The main characteristics of fungi.
1. They are an important component in the energy cycle.
2. They are eukaryotic organisms that do not contain chlorophyll, with cell wall containing
chitin .
3. They are aerobic, have chemohetrophic type of nutrition.
4. Some fungi are small in size ( about 3µ. in diam.) where as others are large and can be
seen by the naked eye.
5. They have no organic level differentiation.
6. The cell membrane contains sterols.
7. Moisture is necessary for the growth of molds and yeasts, they prefer moderate temp.
8. All fungi need a protein source and carbohydrate source.
9. Fungi are able to tolerate a wide rang of PH
10. They may be unicellular or multicellular.
a) Yeasts are generally unicellular and attatchment of one cell to another give rise to
pseudohyphae
b) Molds are multicellular filamentous forms of fungi consisting of thread like filaments
termed hyphae. Mass of hyphae called mycelim .. hyphae or mycelim is long selender
branching tube , may be septate or asptate
c) Many of the fungal pathogen are dimorphic or diphasic, with a yeast (Y) and a mycelial
(M) phase. yeast develop at 37C and mycelim develop at room temp. 24-30
11. Many fungi are responsible for much of the disintegration of organic matter and they
affect us directly by destroying food, Other fungi are beneficial which are the basis of a
number of industrial processes involving:
a) Fermentation such as
1. making of bread.
2. alcoholic fermentation.
3. preparation of certain cheeses.
b) Production of many organic acids.
c) Responsible for the manufacture of a number of antibiotic drugs as penicillin which is
produced by penicillium
12. Some cause diseases in plants, animal and harm man more directly.
There are four type of mycotic diseases:
1) Hypersensitivity.
2) Mycotoxicoses.
3) Mycetismus.
4) Infection: pathogenic fungi do not produce toxins but they show physiologic
modifications during a parasitic infection
Classification of fungi:
There are four (4) important classes of medically important fungi
1. class Zygomycetes
2. class Ascomycetes
3. class Basidiomycetes
4. class Deutromycetes
Fungi in class Zygomycetes have wide
mycelium. And it is aseptate
In Ascomycetes, Basidiomycetes and
Deutromycetes, the mycelium is less than 5µ.
in diam and it is septated
Reproduction of fungi
Fungi reproduce by spores either sexually or asexually. The spore is a resistant unit of fungi.
Sexual reproduction involve three (3) processes
a) Plasmogamy i.e. fusion of protoplasm of (2) sex cells to form a pigmass.
b) Karyogamy i.e. fusion of (2) nuclei to form one mass.
c) Meosis i.e. reduction division.
Sexual reproduction in Zygomycetes
Plasmogamy --> Karyogamy --> Meosis
--> 4 Zygospores.
Sexual reproduction in Ascomycetes
Plasmogamy --> Karyogamy --> Meosis --> 4 Ascospores
mitosis
8 Ascospores
(inside
ascus)
Sexual reproduction in Basidiomycetes
plasmogamy --> Karyogamy --> Meosis 4 basidiospores (exogenous)
Deutromycetes have no sexual reproduction only asexual form
Asexual spores
The morphology, arrangement and mode of derivation of spores serve as important criteria
by which genus and species identification can be made . There is no karyogamy or
plasmogamy or meosis the production occir by mitosis
1) Sporangiospores:
Produced in sac-like structure called sporangium .
2) Arthrospores (arthroconidia): They formed due to fragmentation of the mycelium .
3) Blastospores (Blastoconidia): Produce by budding and separation from the parent cell
4) Chlamydospores (chlamydoconidia): cell enlarge to develop thick-walled resistant
resting spoe .. when formed at the end of hyphae termed terminal or between hyphae
termed intercalary
5) Conidia: Usually produced terminally or laterally on hyphae or special structure,
conidiophores, and are borne externally as a single cell.
A. conidia either unicellular (microconidia)
B. multicellular
(macroconidia) .
