MYCOLOGY
Fungi
- Classified as thallophytes, have true nuclei and are heterotrophic members of the plat family that lack
stems and roots
- Chitin in the cell wall
- Ergosterol in the cell membrane
- Reproduction by means of spores, produced asexually or sexually
- Lack of susceptibility to antibacterial antibiotics
- Do not contain chlorophyll
- Saprophytic nature (derive nutrition from organic materials)
Basic Morphologic Forms
- Mold Phase (filamentous) – multicellular; cottony, woolly, or powdery colonies; mycelial mass; grows at
25°C to 30°C
- Yeast Phase – moist, creamy (resembling bacterial colonies), opaque, or pasty colonies; grows from 35°C
to 37°C
- Monomorphic Fungi – has one growth phase (e.g., Sepedonium)
- Dimorphic Fungi – can demonstrate both phase; when dimorphism is temperature-dependent, the fungi
is designated as thermally dimorphic
Medically Important Dimorphic Fungi:
1. Histoplasma sp.,
2. Blastomyces spp.,
3. Coccidioides spp.,
4. Cokeromyces recurvatus
5. Emergomyces spp.,
6. Paracoccodioides spp.
Fundamental Unit and Different Classifications
Hyphae – microscopic units of fungi
- Septate hyphae – divided by crosswalls
- Aseptate / Coenocytic hyphae – no crosswalls / divisions
- Pseudohyphae - chain of cells formed by budding that resemble true hyphae (w/c are not constricted at
the septa); constricted at the septa, form branches that begin with septation, and have terminal cells
smaller than other cells
Mycelium – an intertwining structure composed of hyphae (tubular filaments); consists of:
- Vegetative portion (thallus) – grows in or on a substrate and absorbs water and nutrients
- Reproductive, or aerial part – contains fruiting bodies that produce the reproductive structures, known
as conidia and spores; the aerial part extends above the agar surface
, Reproduction: Sexual and Asexual
A. Sexual Reproduction – meiosis, or reduction division of two fertile cells, followed by a merging of
the cells and nuclear fusion, occurs
Perfect fungi – a fungi that exhibit a sexual phase
Spores in Sexual Reproduction:
1. Ascospores – contains in a saclike ascus
2. Zygospores – involve the fusion of 2 identical cells arising from the same hypha
3. Oospores – involve the fusion of cells from two separate, nonidentical hyphae
4. Basidiospores – contained in a club-shaped basidium
A. Asexual Reproduction – involve only mitosis, w/ nuclear and cytoplasmic division
Imperfect fungi (or fungi imperfecti) – do not exhibit sexual reproduction
Conidiogenesis (conidia formation):
- Blastic conidiogenesis – parent cell enlarges, a septum forms, and the enlarged portion splits off to form
a daughter cell
- Thallic conidiogenesis - septum forms first, and new growth beyond the septum becomes the daughter
cell
Spores in Asexual Reproduction:
1. Conidia – produced either singly or multiply in long chains or clusters by specialized vegetative hyphae,
known as conidiophores (may branch into secondary segments, known as phialides, which then
produce the conidia)
Macroconidia – multicellular; large; usually septate; and club, oval, or spindle shaped
Microconidia – small; unicellular with a round, elliptical, or pyriform (pear) shape.
sessile microconidia - borne directly on the hyphae
pedunculate microconidia – borne on the end of a short conidiophore
2. Blastoconidia (blastospores) – daughter cell buds off the mother cell and is pinched off (budding); e.g.
yeasts, including Candida; may form pseudohyphae
3. Chlamydoconidia (chlamydospores) - thick-walled, resistant, resting spores produced by “rounding up”
and enlargement of the terminal hyphal cells; spores germinate into a new organism when favorable
environmental conditions exist;
terminal arrangement – may form at the hyphal tip;
sessile arrangement – may form on the hyphal sides;
intercalary arrangement – may form within the hyphal strand
4. Arthroconidia (arthrospores) – simple fragmentation of the mycelium at the septum into rectangular-,
cylinder-, or cask-shaped spores; useful identification characteristic of the dimorphic fungus Coccidioides
immitis and Geotrichum candidium, a yeast
5. Sporangiospores – contained in sporangia, or sacs, and produced terminally on sporangiophores or
aseptate hyphae; unique to Zygomycetes.
Fungi
- Classified as thallophytes, have true nuclei and are heterotrophic members of the plat family that lack
stems and roots
- Chitin in the cell wall
- Ergosterol in the cell membrane
- Reproduction by means of spores, produced asexually or sexually
- Lack of susceptibility to antibacterial antibiotics
- Do not contain chlorophyll
- Saprophytic nature (derive nutrition from organic materials)
Basic Morphologic Forms
- Mold Phase (filamentous) – multicellular; cottony, woolly, or powdery colonies; mycelial mass; grows at
25°C to 30°C
- Yeast Phase – moist, creamy (resembling bacterial colonies), opaque, or pasty colonies; grows from 35°C
to 37°C
- Monomorphic Fungi – has one growth phase (e.g., Sepedonium)
- Dimorphic Fungi – can demonstrate both phase; when dimorphism is temperature-dependent, the fungi
is designated as thermally dimorphic
Medically Important Dimorphic Fungi:
1. Histoplasma sp.,
2. Blastomyces spp.,
3. Coccidioides spp.,
4. Cokeromyces recurvatus
5. Emergomyces spp.,
6. Paracoccodioides spp.
Fundamental Unit and Different Classifications
Hyphae – microscopic units of fungi
- Septate hyphae – divided by crosswalls
- Aseptate / Coenocytic hyphae – no crosswalls / divisions
- Pseudohyphae - chain of cells formed by budding that resemble true hyphae (w/c are not constricted at
the septa); constricted at the septa, form branches that begin with septation, and have terminal cells
smaller than other cells
Mycelium – an intertwining structure composed of hyphae (tubular filaments); consists of:
- Vegetative portion (thallus) – grows in or on a substrate and absorbs water and nutrients
- Reproductive, or aerial part – contains fruiting bodies that produce the reproductive structures, known
as conidia and spores; the aerial part extends above the agar surface
, Reproduction: Sexual and Asexual
A. Sexual Reproduction – meiosis, or reduction division of two fertile cells, followed by a merging of
the cells and nuclear fusion, occurs
Perfect fungi – a fungi that exhibit a sexual phase
Spores in Sexual Reproduction:
1. Ascospores – contains in a saclike ascus
2. Zygospores – involve the fusion of 2 identical cells arising from the same hypha
3. Oospores – involve the fusion of cells from two separate, nonidentical hyphae
4. Basidiospores – contained in a club-shaped basidium
A. Asexual Reproduction – involve only mitosis, w/ nuclear and cytoplasmic division
Imperfect fungi (or fungi imperfecti) – do not exhibit sexual reproduction
Conidiogenesis (conidia formation):
- Blastic conidiogenesis – parent cell enlarges, a septum forms, and the enlarged portion splits off to form
a daughter cell
- Thallic conidiogenesis - septum forms first, and new growth beyond the septum becomes the daughter
cell
Spores in Asexual Reproduction:
1. Conidia – produced either singly or multiply in long chains or clusters by specialized vegetative hyphae,
known as conidiophores (may branch into secondary segments, known as phialides, which then
produce the conidia)
Macroconidia – multicellular; large; usually septate; and club, oval, or spindle shaped
Microconidia – small; unicellular with a round, elliptical, or pyriform (pear) shape.
sessile microconidia - borne directly on the hyphae
pedunculate microconidia – borne on the end of a short conidiophore
2. Blastoconidia (blastospores) – daughter cell buds off the mother cell and is pinched off (budding); e.g.
yeasts, including Candida; may form pseudohyphae
3. Chlamydoconidia (chlamydospores) - thick-walled, resistant, resting spores produced by “rounding up”
and enlargement of the terminal hyphal cells; spores germinate into a new organism when favorable
environmental conditions exist;
terminal arrangement – may form at the hyphal tip;
sessile arrangement – may form on the hyphal sides;
intercalary arrangement – may form within the hyphal strand
4. Arthroconidia (arthrospores) – simple fragmentation of the mycelium at the septum into rectangular-,
cylinder-, or cask-shaped spores; useful identification characteristic of the dimorphic fungus Coccidioides
immitis and Geotrichum candidium, a yeast
5. Sporangiospores – contained in sporangia, or sacs, and produced terminally on sporangiophores or
aseptate hyphae; unique to Zygomycetes.
