Mycology: Classification & General Properties of Fungi (Lec. 1) PDF

Mycology Classification & General Properties of Fungi Lec.1 Definitions Mycologists--scientists who study fungi Mycology--Study of fungi. Mycoses--diseases caused by fungi Of the several thousands of species of fungi that are known, less than 100 are pathogenic to man. Medical Mycology--- is the stu...

Mycology Classification & General Properties of Fungi Lec.1 Definitions Mycologists--scientists who study fungi Mycology--Study of fungi. Mycoses--diseases caused by fungi Of the several thousands of species of fungi that are known, less than 100 are pathogenic to man. Medical Mycology--- is the study of mycoses of man and their etiologic agents General characteristics of fungi Fungi are eukaryotic; differ from bacteria and other prokaryotes. 1. 2. 3. 4. 5. Cell walls containing chitin (rigidity & support), mannan & other polysaccharides Cytoplasmic membrane contains ergosterols. Possess true nuclei with nuclear membrane & paired chromosomes. Divide asexually, sexually or by both Unicellular or multicellular 4 Fungi differ from bacteria in the following points:Prokaryote (Bacteria) Diameters nuclear membrane Chromosomes Division cytoplasm Cell wall Cell membrane Ribosome 1 micron Eukaryotes (Fungi) 4-15microns No nuclear membrane Nuclear membrane Single chromosome multiple Binary fission No organelles Peptidoglycan No ergosterol 70 S Mitotic division Organelles Chitin Ergosterol 80 S FUNGAL CELL STRUCTURE General characteristics of fungi Macroscopic and microscopic forms. Macroscopic fungi ▪ Often called fleshy fungi ▪ Are filamentous organisms Microscopic fungi exist as either Molds that grow on bread, fruits and cheese or Yeasts used in baking industry 7 (3-15 μm) Fungal cell membrane Consist of ergosterol. Ergosterol is the site of action of antifungal drugs, amphtericin B & azole group General characteristics of fungi Fungi are non-photosynthetic organisms ▪ Do not contain chlorophyll ▪ Are unable to manufacture their own nutrients, ▪ Depend on an external source of organic compounds for growth and survival (Chemoheterotrophs). ▪ Nutrients are usually obtained from dead organisms. But Some fungi use living tissue as a food source e.g. Candida Fungi are non motile Food industry: bread, alcohol, edible fungi (mushrooms), cheeses BREAD MOLD 10 General characteristics of fungi Absorptive heterotrophs (digest food first & then absorb it into their bodies  Release digestive enzymes to break down organic material or their host  7 ABSORPTIVE HETEROTROPH  Fungi get carbon from organic sources  Tips of Hyphae release enzymes  Enzymatic breakdown of substrate  Products diffuse back into hyphae Nucleus “directs” the digestive process Digested material is then used by the hypha metabolism of fungi Saprophytic fungi Most fungi: Saprophytic, free living organisms Obtain nutrients from dead organic matter Important decomposers in biogeochemical cycles Mutualistic Associations Many fungi have evolved successful relationships with plants or microbes in which both partners benefit Example Lichens: association of fungi with algae or cyanobacteria Mycorrhizae: association of fungi with plant roots 13 Mycorrhizae Lichens Parasitic fungi ▪ Some fungi acquire nutrients by attacking live animals or plants. A few fungi act like predators & capture prey like roundworms Predaceous Fungi feeding on a Nematode (roundworm) General characteristics of fungi Most fungi are obligatory aerobes, some are facultative anaerobes, but none are obligatory anaerobes. General characteristics of fungi Simplest fungus :- Unicellular budding yeast Hypha :- Elongation of apical cell produces a tubular, thread like structure called hypha Mycelium :- Tangled mass of hyphae is called mycelium. Fungi producing mycelia are called molds or filamentous fungi. Hyphae may be septate or non-septate 17 General characteristics of fungi Mold are classified and identified partially on the basis of whether the hyphae are septate or aseptate. Septate hyphae Filaments with cross-walls or septa that partition the hyphae in to individual cellular compartments. Have pores that allow the migration of cytoplasm and many organelles. Aseptate hyphae - no physical boundaries to distinguish individual cells in the hyphae. 18 septate and aseptate hyphae 19 the vegetative part of a fungus, consisting of a network of fine white filaments (hyphae). MODIFICATIONS OF HYPHAE HAUSTORIA – parasitic hyphae on plants & animals 23 HAUSTORIA Morphological Systematic Clinical Morphological Classification Depending on cell morphology 1. Yeasts 2. Yeast like fungi 3. Molds 4. Dimorphic fungi 24 1. Yeasts are single cells, usually spherical to ellipsoid in shape and occurs singly, in pair or form a chain(bud) Structure mostly found inside tissue or at body temperature Form psedo hyphae not a true hyphae Pseudo hyphae 25 Yeasts Unicellular fungi which reproduce by budding On culture produce smooth, creamy colonies e. g Cryptococcus neoformans (capsulated yeast) 26 Yeast colonies 2. Yeast like fungi Grow partly as yeasts and partly as elongated cells resembling hyphae which are called pseudo hyphae. e.g. Candida albicans yeast and its pseudo hphae 28 3.Molds/ Filamentous fungi Form true mycelia & reproduce by formation of different types of spores. Vegetative/ aerial hyphae e.g. Rhizopus, Mucor 29 Hyphae Hyphae grow as an intertwined mass of filaments collectively called mycelium ❖ When mold grow on substrate it can form : Vegetative mycelium (Thallus) ▪ Nutrient absorbing and water exchanging portion of the fungi ▪ Grows in or on a substrate. ▪ Are actively growing and form the main body of the colony. Arial hyphae (mycelium) ▪ Fungal filaments or hyphae that protrude above the surface ▪ Produce asexual spore 30  Hyphae HYPHAE form network called mycelia that run through the thallus (body) 20 4. Dimorphic fungi Some fungi grow only in the yeast form; others grow only as molds. but there are fungus that exist as mold and yeast depending on certain growth conditions; such phenomenon is dimorphism For example, many fungi grow as molds at room temperature (240c) but transforms into yeasts at human body temperature (370c) Most of the more dangerous human pathogenic fungi are dimorphic e.g. Histoplasma capsulatum 32