Kingdom Fungi

1
Kingdom Fungi

• The characteristics of fungi
• The evolution of the fungi
• Fungal classification
• Fungal life cycles
• Human-Fungus Interactions

2
The Characteristics of Fungi

• Body form
• unicellular (yeasts)
• filamentous (tube-like strands called hypha
  (singular) or hyphae (plural)
• mycelium aggregate of hyphae
• Some fungi are dimorphic!
• Multicellular
• sclerotium hardened mass of mycelium that
  generally serves as an overwintering stage.
• multicellular, such as mycelial cords,
  rhizomorphs, and fruit bodies (mushrooms)

3
The Characteristics of Fungi

• Heterotrophy - 'other food'
• Saprophytes or saprobes - feed on dead tissues or
  organic waste (decomposers)
• Symbionts - mutually beneficial relationship
  between a fungus and another organism
• Parasites - feeding on living tissue of a host. 
• Parasites that cause disease are called
  pathogens.

4
Heterotrophic by Absorption

• Fungi get carbon from organic sources
• Hyphal tips release enzymes
• Enzymatic breakdown of substrate
• Products diffuse back into hyphae

Products
Enzymatic breakdown
Nucleus hangs back and directs
Enzymes
Product diffuses back into hypha and is used
5
Hyphae

• Tubular
• Hard wall of chitin
• Crosswalls may form compartments ( cells)
• Multinucleate
• Grow at tips

6
Hyphal growth

• Hyphae grow from their tips
• Mycelium extensive, feeding web of hyphae
• Mycelia are the ecologically active bodies of
  fungi

This wall is rigid
Only the tip wall is plastic and stretches
7
Modifications of hyphae
8
Fungi as Saprobes and Decomposers
9
Fungi as Symbionts (Mutualism)
10
Mycorrhizae

• Fungus roots
• Mutualism between
• Fungus (nutrient water uptake for plant)
• Plant (carbohydrate for fungus)
• Several kinds
• Zygomycota hyphae invade root cells
• Ascomycota Basidiomycota hyphae invade root
  but dont penetrate cells
• Extremely important ecological role of fungi!

11
Ectomycorrhizae
Russula mushroom mycorrhizas on Western Hemlock
root
Mycorrhiza cross sections
Fungal hyphae around root and between cells
12
Lichens

• Mutualism between
• Fungus structure
• Alga or cyanobacterium provides food
• Three main types of lichens
• Crustose lichens form flat crusty plates. 
• Foliose lichens are leafy in appearance, although
  lobed or branched structures are not true leaves.
  
• Fruticose lichens are even more finely branched
  and may hang down like beards from branches or
  grow up from the ground like tiny shrubs.

13
Lichen internal structure

• Lichens are natures biological monitors of
  pollution and air quality
• Thalli act like sponges
• Some species more sensitive to pollution
• Which species are present can indicate air
  quality
• Most resistant species can also be analyzed for
  pollutants, including bioaccumulation of heavy
  metals and radioactive isotopes

Lobaria
14
Fungi as Parasites Pathogens
15
Fungi are Spore-ific!!!

• Spores - asexual (product of mitosis) or sexual
  (product of meiosis) in origin.
• Purpose of Spores
• Allows the fungus to move to new food source.
• Resistant stage - allows fungus to survive
  periods of adversity.
• Means of introducing new genetic combinations
  into a population

16
Reproduce by spores

• Spores are reproductive cells
• Sexual (meiotic in origin)
• Asexual (mitotic in origin)
• Formed
• Directly on hyphae
• Inside sporangia
• Fruiting bodies

Penicillium hyphae with conidia
Pilobolus sporangia
Amanita fruiting body
17
Hyphal growth from spore
germinating spore
mycelium

• Mycelia have a huge surface area

18
The Characteristics of Fungi

• Fungus is often hidden from view. It grows
  through its food source (substratum), excretes
  extracellular digestive enzymes, and absorbs
  dissolved food.
• Indeterminate clonal growth.
• Vegetative phase of fungus is generally
  sedentary.

19
The Characteristics of Fungi

• Cell wall present, composed of cellulose and/or
  chitin.
• Food storage - generally in the form of lipids
  and glycogen.
• Eukaryotes - true nucleus and other organelles
  present.
• All fungi require water and oxygen (no obligate
  anaerobes).
• Fungi grow in almost every habitat imaginable, as
  long as there is some type of organic matter
  present and the environment is not too extreme.
• Diverse group, number of described species is
  somewhere between 69,000 to 100,000 (estimated
  1.5 million species total).

20
Generalized Life Cycle of a Fungus
21
Evolution of the fungi
22
asci
basidia
zygosporangia
Classification Phylogeny
motile spores
23
Chytridiomycota chytrids

• Simple fungi
• Produce motile spores - zoospores
• Mostly saprobes and parasites in aquatic habitats
• Could just as well be Protists

Chytridium growing on spores
Chytriomyces growing on pine pollen
24
Zygomycota zygote fungi
Rhizopus on strawberries

• Sexual Reproduction - zygosporangia
• Asexual reprod. common (sporangia bags of
  asexual spores)
• Hyphae have no cross walls
• Grow rapidly
• Decomposers, pathogens, and some form mycorrhizal
  associations with plants

Rhinocerebral zygomycosis
25
Sexual zygsporangium with one zygospore
Asexual sporangium with spores inside
Life cycle of Rhizopus
26
Ascomycota sac fungi

• Sexual Reproduction asci (sing. ascus)
• Asex. Reprod. common
• Cup fungi, morels, truffles
• Important plant parasites saprobes
• Yeast - Saccharomyces
• Decomposers, pathogens, and found in most lichens

A cluster of asci with spores inside
27
Sac fungi diversity
28
Basidiomycota club fungi

• Sexual Reproduction basidia
• Asexual reprod not so common
• Long-lived dikaryotic mycelia
• Rusts smuts plant parasites
• Mushrooms, polypores, puffballs, boletes, birds
  nest fungi
• Enzymes decompose wood, leaves, and other organic
  materials
• Decomposers, pathogens, and some form mycorrhizal
  associations with plants

SEM of basidia and spores
29
Mushroom Life Cycle
mycelium and fruiting body are dikaryotic
haploid mycelium
Hyphal fusion of haploid mycelia
N 2N NN
Meiosis
Nuclear fusion in basidium
young basidia - the only diploid cells
30
Bioluminescence in Mycena
31
Some fungi have more than one scientific name
Why?

• Teleomorph the sexual reproductive stage
  (morph), typically a fruiting body (e.g.,
  Morchella esculenta, Agaricus brunescens).
• Anamorph an asexual reproductive stage (morph),
  often mold-like (e.g. Aspergillus flavus,
  Fusarium solani). When a single fungus produces
  multiple morphologically distinct anamorphs, they
  are called synanamorphs.
• Holomorph the whole fungus, including all
  anamorphs and the teleomorph.

32
Deuteromycota Form Phylum Imperfect Fungi

• Fungi that seldom or never reproduce sexually.
• Asexual reproduction by vegetative growth and
  production of asexual spores common.

33
Yeasts

• Single celled fungi
• Adapted to liquids
• Plant saps
• Water films
• Moist animal tissues

Candida
Saccharomyces
34
Molds

• Rapidly growth
• Asexual spores
• Many human importances
• Food spoilage
• Food products
• Antibiotics, etc.

Noble Rot - Botrytis
Antibiotic activity
35
HUMAN-FUNGUS INTERACTIONS

• Beneficial Effects of Fungi
• Decomposition - nutrient and carbon recycling.
• Biosynthetic factories. Can be used to produce
  drugs, antibiotics, alcohol, acids, food (e.g.,
  fermented products, mushrooms).
• Model organisms for biochemical and genetic
  studies.
• Harmful Effects of Fungi
• Destruction of food, lumber, paper, and cloth.
• Animal and human diseases, including allergies.
• Toxins produced by poisonous mushrooms and within
  food (e.g., grain, cheese, etc.).
• Plant diseases.

36
Fungi

• Classification of fungal diseases (mycoses)
• Superficial, cutaneous, subcutaneous
• Systemic and opportunistic
• Poisoning and allergies
• Treatment
• Azole drugs, amphotericin B, others

37
Cutaneous and subcutaneous

• Dermatophytes various genera
• Cause skin and nail diseases
• Referred to as tinea (worm) because of the
  ring-like appearance on scalp and skin.
• Cause ringworm, jock itch, athletes foot, etc.
• Limited to outer layer of skin
• Sporothrix schenkii
• Acquired from soil and plant material
• Infects deeper into skin, but not systemic

38
Systemic Mycoses

• Generally acquired by inhalation of spores
• Lung infections, may spread beyond into other
  tissues
• Blastomyces (blastomycosis)
• Coccidiodes (coccidiomycosis)
• Histoplasma (histoplasmosis)
• Most common in this area (Ohio and Miss. River
  valleys)
• Soil contaminated with bird or bat droppings
• Many people exposed with asymptomatic cases
• Many test positive for exposure

39
Opportunistic infections

• Aspergillus (aspergillosis)
• Variety of species, very common in soil, plant
  materials
• Serious infections in immunocompromised
• Allergies to A. fumigatus
• Poisoning from aflatoxin from A. flavus
• Candida (candidiasis)- normal microbiota
• Cause of vaginal infections, diaper rash, thrush
• Capable of infecting any part of the body
• Dangerous in cancer patients, HIV infections, etc.

40
Opportunists-2

• Cryptococcus neoformans
• Inhalation of spores
• Can infect many parts, but has predilection for
  CNS
• Particularly serious in AIDS
• Pneumocystis carinii
• Very protozoan like, but is a fungus
• Most cases associated with AIDS
• Serious lung infections PCP (P. carinii
  pneumonia)

41
Fusarium

• ATLANTA, Aug. 23 -- Minus a smoking gun, CDC
  researchers have nonetheless indicted a contact
  lens solution that was removed from the market
  earlier this year in the wake of a widespread
  outbreak of Fusarium keratitis.
• Contact lens wearers should not use ReNu with
  MoistureLoc, made by Bausch Lomb of Rochester,
  N.Y., said Douglas Chang, M.D., of the CDC here,
  and colleagues.
• http//www.medpagetoday.com/Ophthalmology/GeneralO
  phthalmology/tb/3980