This document discusses fungi. It begins by defining key terms like mycology and mycoses. It then describes the characteristics of fungi, including their eukaryotic nature and ability to withstand extreme conditions. The document outlines fungal structure, describing their cell walls, membranes, and both sexual and asexual reproduction. It also classified fungi into four main morphological groups: molds, yeasts, dimorphic fungi, and yeast-like fungi. The document concludes by discussing fungal pathogenesis, categorizing mycoses into superficial, cutaneous, subcutaneous, and systemic infections.

1. FUNGI
By Mr. Vincent Ejakait

2. Content
 Definition
 Characteristics
 Structure
 Classification
 Pathogenesis
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3. Definitions
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4. Definitions
 Mycology: Is the study of fungi
 Fungi are a group of eukaryotic organisms with
a diversity of morphological appearances
depending on species. Mainly molds and yeasts
 Mycoses: Fungal infection
 Mycologist: scientists who study mycologyMr. Ejakait
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5. Importance
 Nutrition: Edible mushrooms
 Industrial use: (Penicillium) ripens cheese,
adds flavor
 Fermentation: Brewers’ and Baker’s yeast
 Plant pathology: most plant diseases are
caused by fungi
 Medical importance: 50-100 species recognized
human pathogens
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6. Characteristics
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7. General characteristics
 Eukaryotic in nature.
 Unicellular/Multicellular
 Mostly soil saprophytes
 Don’t possess chlorophyll
 Fungi are able to withstand certain extreme
environmental conditions better than most
other microorganisms.
 Fungi are heterotrophic, using a wide variety
of materials for nutrition.
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8. Structure (Morphology)
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9. Morphology
• Eukaryotic in nature: have a nucleus enclosed
within membranes
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10. Morphology cont..
 Cell wall: made up of chitin, glucans, mannans
and complex polysaccharides.
 Cell wall consists of chitin not peptidoglycan like
bacteria. Thus fungi are insensitive to antibiotics
such as penicillins.
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11. Fungal cell wall
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12. Morphology cont..
 Consist of ergosterol rather
than cholesterol like
bacterial cell membrane.
 Ergosterol is the site of
action of antifungal drugs
e.g. amphotericin B & azole
group
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13. Morphology cont..
 Cell division (reproduction) is:
 Sexual
 Asexual Sexual Asexual
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14. Morphology cont..
 May be unicellular like Yeast or
 May be multicellular like Mould
Unicellular fungi Multicellular fungi
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15. Morphology cont..
 Elongation of cell produces a tubular thread
like structure called hypha
 Tangled mass of hypha is called mycelium
 Fungi which forms mycelium is called moulds
or filamentous fungi
 Hypha may be septate or non-septateMr. Ejakait
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16. Hypha
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17. Septate vs Non-septate hypha
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18. Classification
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19. Classification of fungi
Morphological classification
Fungi are grouped into 4 morphologic classes:
1. Moulds
2. Yeasts
3. Dimorphic fungi
4. Yeast-like fungi
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20. 1. Moulds
 Also called filamentous fungi
 They are Multicellular
 Composed of branching filaments (hyphae)
 Has spores which are resistant resting or
dormant cells.
 Reproduction can be sexual or asexual
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21. Moulds
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22. 2. Yeasts
 Predominate unicellular
 They are commonly oval, but some are elongated
and some spherical.
 Yeasts have no flagella or other locomotory
organelles seen in bacteria.
 Reproduce by budding.
 The only pathogenic yeast is Cryptocoocus
neoformans
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23. Mr. Ejakait
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24. 3. Yeast – like fungus
 Grows partly as yeasts and
partly as elongated cells
resembling hyphae
 Such hyphae form
psuedomycelium
 Example include Candida
albicans
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25. 4. Dimorphic
 Can occur as filaments (moulds) or as yeasts
depending on the condition of growth
 They are in mold form at 25oC and yeast form at
37oC.
 Mould in the cold and yeast in the heat.
 Most Fungi causing systemic infections are
dimorphic fungi
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26. Mr. Ejakait
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27. Pathogenesis
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28. Mycoses
 Mycoses refers to the fungal infection.
 It can be divided into 4 broad categories:
1. Superficial mycoses
2. Cutaneous mycoses
3. Subcutaneous mycoses
4. Systemic mycoses
 Opportunistic mycosesMr. Ejakait
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29. a. Superficial mycoses
 Surface infections limited to outermost layers
of skin and hair.
 Only in the dead layers of skin
 No inflammatory response
 Only cosmetic problems
 Examples: Pityriasis Versicolor, Tinea nigra,
Piedra
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30. Pityriasis versicolor
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31. Tinea nigra
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32. Piedra
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33. b. Cutaneous mycoses
 Fungal infections extending
deeper into the epidermis
and its integuments.
 Also called Dermatophytosis
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34. Cutaneous mycoses cont..
 Classified based on location of infection
 Tinea pedis – on the feet or between the toes
 Tinea corporis – between the fingers, in
wrinkles on the palms
 Tinea cruses – lesions on the hairy skin around
the genitalia
 Tinea capitis – scalp and eyebrows
 Onychomycosis – chronic infection of the nail
bed
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35. Tenia
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36. c. Subcutaneous mycoses
 Infections involving
dermis, subcutaneous
tissue, muscles and
fascia.
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37. d. Systemic mycoses
 Infections originating primarily in the lungs
(acquired by inhalation) and spreading to
other organs.
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38. Opportunistic mycoses
Besides the above four mentioned types, this
category includes infections in which fungi of no
significance or low virulence infect humans with
compromised immune system.
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