Lecture1
Medical Mycology
INTRODUCTION
Dr. Mosaab Omar
Terminology
Mycologists:

Scientists who study fungi
Mycology : is the study of fungi


Myco- = fungi
-ology = the study of
Mycoses:

are the diseases caused by fungi
Medical Mycology:

is the study of mycoses of man and their
etiologic agents
What are fungi?
I- Somatic structure:
1- Fungi are microorganisms that are eukaryotic, nonmotile, non- chlorophyllous.
2- Fungal body is usually filamentous (hyphae, mycelia)
or unicellular (yeasts).
3- Some fungi live as plasmodia ( myxomycetes).
4- Cell wall of true fungi is composed of chitin, (as in
insects). Others have cellulosic walls.
5- Cell membranes have ergosterol (not cholesterol).
6- Cell contents include cytoplasm, nuclei, ribosomes,
golgi apparatus, mitochondria, lysosomes, glycogen,
lipids, crystals, vacuoles and endoplasmic reticulum.
the vegetative part of a fungus, consisting of a network of fine white filaments
(hyphae).
Filamentous Fungi
1.The basic morphological elements of
filamentous fungi are long branching
filaments or hyphae, which intertwine
to produce a mass of filaments or
mycelium
2.Colonies are strongly adherent to the
medium and unlike most bacterial
colonies cannot be emulsified in water.
Mycelia & Conidia
3. The surface of these colonies may be
velvety, powdery, or may show a
cottony aerial mycelium.
4. Pigmentation of the colony itself and of
the underlying medium is frequently
present.
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Colony Morphology
Yeasts
1. These occur in the form of round or oval
bodies which reproduce by the formation of
buds known as blastospores.
2. Yeasts colonies resemble bacterial colonies
in appearance and in consistency.
3. The only pathogenic yeast in medical
mycology is Cryptococcus neoformans.
Yeast colonies
Mucoid
colonies
Cryptococcus neoformans
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Yeast-Like
1.These are fungi which occur in the form of
budding yeast-like cells and as chains of
elongated unbranched filamentous cells
which present the appearance of broad
septate hyphae. these hyphae intertwine
to form a pseudomycelium.
2. The yeast like fungi are grouped together
in the genus Candida.
Candida Colonies
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Candida albicans
SEM
Thermally Dimorphic Fungi
These are fungi which exhibit a
filamentous
mycelial
morphology
(saprophytic phase) when grown at
room temperature 27oC, but have a
typical yeast morphology (parasitic
phase) inside the body and when
grown at 37oC in the laboratory (e.g.
Histoplasmosis).
Histoplasma capsulatum 27oC
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Histoplasma capsulatum 37oc
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II- Mode of living:
1- Most fungi are saprophytic living on dead organisms.
They secrete digestive enzymes into the medium, then
absorb the nutrients (external digestion, they digest
then ingest).
2- Some fungi are parasitic (internal or external parasites)
of living plants or animals.
3- Other fungi are symbiotic (mutualistic) e.g. lichens (
fungus + alga) and mycorrhizae (fungus + plant roots).
4- Few are predators that capture nematodes.
- Tinea barbae in man
- Cattle ringworm showing
multiple crusting lesions.
- T. verrucosum was isolated
Fungal spores
III- Occurrence: (everywhere)
1- Indoor Air (homes, schools, hospitals,
caves, offices, air conditioning filters,….)
2- Outdoor Air (open air, fields, gardens)
3- Fresh and marine water, aquatic
animals e.g. fish and fish eggs.
4- Soil (rhizosphere soil) and plant roots
5- Vegetation (leaves, stems, flowers, fruits
of plants), wood, paper, carpets etc.
6- Stored seeds, food, fruits, vegetables.
7- Animal dung, bird dropings, wastes
Occurrence: (continued)
8- Keratinaceous materials (hair, skin, nails,
hooves, bird feather)
9- Insects and arachnides, nematodes
10- Fungi ( mushrooms, Rhizopus)
11- Some pathogenic fungi are adapted to
humans (anthropophilic) and animals
(zoophilic).
12- Some fungi tolerate extreme conditions
of temperature, pH and water activity
IV- Reproduction:
1- Vegetative:
a- Fragmentation of mycelium
b- Fission of yeast cells
c- Budding of yeast cells
2- Asexual spore formation:
a- sporangiospores inside sporangia
( if motile: zoospores in zoosporangia)
b- conidia on conidiophores (DTR)
Fission yeast:
SchizoSaccharomyces
octosporus
Budding yeast
Saccharomyces
cervisiae
A
b
Asexual spore formation:
a- sporangiospores inside sporangia
b- zoospores in zoosporangia
c- conidia on conidiophores
c
3- Sexual spore formation:
(involves plasmogamy, karyogamy, and meiosis)
Kinds of sexual spores:
a- Oospores: (1 to several inside oogonium) formed
by contact of antheridia and oogonia
b- Zygospores: naked, multinucleate, thick walled
spores formed by fusion of gametangia (+ & -)
c- Ascospores: ( 8 inside each ascus) formed by
Contact of antheridia and ascogonia
d- Basidiospores :( 4 on each basidium) formed
after: - Clamp connections
- Spermatization - Somatogamy
Oogonium
Oospore
Gametangia
Zygospore
Antheridium
Oospores
zygospores
ascospores
ascus
Ascospores
8 ascospores
inside each
ascus
Basidiospores
4 basiospores
outside each
basidium
VI- Economic importance of fungi:
a- Positive role:
1 – Food:Edible mushrooms, morels and truffles
used as food.
2 – Biotechnology: Processing good quality of
bread (bakery yeast) , cheese (roqueforti and
camemberti) and other kinds of food (tempeh).
3- Vitamins (by yeasts) & mycoproteins
(Fusarium)
4- Traditional medicine: in China, Cordyceps
sinensis and Coriolus versicolor are used to
strengthen the body immune system of tumor
patients
5 - Production of medically and industrially
important compounds such as:
- Antibiotics: penicillin, cephalosporin, fusidin
and griseofulvin
- Immunosuppressive agents: cyclosporine
- Cholesterol lowering agents: simvastatin
- Antallergic: Corticosteroids.
- anticancer compounds from Coriolus
versicolor
- Organic acids ( citric , gluconic, oxalic,
fumaric,..)
- Alcohols (ethanol) and glycerol.
- Hydrolytic enzymes ( proteases, cellulases,
pectinases, lipases , amylases, …etc.)
6 –Improving soil fertility: fungi are
important decomposers & recyclers of
nutrients in the environment .
7- Better plant growth and higher
productivity: Some fungi form symbiotic
mycorrhizal associations with roots of
several plants .
8- Biocontrol agents : Certain fungi are used
to control harmful insects, nematodes,
weeds, and even other fungi.
b- Negative role:
1- Several fungi deteriorate food of man and
feedstuffs of animals and birds.
2- Others produce harmful hallucinogenic,
carcinogenic or deadly toxins.
3 - Destructive plant diseases are caused by
several air or soil borne fungi (blights, mildews,
rusts, smuts, rots,...)
4 – Many fungi are involved in allergy as well as
superficial, subcutaneous or systemic diseases
of man, animals and birds.
5- Certain fungi attack fish and their eggs , others
are harmful to benificial insects as silkworms
and honey bees.