Mycology

• Fungi are eukaryotic, non-photosynthetic heterotrophs that produce exoenzymes and obtain nutrients by absorption.
• Fungi have a complex classification system based on morphology, physiology, the presence of macromolecules and sexual mating.
• The form of a fungal species during its sexual reproductive life cycle is termed teleomorph, while its asexual form is referred as anamorph.
• Reproduction by spore formation may be either sexual or asexual.
• Fungi that lack of meiotic stage are referred as mitosporic fungi.
• Fungal species may be saprophytic, parasitic or mutualistic.
• Fungi of veterinary importance are found in the three phyla Ascomycota, Basidiomycota and Zygomycota.
• The two main morphological fungal forms are moulds and yeasts.
• Moulds grow as branching filaments called hyphae, whereas the unicellular yeasts have an oval or spherical appearance.
• Dimorphic fungi occur in both mould and yeast forms.
• Fungi such as Candida albicans, which produce forms additional to the two major forms, are described as polymorphic.
• Hyphal cell walls are mainly composed of carbohydrate components including chitin macromolecules with cellulose cross-linkages.
• Fungi: growth, reproduction and colonial formation involve spores, hyphae, mycelium, aerial hyphae, and spore bearing structures.
• Mycological culture is performed on Sabouraud dextrose agar (SDA) at 27 - 37 ° C.
• In yeasts, cell walls contain protein complexed with polysaccharides and, in some species, a range of lipid compounds.
• Both moulds and yeasts have nuclei with well defined nuclear membranes, mitochondria and networks of microtubules.
• Colony textures can be described as rugose, umbonate, verrucose.
• Stages in the germination of a fungal spore leading to the development of a branched hyphae include septate hyphae, aseptate hyphae, vegetative and aerial hyphae.
• Factors which may predispose to fungal invasion of tissues include immunosuppression, prolonged antibiotic therapy, immunological defects, immaturity, ageing and malnutrition, exposure to heavy challenge of fungal spores, traumatized tissues, and persistent moisture on skin surface.
• Mechanisms involved in fungal diseases include tissue invasion (mycosis), toxin production (mycotoxicosis), and induction of hypersensitivity.
• Fungal diseases are categorized according to sites of infection into superficial mycoses (affecting the epidermis, other keratinized structures, and mucous membranes), subcutaneous mycoses (affecting the subcutaneous tissues), and systemic mycoses (affecting the respiratory and digestive tracts, and other organ systems).
• Asexual spores are produced by fungi of veterinary importance.
• Diagnosis of fungal diseases involves clinical signs and history of the disease, samples from hair, skin, biopsies, and direct microscope observation.
• In the bilayered cell membrane of fungi, cholesterol is present.
• Favic chandeliers, racquet hyphae, spiral hyphae are diagnostic structures of fungi.