Fungi PDF

FUNGI General characteristics of fungi Fungi of medical interest FUNGI CLASSIFICATION  WHY ARE FUNGI NON CONSIDERED PLANTS? FUNGI PLANTS o They are heterotrophs: they do not make o They are autotrophs: they use their own...

FUNGI General characteristics of fungi Fungi of medical interest FUNGI CLASSIFICATION  WHY ARE FUNGI NON CONSIDERED PLANTS? FUNGI PLANTS o They are heterotrophs: they do not make o They are autotrophs: they use their own food; they must obtain it from photosynthesis to make their own food the organisms or materials on which they o They have a cell walls of cellulose live (lignin, chitin, cellulose, keratin) o They have important role in decomposing organic matter and returning essential minerals to the soil o They have a cell walls of chitin o Fungi are used in industries for manufacturing large varieties of useful materials for mankind such as primary/secondary metabolites, enzymes, and products  MAIN USES OF FUNGI Alcohol production Saccharomyces cerevisiae. The fermentation of materials rich in sugars produced alcohol (beer, wine, and sake) Drug industries (medicine) Fungi are involved in the industrial processing of profitable products in medicine: o Lovastatin and squalestatin (anti-cholesterol statins) are secondary metabolites of Aspergillus spp. o Penicillin (antibiotic) is obtained from Penicillin moulds o Cyclosporin A (immunosuppressant agent) is produced by Trichoderma polysporum and Cylindrocarpon lucidum as primary metabolites Food processing Soya sauce, Blue cheese, Colours, Flavours  FUNGI AND DISEASES Especially among immunocompromised or hospitalized patients with serious underlying diseases, fungi serve as OPPORTUNISTIC PATHOGENS, causing considerable morbidity and mortality. The list of opportunistic fungal pathogens increases each year and there are NO nonpathogenic fungi!  FUNGAL STRUCTURE Fungi are eukaryotic organisms that contain a well-defined nucleus, mitochondria, Golgi bodies, and endoplasmic reticulum. It is remarkable that a fungal cell shows great similarity with a human cell. The similarity between a human cell and a fungal cell is one of the reasons why fungal infections are difficult to treat: drugs that are toxic to a fungal cell are also toxic to human cells!  FUNGAL STRUCTURE Cell membrane consists of lipoproteins, phospholipids, and ergosterol Ergosterol differs from cholesterol in having an additional double bond in a ring of the steroid nucleus and a double bond and an extra methyl group in the alkyl side chain  FUNGAL STRUCTURE o Rigid cell wall does not contain peptidoglycan and consists of 80% polysaccharides (chitin, glucan, and mannan) and 20% of glycoproteins (mannoproteins) and lipids Chitin is a long-chain polymer of N-acetylglucosamine, a derivative of glucose; the structure of chitin is comparable to the cellulose structure Glucan is a branched polymer of glucose which exists in three form: ß-1,6-glucan, ß-1,3-glucan, and ß-1,3- ß-1,6-complexed with chitin Mannan is a polymer of the sugar mannose and it is found in the outer layers of the wall  FUNGAL STRUCTURE YEASTS – unicellular organisms: MOLDS – pluricellular organisms: single budding cells threadlike tubular structures, hyphae  MOLDS Ma Mvi Vegetative mycelium (Mvi): nutritive function Aerial mycelium (Ma): reproductive function, contains the reproductive cells or spores FUNGAL STRUCTURE DIMORPHIC FUNGI: mold + yeast  FUNGAL STRUCTURE «SPECIAL» DIMORPHIC FUNGI: Candida spp. Candida spp. can undergo yeast-mold transition Candida albicans. Microscopic morphology in cornmeal agar showing large chlamydospores (black The phenotypic switching explains their ability arrow), blastoconidia (red arrow), hyphae, and pseudohyphae. to survive in many different microenvironmental niches within the host  YEAST REPRODUCTION Reproduction in yeasts is always asexual by budding from a conidiogenic cells, and by binary fission (less frequently). When daughter cells do not separate from the mother cell and produce other cells → pseudomycelium with pseudohyphae formation These are elongated yeast cell chains, each cell retains its individuality  MOLD REPRODUCTION Fungi reproduce by formation of spores that may be: sexual (involving meiosis, preceded by fusion of the nuclei of two compatible mating types) asexual (involving mitosis only) The two modes can alternate with different rhythms and frequencies in the various species and according to the different environmental conditions Spores are the structures dedicated to sexual reproduction (not survival!) Conidia and sporangiospores (or asexual spores) are the structures used for asexual reproduction → The pathogenic fungi for humans mainly undergo asexual reproduction  MOLD REPRODUCTION Molds can reproduce asexually and sexually. Asexual reproduction occurs: o By sporangiospores o By conidio(spores)  MOLD REPRODUCTION Molds can reproduce asexually and sexually. Sexual reproduction involves three phases: o Plasmogamy: fusion of cytoplasm o Karyogamy: fusion of nucleus o Meiosis: reductional nuclear division  DISEASES CAUSED BY FUNGI To date, more than 100,000 species of fungi have been fully described ► fewer than 500 are associated with humans: