Mycology is the study of fungi, which is branch of biology.

Approximately 80,000 species of fungi have been described.

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.

absorb

Extra enzyme

Insoluble polymer Fungi

Soluble organic materials

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, many of them can

grow in medium that have a PH 2-10, although they prefer a

neutral PH.

10. They may be unicellular or multicellular.

11. Yeasts are generally unicellular and produce circular restricted

pasty or mucoid colonies.

11. Molds are multicelled filamentous forms of fungi consisting of

thread like filaments termed hyphae.

septate hyphae

hypha

aseptate

Many of the fungal pathogen are dimorphic or diphasic, with a yeast (Y) and a mycelial (M) phase.

11. Many fungi are responsible for much of the disintegration of organic matter and they affect us directly by destroying food,

fabrics, leathers and other consumer. Other fungi are beneficial which are the basis of a number of industrial processes involving:

A.Fermentation such as

a. making of bread.

b. alcoholic fermentation.

c. 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

M

30°C

Y

37°C

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 (lower fungi).

2.class Ascomycetes Telomorphic or

3.class Basidiomycetes perfect fungi.

4.class Deutromycetes anamorphic or imperfect fungi

Fungi in class Zygomycetes have wide mycelium.

Nuclei

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

1.Plasmogamy i.e. fusion of protoplasm of (2) sex cells to form a pigmass.

2.Karyogamy i.e. fusion of (2) nuclei to form one mass.

3.Meosis i.e. reduction division.

A. Sexual reproduction in Zygomycetes

Plasmogamy Karyogamy Meosis

+ -

Exp: Rhizopus, Mucor 4 Zygospores.

Resting

B. Sexual reproduction in Ascomycetes

Resting Plasmogamy Karyogamy Meosis

4 Ascosporesmitosis8 Ascospores (inside ascus)

C. Sexual reproduction in Basidiomycetes

resting

EX.P: Mushroom

Basidium

Basidiospores

plasmogamy Karyogamy Meosis

4 basidiospores (exogenous)

D. 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

1.Sporangiospores:

Sporangiospores

Sporangium Sporangiophores

2. Arthrospores (arthroconidia): They formed due to fragmentation of the mycelium

EX.P: Geotrichum, Trichosporon

EX. P: Rhizopus

3. Blastospores (Blastoconidia): Produce by budding and separation from the parent cell

EX.P: Candida

4. Chlamydospores (chlamydoconidia):

Terminal Intercalary

+

5. Conidia: Usually produced terminally or laterally on hyphae or

special structure, conidiophores, and are borne externally as a

single cell.

conidia either unicellular (microconidia) or multicellular

(macroconidia) EX.P: penicillium, Dermatophytes.

unicellular

multicellular