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Course: Microbial Physiology
Lecturer: Dr. Weam Saad
Lecture: Fungi
Fungi Physiology
The term "mycology" is derived from Greek word "mykes" meaning
mushroom. Therefore mycology is the study of fungi .
Importance of fungi: Fungi inhabit almost every niche in the environment
and humans are exposed to these organisms in various fields of life .
Beneficial Effects of Fungi :
1. Decomposition - nutrient and carbon recycling .
2. Biosynthetic factories. The fermentation property is used for the
industrial production of alcohols, fats, citric ,oxalic and gluconic
acids .
3. Important sources of antibiotics, such as Penicillin .
4. Model organisms for biochemical and genetic studies. Eg: Neurospora
crassa
and Saccharomyces cerviciaeis extensively used in
recombinant DNA technology, which includes the Hepatitis B
Vaccine .
5. Some fungi are food (mushroom) and Yeasts provide nutritional
supplements such as vitamins and cofactors, Penicillium is used to
flavor Roquefort and Camembert cheeses .
6. Fungi (Leptolegnia caudateand and Aphanomyces laevis) are used to
infect mosquito larvae and help in malaria control .
Harmful Effects of Fungi :
1. Destruction of food, lumber, paper, and cloth .
2. Animal and human diseases, including allergies.
3. Toxins produced by poisonous mushrooms and within food
(Mycetism and Mycotoxicosis
4. Cause many Plant diseases.
5. Spoilage of agriculture such as vegetables and cereals in the stores.
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6. Damage the products such as magnetic tapes and disks, glass lenses,
bones and wax .
General properties of fungi :
1. They are eukaryotic; cells contain membrane bound cell organelles
including nuclei, mitochondria, Golgi apparatus, endoplasmic
reticulum, lysosomes etc. They also exhibit mitosis .
2. Have ergosterols in their membranes and have 80S ribosomes .
3. Have a rigid cell wall and are therefore non-motile, a feature that
separates them from animals. All fungi possess cell wall made of chitin.
4. Are chemoheterotrophs (require organic compounds for both carbon
and energy sources) and fungi lack chlorophyll and are therefore not
autotrophic .
5. Fungi are osmiotrophic; they obtain their nutrients by absorption .
6. They obtain nutrients as saprophytes (live off of decaying matter) or as
parasites (live off of living matter). Source for C and N is only organic
compounds.
7. Optimum temperature to grow are 25-35
o
C, some can grow 35-47
o
C.
8. Optimum pH 4.0-4.5.
9. All fungi require water and oxygen and there are no obligate anaerobes.
10. Typically reproduce asexually and/or sexually by producing spores.
11. They grow either reproductively by budding or non-reproductively by
hypha tip elongation .
12. Food storage is generally in the form of lipids and glycogen .
Classification of fungi :
Fungi were initially classified with plants ( old classification Monera,
Protista, Fungi, Plantae and Animalia.) . classification based on Morphology :
1. Moulds (Molds): Filamentous fungi Eg: Aspergillus sps, Trichophyton
rubrum.
2. Yeasts: Single celled cells that buds Eg: Cryptococcus neoformans, and
Saccharomyces cerviciae
.
3. Yeast like: Similar to yeasts but produce pseudohyphae Eg: Candida
albican
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4. Dimorphic: Fungi existing in two different morphological forms at two
different environmental conditions .They exist as yeasts in tissue and
in vitro at 37
o
C and as molds in their natural habitat and in vitro at room
temperature. Eg: Histoplasma capsulatum, Blastomyces dermatidis.