Transcript Document

Fungus( plural: Fungi)
Six Kingdoms of Classification
◎ Before the introduction of molecular methods for phylogenetic
analysis, taxonomists considered fungi to be members of
the Plant Kingdom because of similarities in lifestyle: both fungi
and plants are mainly immobile, and have similarities in general
morphology and growth habitat.
Like plants, fungi often grow in soil, and in the case
of mushrooms form conspicuous fruiting bodies, which
sometimes bear resemblance to plants such as mosses.
Some morphological, biochemical, and genetic features are
shared with other organisms, while others are unique to the fungi,
clearly separating them from the other kingdoms
2n
1n
Life Cycle of Fungus
◎ Fungi lack chloroplasts and are heterotrophic organisms,
requiring preformed organic compounds as energy sources.
◎The cells of most fungi grow as tubular, elongated, and
filamentous structures and are called hyphae, which may
contain multiple nuclei and extend at their tips.
In contrast, similar-looking organisms, such as
filamentous green algae, grow by repeated cell division within
a chain of cells.
◎ Most important of all, the fungal cell wall is composed of glucans
and chitin.
Chitin is a long-chain polymer of a N-acetylglucosamine, a derivative
of glucose.
N-Acetylglucosamine is a monosaccharide derivative of glucose.
Phylogenesis
◎ What role do fungi play in food chains?
Bacteria and fungi are decomposers. They break down waste
products and dead organisms for food. These broken down
materials are returned to the soil to be recycled and used by
plants again. An example of this would be a fungus growing on a
log.
◎ What is the relationship between fungi and other organisms?
Nearly all plants depend on symbiotic fungi, known as
mycorrhizae, which help their roots absorb minerals and water
from the soil.
A lichen is a combination of a green alga and a fungus. The
alga receives from the fungus both attachment and protection
from desiccation; The fungus benefits from the product of
photosynthesis released by the alga.
mycorrhizae
lichen
◎ What can we benefit from fungi?
Fungi are used by humans for food( mushroom) and to
produce food ( bread and citric acid) and drugs( alcohol
and penicillin).
When the anticancer drug taxol, which is produced by
yew trees, was discovered, the yew forests of the U.S.
Northwest coast would be decimated to harvest the drug.
However, the fungus Taxomyces also produces taxol.
And what diseases can fungi cause?
Fungal infections can range from being only the
epidermis to being deep within the body…
To reveal “The Secrets of Fungi” we probe into it from
microcosmic and macrocosmic structures of fungi,
mechanism of reproduction, evolution, roles in
ecosystem, and finally, their application.
1. Microcosmic view
2. Macrocosmic view
3. Reproduction
4. Evolution
5. Roles in ecosystem
6. Application
Microcosmic view
Septate hyphae
Septum
Coenocytic hyphae
Septate hyphae have septa( singular: septum), which divide them
into distinct, uninucleate( one-nucleus) cell-like units.
Coenocytic hyphae contain no septa and appear as long continuous
cells with many nuclei.
Septate hyphae
The portion of a hypha that obtains nutrients is called
vegetative hypha.
The portion concerned with reproduction is the
reproductive or aerial hypha.
Filamentous fungi can reproduce asexually and sexually.
Conidium
(n)
Sporangium
(n)
Sporangiospore
Two types of asexual spores:
Conidium( plural:conidia): A multicellular spore that is not enclosed in a sac.
Sporangiospore: Formed within sporangium, or sac.
One characteristic feature of fungal sexual reproduction.
Zygospore
(2n)
Zygosporangium
A zygospore results from the fusion of the nuclei of two cells
Sporangium
(n)
Zygosporangium
(2n)
Budding
pseudohypha
Some yeasts produce buds that fail to detach themselves, forming a
short chain of cells called pseudohypha.
Macrocosmic view - mushroom
Fruiting structure
(2n)
Basidiospores(n) are formed by meiosis.
Reproduction
Spore of asexsual and sexual reproduction
1.Conidiospore
-arthroconidium
-blastoconidium
-chlamydoconidium
2.Sporangiospore
Asexsual reproduction
1.Yeast budding
2.Frangmentation
3.Sporulation
Sexual reproduction
Always under three steps
Conidiospore
a unicellular or multicellular spore that is not enclosed by
sac
Conidia are produced in a chain at the end of a
conidiophore
1.Conidia formed by the
fragmentation of a
septate hypha into a
single,slightly thickened
cells are called
arthroconidia
2.Another type of conidia
consists of buds coming
off the parent cell are
called blastoconidia
3.The other type of
conidia is a thick –walled
spore form by roundling
and enlargement within a
hyphal segment are
called chlamydoconidia.
Sporangiospore
It is formed within a sporangium(sac) at the
end off an hypha
Asexual reproduction
1. Bud formation in yeasts
In its simplest form asexual reproduction is by budding or
binary fission. The onset of the cellular events is
accompanied by the nuclear events of mitosis.
The initial events of budding can be seen as the
development of a ring of chitin around the point where the
bud is about to appear.
When chains of yeast cell do not fully seperated this can
create a pseudomycelium
2. Fragmentation
Many fungi can reproduce by fragmentation. Any mycelium that is
fragmented or disrupted, provided that the fragment contains the
equivalent of the peripheral growth zone, can grow into a new colony
3. sporulation
Asexual reproduction is extremely important to
fungi. It is responsible for the production of large
numbers of spores throughout the year. These
asexual spores are formed on a phase of the
fungal life cycle termed as the mitosporic, or
anamorphic phase. There can be more than one
mitosporic state for each species of fungus, and
in some cases the mitosporic state of very
different species can look very similar. mitosporic
states.
The onset of asexual reproduction is controlled
by many different things. Some are
environmental, like nutrient levels, CO2 levels,
light levels. Others can fungi have internal time
clocks and sporulate anyway in a preset part of
the fungal life cycle designed to spread and
maximize colonization during one season.
Sexual reproduction
Sexual spore result from the fusion of nuclei from two opposite matting
strains of the same species of fungi.
Sexual reproduction always undergos the following three steps
1.Plasmogamy: a haploid nucleus of a donor cell (+) penetrates
the cytoplasm
Of a recipient cell (-)
2.karyogamy: the (+) and the (-) fuse to form a diploid zygote
nucleus.
3.meiosis: the diploid nucleus gives rise to haploid nuclei
(sexual),may be genetic recombination.
Fungi produce sexual spore less frequently then asexual one.
Some classes of fungi
Zygomycota(conjugation fungi)
They are saprophytic molds that have coenocytic hyphae.
The black bread mold is the one.(the dark sporangiospore inside
the sporangium gives it the descriptive name)
The asexual spores of them are sporangriospores.
The sexual spores are zygospores.(a large spore enclosed in a
thick wall)
Microsporidia
Are unusual eukaryote because it lacks of
mitochondria.
Their sexual reproduction has not been
observed but probably occurs within the host.
Ascomycota
A sac fungi,their asexual spores are usually conidia produced in a long chain
from the conidiophore.
Conidia means dust, meaning that the spore can freely detach from the chain
Ascosporeresult from the fusion of two cells that can be either morphologically
similar or disimilar.
These spores are produced in a saclike structure, called an ascus
(that’s what their name come from)
Basidiomycota
Also called club fungi possess septate hyphae.
Basidiospores are formed externally on a base pedestal
Called a basidium.
Usually four basidiospores per basidium.
By the way , the fungi produce sexual and asexual spores are
teleomorphs, the one only have asexual are anamorphs.
Evolution
Fossil record
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In contrast to plants and animals, the early
fossil record of the fungi is meager.
Fruiting bodies are soft,
fleshy, and easily
degradable tissues.
Often recovered from a permineralized plant
or animal host.
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The earliest fossils date to
the Proterozoic eon, 1430 million years ago.
In Paleozoic Era (542–251 Ma), the fungi
appear to be aquatic and have flagellumbearing spores.
Landing
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Ecological strategies for obtaining nutrients
for a terrestrial lifestyle
includes parasitism, saprobism, and the
development of mutualistic relationships such
as mycorrhiza and lichenization
The fungi probably colonized the land during
the Cambrian (542–488.3 Ma), long before
land plants.
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Fungal fossils do not become
common and uncontroversial
until the early Devonian
(416–359.2 Ma).
Abundant in the Rhynie chert
At about the same time, approximately 400 Ma, the
Ascomycota and Basidiomycota diverged, and all
modern classes of fungi were present by the
Late Carboniferous (318.1–299 Ma).
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Role in ecosystem
An important role
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Fungi occur in every environment
on Earth and play very important roles in
most ecosystems.
Along with bacteria, fungi are the
major decomposers in most terrestrial (and
some aquatic) ecosystems
An essential role in nutrient cycling,
especially as saprotrophs and symbionts,
degrading organic matter to inorganic
molecules
With plants
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Mycorrhizal symbiosis between plants and
fungi is of significant importance for plant
growth and persistence in many ecosystems
With algae and cyanobacteria
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Lichens are formed by a symbiotic
relationship between algae or cyanobacteria
and fungi
Lichens occur in every ecosystem on all
continents, play a key role in soil formation
and the initiation of biological succession and
are the dominating life forms in extreme
environments
With insects
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Many insects also engage in mutualistic
relationships with fungi
Females of several wood wasp species inject
their eggs together with spores of the woodrotting fungus Amylostereum areolatum into
the sapwood of pine trees
As pathogens and parasites
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Many fungi are parasites on
plants, animals, and other fungi
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Some fungi can cause serious diseases in
humans
Candidiasis(念珠菌症)
Eumycetoma(足菌腫)
初期會形成暗紅色丘疹、結節、
膿皰，之後逐漸發展成腫塊和多
發性膿腫。病情如延誤，膿腫會
侵入附近深部組織，包括肌肉、
肌腱、筋膜、骨骼，引起骨膜炎、
骨髓炎和骨壞死，可能導致截肢。
Application
In food
In diseases
In medication
In food
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Saccharomyces cerevisiae(釀酒酵母)
a single-celled fungus, is used to
make bread and other wheat-based products.
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Life cycle: haploid and diploid.
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A model organism
In Medicine
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Ganoderma lucidum (靈芝)
a polypore mushroom that is soft (when fresh),
corky, and flat.
(young Sporocarp)
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Triterpenoids(三帖類)
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Polysaccharides(多醣體)
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Cordyceps sinensis (冬蟲夏草)
is a fungus that parasitizes larvae of ghost
moths and produces a fruiting body valued as
an herbal remedy.
In diseases
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Candida albicans (白色念珠菌)
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Trichophyton rubrum(紅色毛癬菌 )
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Cryptococcus neoformans(新型隱球菌 )