General characteristics of Fungi

1. Chapter 2
General Characteristics of
Fungi
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2.  Diverse and Widespread but adapted to dark, moist environments
Closer to animal than to plants
Over 100,000 species known
Range from single celled (microscopic e.g. yeast) to those that have
fruiting structures (eg. mushrooms)
 Kingdom Fungi divided into five main phyla based on the way they
reproduce and molecular biology
Chytridiomycota, Zygomycota, Ascomycota, Basidiomycota and
Deutromycota (Imperfect Fungi)
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3. 1. Most fungi are multi-cellular eukaryotes; but, a few are unicellular like yeast
2. Fungi are non-motile
 3. Most are heterotrophic and consume organic matter. They lack chlorophyll
 A. Those that obtain nourishment from non-living (dead) hosts are called
saprophytes
 B. Those that obtain nourishment from living hosts are called parasites
 4. Most fungi are decomposers that produce powerful digestive enzymes that they
introduce into their immediate environment to break down organic matter
 A. They can destroy and damage stored food and goods
 B. They can damage live timber
 C. In partnership with bacteria, fungi are considered the earth's decomposers
5. In the vegetative condition, the fungus body (thallus) is called a mycelium
6. The mycelium is the food-absorbing portion of the fungal body cross walls
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4. 7. The mycelium is actually a network of filaments called hyphae
8. There are 2 kinds of hyphae
 A. Septate -hyphae that are divided into successive compartments by cross walls or
septa
 B. Coenocytic (or non septate) -hyphae that are continuous and are without cross walls
9. Unlike plant cells, fungal cell walls contain chitin rather than cellulose (recall chitin is
found in the exoskeleton of insects and other arthropods)
10. The energy reserves of fungi is not starch -like plants; but, is glycogen -like animals
11. Reproduction is by motile -or non-motile spores that may be produced sexually or
asexually 4

5. 12. Some uses of fungi
 A. Baking
 B. Cheese production
 C. Brewing of beer
 D. Wine making
13. There are approximately 200 species of edible fungi and about 70 poisonous
species
14. Fungi include over 100,000 species
15. Fungi are found in a wide variety of habitats; but, seem especially adapted to
dark, moist environments
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6. 16. Fungi play an important role in ecosystems, decomposing dead
organisms, fallen leaves, feces, and other organic materials.
This decomposition recycles vital chemical elements back to the
environment in forms other organisms can assimilate.
Most plants depend on mutualistic fungi to help their roots absorb
minerals and water from the soil.
Humans have cultivated fungi for centuries for food, to produce antibiotics
and other drugs, to make bread rise, and to ferment beer and wine
chitin (chitin synthase) is a target for the polyoxin antibiotics that are used
against fungi
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7. Fungi are haploid (having a single set of unpaired chromosomes), whereas the other major groups
of eukaryotes are diploid (containing two complete sets of chromosomes, one from each parent)
 Fungal cell membranes contain ergosterol, whereas animals have cholesterol and plants have
sitosterol and other 'phytosterols'.
Several antifungal drugs (e.g. ketoconazole) used in human therapy act by blocking ergosterol
synthesis. The antifungal antibiotics (e.g. nystatin, amphotericin B) combine with ergosterol in
fungal membranes. And several fungicides used for plant disease control act by disrupting specific
steps in the ergosterol synthesis pathway.
 Fungi synthesise the amino acid lysine by a unique pathway, different from that of other
organisms.
 Fungi have characteristic soluble carbohydrates (the disaccharide trehalose and polyhydric
alcohols like mannitol and arabitol) and storage compounds (e.g. glycogen), differing from those
of most plants and animals.
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8. Fungi have several characteristic ultrastructural features, such as plate-like
cristae in the mitochondria (like animals), and tubular unstacked Golgi
cisternae (unlike animals or plants).
 The microtubules of fungi have unique binding affinity for anti-tubulin
agents. In particular, fungal tubulins bind to the antibiotic griseofulvin
(used to treat some fungal infections of humans) and to the benzimidazole
fungicides (used widely for control of fungal pathogens of plants).
 Finally, fungi differ from other organisms in a range of biochemical and
molecular features such as the regulation of some enzymes, some aspects
of mitochondrial codon usage, etc.
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9. MORPHOLOGY OF FUNGI
1. Yeast
2. Yeast-like
3. Mold (hyphae)
4. Dimorphic Fungi
1. YEASTS
1. Unicellular organisms
2. Round or oval fungi that bud or pinch off
3. Growth resembles bacteria
4. Much larger than bacteria
2. YEAST-LIKE (PSEUDOHYPHAE) – Candida /Candida albicans
parasitizes a host using its Pseudohyphae.
• Budding yeast with septum.
• The septum has formed between the daughter bud and the mother
cell.
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10. 3. HYPHAE (MYCELIUM)
• Multi-cellular filamentous structures.
• Cylindrical, branching filaments composed of tubular
cell.
• wall filled with cytoplasm and organelles
• A mass of hypahe is called Mycelia.
• Hyphae
1. Septate – filaments have crosswalls or septa.
Ex. Aspegillus
2. Aseptate – filaments lack crosswalls; also called
coenocytic.
Ex. Mucor
Cont.
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11. Fungal Hyphae Cells
1- Hyphal wall 2- Septum 3- Mitochondrion 4- Vacuole 5-
Ergosterol crystal 6- Ribosome 7- Nucleus 8- Endoplasmic
reticulum 9- Plasma membrane 10- Golgi apparatus
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3 4
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6 7
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12. Cont.
4. DIMORPHIC FUNGI (FUNGAL DIMORPHISM)
• Yeast
• (Parasitic or Pathogenic Form).
• Seen in human tissue, exudates, or if cultured in an incubator at 37 °C.
• Mycelium
• (Saprophytic or Mold Form).
• Form observed in nature or if incubated at 25 °C.
• Conversion to the yeast form essential for pathogencity.
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