The characteristics of fungi The evolution of the fungi Fungal classification Fungal life cycles

1. Mycology: study of fungi
• The characteristicsThe characteristics
of fungiof fungi
• The evolution ofThe evolution of
the fungithe fungi
• FungalFungal
classificationclassification
• Fungal life cyclesFungal life cycles

2. Mycelium (Mycelium (aggregate of
hyphae)
fruiting bodiesfruiting bodies
both are
composed
of hyphae(
tube-like
strands)

3. HyphaeHyphae
• Tubular
• Hard wall of chitin
• Crosswalls may
form compartments
• Grow at tips

5. Hyphal growthHyphal 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

8. The Characteristics of FungiThe 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).

9. The Characteristics of FungiThe 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.

10. The Characteristics of FungiThe Characteristics of Fungi
• Fungus is often hidden from view. It grows
through its food source (substratum),
excretes extracellular digestive enzymes,
and absorbs dissolved food.

11. Heterotrophic by AbsorptionHeterotrophic by Absorption
• Fungi get carbon from organic sources
• Hyphal tips release enzymes
• Enzymatic breakdown of substrate
• Products diffuse back into hyphae
Product diffuses back
into hypha and is used
Nucleus hangs back
and “directs”

12. Types of fungal hypha
Classification based on cell division
• Septate (with septa i.e hyphae are divided into
sections by cross walls called septa )
* Aspergillus and many other species have septate hyphae.
• Aseptate or coenocytic (without septa)
* Non-septate hyphae are associated with Mucor, some
zygomycetes, and other fungi.
• "Pseudohyphae" are distinguished from true hyphae
by their method of growth and lack of cytoplasmic
connection between the cells.
* Yeast can form pseudohyphae. They are the result of a sort
of incomplete budding where the cells remain attached
after division.

13. Types…
Classification based on cell wall and overall form
• Characteristics of hyphae can be important in
fungal classification. In basidiomycete taxonomy,
hyphae that comprise the fruiting body can be
identified as generative, skeletal, or binding
hyphae.
• Generative hyphae are relatively undifferentiated
and can develop reproductive structures. They are
typically thin-walled, occasionally developing
slightly thickened walls, usually have frequent
septa, and may or may not have clamp
connections

14. Types…
• clamp connection is a structure formed by
growing hyphal cells of certain fungi. It is
created to ensure each septum, or segment
of hypha separated by crossed walls,
receives a set of differing nuclei, which are
obtained through mating of hyphae of
differing sexual types. It is used to create
genetic variation within the hypha.

15. Types…
• Skeletal hyphae are of two basic types.
1. The classical form is thick-walled and very long
with little cell content. They have few septa and
lack clamp connections.
2. Fusiform skeletal hyphae often exceedingly
broad, hence giving the hypha a fusiform shape.
-having a spindle-like shape that is wide in the
middle and tapers at both ends
• Binding hyphae are thick-walled and frequent
branched. Often they resemble deer antlers or
defoliated trees because of the many tapering
branches.

16. Types…
• Based on the generative, skeletal and binding
hyphal types, in 1932 E. J. H. Corner applied the
terms monomitic, dimitic, and trimitic to hyphal
systems, in order to improve the classification of
polypores.
• Every fungus must contain generative hyphae. A
fungus which only contains this type, as do fleshy
mushrooms such as agarics, is referred to as
monomitic.

17. Types…
• Skeletal and binding hyphae give leathery and
woody fungi such as polypores their tough
consistency. If a fungus contains all three types
(example: Trametes), it is called trimitic.
• If a fungus contains generative hyphae and just
one of the other two types, it is called dimitic. In
fact dimitic fungi almost always contain
generative and skeletal hyphae; there is one
exceptional genus, Laetiporus that includes only
generative and binding hyphae.

18. Types…
• Fungi that form fusiform skeletal hyphae bound by
generative hyphae are said to have sarcodimitic hyphal
systems. A few fungi form fusiform skeletal hyphae,
generative hyphae, and binding hyphae, and these are said
to have sarcotrimitic hyphal systems. These terms were
introduced as a later refinement by E. J. H. Corner in 1966.
Classification based on refractive appearance
• Hyphae are described as "gloeoplerous" ("gloeohyphae") if
their high refractive index gives them an oily or granular
appearance under the microscope. These cells may be
yellowish or clear (hyaline).

19. Modifications of hyphaeModifications of hyphae

20. Fungi as Saprobes andFungi as Saprobes and
DecomposersDecomposers

21. Fungi as Symbionts (Mutualism)Fungi as Symbionts (Mutualism)

22. MycorrhizaeMycorrhizae
• Mycor: Greek for Fungus –
• Rhiza = Greek for Root.
• “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 don’t penetrate cells
• Extremely important ecological role of fungi!

23. What are mycorrhizae? An intimate and often beneficial
soil association between fungi and roots.
Flow of complex carbons compoundsFlow of complex inorganic nutrients
Mycorrhizal fungi
Plants
Soil chemistry factors effect to what extent this association is
beneficial to plants.

24. Classification of Mycorrhizae
• Two main types well studied in
agriculture
1.Endomycorrhizae
2.Ectomycorrhizae

26. Endomycorrhizae
• penetrate the cell wall
• Proliferate around root
• Common in grasses, herbs, and tropical
trees
• vesicular arbuscular mycorrhizae (VAM)

27. e.g Endomycorrhizae -> Vesicular
arbuscular mycorrhizal (VAM)fungi
• VAM fungi belonging to the order glomales of
phylum zygomycota
-Important component of the soil
-90% of all plant species

28. Role of VAM fungi on plants:
-enable plants to absorb minerals eg. P, Mo, Co.
- enable plants to absorb poorly mobile nutrients
eg. zinc
-improve plant-water relations
-reduce root attacks by pathogenic fungi
-alleviate environmental stresses
-increase nitrogen fixation
-influence soil development

29. Ectomycorrhizae
• do not penetrate cell wall
• form a thick mantle of hyphae (haustoria)
at the root tip, or penetrate root between
cortical cells
• Common in temperate zone trees and
shrubs

30. ““Ecto”mycorrhizaeEcto”mycorrhizae
Russula
mushroom
mycorrhizas on
Western
Hemlock root
Fungal hyphae
around root and
between cells
Mycorrhiza cross sections

31. Role of Ectomycorrhizae on
Plants
• Increase in nutrient uptake
• Selective uptake of certain elements
• Increase in drought resistance
• Increase in survival after outplanting
• Increase in growth rate
• Protection from certain fungal root
pathogens

32. LICHENSLICHENS
Combination of a green alga (or cyanobacterium) and a fungus.Combination of a green alga (or cyanobacterium) and a fungus.
Mutualistic relationship in which each partner benefits.Mutualistic relationship in which each partner benefits.
* AlgaAlga: Provides nutrients by photosynthesis to fungus.: Provides nutrients by photosynthesis to fungus.
* FungusFungus: Provides attachment and protection from: Provides attachment and protection from
desiccation.desiccation.
20,000 species of lichens occupy unique habitats, in which either20,000 species of lichens occupy unique habitats, in which either
fungi or algae could not survive alone: rocks, cement, rooftops,fungi or algae could not survive alone: rocks, cement, rooftops,
trees, and newly exposed soil.trees, and newly exposed soil.
Grow very slowly, secreting acids that break down rocks.Grow very slowly, secreting acids that break down rocks.
Accumulate nutrients needed for plant growth.Accumulate nutrients needed for plant growth.
Sensitive to air pollution.Sensitive to air pollution.
Major food source for tundra herbivores (caribou andMajor food source for tundra herbivores (caribou and
reindeer).reindeer).

33. LichensLichens
• 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 from branches or grow up from the ground like
tiny shrubs.

34. Crustose
Foliose
Fruticose

35. Lichen structureLichen structure
Lobaria

36. Lichens are nature’s biologicalLichens are nature’s biological
monitors of pollution and airmonitors of pollution and air
qualityquality
* Some species more sensitive to pollution
* some species can indicate air quality
* Most resistant species can also be analyzed
for pollutants, including bioaccumulation of
heavy metals and radioactive isotopes

37. Fungi as Parasites & PathogensFungi as Parasites & Pathogens

39. Fungi are Spore-ific!!!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

40. Reproduce by sporesReproduce by spores
• Formed:
* Directly on hyphae
* Inside sporangia
* Fruiting bodies
Amanita fruiting body
Pilobolus sporangia
Penicillium hyphae

41. Hyphal growth from sporeHyphal growth from spore
mycelium
germinating
spore
• Mycelia have a huge surface area

42. Generalized Life Cycle of a FungusGeneralized Life Cycle of a Fungus

43. Evolution of the fungiEvolution of the fungi

45. Classification
& Phylogeny
motile spores
zygosporangia
asci
basidia

46. 46
Phylogenetic Relationships
There are five major fungal phyla
-Based on mode of sexual reproduction

47. Chytridiomycota – “chytrids”Chytridiomycota – “chytrids”
• Chytridiomycetes or chytrids are members of the
phylum Chytridiomycota
• Most closely related to ancestral fungi
• Only fungi with flagellated spores
• Simple fungi
• Produce motile spores - zoospores
• Mostly saprobes and parasites in aquatic habitats
• Have chitin in their cell walls
• Life cycle has both haploid and diploid multicellular
stages

49. What is Chytridiomycosis?
Amphibian disease caused by a Chytrid Fungus
Batrachochytrium dendrobatidis
• Fungus that infects the skin of amphibians
• Mortality rates frequently 100%
• Some amphibian species have become extinct
• Most species decline in numbers

50. 50
Batrachochytrium
dendrobatidis causes
chytridiomycosis
-Responsible for
the worldwide
decline in
amphibian
populations

51. Some amphibians are reported
to be extinct due to
Chytridomycosis
Golden Toad
(Bufo periglenes)