General properties
and
classification of fungi
ลักษณะทั่วไปของรา
และการจัดจาแนก
ผศ. มาลี เมฆาประทีป
ภาควิชาจุลชีววิทยา คณะแพทยศาสตร์ มช.
10/09/15
Fungi are closely to plants and animals
2
Fungi are eukaryotic cells
• Cells contain membrane bound cell
organelles including nuclei, mitochondria,
golgi apparatus, endoplasmic reticulum,
ribosomes, vacuoles etc.
•
3
Fungi are heterotrophs
• Fungi lack chlorophyll
and are therefore not
autotrophic
(photosynthetic) like
plants and algae;
rather they are
heterotrophic
absorptive organisms
that are either
saprophytes (living on
dead organic matter)
or parasites
(utilizing living
tissue).
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Fungal cell wall
• Like plants, fungi have rigid cell walls
and are therefore non-motile, a feature
which separates them from animals. Most
of Cell wall are polysaccharide composed
of chitin, glucan, mannan and chitosan.
• Ergosterol is a component of fungal cell
membranes, serving the same function as
cholesterol in animal cells. It does not
occur in plant or animal cells.
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Growth
• The optimal temperature for growth in
vitro for the most pathogenic fungi is
from 25 to 35oC.
• Fungi prefer acid pH, most mycologic
media have a pH range of 6 to 6.8.
• Fungi do not require light for growth,
but light is known to affect asexual
or sexual sporulation in many fungi.
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Nutritional requirements
• All fungi are heterotrophs requiring organic
nutrients; they absorb rather than ingest
their food.
• Many fungi can grow on simple medium
containing carbohydrates, inorganic or
organic source of nitrogen and various
mineral elements. None can use atmospheric
nitrogen.
• Glucose is the best source of carbon, and
organic nitrogen or ammonium compounds is the
best sources of nitrogen.
• Most fungi do not require exogenous vitamins.
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Fungi occur in two basic growth forms
• A unicellular form or yeast which is
defined morphologically, as a single-celled
fungus that reproduces by simple budding to
form blastoconidia. Colonies are usually
moist or mucoid.
• A filamentous form or mold which is a
vegetative growth of filaments. Reproduction
is by spores or conidia. Moulds produce a
great variety of conidia which are borne on
specialized hyphae or conidiophores. Many
moulds can be identified by the morphology
of these spores and by their arrangement on
the hyphae.
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Yeast?
Mold?
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YEAST : สา่ หรือ ยีสต์
Yeast
colony
Yeast-like
colony
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MOLD / MOULD : ราสาย
conidia / spore
conidiophore
aerial hyphae
Vegetative hyphae
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MOLD
•
•
There are two kinds of hyphae;
non-septate (coenocytic) and septate.
The septa divide the hyphae into
compartments but not into cells. In
some groups nuclei and/or cytoplasm
can flow through a hole or pore in the
centre of these septa.
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MOLD
•
Fungi with non-septate hyphae typically
belong to the Zygomycetes. Non-septate
hyphae are considered to be more primitive
because if a hyphal strand is damaged the
entire strand dies.
• Septate
hyphae are typically found in the
Basidiomycetes and Ascomycetes, the latter
also includes conidial fungi. When a
septate hyphal strand is damaged, the pores
between adjacent compartments can be
plugged, thus preventing death of the whole
hyphal strand.
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Filamentous colony
velvety
Glabrous
Powdery
Velvety
Fluffy
powdery
Cottony
granular
fluffy
cottony / wooly
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Sporulation of fungi
•
•
•
Fungi reproduce asexually (anamorphic
state) or sexually (teleomorphic state)
and some reproduce by both means.
Most fungi that cause human infections
reproduce only asexually in clinical
laboratory.
In some species the teleomorphic state
is known, but in many cases it is not
known.
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Asexual reproduction
• Asexual propagules are termed either
spores or conidia, and which arise
following mitosis of a parent nucleus.
Conidia arise either by budding off
conidiogenous hyphae or by
differentiation of preformed hyphae.
• Asexual forms of reproduction
represent the major method for the
maintenance and dissemination of many
fungi.
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Asexual sporulation of yeast
 Blastoconidia
Budding
Binary fission
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Asexual sporulation of mold
 Sporangiospore
http://www.fungionline.org.uk/6asexual/6zygo.html
 Zoospore
(in Oomycota)
http://www.fungionline.org.uk/6asexual/5oomyco.html
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Asexual sporulation of mold
 Blastoconidia
 Arthroconidia
 Annelloconidia
annellide
 Phialoconidia
 Chlamydoconidia
http://www.fungionline.org.uk/6asexual/4chytrid.html
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Sexual reproduction
 Sexual propagules are produced by the
fusion of two nuclei that then generally
undergo meiosis.
 If a sexual spore is produced only by
fusion of a nucleus of one mating type
with a nucleus of another mating type
(+ and - strains), the fungus is said to
be heterothallic.
 In contrast,
homothallic moulds
produce
sexual spores following the fusion of two
nuclei from the same strain (sexually self
fertile).
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Sexual reproduction
 Sexual methods of reproduction involve;
plasmogamy
(cytoplasmic fusion of two cells)
karyogamy
(fusion of two nuclei)
genetic recombination and meiosis
 The resulting haploid spore is said to
be a sexual spore, e.g. zygospores,
ascospores and basidiospores.
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Classification of fungi
 Kingdom Fungi
• Separation of taxa is still primarily based
on the method of spore production of the
perfect or sexual state and three major
phylums, the ZYGOMYCOTA, ASCOMYCOTA and
BASIDIOMYCOTA are generally recognized.
• However mycologists often recognize an
additional artificial phylum called the
DEUTEROMYCOTA to accommodate of those fungi
without a perfect state (Fungi imperfecti).
• [Kingdom Protista, Phylum OOMYCOTA
reproduce sexual oospore, asexual zoospore]
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Classification of medically importance fungi
Fungi
Kingdom
Phylum Zygomycota
Class
Zygomycetes
Trichomycetes
Examples
Rhizopus,
Mucor,
Absidia,
Basidiobolus ranarum,
Conidiobolus coronatus,….
Ascomycota
Basidiomycota
Deuteromycota
Fungi imperfecti
Ascomycetes
Hemiscomycetes
Holobasidiomycetes
Heterobasidiomycetes
Blastomycetes,
Coelomycetes,
Hyphomycetes
Histoplasma capsulatum,
Blastomyces dermatitidis,
Piedraia hortae,
Aspergillus fumigatus,
Penicillium marneffei,
cup fungi,…..
Cryptococcus neoformans,
most mushrooms and
toadstools,….
Candida,
Rhodotorula,
Fusarium,
Penicillium,
Aspergillus,
Curvuaria,
Phialophora,…..
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Classification of fungi
Phylum Zygomycota
• Fast growing, largely saprobic fungi
with non motile cells.
• Hyphae coenocytic and mostly aseptate.
• Asexual spores include sporangiospores
contained in sporangia borne on simple
or branched sporangiophores.
• Sexual reproduction is a thick-walled
sexual resting spore called a
zygospore.
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Zygospore
http://mac122.icu.ac.jp/biobk/BioBookDiversity_4.html
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Classification of fungi
Phylum Ascomycota
• Hyphae septate with simple septal
pores, cytoplasmic and nuclear
migration not inhibited.
• Asexual reproduction is by conidia.
• Sexual reproduction is by the formation
of endogenous ascospores, typically
eight, in an ascus. Asci are often
housed in a fruiting body or ascocarp
e.g. cleistothecium, perithecium and
apothecium.
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Ascospore
ascus
http://www.fungionline.org.uk/6asexual/4chytrid.html
ascocarp
ascocarp
http://kentsimmons.uwinnipeg.ca/16cm05/16lab05/lb2pg06.htm
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Classification of fungi
Phylum Basidiomycota
• Hyphae septate with complex septal
pores called dolipores which allow
cytoplasmic but not nuclear migration.
• Hyphae are dikaryotic and can often be
distinguished by the presence of clamp
connections over the septa.
• Sexual reproduction is by the
formation of exogenous basidiospores,
typically four, on a basidium.
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Basidiopspore
basidiocarp
http://sl.iciba.com/viewthread-48-486564-1.shtml
30
Basidiopspore of Cryptococus neoformans
basidiospore
dikaryon
clamp connection
basidium
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Classification of fungi
Form Phylum Deuteromycota
• Mycelial moulds which reproduce asexually by
conidia on hyphae or aggregations of hyphae.
No sexual state is present.
• Hyphae are septate,having simple ascomycetous
septal pores.
• Parasexual cycle, resembles sexual
reproduction, is served as a nonsexual
mechanism for transferring genetic material
without meiosis or the development of sexual
structures.
• This class contains the majority of medically
important fungi.
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FUNGAL PATHOGENESIS
 Physiologic barriers to fungal growth
within human body are temperature and
tissue redox potential.
 Non specific host defenses;
saliva/sweat, normal flora, skin and
mucosa.
 Host cellular defenses; neutrophils,
mononuclear phagocytes, CMI
 Basic mechanism of fungal pathogenicity
is its ability to adapt to tissue
environment and to withstand lytic
activity of host cellular defenses.
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FUNGAL PATHOGENESIS
 In general, human mycoses is related to the
immunological status as well as predisposing
factors of the host, rather than to the
infecting organism.
 A small number of fungi have the ability to
cause infections in normal healthy humans by
 Growth at elevated temperature
 having a unique enzymatic capacity
 exhibiting thermal dimorphism
 having an ability to block the cell-mediated
immune defences of the host.
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FUNGAL PATHOGENESIS AND OUTCOMES
Sources
Saprophytes,
contaminants,
fungal flora
or pathogens
Route of
inoculation
Skin
contact or
endogenous
infection
Tissues involved
Outer dead layers of
skin and hair
Keratinized portions
of hair, skin and
nails
Outcomes
Superficial mycoses
Cutaneous mycoses
Mucous membranes
Mushrooms
Traumatic
Muscle, bone and
connective tissues
Subcutaneous mycoses
Inhalation
Respiratory tract,
any organ or tissues
Opportunistic fungal
infections,
systemic diseases,
or hypersensitivity
Ingestion,
inhalation
or skin
Alimentary tract /
any organ or tissue
Mycotoxicoses
Ingestion
Alimentary tract /
any organ or tissue
Mushroom poisonings
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ึ ษาสามารถจะ :เมือ
่ จบการบรรยาย นั กศก
• บรรยายลักษณะโคโลนี และโครงสร้างของราภายใต้กล้องจุลทรรศน์ได้ ทา
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• บอกชนิดและการจัดจาแนกราเบื้องต้นได้อย่างถูกต้อง
• อธิบายแหล่งของเชื้อและช่องทางเปิดรับ และความสาคัญของราทางการ
แพทย์ได้พอสังเขป
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