BIOS-110 Fungal Biology
Lecture 3 - Fungal nutrition, growth and
reproduction
• Describe the features of a typical mycelial colony
and how this relates to what we know about how
fungi grow
• Outline the two ways in which yeast cells divide
• Define heterotrophic nutrition and describe how
fungi obtain their nutrition
• Describe how a fairy ring is formed (structure and
nutrition of the fairy ring fungus).
• Outline the different functions of spores.
• Outline the different spore dispersal
mechanisms.
Tip initiation and branching
• Apical dominance occurs in hyphae
• Several factors influence branching
• Higher nutrient quality of growth medium →
more branches → dense mycelium
• Mycelial regulation – some evidence
• Branch position, often behind septum – vesicle
trapping?
Fungionline.org.uk/images/1intro/hyphae1.JPG
Image from MAF slides
Image from MAF slides
http://msue.anr.msu.edu/news/managemen
t_of_soybean_white_mold
Powdery mildew on pea
Mycelium and spores
Mycelium of Sclerotinia
infecting beans
http://www.gettyimages.co.nz/detail/illustration/athletes-foot-fungusstock-graphic/125744200
Hyphae of Athlete foot fungus
Powdery mildew (Erysiphe pisi)
Germinating spore
Colony forming
Hyphae – branching
and growing
Image: RE Falloon, PW Sutherland & IC Hallett
Falloon et al. 1989. Can. J Bot 67: 3410-3416.
Image: RE Falloon, PW Sutherland & IC Hallett
Image: RE Falloon, PW Sutherland & IC Hallett
Sporulation, chains of spores
Upright branches in older part of colony
Colony profile
1. Apical growth means that
• Mycelium expands in
diameter
• Often circular or
spherical shape
• Limited only by nutrients
• Outer edges of mycelium youngest and inner
regions oldest
From: Young persons guide to the Fungi
Kendrick A
• The largest organism (by area) is a fungus –
Armillaria spp. (honey fungus) colony in a forest in
Oregon
• Diameter 8.9 km (890 hectares/2200 acres)
• Total colony mass 605 tons
• Estimated to be 2400 years old
2. Outer hyphae grow towards fresh food substrates
– drives growth
3. Hyphal branches may fuse where they touch
(anastomose)
Rhizoctonia solani hyphal anastomosis
From Modern Mycology, Deacon
4. In older regions of the
mycelium, substrate nutrients
exhausted, so growth
ceases;
→ Existing components used
to produce spores
→ Hyphae die (autolysis)
Image E. Bourguignon LU
http://djsgrowers.blogspot.co.nz/2013/01/what-is-difference-between-noble-rot.html
Botrytis cinerea lesion on
grape leaf
Botrytis cinerea rot of grape berries
https://www.flickr.com/photos/essjay/164675851
http://www.mattersingray.com.au/h73rdr53s/staff_room/magazine
s/images/ringworm.jpg
Ring worm on scalp
Basket fungus (Ileodictyon cibarium)
Unicellular fungi
• Yeasts most common types
• Cell structure similar to hyphal compartment
Sacchromyces internal structure
(from Microbiology, Prescott )
http://www.rpi.edu/dept/chem-eng/Biotech-Environ/beer/yeast/yeast2.htm
Growth by increase in number of individuals. Two ways:• Fission
Each cell grows to maximum size, doubles all
components, new wall divides cell through centre
• Budding
Parent cell produces a small ‘knob’ on outside which
grows until large enough to be independent – is ‘walled’
ppdictionary.com/fungi
off.
N.B. High rate of
multiplication
1 cell → 1 billion in 10 h
Dimorphic fungi
From: Fungi, man and his environment, Cook RC
• These convert between mycelial and unicellular forms.
Environment changes trigger it
https://www.broadinstitute.org/files/news
/images/2011/schizo-fissionyeast-v2.jpg
Nutrition
Heterotrophic – preformed organic material
1. External digestion
• fungi grow into/next to food sources
• hyphal tip secrete enzymes to OUTSIDE
• degrade food into small soluble
molecules
2. Adsorptive nutrition
Breakdown product absorbed, often by cells
in position 3-10 behind tip
polysaccharide
E
TIME 0
Enzymes
E
E
TIME 12h
E
E
E
E
TIME 24h
E
E
E
E
E
E
TIME 36h
Image Eirian Jones
E
E
E
E
Nutrition
3. Complex enzyme systems
Enzymes ‘turned’ on & off in response to
nutrient types
4. Excretion of wastes, antibiotics etc.
Causes ‘staling’ of medium
Commonly seen fungal growths
1. Foliar diseases
e.g. Botrytis rot in grapes
http://djsgrowers.blogspot.co.nz/2013/01/what-is-difference-between-noble-rot.html
Botrytis cinerea rot of grape berries
2. Ringworm in humans and animals
• Symptoms – expanding, itchy, pink rings on
skin
• Centre of lesions are dry and scaly
• Transmission - usually by dead skin cells
on furniture etc.
- rarely from animals
http://www.mattersingray.com.au/h73rdr53s/staff_room/magazines/i
mages/ringworm.jpg
https://i.ytimg.com/vi/G2U1CbMazQg/hqdefault.jpg
3. Fairy rings
• Expanding rings of lush grass
growth in pasture and lawns
• Fungus grows in soil
• At advancing front, it produces enzymes which
degrade soil organic matter
→ nutrients products into soil
→ Absorbed by fungus & adjoining grass roots
→ Lush grass growth
• Fungal front grows on
• Behind, a starvation zone (water, nutrients efficient
fungus) → grass dies
also produces Hydrocyanic acid – toxic to grass roots
• As old fungal hyphae break down, they release their
components into the soil → grass recovers
http://www.interhort.com/_images/_cms/Image
/Fairy_Ring_400.jpg
Fungal colony
From: The Biology of Fungi, Ingold CT
Advancing edge of
fungal colony
Dying rear of
fungal colony
Fungus grows 10-15 cm /year
http://www.cpbr.gov.au/fungi/imagesmisc/mycelium/mycelium2g.gif
Fairy rings - Marasmius oreades
http://www.lawnscience.co.uk/lawn-issues/fairy-rings/
http://www.k-state.edu/turf/images/problem-solver/off-color/dark/fairyring/fairy_ring.jpg
http://www.daviddarling.info/images/fairy_ring_in_field.jpg
Fungal reproduction
Fungi grow vegetatively (only hyphae) as long as
nutrients available – Assimilative mode
When food runs out, fungus switches to
reproductive mode – produces spores.
Outer edge of colony – fresh substrate (1)
Centre, older regions of the mycelium (2) substrate
nutrients exhausted
1
→ growth ceases
→ Existing components used to
2
produce spores
→ Hyphae die (autolysis)
Image E. Bourguignon LU
Fungal reproduction
1. Almost all fungi produce SPORES on special
hyphal branches
From: The Biology of Fungi, Ingold CT
2) Most fungi produce both an ASEXUAL and a
SEXUAL spore type
3) There is a great variety of forms in spores and
spore-bearing structures – basis of classification
(from Plant Pathology, Agrios)
Spore structure
1. Most spores have:• Multilayered wall, often impregnated with
pigments and lipids
• Cytoplasm with a low water content &
high storage materials e.g. lipids,
glycogen, trehalose
• Little internal differentiation
• Low metabolic rate
BIOS-110 Fungal Biology
Lecture 3 - Fungal nutrition, growth and
reproduction
• Describe the features of a typical mycelial colony
and how this relates to what we know about how
fungi grow
• Outline the two ways in which yeast cells divide
• Define heterotrophic nutrition and describe how
fungi obtain their nutrition
• Describe how a fairy ring is formed (structure and
nutrition of the fairy ring fungus).
• Outline the different functions of spores.
• Outline the different spore dispersal
mechanisms.