Lecture 2
Fungi
Classification of fungi
Classification of Fungi

Over 60,000 species of fungi are known.
 Fungi are classified primarily by their method of
reproduction (both sexual and asexual).
 Two kingdom system was used until Whitaker (1969)
proposed that organisms be classified into five
kingdoms: - Monera (=Bacteria), Protista (=Mostly Algae
and Protozoans), Plantae (=Plants), Mycetae (=Fungi)
and Animalia (=Animals).
 Fungi are grouped into phyla, or divisions, based on
their shape, size, function, biochemistry and more
recently, their DNA and RNA sequences.
 Fungi belong to Domain-Eukarya and Kingdom -Mycetae (=Fungi),
the classification of fungi, as proposed by Ainsworth (1973), is
commonly followed:-
The more recent systems of classification that is based, in
part, on molecular research are:-
Zygomycota
 1% of all known species of fungi
 Primary colonizers of most substrates.
 Most species have thallus of coenocytic hyphae;
except at bases of reprod. Structures.
 Haploid nuclei in vegetative stage
 no flagellated cell stages in life cycle
 Produce non-motile asexual spores in sporangia.
 No zoospores. The resting spore is a zygospore,
produced by the fusion of two morphologically similar
gametes.
 saprobes, parasites & pathogens, mutualists
A
D
B
C
Rhizopus stolonifer
(AUMC photos)
Zygomycota
Fungi
Helpful or harmful role
Rhizopus, Absidia,
Mucor, Circinella,
Rhizomucor, etc..
Deterioration of bread, fruits
and vegetables, Human
zygomycosis, Biotechnology.
Conidiobolus,
Basidiobolus
Human zygomycosis
Conidiobolus,
Insect pathogens
Erynia, Zoophthora
Entomophthora,
Glomus, Gigaspora Symbiotic relationship with
(mycorrhyzal fungi) plant roots
Circinella
• Pilobolus grows on cattle dung.
• Characterized by forcibly
discharged sporangia (> 2meters!)
• It is involved in carrying the
cattle lungworm (Dictyocaulus
viviparus(
Progametangia
Gametangia
Zygospore
Entomophthora muscae: Fungal growth on
abdomen , legs and wings of house fly
Zygorhynchus
Absidia
Zygospores of Absidia
and Zygorhynchus
Basidiomycota
These are the most structurally complex fungi, and
include what we commonly call mushrooms, toadstools
and bracket fungi.
Basidiomycetes
are
characterized
by
a
septate
mycelium.
Saprobes and parasites (esp. of plants), terrestrial.
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
Genera of medical importance include:
1.
Teleomorphs of known pathogenic fungi, e.g.
Filobasidiella.
2.
3.
Coprinus and Schizophyllium agents of
basidiomycosis.
Mushroom poisoning by Amanita, Lepiota,
Coprinus and Psilocybe etc
Amanita muscaria
ASCOMYCOTA
Classification -based largely on morphology, anatomy,
and life history.
For yeasts, physiological characters are especially
important (ability to ferment specific sugars) is useful in
delimiting species.
Sexual reproduction results in the formation of an ascus
which contains 4, 8, or multiples of 4 or 8 ascospores.
Asci may be naked (not surrounded by fungal tissue or
surrounded by an ascoma.
Medically important genera include the
teleomorphs of known pathogenic fungi
e.g. Arthroderma, Nannizzia, Ajellomyces,
Pseudallescheria, Eurotium etc., agents of
mycetoma,
like
Leptosphaeria
and
Neotestudina, and of black piedra, like
Piedraia hortae.
Deuteromycota
A class of 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.
This class contains the majority of medically important
fungi.
These include the agents of hyalohyphomycosis,
aspergillosis, dermatophytosis and the dimorphic
pathogens, like Histoplasma capsulatum
Identification of the hyphomycetes is primarily based on
microscopic morphology of the conidia.
Liver cancer caused by aflatoxin
in improperly stored food
Aflatoxicosis, fatty liver,
chicken