BIOS-110 Fungal Biology Lecture 3 - Fungal nutrition, growth and reproduction

Transcription

1 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.

2 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

3 Image from MAF slides Image from MAF slides Powdery mildew on pea Mycelium and spores t_of_soybean_white_mold Mycelium of Sclerotinia infecting beans Hyphae of Athlete foot fungus

4 Powdery mildew (rysiphe pisi) Germinating spore Colony forming Image: R Falloon, PW Sutherland & IC Hallett Hyphae branching and growing Falloon et al Can. J Bot 67: Image: R Falloon, PW Sutherland & IC Hallett Sporulation, chains of spores Image: R Falloon, PW Sutherland & IC Hallett Upright branches in older part of colony

5 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 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 stimated to be 2400 years old From: Young persons guide to the Fungi Kendrick A

6 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

7 4. In older regions of the mycelium, substrate nutrients exhausted, so growth ceases; xisting components used to produce spores Hyphae die (autolysis) Image. Bourguignon LU

8 Botrytis cinerea lesion on grape leaf Botrytis cinerea rot of grape berries s/images/ringworm.jpg Ring worm on scalp Basket fungus (Ileodictyon cibarium)

9 Unicellular fungi Yeasts most common types Cell structure similar to hyphal compartment Sacchromyces internal structure (from Microbiology, Prescott )

10 Growth by increase in number of individuals. Two ways:- Fission ach 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 off. N.B. High rate of multiplication 1 cell 1 billion in 10 h ppdictionary.com/fungi Dimorphic fungi From: Fungi, man and his environment, Cook RC /images/2011/schizo-fissionyeast-v2.jpg These convert between mycelial and unicellular forms. nvironment changes trigger it

11 Nutrition Heterotrophic preformed organic material 1. xternal digestion fungi grow into/next to food sources hyphal tip secrete enzymes to OUTSID degrade food into small soluble molecules 2. Adsorptive nutrition Breakdown product absorbed, often by cells in position 3-10 behind tip

12 polysaccharide nzymes TIM 0 TIM 12h TIM 24h Image irian Jones TIM 36h

13 Nutrition 3. Complex enzyme systems nzymes turned on & off in response to nutrient types 4. xcretion of wastes, antibiotics etc. Causes staling of medium

14 Commonly seen fungal growths 1. Foliar diseases e.g. Botrytis rot in grapes Botrytis cinerea rot of grape berries

15 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 mages/ringworm.jpg

16 3. Fairy rings xpanding 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 /Fairy_Ring_400.jpg 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

17 From: The Biology of Fungi, Ingold CT Fungal colony Advancing edge of fungal colony Fungus grows cm /year Dying rear of fungal colony

18 Fairy rings - Marasmius oreades

19 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 growth ceases xisting components used to produce spores Hyphae die (autolysis) 1 2 Image. Bourguignon LU

20 Fungal reproduction 1. Almost all fungi produce SPORS on special hyphal branches From: The Biology of Fungi, Ingold CT 2) Most fungi produce both an ASXUAL and a SXUAL spore type 3) There is a great variety of forms in spores and spore-bearing structures basis of classification

21 (from Plant Pathology, Agrios)

22 1. Most spores have:- Spore structure 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

23 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.