Fungi are a diverse group of organisms that play an essential role in ecosystems by breaking down organic material. They absorb nutrients from outside their bodies and exhibit diverse lifestyles including as decomposers, parasites, and mutualists. Fungi are made of filamentous hyphae that may be septate or coenocytic. They reproduce both sexually through structures like basidia and ascoyci that produce spores, and asexually through spores. Major fungal groups include chytrids, zygomycetes, ascomycetes, and basidiomycetes which vary in morphology and life cycles. Fungi are vital decomposers in ecosystems and have

1. FUNGI

2. Overview: Fungi The Mighty
Mushrooms
• Fungi are diverse and widespread
• They are essential for the well-being of most
terrestrial ecosystems because they break
down organic material and recycle vital
nutrients

3. Fungi are heterotrophs that feed by
absorption
• Despite their diversity, fungi share key traits, most importantly the way
in which they derive nutrition
• Fungi are heterotrophs and absorb nutrients from outside of their body
• Fungi use enzymes to break down a large variety of complex
molecules into smaller organic compounds
• The versatility of these enzymes contributes to fungi’s ecological
success
• Fungi exhibit diverse lifestyles:
– Decomposers
– Parasites
– Mutualists

4. • What are fungi?
• Eukaryotic, spore-bearing, heterotrophic organisms that produce
extracellular enzymes and absorb their nutrition.
• What is mycology?
• Mycology is the study of fungi. The disease caused by fungi is
called MYCOSES.
General information's about FUNGI:
• Fungi are not plants or animals, they form a separate group of
higher organisms, distinct from both plants and animals, which
differ from other groups of organisms in several major respects:
First:
• Fungal cells are encased within a rigid cell wall, mostly composed
of chitin and glycan. These features contrast with animals, which
have no cell walls, and plants, which have cellulose as the major
cell wall component.

5. • Second:
• Fungi are heterotrophic. This means that they are
lacking in chlorophyll and cannot make their organic food
as plants can, through photosynthesis. Fungi live
embedded in a food source or medium, and obtain their
nourishment by secreting enzymes for external digestion
and by absorbing the nutrients that are released from the
medium. Some live on humans e.g. the cause ringworm
infections. Some live on insects, or plants.
•
• Third:
• Fungi are simpler in structure than plants or animals.
There is no division of cells into organs or tissues.

6. Structure of Fungi

7. The basic structure of the fungi:
• The basic structural unit of fungi is either a chain of
tubular, filament-like cells, termed a hypha or hyphae
(plural) or an independent single cell.
• The living body of a fungus is called a mycelium which is
made up of a branching network of filaments known as
hyphae.
• Fungal cell differentiation is no less complicated than is
found in plants or animals, but it is different. Many fungal
pathogens of humans and animals change their growth
form during the process of tissue invasion. These
dimorphic pathogens usually change from a multicellular
hyphal form in the natural environment to a budding,
single-celled form in tissue.

8. The Fungal Cell Wall
Rigid structure
surrounding the cell

9. Fungal Morphology
• The morphology of multicellular fungi enhances
their ability to absorb nutrients
• Fungi consist of mycelia, networks of
branched hyphae adapted for absorption
• Most fungi have cell walls made of chitin

10. • hyphae - the vegetative bodies of most
fungi, constructed of tiny filaments
• mycelium -an interwoven mat of hyphae

11. Septate hypha:
• multicellular
• walls divided by septa
Ceonocytic hypha:
• continuous cytoplasm
mass
• multinucleate
• no septa

12. Haustoria:
• Modified hyphae found in parasitic fungi
• Function: absorb nutrients from host
• Some fungi even have hyphae adapted for
preying on animals.

13. Specialized Hyphae in Mycorrhizal Fungi
• Some unique fungi have specialized hyphae
called haustoria that allow them to penetrate
the tissues of their host and extract nutrients
plant cell wall
haustorium
plant cell plasma membrane
hypha
modified portions of the hyphae can constrict
arround a nematode in less than a second

14. • Mycorrhizae are mutually beneficial
relationships between fungi and plant roots
• Ectomycorrhizal fungi form sheaths of
hyphae over a root and also grow into the
extracellular spaces of the root cortex
• Arbuscular mycorrhizal fungi extend hyphae
through the cell walls of root cells and into
tubes formed by invagination of the root cell
membrane

15. Reproduction
• Most fungi reproduce both sexually and asexually.
• Asexual reproduction – production of various types of
spores
– Sporangiophores- upright stalk with an enclosed sac (
bread mold)
– Conidia - upright stalk with no enclosed sac (penicillin)
– Fragmentation – hyphae dry out and shatter releasing
individual cells that act like spores (athlete’s foot)
– Budding – small offspring

16. • Sexual reproduction
– “plus and minus” mating types
– Hyphae of different mating types fuse and give rise to
a specialized structure that produces spores ( diploid)
– Most fungi are haploid throughout most of their life
cycle
• When environmental conditions are favorable, asexual
reproduction occurs rapidly. When unfavorable
conditions stress the organism, sexual reproduction
occurs and the offspring have an increased likehood that
they will be better suited for the environment.

17. Morphological groups of Fungi
1. The single-celled fungi are yeasts
2. The multicellular fungi are molds
3. Dimorphism
– Grow as molds in vitro on artificial culture medium, but as
yeasts in vivo in infected tissue.

18. • Unicellular fungi (nonfilamentous)
• Can use oxygen
• Capable of facultative anaerobic growth
• Asaxual reproduction - mitosis
– Fission yeasts divide symmetrically
• daughter cells separated by formation of a septa in the center (fission)
– Budding yeasts divide asymmetrically
• protuberance(bud)
• elongates
• parent cell’s nucleus divides
• one nuclei migrate to the bud
• cell wall material is then laid down between the bud and parent cell
• the bud eventually breaks away
• If fails to separate - pseudohyphae
• Sexual reproduction - meiosis
– Form zygote
– Form spores
1. Yeasts

19. 2. Multicellular Fungi
• The fungal thallus (body) consists of
hyphae ( long filaments of cells joined
together)
• A mass of hyphae is called mycelium.
Figure 12.1a
Figure 12.1b
• A hypha is a tubular structure that grows by
elongation.
– Septate hyphae - contain cross-walls (septa)
– Coenocytic hyphae - contain no septa (long,
continuous cells with many nuclei)

20. • Vegetative hyphae
• The portion that obtain nutrients
• Fungal hyphae have a small volume but
large surface area, enhancing the fungal absorptive capacity
• Aerial hyphae
• The portion concerned with reproduction
• Produce spores
Mold mycelium
Figure 12.2

21. • Pathogenic dimorphic fungi are yeast like at 37°C and mold
like at 25°C
3. Dimorphic fungi

22. Dimorphic fungi:
• Dimorphism this term is used to describe
a fungus which occurs in two different
forms (temperature and place), for
example, some pathogenic fungi are
filamentous in culture(Labs) and yeast-like
in infected tissues.
• 37°C yeast
• 20 – 30° C moulds.
• Examples:
– Paracoccidioides brasiliensis

23. Fungi produce spores through sexual or
asexual life cycles
• Fungi propagate themselves by producing vast
numbers of spores, either sexually or asexually
• Fungi can produce spores from different types
of life cycles

24. Zygomycete
Basidiomycete
Ascomycete
* Formation of spores within
zygosporangium.
* No cross walls between cells.
Formation of spores in
ascus.
Formation of spores on
basidium.
Classification
using sexual reproduction
(more later)
Modified from Outlaw lecture

25. Spores
Spore-producing
structures
GERMINATION
ASEXUAL
REPRODUCTION
1.Mycelium
Key
Heterokaryotic
(unfused nuclei from
different parents)
Haploid (n)- most of the life cycle
Diploid (2n)
SEXUAL
REPRODUCTION
KARYOGAMY
(fusion of nuclei)
PLASMOGAMY
(fusion of cytoplasm)
Heterokaryotic
stage
Zygote
Spores
GERMINATION
MEIOSIS
from hours to centuries
can go by before this
takes effect
different hypha attracted
by pheromones fuse
although the cells fuse
the nuclei don't; it is
said to be dikaryotic
Generalized Cycle of Fungi
Mitosis

26. • Many molds and yeasts have no known sexual
stage
• Mycologists have traditionally called these
deuteromycetes, or imperfect fungi

27. The ancestor of fungi was an aquatic, single-
celled, flagellated protist
• Fungi and animals are more closely related to
each other than they are to plants or other
eukaryotes
• Fungi, animals, and their protistan relatives
form the opisthokonts clade
• DNA evidence suggests that fungi are most
closely related to unicellular nucleariids while
animals are most closely related to unicellular
choanoflagellates

28. Animals (and their close
protistan relatives)
Other fungi
Nucleariids
Chytrids
UNICELLULAR,
FLAGELLATED
ANCESTOR
Opisthokonts

29. • This suggests that fungi and animals evolved
from a common flagellated unicellular ancestor
and multicellularity arose separately in the two
groups
• The oldest undisputed fossils of fungi are only
about 460 million years old
Fossil fungal hyphae and spores
from the Ordovician period (~460
mya)

30. The Move to Land
• Fungi were among the earliest colonizers of
land and probably formed mutualistic
relationships with early land plants

31. Fungi have radiated into a diverse set of
lineages
• Molecular analyses have helped clarify
evolutionary relationships among fungal
groups, although areas of uncertainty remain
Chytrids
Zygomycetes
Glomeromycetes
Ascomycetes
Basidiomycetes

32. Chytrids (1,000 species)
Chytrids phylum Chytridiomycota
• Found in freshwater and terrestrial habitats
• Decomposers, parasites, or mutualists
• According to molecular evidence chytrids diverged in early evolution
• Chytrids are unique among fungi in having flagellated spores, zoospores
• Molecular data indicate that some “chytrids” are actually more closely
related to another fungal group, the zygomycetes; chytrids are a
paraphyletic group
hyphae
zoospore
1,000 species

33. Zygomycetes (1,000 species)
Zygomycetes (phylum Zygomycota, zygo=egg) exhibit great diversity
of life histories
They include fast-growing molds, parasites, and commensal symbionts
The zygomycetes are named for their sexually produced zygosporangia
which are resistant to freezing and drying, can survive unfavorable
conditions
•The life cycle of black bread mold (Rhizopus stolonifer) is fairly typical of
the phylum
1,000 species
sporebearing hypha

34. Rhizopus
growing
on bread
SEXUAL
REPRODUCTION
Young
zygosporangium
(heterokaryotic)
Gametangia with
haploid nuclei
Mating
type (–)
Mating
type (+)
Diploid (2n)
Haploid (n)
Heterokaryotic (n + n)
PLASMOGAMY
Key
Diploid
nuclei
Zygosporangium
100 µm
KARYOGAMY
MEIOSIS
Sporangium
Spores
Dispersal and
germination
ASEXUAL
REPRODUCTION
Dispersal and
germination
Sporangia
Mycelium
50 µm Life Cycle of Zygomycete
1. mycella of different mating types
(+) and (-) mate
hyphal extensions
enclosing haploid nuclei
meat
zygosporangium forms
containing multiple
haploid nuclei from
both parents
tough wall is developed to protect
the zygosporangium
when conditions are favorable,
karyogamy occurs
sporangia produces identical
haploid spores

35. 160 species
Fungal hypha
The glomeromycetes (phylum Glomeromycota, glomero= round) were
once considered zygomycetes
They are now classified in a separate clade
Glomeromycetes form arbuscular mycorrhizae
plant root
mycelum

36. Ascomycetes (65,000 species)
Ascomycetes (phylum Ascomycota, asca=sac) live in marine, freshwater,
and terrestrial habitats; include plant pathogens, decomposers, and
symbionts
The phylum is defined by production of sexual spores in saclike asci,
contained in fruiting bodies called ascocarps
Commonly called sac fungi ascomycetes vary in size and complexity from
unicellular yeasts to elaborate cup fungi and morels
Asexual spores called conidia are not formed inside sporangia; they are
produced asexually at the tips of specialized hyphae called conidiophores
65,000 species
ascocarp

37. Key
Haploid (n)
Diploid (2n)
Dikaryotic (n + n)
Conidiophore
Mycelium
ASEXUAL
REPRODUCTION
Germination
Hypha PLASMOGAMY
Conidia;
mating type (–)
Mating
type (+)
SEXUAL
REPRODUCTION
Dikaryotic
hyphae
Ascus (dikaryotic)
Mycelia
KARYOGAMY
Diploid nucleus
(zygote)
Germination
Asci
Dispersal
Dispersal
Ascocarp
Eight
ascospores
Four
haploid
nuclei
MEIOSIS
conidia (n)
1.pigmented haploid spores
known as conidia are
produced
Life Cycle of the Ascomycete Neurospora crassa
specialized hyphae fuse
after plasmogamy dikaryotic
asci are produced
karyogamy occurs
within each ascus
producing 2n nucleus
each haploid nucleus divides once by
mitosis yealding 8 nuclei, cell walls
develop forming the 8 spores
ascospores are discharged
through an opening, new
mycelia will be generated

38. Common edible morel, Morchella esculenta (ascomycete)

39. World’s most expensive truffle
White Alba
Almost 3 pounds
$112, 000
Photo from Wikipedia
Truffles
Black truffle
(Tuber melanosporum)

40. Botryosphaeria dothidea on Adina apple
Thanks to Robert Hebert and Kim Riddle for this image.

41. Basidiomycetes (30,000 species)
Basidomycetes (phylum Basidiomycota, basidia= little pedestal)
include mushrooms, puffballs, shelf fungi
Mutualists, and plant parasites
The phylum is defined by a clublike structure called a basidium, a
transient diploid stage in the life cycle
The basidiomycetes are also called club fungi
30,000 species

42. Maiden veil fungus
(Dictyphora), a
fungus with an odor
like rotting meat

43. Basidium
SEXUAL
REPRODUCTION
Diploid (2n)
Haploid (n)
Dikaryotic (n+n)
Key
PLASMOGAMY
Mating
type (+)
Dikaryotic mycelium
Mating
type (–)
Basidia
(n+n)
Gills lined
with basidia
Basidiocarp
(n+n)
KARYOGAMY
Diploid
nuclei
MEIOSIS
Basidium
Dispersal and
germination
Basidiospores
(n)
Basidium with
four basidiospores
1 µm
Haploid
mycelia
1.2 haploid mycelia undergo plasmogamy
environmental cues induce
the growth of basidiocarp
karyogamy produces
diploid nucleus which
will undergo meiosis
basidiospore product of meiosis

45. Polypore example
Polyporus arcularius

46. Shelf fungus example
Ganoderma applanatum

47. Puffball
Calostoma cinnabarina

48. Netted stinkhorn
Dictyophora duplicata

49. White-egg bird’s-nest
Crucibulum laeve

50. Earthstar
Geastrum saccatum

51. Corn smut
Ustilago maydis

52. Fungi play key roles in nutrient cycling,
ecological interactions, and human welfare
• Fungi interact with other organisms in many ways
• Fungi are efficient decomposers
• They perform essential recycling of chemical elements
between the living and nonliving world
• Fungi form mutualistic relationships with plants, algae,
cyanobacteria, and animals
• All of these relationships have profound ecological effects

53. Fungus-Plant Mutualisms
• Mycorrhizae are enormously important in
natural ecosystems and agriculture
• Plants harbor harmless symbiotic endophytes
that live inside leaves or other plant parts
• Endophytes make toxins that deter herbivores
and defend against pathogens

54. Fungus-Animal Symbioses
• Some fungi share their digestive services with
animals
• These fungi help break down plant material in
the guts of cows and other grazing mammals
• Many species of ants and termites use the
digestive power of fungi.

55. Lichens
• A lichen is a symbiotic association between a
photosynthetic microorganism and a fungus in
which millions of photosynthetic cells are held
in a mass of fungal hyphae
fruticose lichen
crustose lichen
foliose lichen

56. • The fungal component of a lichen is most often
an ascomycete
• Algae or cyanobacteria occupy an inner layer
below the lichen surface
ascocarp
algal layer
hyphae
soredia

57. • The fungi of lichens can reproduce sexually and asexually
• Asexual reproduction is by fragmentation or the formation
of soredia, small clusters of hyphae with embedded algae
• Lichens are important pioneers on new rock and soil
surfaces
• Lichens are sensitive to pollution, and their death can be a
warning that air quality is deteriorating

58. Fungi as Pathogens
• About 30% of known fungal species are
parasites or pathogens, mostly on or in plants
• Some fungi that attack food crops are toxic to
humans
• Animals are much less susceptible to parasitic
fungi than are plants
• The general term for a fungal infection in
animals is mycosis

59. Disseminated Histoplasma
capsulatum, skin infection.
Ringworm skin infection: Tinea corporis

60. Dermatophytes
Tinea pedis
Onychomycosis
Tinea corporis

61. Fig. 31-25
(c) Ergots on rye
(a) Corn smut on corn (b) Tar spot fungus on
maple leaves