MYCO 4.1A,B,C | Fungal Ecological Roles, Fungi-Fungi Interactions, Fungal Mutualisms pt. 1

Fungi have critical roles in both terrestrial and aquatic environments, including _

bdnsi

• Biotransformation, mineralization, & remediation

• Decomposition of organic matter & carbon cycling

• Nitrogen fixations & conversions

• Symbioses (endophytes, lichens, AMF, etc.)

• Interactions with terrestrial, aquatic, and marine flora & fauna

_ is the biochemical modification of 1 or more chemical compounds

Biotransformation

Biotransformation refers to the biochemical modification of 1 or more compounds, including reducing the environmental impact of metals, pharmaceuticals & personal care products, pesticides, and plastics, through 2 main processes:

• Intracellular enzymatic processes

  • Cell-wall bound enzymes pqdt

    • Phenol monooxygenases

    • Quinone reductases

    • Dehalogenases

    • Transferases

  • Cytochrome P450 monooxygenases, nitroreductases

• Extracellular enzymatic processes llmco

  • Laccases

  • Lignin peroxidases

  • Manganese peroxidases

  • Chloroperoxidases

  • Oxidoreductases

• Transforming pollutants into products including mdo

  • metabolites (more/less harmful to environment)

  • degradation products (complex > simple),

  • organic molecules

    • phosphate > ATP (inorganic > organic) = assimilation

    • ATP > phosphate (organic > inorganic) = mineralization

Biotransformation produces products, including:

mdo

• Metabolites (could be less or more harmful)

• Degradation products (complex > simpler)

• Organic molecules (organic > organic; inorganic > organic, e.g., phosphate > phosphorus, e.g., ATP via assimilation)

_ is the decomposition of chemical compounds in organic matter and their release in soluble inorganic forms that may be available to other organisms, e.g., phosphorus tends to bind to soil particles and complex with metals in the soil, making it unavailable to organisms even when it is present

Mineralization

Explain how fungi (AMF) accelerates phosphorus mineralization

• Increased plant P limitation and P demand induce their relationship with AMF, which enhances P uptake through 2 key mechanisms:

  • (1) extending their hyphae into the soil, thus increasing surface area for phosphorus absorption; and

  • (2) accelerating acid phosphatase enzyme production, which helps release phosphorus from organic matter

• These processes facilitate the transformation of occluded P into labile or moderately labile Po mineralization, ultimately contributing to the labile Pi supply, and help meet plant P limitation & demand

_ is the enzyme whose production is increased by AMF to help meet plant phosphorus demand & limitation, as these help release phosphorus from organic matter

acid phosphatase enzymes

_ employs the use of living organisms, the removal, and/or the degradation of contaminants, pollutants, and toxins from soil, water, and other environments

Bioremediation

Explain 2 bioremediation processes fungi help facilitate

bbd hbr

• Benzo[a]pyrene biodegradation

  • Benzo[a]pyrene = polycyclic aromatic hydrocarbon (PAH); known pollutant from pesticides, fertilizes

  • Fungi help oxidize benzo[a]pyrene into smaller, more degradable compounds via their manganese peroxidase (MnP) enzymes, transforming these into: qhg

    • Quinones,

    • Hydroxylated intermediates (hydroxybenzo[a]pyrenes, trans-dihydrodiols), and

    • Glucuronic acid & sulfate conjugates (all of which are more water-soluble + can be further metabolized)

  • with CO2 as the final breakdown product, indicative of complete mineralization of benzo[a]pyrene

• Heavy metal bioremediation

  • Fungi also contribute to heavy metal bioremediation via various mechanisms including: dbs gsv

    • Dissolution of primary minerals by secreting organic acids, e.g., citrate and oxalate, into the environment, thus triggering the release of heavy metals

    • Biosorption of Me+ using biomolecules, e.g., phytochelatins & metallothioneins, that store or detoxify Me+ within plant cells

    • Secondary mineral transformation, where fungi precipitate Me+ as secondary minerals

    • Use of glomalin (AMF glycoprotein) as Me+ sink

    • Siderophores chelating metals, making these more bioavailable or less toxic

    • Volatilization & uptake, where metals are absorbed by fungi, stored in vacuoles, or volatilized as gaseous compounds

T/F: As long as fungi make something less toxic or polluted, it can already be considered a bioremediation mechanism

TRUE

T/F: In biotransformation, the end products are always non-toxic metabolites that are harmless to the environment

FALSE

The end products of biotransformation are not always non-toxic. Sometimes, they can be more toxic than the original compound or may require further degradation

T/F: Phosphorus mineralization by fungi in the soil results in the formation of organic phosphorus that plants can directly absorb

FALSE

Phosphorus mineralization by fungi results in the conversion of organic phosphorus into inorganic phosphate, which plants can absorb

Fungi as _ degrade organic matter and release carbon

saprotrophs

Fungi help in the cycling of nutrients and organic matter and the release of carbon as _

pems

• Pathogenic fungi dm

  • Decay of plant materials

  • Modifying root exudates

• Endophytic fungi nnc

  • Nutrient uptake

  • Nutrient exchange

  • Carbon sequestration

• Mycorrhizal fungi nnle

  • Nutrient uptake

  • Nutrient exchange

  • Diminish nutrient leaching

  • Reduce erosion

• Saprophytic fungi dps

  • Decomposition

  • Pedogenesis (study of soil origin & formation)

  • Soil fertility change

Decomposition is carried out in a series of steps dependent on _

flux of fungal inhabitants in an ecosystem

T/F: Fungi can help release inorganic matter from the environment via bioremediation, while they help release organic matter (and cycle carbon) from the environment via saprotrophic action

FALSE

Fungi can help release inorganic matter from the environment via biomineralization, while they help release organic matter (and cycle carbon) from the environment via saprotrophic action

The most important role of fungus is as _ since these aid in the decomposition & decay process of living things, meaning organic materials, such as carbon & sometimes nitrogen, trapped in dead organic matter will not be available to other organisms in the environment unless fungal depolymerase break these down and allow their release

saprotrophs (saprophytes)

Explain why fungi as saprotrophs is one of their most important roles in ecosystem

This is because saprotrophic fungi aid in the decomposition & decay process of living things, meaning organic materials, such as carbon & sometimes nitrogen, trapped in dead organic matter will not be available to other organisms in the environment unless fungal depolymerases break them down and allow their release

T/F: Carbon is one of the most mobile elements in the environment, thus it is necessary to interconvert this at a fast rate; limiting factor is usually the amount of carbon that can be taken from the dead organic material

TRUE

Carbon is one of the most mobile elements in the environment; the limiting factor is usually _

the amount of carbon that can be taken from the dead organic material (made available by depolymerases of saprotrophic fungi)

_ is the process of chemoheterotrophic (carbon & energy source = organic compounds) extracellular digestion involved in the processing of decayed (dead/waste) organic matter

Saprotrophy

_ is carried out in a series of steps dependent on flux of fungal inhabitants in an ecosystem

Decomposition

Explain fungi saprotrophic decomposition sequence

ewp psd

1. Epiphytic fungi: live on the host surfaces & start decomposition while the host is still alive

2. Weak parasites: infect weakened host but will not necessarily cause rapid death

3. Pioneer saprotrophic fungi: colonize dead organic matter after host death

4. Polymer-degrading fungi: as decomposition progresses, they break down complex macromolecules, e.g., cellulose, into simpler compounds

5. Secondary opportunistic fungi: take advantage of partially metabolized compounds & continue degradation

6. Degraders of recalcitrant compounds: dominate the final stage of decomposition, as these are capable of breaking down compounds highly resistant to degradation

_ are chemical compounds highly resistant to degradation, whether via biological, physical, or chemical processes and thus persist in the environment for long periods because they are not easily broken down under natural conditions

Recalcitrant compounds

T/F: Degraders of recalcitrant compounds are the final and often longest-lasting fungal actors in decomposition

TRUE

They specialize in breaking down very resistant materials like lignin and melanin, and persist longer because of the difficulty of their task

T/F: Fungal decomposition contributes to atmospheric CO₂ increase by mineralizing organic carbon into CO₂ during saprotrophic activity

TRUE

Fungal respiration during saprotrophic breakdown releases CO₂ from organic matter — a major step in the carbon cycle. So yes, fungi are carbon cyclers and carbon releasers

Fungi play an essential role in nitrogen (N) cycling since they can _

• Mineralize organic N (convert organic → inorganic)

• Assimilate inorganic N to build their biomass

Explain role of fungi in nitrogen fixation & conversions

• Nitrogen-fixing bacteria (in root nodules of legumes + soil) are mainly responsible for nitrogen fixation

  • Atmospheric N2 → NH4+

• Decomposers (aerobic & anaerobic bacteria & fungi) break down organic N2 from dead organisms into NH4+ via ammonification

  • Organic N2 → NH4+

• Nitrification (by nitrifying bacteria)

  • NH4+ → NO2- → NO3-

• Assimilation is when plants absorb NO3- or NH4+ & convert these back to organic N2

  • NO3- or NH4+ → organic N2

• Denitrification is when denitrifying bacteria/fungi return N to atmosphere

  • NO3- → NO2- → NO → N2O

• 3 primary roles of fungi in nitrogen conversion dan

  • Fungal denitrification

    • NO3- → NO2- → NO → N2O

    • Nar, NirK, P450 Nor

    • don’t usually reach N2

  • Ammonia fermentation

    • In low-O2 conditions, fungi can use ammonium as energy source

    • NH4+ → ATP + byproducts

  • Nitric oxide (NO) detoxification

    • Fungi have enzymes like Fhb & GSNOR that detoxify NO

    • NO → harmless compounds

Enumerate & explain the 3 roles of fungi in nitrogen conversion

*Order = principal activities their most involved in

1. Fungal denitrification

   • NO3- → (Nar) NO2- → (NirK) NO → (P450 Nor) N2O

2. Ammonia fermentation

   • Under low-O2 conditions, fungi can use NH4+ as energy source

   • NH4+ → ATP + byproducts

3. NO detoxification

   • Fungi have Fhb & GSNOR enzymes that can detoxify nitric oxide (NO)

T/F: In fungal denitrification, nitric oxide (NO) is the final product excreted into the environment

FALSE

NO is intermediate; fungi can further reduce it to N₂O using P450 Nor

T/F: Fungi contribute to nitrification by converting ammonium (NH₄⁺) to nitrites (NO₂⁻)

FALSE

• That’s the bacterial nitrifiers’ job, e.g., Nitrosomonas

• Fungi don’t do nitrification NH4+ → NO2- → NO3-,

  • Only ammonification organic N2 → NH4+

  • denitrification NO3- → NO2- → NO → N2O

Fungi form several types of symbioses with other organisms in many kinds of habitats, including _

eml

• Endophytes

  • Neotyphodium spp. are common endophytes within leaf tissues

• Mycorrhizae

  • Mycorrhizae are associated with roots of > 90% of all plant species

  • Can turn parasitic quickly when certain conditions are not met

• Lichens

  • Lichens are any of about 15,000 species of organisms that consist of symbiotic associations of algae (usually green) or cyanobacteria and fungi (mostly ascomycetes and basidiomycetes)

T/F: Both fungi and bacteria can fix nitrogen

FALSE

Fungi do not fix atmospheric nitrogen (N₂)

_ are any of about 15,000 species of organisms consisting of a symbiotic association between algae (usually green) or cyanobacteria and fungi (mostly ascomycetes and basidiomycetes)

Lichens

Explain the 3 primary ecological roles of aquatic fungi

1. Mycoloop = parasitic fungi rendering inedible phytoplanktons edible to zooplankton grazers either via fragmentation or by producing spores (that zooplankton can eat)

   1. enables energy transfer UP the food chain to zooplankton then to fish

2. Mycoflux = any fungal interaction leading to the aggregation or disintegration of organic matter, thus affecting aquatic carbon matter (DissolvedOM, ParticulateOM)

   1. affects carbon state of water (from particulate to dissolved)

   2. changes how carbon moves (fluxes) thru water column

3. Benthic shunt = fungal colonization of organic litter rendering it palatable to macrozoobenthos, which become food for higher trophic levels, such as fish, thus increasing trophic transfer efficiency of the aquatic food web

*autochthonous OM = originates w/in ecosystem; allochthonous = from outside the ecosystem

T/F: In aquatic mycoflux, DOM will remain suspended in water column, while POM aggregates or sinks to bottom of aquatic environment (sediment = benthic)

TRUE

T/F: Mycoflux only increases carbon availability by disintegrating organic matter into DOM

FALSE

Mycoflux also causes aggregation, which may sink and reduce availability

T/F: Benthic shunt results in decreased carbon retention in the sediment since fungi make litter float

FALSE

The benthic shunt retains carbon in sediments and simply makes it available to benthic feeders

T/F: In the mycoflux, fungal activity can indirectly alter the sinking rate of organic particles

TRUE

By aggregating or breaking down POM, fungi influence whether particles sink or stay suspended

T/F: Mycoflux interactions can paradoxically lead to both carbon retention in sediments and increased availability in the water column

TRUE

• Aggregation = sinking POM (retention in sediments);

• Disintegration = DOM, stays suspended in water column

T/F: DOM is a form of carbon more likely to be affected by fungal disintegration, whereas POM is influenced by aggregation

TRUE

Fungal disintegration often produces DOM; aggregation deals with POM

Environmental interactions between fungi can fall under 1 of 3 categories, including _

• (A) Exclusion = ability of 1 species to exclude another through indirect competition (exploitation competition) through various means, e.g., hogging resources/space

• (B) Antagonism = ability of 1 species to exclude or replace another by directly affecting another organism through antibiotic production, parasitism, etc. (interference competition/combat)

• (C) Coexistence = ability of 2 species to coexist (commensalism) to the benefit of 1 or both (mutualism)

T/F: Fungi-fungi interactions are difficult to observe in nature and study in situ, especially mutualism

TRUE

• Usually, one must go into lab to replicate the same conditions

• Mutualisms are rare bc a lot of fungus usually have the same needs, occupy same niche, and share the same resource

Exclusion vs. Antagonism

• Exclusion = when 1 species excludes another via indirect or exploitation competition, e.g., hogging resources or space

• Antagonism (interference competition/combat) = when 1 species excludes or replaces another by directly affecting another organism through ap antibiotic production, parasitism, etc.

_ happens when 1 species bars another from accessing a resource, e.g., take-all patch disease of fine turf grasses caused by monopoly of Gaeumannomyces graminis

Exploitation competition (exclusion)

Explain 1 example of exploitation competition (exclusion) between fungi

Take-all patch disease of fine turf grasses

• (A) Discoloration of grass caused by Gaeumannomyces graminis when natural fungal competitor is reduced or destroyed

• (B) G. graminis perithecium (ascocarp) releasing ascopores, which quickly invade grasses

• (C) This can be prevented through biocontrol by nonpathogenic fungal competitor Phialophora graminicola, which protects roots of grasses by (D) ensheathing the cortex (steele) with its own hyphae,

• (E,F) thus preventing colonization of vascular tissues by G. graminis

Give 3 ways through which fungi can become antagonistic to other fungi

ahm

1. Antibiotic production

2. Hyphal interference

3. Mycoparasitism

   1. Biotrophic

   2. Necrotrophic

_ species are a model of antibiotic production to antagonize other fungi because they produce _

• Trichoderma

• several volatile & nonvolatile compounds active against fungi, bacteria, or both including vtg6

  • Viridin

  • Trichodermin

  • Gliotoxin

  • 6-PAP

Explain 1 example of antagonism thru antibiotic production between fungi

• Trichoderma species are well-known for their ability to antagonize other fungi through antibiotic production

• This is because they can produce several volatile & nonvolatile compounds, active against fungi, bacteria, or both, including vtg6

  • Viridin

  • Trichodermin

  • Gliotoxin

  • 6-PAP

• These antifungals are effective against fpancp

  • Fusarium proliferatum

  • Penicillium brevicopactum

  • Aspergillus flavus

  • Neofusicoccum batangarum

  • Colletotrichum gloeosporioides

  • Phytophthora parvispora

T/F: Trichoderma is a very common soil fungus

TRUE

You can find it by digging >5 cm of soil, especially in tropical environments

Antifungals vs. Mycotoxins

• Antifungals = substances that kill or inhibit growth of fungi, often used in treating fungal infections in vertebrates

  • Has effect on fungus

• Mycotoxins = toxic secondary metabolites produced by certain fungi, often under stress conditions

  • Effect of fungus on vertebrates

_ is an antagonistic fungal strategy for killing or inhibiting other fungi at points of contact

Hyphal interference (HI)

T/F: Hyphal interference is a form of fungal parasitism

FALSE

No hyphal invasion occurs in HI

Explain mechanism of hyphal interference (HI)

Coiling of hypha of 1 species around another results in loss of normal membrane integrity → turgor pressure → hyphal death

_ refers to the behavior of several fungi that antagonize other fungi at points of contact, e.g., Podospora anserina

Hyphal interference (HI)

Explain 1 example of antagonism thru hyphal interference between fungi

• Hypha of Podospora anserina have coiled around C. globosum hypha, which has been killed via HI bc coiling around hypha leads to loss of normal membrane integrity > turgor pressure > hyphal death

• Dead C. globosum hypha is stained Trypan blue, unlike living P. anserina ones

*HI not parasitic = no hyphal invasion occurs
HI = behavior of several fungi to antagonize others at points of contact

Explain autolytic activity of Podospora

Podospora has autolytic ability and can perform hyphal interference on itself, observed as ascocarp containing only 2 ascospores instead of 4, to control the number of viable spores that it produces as a response to changing environmental conditions

T/F: Fungi that do hyphal inteference usually attack only at 1 point

FALSE

They attack at multiple points

_ refers to when a fungus lives on or inside another fungus and feeds on it, often harming it but not necessarily killing the host in the process

Mycoparasitism

The fungi that parasitize other fungi can be grouped into 2 broad categories: _

• Biotrophic mycoparasites establish a specialized feeding relationship, usually by producing a haustorium to penetrate and absorb nutrients from living fungal hyphae

• Necrotrophic mycoparasites invade and destroy a wide range of fungal cell hosts using inhibitory toxins or metabolites then feed on dead cell contents

_ refers to the group of mycoparasites that establish a specialized feeding relationship, usually by producing a haustorium to penetrate and absorb nutrients from living fungal hyphae

Biotrophic mycoparasites

_ is the most common mechanism of infection

Haustorium production

Explain mechanism of biotrophic mycoparasitism

• Most common mechanism of infection = haustorium production

• Spore or hypha of mycoparasite forms an infection peg that penetrates host cell wall

• It forms a haustorium inside host cell but outside host cell membrane; surrounded by extrahaustorial membrane + matrix > host cytoplasm

  • Neck band seals haustorium to allow tight control of nutrient flow

• Eventually, effector molecules are secreted by mycoparasite to manipulate fungal host cell

• These are delivered via secretory pathway and released via exocytosis into host interface (extrahaustorial matrix)

• Then possibly taken in by host cell via endocytosis (?)

Explain mechanism of necrotrophic mycoparasitism

• Trichoderma detects chemical signals from host & grows toward it

• It attaches to host hyphae then releases ROS + inhibitory compounds > distressed host hyphae

• Can also modulate hydrophobicity to improve adhesion & penetration

• SCf (protein complex) may interact with host signaling pathways, including MAPK + G protein that control chitin synthesis & virulence genes, allowing parasite to reduce host virulence and thus increase Botrytis vulnerability

• Once growing branch is cut off, they feed on dead parts

T/F: Necrotrophic mycoparasitism has more pronounced immediate effects than biotrophic mycoparasitism

TRUE

Bc biotrophic mycoparasites will try to keep their hosts well & alive

T/F: Both biotrophic and necrotrophic mycoparasites are host-specific

TRUE

_ refers to the group of mycoparasites that invade and destroy wide range of fungal cell hosts using inhibitory toxins or metabolites and then feed on dead cell contents

Necrotrophic mycoparasites

Explain 2 examples of biotrophic mycoparasitism (fungi-fungi)

• Biotrophic mycoparasites seldom kill their fungal hosts because they need to feed on living tissues

• (A) Piptocephalis unispora penetrating its fungal host C. recurvatus using an appressorium with a haustorium

  • Extrahaustorial membrane = where nutrient exchange happens

• (B) Mycoparasitism of Rhizoctonia solani by Verticillium bigattum showing spirally germinating spores continuing to attack living hyphae along multiple points

T/F: In biotrophic parasitism, the extrahaustorial membrane originates from the pathogen to protect the haustorium from the host's immune system

FALSE

The extrahaustorial membrane is host-derived, not pathogen-derived. It’s a modified host plasma membrane that surrounds the haustorium, maintaining separation while allowing nutrient exchange.

T/F: Both biotrophic and necrotrophic mycoparasites manipulate host gene expression using effector proteins

TRUE

Both use effectors, but for different goals:

• Biotrophs use effectors to suppress immunity and maintain host viability.

• Necrotrophs may use effectors or toxins to induce cell death or weaken defenses.

T/F: Necrotrophs can benefit from delayed host cell death to maximize nutrient yield before consumption

TRUE

While necrotrophs do kill, some may delay or modulate host death strategically to optimize breakdown and access to nutrients. Timing is everything in fungal warfare. So it's mostly true, depending on the species.

T/F: Biotrophic mycoparasites tend to kill their fungal cell hosts

FALSE

Biotrophic mycoparasites seldom kill their hosts because they need to feed on living tissues

T/F: Necrotrophic mycoparasites kill their fungal hosts and feed on dead tissues and exudates

TRUE

Give 2 examples of necrotrophic mycoparasitism (fungi-fungi)

• Necrotrophic mycoparasites kill their fungal hosts and feed on the dead tissues and exudates

• (A) Hypha of Botrytis cinerea contacting hypha of Pythium oligandrum, causing lysis of B. cinerea & subsequent invasion + hyphal branching (growth) of P. oligandrum

• (B) Antagonism of hyphal compartment of Fusarium oxysporum by Clonostachys rosea

  • The damaged compartment lost its turgor, while the adjacent compartments were unaffected

Apart from lichens, _ are uncommon between fungi

mutualism and commensalism

_ is when both organisms benefit from their association with each other

Mutualism

_ is when 1 organism benefits; the other is neither harmed nor benefitted

Commensalism

T/F: The relationship between Chaetomium thermophile and Thermomyces lanuginosus can be considered syntrophic

TRUE

Tl can only survive in cellulosic compost substrates w/ nitrate by using Ct degradation products, while Ct metabolism is improved when grown with Tl

Give 1 example of mutualistic interaction between fungi

• Thermomyces lanuginosus (Tl) = non-cellulosic compost fungus nccf

• Chaetomium thermophile (Ct) = cellulose-degrading compost fungus

• When Tl & Ct are grown separately on filter paper + nitrate,

  • Ct can grow bc it is cellulose-degrading, nitrate-metabolizing

  • Tl can’t bc it’s non-cellulosic, non-nitrate-metabolizing

• However, when Tl + Ct were grown together on filter paper + nitrate,

  • Ct provides degradation products that Tl can then use as C & N sources

*Growth of fungi in compost heaps (waste organic matter) = where fungal mutualism is usually observed

Between full mutualism - commensalism
Ammensalism = 1 harmed; 1 unaffected

_ species have been used as plant-protective biocontrol agents

Trichoderma

• Trichoderma species have been used as plant-protective biocontrol agents, as these are capable of: _(6)

• These are mainly used to _

• Spray soil w/ Trichoderma

• Exclusion = af ; antagonism = bec

  • cmai ab

  • Competition (exclusion)

  • Mycoparasitism (antagonism)

  • Antibiosis (antagonism)

  • Induced systemic resistance

  • Antagonism (antagonism)

  • Blocking a pathogen signal (exclusion)

• Mainly used to cpe

  • Control soil-borne diseases and some leaf & panicle diseases of various plants

  • Promote plant growth, increase nutrient utilization efficiency, enhance plant resilience

  • Establish a safe, low-cost, effective, eco-friendly slee biocontrol agents for different crop species

How does a fungus (e.g., Trichoderma) induce higher systemic resistance in plants?

Trichoderma can boost plant immunity by colonizing the roots and sending signals that “prime” the plant’s defense system, as these can activate hormone pathways, e.g., jasmonic acid, so that plants would respond faster & stronger when real pathogens attack

Explain Trichoderma species as biocontrol agents

• Trichoderma species have been used as plant-protective biocontrol agents

• Bc they’re capable of cmai ab

  • Competition (exclusion)

  • Mycoparasitism (antagonism)

  • Antibiosis (antagonism)

  • Induced systemic resistance

  • Antagonism

  • Blocking a pathogen signal (exclusion)

• And thus mainly used to cpe

  • Control soil-borne diseases and some leaf & panicle disease of various plants

  • Promote plant growth, increase nutrient utilization efficiency, & enhance plant resilience

  • Establish safe, low-cost, effective, eco-friendly biocontrol agents for different crop species

_ has been tested as biocontrol agents for conifer pathogens

Podospora hyphal interference (HI)

The formation of a barrage zone in an experimental setup is indicative of _ often due to _

• Antagonism (non-fusion)

• Chemical or physical defense between fungi

Explain Podospora as biocontrol agents against conifer pathogens

• Heterobasidion annosum infection on 5yo (A) & 12yo (B) Scots pine trees (rotting of roots + stems),

• showing (C) cell wall degradation & (D) fungal hyphal penetration

  • When plants age, they produce sclerenchyma, which has lignin + suberin for conducting water

  • When fungus secretes enzymes, these cause de-lignification of sclerenchyma, and bc lignin is degraded, sclerenchyma can no longer hold water and thus plant dies

• (E) Experimental setup showing (F) barrage zones between Podospora & Heterobasidion

  • Barrage zone = visible line/area of interaction where 2 fungal colonies meet but don’t grow into each other often due to antagonism

• (G) total overgrowth of Podospora at 20 days after HI

T/F: Podospora HI has been experimentally shown to penetrate Heterobasidion hyphae

TRUE

Based on the data, hyphal penetration was observed, which supports its role in direct antagonism

Why must one be cautious in testing out biocontrol agents in situ?

Bc you are introducing something not native to the environment and thus could have potential ecological effects, e.g., affect nutrient deposition, cause nutrient imbalance, etc.

_ refers to any of several prolonged living arrangements between members of 2 different species, including _

• Symbiosis mcp

  • Mutualism

  • Commensalism

  • Parasitism

Fungi have several symbiotic associations with _

paa

• Plants

• Algae / cyanobacteria

• Animals

_ is when fungi and their partners become so intimately dependent on one another that they have lost the ability to live alone

Obligate symbioses

Explain common types of symbiosis, fungus + their partners

mlger b&a sf

1. Mycorrhizae

   1. F: Asco-, Basidio-, Glomero-

   2. P: Land plants, e.g., Gymnosperms, Angiosperms, Bryophytes, Pteridophytes gabp

2. Lichens

   1. Asco-, sometimes Basidio-

   2. Green algae / cyanobacteria

3. Geosiphon pyriforme

   1. Glomerales-like fungus

   2. Nostoc (cyanobacterium)

4. Fungal endophytes of grasses

   1. Neotyphodium, Clavicipitaceous fungi

   2. Several grasses of family Poaceae

5. Rumen symbioses

   1. Obligately anaerobic Chytridiomycota

   2. Ruminant animals

6. Bark beetles & ambrosia fungi

   1. Various Basidio-, Asco-, mitosporic fungi

   2. Beetles

7. Siricid wood wasps

   1. Amylostereum areolatum (Basidio)

   2. Trees

8. Fungus gardens of leaf-cutting ants, termites, wood-boring beetles

   1. Basidio (Termitomyces, Leugaricus)

   2. Ants, termites, beetles

T/F: Fungi are involved in a wide range of intimate symbiotic associations with other organisms that shape many aspects of global ecology

TRUE

Explain 3 main types of symbioses

• Symbiosis = any of several prolonged living arrangements between members of 2 diff species, including mutualism, commensalism, parasitism

• Fungi have several symbiotic interactions with plants, algae/cyanobacteria, animals

• Obligate symbiosis is when fungi & their partners become so intimately dependent on 1 another that they’ve lost ability to live alone

• Types of symbiosis + fungi + other partners

  • mlger b&a sf

Enumerate examples of mutualistic interactions of fungi with other organisms

pemac elwa

• Plant endophytes

• Mycorrhizae (AMF, EMF)

• Algae & Cyanobacteria as

  • Endophytes

  • Lichens

• Animals symbioses

  • Wood wasps

  • Arthropods

_ live inside plants and may protect them against parasites (have anti-herbivory activity)

Endophytes

T/F: Fungal endophytes derive nutrients from their plant hosts but not to the extent that the plant is robbed off of majority of what it produces

TRUE

_ are mutualists (can be parasitic or commensal) deriving nutrition & safety from within plant tissues; in return, they have anti-herbivory activity, producing compounds such as alkaloids that protect plant against herbivory/parasites

Intracellular endophyte

Explain fungi symbioses as plant endophytes

• Endophytes = live inside plant & may protect them against parasites

• Intracellular endophytes = mutualists (can be parasitic or commensal) deriving nutrition & safety from within plant tissues

• In return, they have anti-herbivory activity, producing compounds, e.g., alkaloids, that protect plant against herbivory/parasites

• In an experiment, they infested (1) a plant with fungal endophytes (Neotyphodium lolii) and (2) a plant with no fungal endophytes with an equal number of aphids

• After several days, they observed that the plant with fungal endophytes had significantly less aphid infestation, supporting the anti-herbivory activity of fungal endophytes in plants