M. Sc., Microbiology Study Material (Semester-I, General Microbiology) Department of Microbiology, School of Bioscience, Periyar University, Salem.

1. 13.04.09 Dr..D.Arvind Prasanth1
Classification & General
Properties of Fungi

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Introduction
 Mykes (Greek word) : Mushroom
 Fungi are eukaryotic protista; differ from
bacteria and other prokaryotes.
1. Cell walls containing chitin (rigidity & support),
mannan & other polysaccharides
2. Cytoplasmic membrane contains ergosterols
3. Possess true nuclei with nuclear membrane &
paired chromosomes.
4. Divide asexually, sexually or by both
5. Unicellular or multicellular

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Introduction
 Simplest fungus :- Unicellular budding
yeast
 Hypha :- Elongation of apical cell
produces a tubular, thread like structure
called hypha
 Mycelium :- Tangled mass of hyphae is
called mycelium. Fungi producing
mycelia are called molds or filamentous
fungi.
 Hyphae may be septate or non-septate

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CLASSIFICATION
 Depending on cell morphology
1. Yeasts
2. Yeast like fungi
3. Molds
4. Dimorphic fungi

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1. Yeasts
 Unicellular fungi which
reproduce by budding
 On culture - produce
smooth, creamy colonies
e. g Cryptococcus
neoformans (capsulated
yeast)

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2. Yeast like fungi
 Grow partly as yeasts and partly as
elongated cells resembling hyphae
which are called pseudohyphae.
e.g. Candida albicans

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3. Molds/ Filamentous fungi
 Form true mycelia &
reproduce by formation
of different types of
spores.
 Vegetative/ aerial
hyphae
e.g. Rhizopus, mucor

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4. Dimorphic fungi
 Occur in 2 forms
Molds (Filaments) – 25C (soil)
Yeasts – 37C (in host tissue)
Most fungi causing systemic infections
are dimorphic:
 Histoplasma capsulatum
 Blastomyces dermatidis
 Paracoccidioides brasiliensis
 Coccidioides immitis
 Penicillium marneffei
 Sporothrix schenkii

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Reproduction in fungi
 Sexual - formation of zygospores,
ascospores or basidiospores
 Asexual reproduction – budding or fission
 Asexual spores are formed on or in
specialized structures.
 Vary in size, shape & colour but these
characteristics are constant for a particular
species.

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Reproduction in fungi
 Micro conidia -
Small, single
celled
 Macro conidia –
Large, single or
many celled

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Systematic classification
 Based on sexual spore formation: 4
classes
1. Zygomycetes
2. Ascomycetes reproduce sexually
3. Basidiomycetes
4. Deuteromycetes (fungi imperfectii)

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1. Zygomycetes
 Lower fungi
 Broad, nonseptate hyphae
 Asexual spores -
Sporangiospores: present
within a swollen sac- like
structure called
Sporangium

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1. Zygomycetes
 Sexual spores -
Zygospore: a resting,
thick walled cell in
between hyphae
e.g. Rhizopus, Mucor

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2. Ascomycetes
 Includes both yeasts & filamentous fungi
 Narrow, septate hyphae
 Asexual spores are called conidia borne on conidiophore

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2. Ascomycetes
 Sexual spores called ascospores
are present within a sac like
structure called Ascus.
 Several asci may be seen within a
fruiting body as seen in Penicillium,
Aspergillus
 Each ascus has 4 to 8 ascospores.

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3. Basidiomycetes
 Sexual fusion results in the formation of a
club shaped organ called base or basidium
which bear spores called basidiospores

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4. Deuteromycetes
or Fungi imperfectii
 Group of fungi whose sexual phases are
not identified.
 Grow as molds as well as yeasts.
 Asexual stage – conidia
e.g. Candida, Cryptococcus

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Vegetative Structures of
Fungi
 Arthrospores –
formed by
segmentation &
condensation of
hyphae
 Chlamydospores –
thick walled resting
spores
e.g. C.albicans

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Fungal Infections/ Mycoses
 Superficial mycoses:
 2 types: surface and cutaneous mycoses
 Skin, hair & nails.
 Mild but chronic disease
 Deep mycoses:
 2 types: subcutaneous & systemic mycoses
 Caused by soil saprophytes
 Infection is accidental
 Range from a symptomatic infection to fatal disease

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Superficial: Surface mycoses
 Live exclusively on dead surfaces of
skin and its appendages
 No contact with living tissue, hence no
inflammatory response
1. Tinea versicolor
2. Tinea nigra
3. Piedra

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Superficial: Cutaneous mycoses
 Cornified layer of skin & its appendages
 Contact with living tissue, hence
inflammatory & allergic responses seen
1. Dermatophytes – skin, hair & nails
2. 3 genera - Trichophyton
Microsporum
Epidermophyton

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Deep mycoses
Subcutaneous mycoses
1. Mycotic Mycetoma
2. Chromoblastomycoses
3. Sporotrichosis
4. Rhinosporidiosis
Systemic mycoses
1. Cryptococcoses
2. Blastomycosis
3. Coccidioidomycoses
4. Histoplasmoses

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Candidiasis
 Caused by candida sps, forms a bridge
between superficial & deep mycoses as
it can cause cutaneous as well as
systemic infections
 Can also cause opportunistic infections

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Opportunistic infections
 Pts with debilitating disease, altered
physiological state
 Mainly caused by fungi which are common lab
contaminant on culture media
 Aspergillus
 Pencillium
 Mucor
 Rhizopus
 Produce serious & fatal infections

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Useful Properties of Fungi
Source of food
e.g. mushrooms
Fermentation - Production of
alcohol, bread, cheese
e.g. Sacchromyces spps
Antibiotic production
e.g. Penicillin from
Penicillium notatum

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Useful Properties of Fungi
Ergot from Claviceps
purpurea, used to induce
uterine contractions
Vaccines for Hepatitis B –
Sacchromyces cerevisiae