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Microbes, Fungi and
Stramenopiles
Lecture 16 - Introduction To Fungi
The Kingdom Fungi
Fungi are NOT plants ( they are closer to animals than to plants)
Very important roles in all ecosystems
→ nutrient cycling
Several organisms are sometimes grouped under the term ‘fungi’
→True fungi
→ Slime moulds
→ Water moulds
But here we consider only true Fungic

From 2 to7 Kingdoms
Animalia
Plantae
Chrimista

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Protozoa
Fungi
Bacteria (prokaryote)
Archaea (prokaryote)

Diversity
Estimated to be >3
...

→ 5
...
5 times!
Perhaps >90-95 % of fungal species yet to be described
...

Many up-to-date checklists available
...

Tedersoo et al
...
Science 346: [10
...
1256688]

⇒ Esher Common, Surrey

→ Heath and semi-natural woodland
→ 3300 species in 380 ha
Kew Gardens, Surrey

⇒

→ Parkland
→ 2600 species in 132 ha
Slapton Ley, Devon
→Parkland
→ 2400 species in 250 ha

⇒

What are Fungi? Ordovician period
Eukaryotic (nuclease surrounded by membrane)
Typically filamentous
→ individually termed hyphae
→ exhibit apical growth ( growth of hyphae at apex but no meristem)
→ form networks of hyphae called mycelium
Heterotrophs (nutrition comes from external sources - cannot manufacture it
themselves )
Reproduce by spores ( do not know their sexual life cycle- may have lost it
and don't need it so they reproduce asexually)
→ both sexual and asexual
They are membrane bound nuclei containing several chromosomes
Range of membrane bound organelles
Inside hyphae can see cytoplasmic streaming (moving nutrients from one place
to another)
Need pre-formed organic compounds as energy sources and as C source for
cellular synthesis
...

On agar, a centrally placed inoculum develops into a circular colony
...

There is a centrifugal flow of nutrients from the centre to the periphery of a
colony
...
Most fungus tissue grows inside opaque
substrates, such as wood or soil
...
(along grain or across grain)

Fungi
True fungi
– Chitin in the cell walls, all probably with a common ancestor
Slime moulds

Microbes, Fungi and Stramenopiles

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- have free-living spores which come together for sexual reproduction (when
environmental conditions are less bad) are but grow as wall-less protoplasmic
stages
...
The cell walls contain chitin and ß-glucans, and their
mitochondria have flattened cristae
Spooner & Roberts (2005) Fungi

Currently 5 phyla
1
...
Glomeromycota
3
...
Ascomycota
5
...
Symbionts (mutualistic or parasitic) that depend on another
organism, or host, for nutrition
→A
...
Mutualistic symbionts of plants
→C
...
Saprotrophs which utilize dead material for nutrition
A) Fungal parasites of plants

Microbes, Fungi and Stramenopiles

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A parasite that causes disease is called a pathogen
Fungi and fungus-like organisms cause more than 70% of all the major crop
diseases
→Blights, rusts, smuts, mildews, vascular wits
Necrotrophic parasites: kill host tissue as part of feeding process
...

Examples: mycorrhizal fungi and the fungi in lichens
C) Fungal Parasites of animals: humans
Rather few fungi infect warm blooded animals
...

Lung infections arise from opportunistic parasites which are generally soil
saprotrophs
...
g
...


⇒Example: White-Face Disease of Bats
...

• In some caves more than 90% of resident bats have succumbed to ‘white
nose syndrome’, caused by the fungus Geomyces destructans
...


⇒Example: Cryptococcus neoformans

• Lung infections - ‘cryptococcosis’ (also fungal meningitis and
encephalitis)
• Mostly in immunocompromised patients
...

Fungi can utilize nearly all organic compounds
...
40% of plant structural material
...
e
...


Take home points
Fungi are heterotrophs, reliant on the degradation of organic materials for
nutrition
Fungi have a critical role in nutrient cycling
Fungi include saprotrophs, parasites (pathogens), mutualists

Lecture 17 - Fungi as Plant Pathogens
Definitions
Plant Pathology = the study of plant diseases
→"Some disturbance in normal life processes which affects either a particular
organ or the entire plant, and which sometimes leads to premature death"
...

→“A harmful deviation from the normal functioning
of physiological processes"
...


Why are plant pathogens important?
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Reduction in crop yield (reduced food production, reduction in timber)
Environmental damage (species of plant to be killed off )
Biodiversity impacts - other organisms ay need it for survival
Economic implications ( farmers get less money)
Social implications (reduction in food means people get less food)
Human health and welfare

A short history
Cereal Rusts
Black stem rust of wheat: environmental conditions made a difference about how
bad the disease was in any give season
Puccinia graminis var
...

➢ Rust outbreaks were so feared that there was a god/goddess
of rust (Robigus) to whom sacrifices and feasts were dedicated
to prevent crop destruction
...

→ By 1880, tea was planted on 120,000 ha, as
coffee production reduced drastically
...

Cereal smut diseases
-Ustilago spp
• All cereals are attacked by smuts
• Most smut fungi attack the internal tissues of the grain, replacing them with
grey, dark brown or black smut spores
...
Rickety children clutching
imploringly the tattered garments barely covering the bones of
their mothers are seen in all quarters of the city
...
K
...
Alexis Millardet noticed grapes covered with a
bluish-white wash along a road in Bordeaux
→Treated grapes had healthy leaves while neighbouring
plants had serious mildew
→The vineyard owner had sprayed the grapes with a
mixture of lime and copper sulphate to discourage thieves
→Millardet experimented with different combinations of
lime, iron, and copper salts
→The best combination was close to the original
formulation
He called it Bordeaux mixture- first development of fungicide

⇒

Panama Disease of Banana Fusarium oxysporum f
...
cubense
→Global value of banana trade in 2016: US $ 11
...
sp
...
’
• Used infected rhizomes to establish new plantations
• Widespread and severe losses, especially in the western tropics
• Switched to Cavendish cultivar

⇒ ‘New’ race emerged – race 4 now widespread

• A threat to the Cavendish group!
• First noted in Australia, Canary Islands, South Africa
• Now widespread
Cocoa witches’ broom - Moniliophthora (Crinipellis) pernicious

Microbes, Fungi and Stramenopiles

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• Cocoa witches’ broom
• The most important disease affecting cocoa production in regions where the
disease occurs
• May reduce harvests by 90%
• Pathogen spreads via wind-borne spores
• Requires very high moisture to germinate and infect hosts
Dutch Elm Disease‘The most destructive plant disease ever recorded"
Chestnut blight - Cryphonectria parasitica
• First reported in USA in 1904 on Castanea dentata in New York City
...
dentata
...

• Estimated >8 billion trees killed in 40 years…

Take home points
Fungal pathogens may cause massive damage to crops, reducing yields and
impacting on human health
...

Fungal pathogens can also be highly destructive to natural ecosystems
...

Simple organic materials are degraded by Ascomycota (or mitosporic species),
with rapid life cycles
...


Wood decay fungi

Microbes, Fungi and Stramenopiles

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Saprotrophic Basidiomycota in the (large) sub-division Agaricomycota (visible
mushrooms)
Class Agaricomycetes
White rot fungi possess a range of oxidase enzymes for lignin degradation
Lead in decomposition and hence in mineralization in woodland ecosystems

White Rot
White rot fungi can degrade lignified cell walls, metabolizing lignin, cellulose,
xylans and pectins
...


⇒ Examples:

• Armillaria spp
...

• Phellinus spp
...

Over 40 species world-wide

⇒

produce aggregated and melanised cords of mycelium in forest that grow from
colonised chunk of wood
A few species pathogenic on trees
Most are saprotrophic on dead wood

⇒

Bioluminescence - Armallaria mellea (maybe luciferase gene)
Ganoderma
Many species worldwide - very common
Temperate and tropical regions
Heartrot of broadleaved trees
Root disease of tropical palms and trees
Phellinus
Many species world-wide

Microbes, Fungi and Stramenopiles

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Heart rot and root rot in tropical and temperate trees ( decay dead material in
centre of tree)

Lignin- Degrading Enzymes

⇒ Possessed by white rot fungi

• Manganese-dependent Lignin peroxidases (MnP)
• Lignin peroxidases (LiP) - less common
• Versatile peroxidases (VPs) -discovered recently
• Laccases

Brown Rot
Brown rot fungi degrade cellulose, xylans and pectins, but have limited effects
on lignin
...

→Examples:
• Serpula lacrymans (dry rot)
• Phaeolus schweinitzii (brown cubical rot)
• Laetiporus sulphureus (yellow polypore;
chicken of the woods)
Serpula lacrymans - Dry-rot
The most significant decay problem on timber in service (buildings)
Causes deep cracks in timber
Spreads across brickwork and plaster via hyphal aggregations = rhizomorphs (
lets out liquid that runs down on walls)
Phaeolus schweinitzii: brown cubical rot
Very common in soils
Significant problem in some managed coniferous forests
Occasional on broadleaved trees
Badly decayed trees liable to snap in winds
Laetiporus sulphureus: chicken of the woods
Very common on old oak trees

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Found on a wide range of broadleaved trees
Occasionally found on yew
Large prominent bracket is annual (orange-yellow) (produce spores)
Possibly a complex of several closely related species
Aerial litter traps in tropical forests
'Glue Fungus' Hymenochaete corrugata
→Glues dead hazel twigs live branches (as living branch declines this twig is in
prime condition to colonise)

Dung fungi (Coprophilous)

⇒Highly successional

• Zygomycota
→2-3 days (gut of cattle) - use nutrients in early stages
• Ascomycota
→ 6-12 days (gut of cattle) • Basidiomycota
→ 9 + days - more complex materials
→ Coprinus spp
...
g
...
, Aspergillus spp
...


Microbes, Fungi and Stramenopiles

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Many Agaricomycetes are involved in saprotrophic degradation
...


Lecture 19 - Fungal lifestyles - symbionts
Symbionts
Symbiosis: two or more organisms living together
Mutualism : both partners are benefitting (ox peckers on buffalo up his nose and
ears extracting parasites and birds gaining food )

⇒ Lichens: fungus + alga or cyanobacteria

→ good example of mutualism - their main structure is a fungus and cannot
generate own sources of carbon so it needs external sources and gets them by
forming associations with these species
→ a lichen is a combination of a fungus which forms main structure and alga or
cyanobacteria that photosynthesise and produce sugars that fungus can utilize

Fungal lifestyles : Mycorrhizal fungi
Classic definition: a mutualist association between plant roots and soil fungi
Over 90% of all land plants so far examined form associations with soil fungi
Mutualism based on the transfer of soil-derived nutrients to the plant from the
fungus and the
reciprocal transfer of photosynthate
→ Association first described by AB Frank (1885) looked at it because Kaiser
Wilhelm wanted German truffles and charged frank with discovering how to grow
German truffles

⇒ Truffle is fruit body mycorrhizal fungus
Mykes - fungus
Rhiza - root
Mycorrhiza = fungus fruit
Association works by pine seedlings which have been inoculated by mycorrhizal
fungi and the fungus has grown out over the substrate ( the soil) and show

Microbes, Fungi and Stramenopiles

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mycelium growing out above substrate
Can use radioactive tracer , in this case P32 and add it down the bottom and
follow where tracer ends up by using radioactivity ( see how P32 is taken up by
fungus and gets transported through mycelium through roots and up to the shootsfungus taking up phosphorus

⇒ Transfer from fungus to the plant

Can do it in reverse by labelling plant with radioactive tracer C14 - plant takes up
radioactive carbon dioxide, fixes it into sugars and these are transported out into
the into the roots and out into the fungus
Autoradiograph - shows the dark lines represent radiation effectively

⇒ radioactive sugars have been transported into mycelium and then around

mycelium so gugus can utilize them

⇒ mutualism based on reciprocal transfer
→ nutrients taken up from soil by fungus transported to the plant and fungus in
return get sugars

Mycorrhizal Fungi Information
Around 420 Million years ago (rhynie chert fossils) Long thin structures - fungal hyphae
→ same structures in roots today - similar to club mosses
→D
...
Read, J
...
Duckett, R
...
Ligrone and A
...
Trans
...
Soc
...
B (2000) 355, 815-831

⇒ all groups of terrestrial plants with exception of mosses since they lack

root structure form associations with mycorrhizal fungi → ubiquitous

Importance of mycorrhiza
Colonisation of plant roots by mycorrhizal fungi can have profound effects on
plant growth
grows bigger with fungi

⇒

→ Big plant/Little plant experiment (plantago lanceolata)
→ There's a cost to the plant : 10-30% of carbon fixed by the plant may be
acquired by the mycorrhizal fungi

Microbes, Fungi and Stramenopiles

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Important in soil formation and stability: colonised and linked my mycorrhizal
hyphae and the combined action of the plant roots binds the soil together
→ length of mycelia in soil 5-640mg-1
→ length per metre of root 50-1200m
The mycelium of mycorrhizal fungi are a very important resource for soil
fungivores
Hyphae extend beyond depletion zones surrounding roots and can penetrate
microsites (where plant roots cannot) - have access to parts that roots dont have
access to
Mycorrhizal hyphae are very efficient at soil exploration and at extracting
nutrients from the soil
→ Hyphae are not simply just physical extensions of the root system
Fungi massively increases the volume of soil which is explored and extracted
for nutrients - better at extracting nutrients than plants themselves

7 Types of mycorrhizas
Arbuscular mycorrhizas (AM) most common - fungi invade plant roots and
cells and produce arbuscules (sites of transfer between fungus and plant- fruit
body and reproduce spores directly on mycelium)
→ Arbuscules last for between 5 and 15 days (penetrates into cell and branches
and divides and start to degrade and cell can be reinvaded)
→ Found in Pteridophytes (ferns) , bryophytes (only liverworts and hornworts
which produce light hairs), angiosperms (flowering plants) , gymnosperms (conifers)
Ectomycorrhizas more restricted - most plants that form ectomycorrhizas are
tree species - long lived woody perennials - colonises root and forms sheath
(mantle) around root to isolate it from soil and it goes between the cells and
forms large surface area where transfer takes place
penetration

⇒ no intracellular

→ 99% of all root tips are colonised by the fungus - fungus separates out plant
from soil - everything going into plant has to go through fungus = control what goes
into and out of plant
→ Fungi massively increases the volume of soil which is explored and
extracted for nutrients - better at extracting nutrients than plants themselves

Microbes, Fungi and Stramenopiles

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Ericoid mycorrhizas
Orchid mycorrhizas
Ectendomycorrhizas
Monotropoid mycorrhizas
Arbutoid mycorrhizas
Weathering of soil minerals by ectomycorrhizal fungi
→Jongmans et al
...
1998
...

The more mycorrhizal fungi in the soil then the greater the number of plant
species you can have growing in that area = increased productivity with
increasing diversity
the more diversity below ground = the greater the diversity that can be sustained
above ground

Microbes, Fungi and Stramenopiles

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Read DJ (1991) Mycorrhizas in ecosystems
...

→ Linked plant traits and mycorrhizal associations to present day ecosystem
→ First showed that all of our ecosystems have developed with the mycorrhizal
association in place and plant traits have evolved in association with the mycorrhizal
fungi associated with particular plant
→ All of our ecosystems are on a gradient from northern boreal down to more
temperate and Mediterranean grasslands
→ Soil characteristics also follow this gradient

⇒ Huge impact in development of all ecosystems we see
Lecture 20 - Kingdom Stramenopila
Stramenopila
Over 25,000 known species
Many more to be discovered
Biflagellate:
→ haploid stage and is male and transfers DNA to female receptive structure
→ Anterior tinsel flagellum
→ Anterior whiplash flagellum
Aquatic and soil-borne

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Cell walls have cellulose
→ (beta-1,4 glucose linkages)
Other Characteristics:
→ Motile spores formed in a sporangium
→ Sexual reproduction by gametangial contact (antheridium attaches to
oogonium (female) and injects DNA into oogonium that goes to form diploid
stage with fusion of DNA in oogonium nucleus)
→ produces sporangium and it ruptures and spores swim away
→ Most of the life cycle is diploid
→ Somatic structures:
– unicellular and holocarpic
– or rhizoidal (hold to substrate)
– or coenocytic hyphae

Stramenopila: the Phyla
Bacillariophyta - diatoms fresh water algae - photosynthetic
Chrysophyta – golden algae -photosynthetic
Oomycota – water moulds
Phaeophyta – brown algae
Rhodophyta – red algae
– could be a separate Kingdom?
Chlorophyta – (many) green algae
– could be a separate Kingdom?

Bacillariophyta: The diatoms
Marine and freshwater planktonic unicellular algae - upper reaches of ocean
Responsible for circa 20% of global carbon fixation (extremely important)
Silicate shell (rigid - usually symmetrical)
Most species are photosynthetic
Chloroplasts are similar to those found in red algae (Rhodophyta
Reproduction is mostly asexual, by binary fission (two halves of silicate shell
separate and a new side is put in - one side is smaller yet forms bigger side reach point where cell size is reduced to limit)

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Sexual reproduction produces the auxospore, lacking the shell
...
5 million
Population in 1851 = 5 million
Starvation and emigration
Heinrich Anton de Bary (1831 – 1888) - father of study of plant diseases
Surgeon, botanist, mycologist
‘Founding Father’ of plant pathology
Studied life histories of ‘fungi’ - thought potatoes were hit by fungi
Elucidated life cycle of ‘Peronospora infestans’
Inoculation tests proved the causal organism
Supported Pasteur’s claim that organisms did not arise spontaneously infections and contaminations causing things to go off

Pythium – important diseases (Oomycota)
Root rot of plants growing in moist conditions (carrot)
Plant pathogenic species tend to be generalists
Parasitic on some true fungi (hyper parasites)
Skin infection on mammals
"damping off" - attacks young plants as they are germinating from the seed
Pre emergence damping off attacks before it can grow above ground and post
emergence damping off - dried out and killed after appearing above ground
Pythium produce Asexual Zoosporangia - enables them to disperse in moist
environments

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Peronospora: ‘Downy Mildews’ (Oomycota)
Obligate parasites - cannot grow in culture and need living host material to grow
Branched, determinate sporangiophores
Sporangiophores protrude through host stomata - spores that emerge are not
motile but still need high humidity

Saprolegniales (Oomycota)
elongated terminal sporangia - difference - terminal sporangium
more than one egg per oogonium
Abundant in water courses- lakes
Can exist saprotrophically on dead organic matter
Several pathogens on fish, fish eggs, amphibians, invertebrates
Saprolegnia – important diseases
→White fin disease of fish (infection - common)
Several species of Oomycete pathogens in the genus Saprolegnia
Very common in freshwater courses throughout the world
...


Phaeophyta – brown algae (multicellular)
Fossil records are sparse - soft tissue
First ‘confirmed’ fossils are from 150-200 million years ago
...
450 million years ago
...

Between 4 and 6 Phyla (uncertainty about red algae and green algae)
...

Highly diverse organisms:
→ Photosynthetic and non-photosynthetic
...


Microbes, Fungi and Stramenopiles

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