Introduction to Mycology

Study Notes

Mycology is the study of fungi.
Fungi are eukaryotic organisms that can produce spores.
Fungi are heterotrophic, meaning they obtain nutrition from organic sources.
Fungi produce extracellular enzymes to break down food.
Fungi have diverse benefits, including decomposition, industrial applications, antibiotic production, and use in biotechnologies.

Fungi are crucial for nutrient recycling and carbon decomposition.
Fungi are used to produce alcohols, fats, acids (citric, oxalic, gluconic), and antibiotics (e.g., Penicillin) through fermentation.
Fungi such as Neurospora crassa are model organisms for biochemical and genetic research.
Saccharomyces cerevisiae is used in recombinant DNA technology.
Edible mushrooms are a valued food source.
Yeasts provide nutritional supplements with vitamins and cofactors.
Penicillium imparts flavor to cheeses like Roquefort and Camembert.
Claviceps purpurea produces ergot alkaloids with therapeutic potential.
Certain fungi control mosquito larvae (e.g., Leptolegnia caudate and Aphanomyces laevis) aiding malaria control.

Fungi can cause significant damage to food, lumber, paper, and cloth.
Fungi cause animal and human diseases, including allergies.
Toxic mushrooms and fungal toxins in food can cause illnesses (Mycetism and Mycotoxicosis).
Fungi are significant plant pathogens.
Fungi spoil agricultural produce, such as vegetables and cereals.
Fungal damage extends to products like magnetic tapes, disks, lenses, statues, and bones.

Eukaryotic: Fungi possess membrane-bound organelles: nuclei, mitochondria, Golgi apparatus, endoplasmic reticulum, and lysosomes. They undergo mitosis.
Ergosterol: Fungi have ergosterol in their cell membranes, unlike the cholesterol found in animal cells.
Rigid Cell Wall: Fungi have a rigid cell wall made of chitin, a polysaccharide.
Non-Motile: Unlike animals, fungi lack flagella and are non-motile.
Chemoheterotrophs: Fungi require organic compounds for both carbon and energy, unlike plants.
Osmiotrophic: Fungi absorb their nutrients.
Saprophytes & Parasites: Fungi obtain nutrients as saprophytes (decomposers) or parasites (live off of living organisms).
Oxygen Requirement: Fungi require water and oxygen to survive; obligate anaerobes are not found in fungi.
Reproduction: Fungi reproduce asexually and/or sexually, producing spores.
Growth: Fungi grow either through budding (yeast) or hyphal tip elongation.
Food Storage: Fungi typically store food in the form of lipids and glycogen.

Fungi were initially classified with plants due to their similarities.
In 1969, Robert Whittaker proposed a five-kingdom classification system (Monera, Protista, Fungi, Plantae, Animalia).

Fungi can be filamentous (hyphal forms) or single-celled (yeast forms).
For classification purposes, fungi are typically studied as molds, yeasts, yeast-like, and dimorphic forms.
Cell Wall: Fungal cell walls are rigid structures mainly composed of chitin. They may also contain mannans, glucans, and other polysaccharides alongside polypeptides.
Plasma Membrane: Fungal cell membranes have a typical bi-layered structure and contain sterols.
Cytoplasm: The cytoplasm contains organelles like mitochondria, Golgi apparatus, ribosomes, endoplasmic reticulum, lysosomes, microtubules, and a nucleus.
Nuclear Membrane: The nucleus is enclosed by a membrane that persists even during metaphase of mitosis, unlike in plant and animal cells.
Chromosomes: The nucleus possesses paired chromosomes.

There are two main types of components in the cell wall:
- Structural Polymers: These provide rigidity and integrity to the wall, primarily through polysaccharide fibrils.
- Matrix Components: These components cross-link the fibrils, providing a coating or embedding for them.
The specific types of components vary across fungal taxonomic groups.
- Chitin: A straight chain of N-acetylglucosamine residues linked by beta-1,4 glycosidic bonds. Chitosan is a derivative of chitin with deacetylated components.
- Glucan: Composed of beta-1,3-linked glucose residues with short beta-1,6-linked branches.