BIOL2044 L5-8 Fungi

L1: Fungi general features...

- No chlorophyll = DON'T photosynthesise

- DO have a cell wall but its made of CHITIN

- Heterotrophs = secrete enzymes to help them absorb nutrients from dead material

- Non vascular = DON'T have a system for moving fluids like plants do

- Have spores = important for reproduction

L1: What are the 3 main groups of fungi ?

- Mushrooms

- Moulds

- Yeast (single celled)

L1: How do nuclei stay separate during fungi division ?

- Thru division and extension of hyphae

L1: Hypha + their classes...

- Hypha = long filamentous structures that make up the body of fungus

- Septate = Presence of internal cell walls creates cell like structures within the fungi

- Aseptate = No internal cell walls so fungi appears as one long structure w no individual cells

L1: Yeast features...

- V simple single celled organisms. Exist normally as single celled but can be multicellular

- Division by budding or fission

- Most common is saccharomyces cerevisae

- Produce sexually via ascospores or basidospores

L1: Mycelium...

- Mass of hyphae. Network of thread like structures that can be found in many places such as soil

L1: Whats the diff between conidiophores and sporangiophore ?

- Conidiophore = aerial hyphae that produces asexual spores on its surface called conidia

- Sporangiophore = hyphae that has asexual spores called sporangiospores

L1: Whats a fruiting body ?

- Multicellular structure that produces and disperses spores for reproduction. For example, aerial spore mushrooms

- Increases SA for quicker reproduction

L1: What are spores + what are the diff kinds ?

- Spore = reproductive structure. Can be haploid or diploid. Important as helps the fungi survive environments stressors such as extreme temps

- Chlamydospore

- Conidiospore

- Zygospores

- Ascospore

- Basidiospore

L1: What are the 3 most important fungi ?

- Ascomycota

- Basidomycota

- Zygomycota

L1: Features of the diff kinds of spores...

- Zygospore = diploid, arising upon fusion of hyphae

- Conidiospore = asexual, at hyphae tip

- Chlamydospore = asexual, is a survival structure formed via thickening of hyphae

- Ascospore = sexual reproduction via an ascus

- Basidispore = via sexual reproduction on basidium

L1: BASIC fungal life cycle...

- Asexual and sexual stages

ASEXUAL CYCLE (based on haploid cells)...

- Mycelium produces spore like structures

- Spores are produced and get distributed to the environment

- Germination occurs

- Mycelium reforms

(No change in ploidy, no sexual component. NO mixing of genetic material)

SEXUAL CYCLE...

- Hyphae of diff mating types fuse (cytoplasms fuse = plasma)

- Nuclei are separate (heterokaryotic stage)

- Nuclei then fuse to form a diploid cell (karyogamy)

- Meiosis triggered in some conditions (change in ploidy back from diploidy to haploidy).

L1: Identifying yeast...

Microscopic vs macroscopic features...

- looking at the shapes of the cells

- looking at the shape of spores

- looking at how they divide (fission or budding)

- Physiology = Looking at growth needs and limits (can they grown in x temp? Can they grow in high salts ?)

L1: What are the environmental roles of fungi ?

- Decomposers = break down dead material

- Symbionts = mutualistic relationship w other species

- Pathogens/ parasites = feed off living organisms

L1: Zygomycota ('Z')...

- Hyphae coenocytic = long, multinucleated fungal filaments that are NOT divided into compartments

- Septate in reproductive hyphae

- Produce dikaryotic zygosporangia which go on to produce spore like structures

- No distinction between individual cells

L1: Lifecycle of zygomycota

ASEXUAL...

- Haploid spores germinate

- Mycelium develops (singe mating type) and produces aerial structures such as sporangia

- Sporangia produce haploid spores which are dispersed around and whole cycle repeats

SEXUAL...

- Hyphae of both mating types need to be present (+ and -)

- When they interact they form GAMETANGIA (fused structures w haploid nuclei)

- Plasmogamy = structure fuses and nuclei are still separate so cells are HETEROKARYOTIC

- Only when formation of mature zygosporangium we have fusion of nuclei and have multiple diploid nuclei within structure

- Meiosis occurs simultaneously w germination of sporangium

- Release of haploid spores into environment

L1: Basidiomycota...

- Septate hyphae

- Club like structures called basidiospores that produce sexual spores

- Fruiting body offers increase SA to aid spore dispersal

L1: Lifecycle of basidiomycetes

- Haploid mycelia grows and interacts. Cells fuse, nuclei remain separate

- Dikaryotic mycelium grows a lot quicker than haploid version

Overtakes haploid parents

- Appropriate environmental cues = dikaryotic mycelium forms the basidiocarp (fruiting body)

- Within structure, on the extremities of gills we have DIKARYOTIC BASIDIA

- Fusion of nucleus to form diploid nuclei

Undergo myotic division to form haploid nuclei within the BASIDIUM

Mature to form BASIDIOSPORES

- 4 spores attached to the basidium

Can go on to form individual single sex mycelium

L1: Ascomycota ('A')

- Sac fungi

- Septate hyphae

- 8 ascospores

L1: Ascomycota life cycle...

ASEXUAL...

- Mycelium produce conidiophore

- Conidiophore develops haploid spores called conidia

- Conidia develop and germinate in the correct conditions

SEXUAL...

- Conidia produced is -ve so needs to fuse with a +ve mating type. Plasmogamy = cells fuse but nuclei stay separate to form an ascus

- When nuclei fuse have a zygote w diploid nucleus

- Meiosis required for there to be a change in ploidy (from diploid to haploid)

- 4 haploid nuclei. Sometimes thru mitotic division to give 8 haploid spores

L1: Decomposers..

- Develop on surfaces of material such as leafs

- Hyphae are able to penetrate into structures such as xylem and phloem

- Secrete enzymes involved in breaking down lignin

- Absorb nutrients from decaying material

L1: Symbionts...

- Have a mutualistic relationship w other species. Examples include lichens and mycorrhiza (2 types)...

- Endomycorrhiza = penetrate into cells directly thru the help of a structure called HAUSTORIUM.

- Ectomycorrhiza = make their way inbetween cells thru a structure called the HARTING NET. Not penetrating cells like endomycorrhiza, simply moving in-between them and hoping on there being 'leaking' carbohydrates etc.

L1: Lichens...

- Appear on rocks

- Fungal hyphae attaches to solid surface

- Ascocarp is the structure that produces asci

- Exchanging nutrients in mutually beneficial relationship

- Algal cells w segments of fungal hyphae break off and form new site

L1: Pathogens/ parasites...

- HOST BODY used to get energy and nutrients

- Opportunistic = only invade given breakdown in defence

- Obligate = CANNOT survive without host

L1: Examples of pathogens/ parasites...

- Rust fungus in plants

- White nose syndrome in bates

- insect pathogen leading to "zombies"

L2: What is the fungus used to produce Quorn + features of Quron?

- Fusarium venenatum

- Quorn is an alternative protein source, has vitamins present, has fibre (normal protein doesn't), has anti-oxidants

- PRODUCTION has low carbon footprint, water footprint and land footprint

L2: Saccharomyces cerevisae fermentation...

- Used in beer production due to it being a sugar fungus so is efficient at sugar fermentation

- Is ethanol tolerant so is able to survive when ethanol is present

- When fermenting produces ethanol. Most species cannot survive in ethanol so this gives saccaromyces a survival advantage as can take over the environment and absorb all the nutrients - doesn't have to compete w other species

L2: Yeast biomass uses ...

- Used to produce nutritional yeast = is dehydrated and ground up

- Yeast is used as a flavour enhancer in many foods such as stock cubes

- Used to form marmite

L2: Production of sake..

- A. oryzae is added to steamed rice which is rich in starch.

- The fungus produces enzymes which are able to break down the starch into sugars

- More steamed rice is added and S. Cerevisiae is added. Simultaneous sacrification and fermentation occurs to produce ethanol

L2: What fungus is used to produce a v sweet wine w lower alcohol percentage ?

- Botrytis cinerea

L2: Side products produced during saccharomyces cerevisae fermentation ...

- CO2. Used in alcohol production to provide the bubbles

- Ethanol produced during dough production. This isn't an issue as during baking will evaporate off

L2: What is the fungus used in soy bean paste fermentation ?

- Aspergillus oryzae

L2: Soybean paste fermentation...

- Aspergillus oryzae is used to breakdown soybean paste which is rich in complex polysaccharides.

- Aspergillus oryzae has enzymatic capability to break these complex polsachs down to release sugars which can be metabolised further

- Slow process but produces other products along the way

L2: Nematophagous fungi...

- nematodes attacks roots of plants. Examples include C. elegans

- Nematophagous fungi ATTACK nematodes

- FOR EXAMPLE, Drechslerella exist in soil and form loops which are comprised of 3 cells. As worm is moving thru soil it may move thru one of these loops which triggers a response in the fungus, causing the cells to swell and close around the worm

- The worm is killed thru the fungus releasing enzymes to breakdown the worm and absorb its nutrients

L2: Botrytis cinerea...

- Used in wine production. Produces a wine that v sweet and has a lower alcohol conc than usual

- Botrytis is a rot that grows on the surface of grapes and its hyphae penetrates thru the grape - usually into the stomatal pores.

- Dehydrates the grape and converts some sugars into glycerol

L2: Magic mushrooms...

- From the species basidiomycota

- Contains hallucinogenic compounds. Similar effects to serotonin which explains the euphoric sensation

- Some of the hallucinogenic compounds thought to be used as insect deterrent. Stops the mushroom being eaten by other insects

- Sound + perception is altered

- More relaxed etc etc. Lots of effects

L2: Biopesticides...

- Entopathogenic fungi infects insects , so used as a biopesticide

LIFECYCLE...

- Spore lands on insect and germinates, producing hyphae or mycelium which penetrates thru insects cuticle (made of chitin, found in some fungi)

- Develops thru insect, producing blastopores

- Mycelium develops aerial structure and produces more spores which are dispersed thru the wind and can land on more insects

- Triggers response in animals which causes them to move an an area of height before they die

L2: industrial enzymes...

- Around 50% of industrial enzymes are from fungi

EXAMPLES...

- Proteases break down protein

- Cellulases break-down cellulose

- Lipases breakdown lipids

- Amylases breakdown starch

L2: Medicines...

- FUNGI AS SOURCE OF MEDICIINES

- Penicillium produces penicillin

- Possible to increase titre 1000x from initial

- Genetic techniques used to increase yield or edit steps in production process

- Change stability of the antibiotic produced

L2: Statins...

- Statins used to control cholesterol.

- Discovered thru fungi producing inhibitors which interact w sterol synthesis and inhibit this

- Fungi are eukaryotes so sim synthesis to us.

- Elements of our synthesis of sterols which can be inhibited by some of the inhibitory compounds produced by fungi

- Can produce anti cancer drugs, immunosuppressants

L3: Poisonous mushrooms...

- Most common is Amanita muscaria.

- Most mushrooms are poisonous as it provides them a beneficial trait to prevent them from being eaten

- If consumed can activate NTMs and cause sedative, hypnotic and depressant or hallucinogenic effects

- Effect liver and kidneys is ingested and can lead tot he failure of these organs and DEATH

L3: What is the component of mushrooms that can cause -ve effects ?

- Muscimol or ibotenic acid

L3: What is a component of many poisonous mushrooms ?

AMATOXINS...

- Cause perforation in the plasma membrane and inhibit RNA poly

- If RNA poly doesn't work a lot of processes DON'T work. Leads to lysis and cell death

L3: Toxic moulds...

- Germinating ascospore makes its way to floral structure of grain

- Mycelium grows in ovary tissue

- Gets nutrients from plant thru vascular bundle

- Mycelium gets larger and produces dense mass

- Can produce honey dew that drips from the grain mass and contains asexually produced conidium

L3: What are produced by toxic moulds + what effects do they have ?

ALKALOIDS...

- Effect the nervous system and have effects such as spasms, fever, hallucinations, nausea, seizures etc etc AND also effect the vascular system (vasoconstriction = constricts capillaries so inhibits flow of blood to extremities). Causes burning sensation

- Vasoconstriction can result in loss of pulse from the extremities. Gangrene can occur and loss of limbs/ death

L3: What was the treatment for toxic moulds ?

- Topical balms = to treat the burning sensation

- Alcohol (wine) = is a vasodilator to increase the blood flow to the extremities

- Vasodilating herbs = improve circulation

L3: What are rusts and smuts + how are they treated ?

- plant pathogens (infect plants). Don't normally kill the plant but cause severe decrease in yield

- Rusts = one host, typically wheat

- Smuts = two hosts.

- BOTH treated w fungicides

L3: Smuts...

- Infection of flower structure of healthy plant, spores germinate and make their way to developing ovaries and mycelium is produced

- Germinated and seeding develops, mycelium hitchhikes and travels up thru plant as plant grows

- When plant develops grains the mycelium infects the grains and the cycle repeats

L3: Rusts...

- Structure appears on leaves of one of the hosts

- On leaf structures spores are released

- Spores carried by wind or insects make their way to the grain

- Germinates on wheat and develops structure which produces further spore bearing structures

- Rusty patterns appear of stalks of the plant

L3: Elm disease...

- Fungus spread by Scolytid beetles (Scolytes multistriatus) which bores under the bark of the tress and facilitates distribution of the fungus

- Over winter as the mycelium develops conidiophores and sticky conidia are produced

- As beetle walks past conidia brushes onto beetle and as the beetle makes its way into new trees and bores into bark it spreads the conidia (FUNGUS)

- Fungus will make its way to the vascular system and block the vascular system so sections of the tree gets starved and die.

L3: Treating dutch elm disease...

- Destroy diseases trees

- Kill beetles

- Vaccinate trees w weaker strain of the disease

L3: Wood decaying fungi + HOW are they treated ?

- Fungi can still cause effects of wood thats no longer attached to the tree. This is called ROT

- Breaks down diff components of the wood to use as energy sources. For example, cellulose, lignin and hemicellulose. Results in diff colours of the rot

- TREATED by controlling the environment (rot like humidity), so keeping the timber dry and ventilated, biological control using competitive species

L3: What do the diff colours of rot indicate + how do they work ?

- BROWN ROT = broken down cellulose and hemicellulose and left behind brown lignin. WORKS by releasing H2O2 to loosen the cell wall of the wood and help infection

- WHITE ROT = broken down brown lignin and left behind cellulose and hemicellulose. Have white carbonate crystals left

L3: Fungal pathogens which can infect people ?

- Candidiasis

- Dermatophytosis

- Aspergillosis

- Cryptococcus

- Fungal allergies

- Microsporidia

L3: Candidiasis + its treatment...

- E.g. oral thrush

- Is dimorphic, grow as single cells

- Form filaments which are vital for the virulence of the fungus

- Have characteristic chlamydospores

- Treated w antifungals that inhibit the features of fungi that are diff to humans. For example, targeting cell wall of the fungus bc humans don’t have cell walls so easy to identify.

L3: Dermatophytosis...

- Fungal infection of the skin and nails. For example, athletes foot, ringworm

- Infection thru spores in the environment. Risk factors = public showers, contact sport inc poor immunity

- Treated thru antifungals

L3: Aspergillosis...

- Aspergillus caused by inhalation of aspergillus spores

- Can get in thru lungs into blood stream = serious effects

- Lrg mass of fungal material in body cavity causes lrg issues

- Treated thru antifungals

L3: Cryptococcus...

- Found in bird dropping and soil. Use urea as nutrient source

Spores germinate in lung and proliferate

- Spores in bloodstream = serious issues such as meningitis

- Meningitis = infection of the lungs which can lead to infection of the meninges (covering of the brain). Or worse still, infection of the actual brain

- Treatment thru antifungals and managing pigeons

L3: Fungal allergy...

- Caused by inhaling spores of moulds and mildews (wide range of species)

- Everyone inhales these spores but some have increased reactions, such as asthma

L4: Microsporidia...

- OPPORTUNISTIC fungi

- First identified in AIDS patients (immunocompromised)

- Microsporidia infects cells. These cells will split and spread into environment

- Identified as Enterocytozoon which have a polar tube that allows them to infect sprioplasma (material that allows the formation of spores in the host cell)

- In humans infection causes diahorrea but can become more serious

L4: What are diff abt microsporidia to the other 3 main fungi ?

- Lack mito so thought to be more primitive (OLDER). Still have mito genes which suggests maybe they had mito at one point

- Obligate = rely on host cell. Explains lack of mito bc get all the nutrients etc from host

- Small genomes

L4: Meront...

- Structure that occurs during the lifecycle of a microsporidia

- No mito and LOTS of ribo

- Has projections to help increase the SA

- One or two nuclei

L4: Spore...

- Helps infect the cell

- One or two nuclei

- Thick wall (protein and chitin layers). Increases resistance

- Rows of circles/ ovals = polar filaments wrapped around spores

- Polar filament

L4: Lifecycle of microsporidia...

- Under certain conditions the spore is triggered to germinate which invovles the posterior vacuole swelling to push out a filament

- Filament pierces thru host cell and spore content is injected into the host cell

L4: What does the spore introduce into the host cell ?

- Spiroplasma which replicates to produce a meront (simplified spore structure)

- Forms sporonts (protective outer layer which matures into fully formed spores). There is a huge number of spores which results in the cell rupturing

L4: Pathogenicity...

- Infect wide range of organs and organisms making them ill

- Can form cysts within tissue of the fish all over.

Cysts will eventually rupture and release more spores (fish dies) and which will reinfect other fish in the environment

- In some arthropods the microsporidia can change the sex determination

- Transmission via spores

L4: Immunity against microsporidia....

- V little is known abt how the immune system fights off microsporidia

- Cellular and non-cellular immunity both play a role

(difficult to understand as part of lifecycle is intracellular)

L4: Host range for microsporidia...

- Drosophila lay their larvae which develop into eggs

- Parasitic wasps attack drosophila larvae and lay their own eggs in the drosophila larvae

- Wasp eggs hatch in the drosophila larvae and wasp larvae eat the guts of the drosophila larvae, BUT the larvae is still in tact

(Microsporidia can utilise both wasps and drosophila. Can easily become incorporated into the drosophila life cycle)