Fundamental Medical Mycology Fungal Characteristics Fungal Classification Fungal Terminology www. mycology.adelaide.edu.au/Fungal_Jungle/kaminski.html Some of the images herein are taken from Kaminski’s “Fungal Jungle” Power Points with some modifications

Biological Relationships Mycology is the study of Fungi. Fungi (singular, fungus) are a group of organisms similar to and different from animals, plants, protists, and bacteria. Fungi AnimalsPlants ProtistsBacteria Multicell √ √ √ One cell √ √ √ Eukaryote √ √ √ √ Phototroph √ X √ Autotroph √ X √ Heterotroph √ √ √ √

Fungal characteristics * The fungi grow as: molds (moulds), yeast, or combinations of the 2 (dimorphism). In that latter case they usually grow as mold in the environment and as yeast-type cells in vivo. * Groups of cells grow via filamentous extensions called “hyphae.” Collectively these are known as “mycelia” - especially true of the molds. * Mold colonies are fuzzy masses of mycelia whereas yeast colonies are smooth and homogeneous like those of bacteria. * Yeast are primarily single celled organisms. * Fungi possess cell walls composed of chitin, but are in most other ways similar to other Eukaryotes.

Fungal characteristics * Fungi generally reproduce both sexually & asexually via production of tough spores. They produce asexual spores called “conidia” at the end of aerial hyphae. Sexual spores vary between groups of molds. Yeast utilize a unique asexual mechanism called “budding.” * All fungi are capable of aerobic heterotrophic respiration. Some are also capable of fermentation. Nutrients are acquired via simple absorption (diffusion). * Fungi, especially molds, are “saprophytes.” They derive neutrients and energy from dead and decaying matter making them critically important to Earth’s nutrient cycle.

Fungal characteristics Fungi inhabit most habitats on planet Earth including terrestrial & aquatic, but most are terrestrial organisms. Some fungi coexist in mutualistic relationships with plants (ex. Mycorhizae), algae (lichens), insects (termites), etc. Most parasitic fungi are plant pathogens, indeed fungi are responsible for the most ecomonically significant plant diseases. …and then there are some fungi that are human pathogens…. 

Fungal characteristics - clinical Fungal pathogens are opportunistic – infection is unlikely in immunocompetent individuals. Normal microbiota (mainly bacterial) prevents fungal infection in most cases. Most human fungal infections are epidermal / peripheral. Internal & systemic fungal infection is limited to immunocompromised individuals for the most part. Non-specific & cell-mediated immunity are the primary means of defense vs fungal infection. Fungi vary in regard to morphology, sexual life- cycles / sexual spores, and the extent of infection (see table 19-3). Fungi are classified primarily on these 3 bases. 