil-dwelling secondary composer. It was traditionally grown in caves
Why is Agaricus breeding simplified?
Because it contains 2 nuclei, so sexual reproduction isn’t necessary and parent/offspring similarity is ensured
What are the steps in Agaricus cultivation?
composting composting
spawining: the finished compost is mixed with grain spawn and run
casing: a layer of peat moss is added to the substrate to encourage mushroom formation. Required for Agaricus and some Psilocybe species
pinning and fruiting: done by simulating autumn to produce mushroom primordia called pins.
What is mycofiltration?
Using fungi as a natural filter to treat agricultural runoff. e.g, pleurotus will grow on many substrates initiating decomposition
What are some examples of fungi of historical importance?
Phytophthora infestans: causes late blight on potatoes, that caused the irish potato famine.
Claviceps purpurea: ergot on rye that cause St. Anothony’s fire. Produced alkaloid mycotoxins including lysergic acid derivative (LSD) that affected humans and animals
How was LSD discovered?
Hoffman produced chemicals, found he was dizzy so injecsted a bit of the purified extract and tripped out
What are necrotrophic fungi?
CAn grow on dead or living plant materials
Produce enzymes and toxins that destroy plant cells
Non-specialised pathogens
able to survive in the absence of a living host
What are some examples of netrotrophic fungi?
Pythium, Fusarium, Rhizoctonia
What are biotrophic fungi?
Can only grow on living plant cells
Don’t produce toxins or enzymes that destroy cells
Infect with a penetration peg and then a haustorium to absorb plant nutrients
Usually infect a narrow range of plants, so are specialized pathogens.
Can survive as mycelium or spores in he absence of a host, but not for long (a couple of years)
What are some examples of biotrophic fungi?
Powdery mildew and rust fungi
Discuss fungal allergies
Fungi can produce millions of spores, released and spread by wind
Cladosporium, alternatia, aspergillus are common in the air in the spring/summer and can cause allergies and asthma
Can be problem in homes in wallpaper, carpet, mattreses
Black mold caused by Stachybotrys can be a problem in wet drywall
What are some characteristics of mycotoxins?
They are toxic at low concentrations
They are prevalent in food and are heat stable
Usually the food is contaminated with the mould
Can cause poisoning in animals
Are more prevalent in hot, humid climates
What are some examples of mycotoxins?
Aflatoxins: produced by aspergillus, common in mouldy peanuts
Trichothecenes: produced by Fusarium. e.g. vomitoxin, zearalenone (common in wheat and barley) also produced by Stachybotrys
Ochratoxins: penicillium and aspergillus
Which fungi produce aflatoxins?
aspergillus
Where are aflatoxins common?
mouldy peanuts
What fungal species produce trichotehcenes?
Fusarium (vomitoxin, zearalenone), stachybotrys
What is a dermatophyte?
A fungus that grows on skin
Discuss what dermatophytes do to skin and hair?
they break down the keratin by producing proteases and peptidases. The tissues respond by producing more cells, which the fungus uses to grow.
