This document provides an overview of fungi, including their classification, structures, reproduction, and role in infections and other applications. It describes the four main classes of fungi based on sexual spore formation - zygomycetes, ascomycetes, basidiomycetes, and deuteromycetes. Fungi can cause superficial infections of the skin/nails or deeper subcutaneous and systemic infections. They also have several useful properties like producing food, antibiotics, and industrial fermentation agents.

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