Introduction to Mycology Lecture Notes PDF

INTRODUCTI ON TO MYCOLOGY GENERAL VETERINARY MICROBIOLOGY  1. Heterotrophic, perform extracellular digestion and absorb nutrients 2. Non-motile, spore-bearing and possess cell walls that resemble those of plants in...

INTRODUCTI ON TO MYCOLOGY GENERAL VETERINARY MICROBIOLOGY  1. Heterotrophic, perform extracellular digestion and absorb nutrients 2. Non-motile, spore-bearing and possess cell walls that resemble those of plants in chemical composition and structure 3. Maybe unicellular (yeast) or multicellular General filamentous colonies (molds and Characterist mushrooms) ics 4. Not photosynthetic and restricted to saprophytic or parasitic existence of Fungi 5. Abundant and widespread in soil, vegetation and in water where they subsist on decaying vegetation and wood  Digestion of these materials accomplished by production of proteolytic, lipolytic and glycolytic enzymes 6. Most fungi grow best at acidic pH of 5.0 and temperature of about 25’C 7. Store glycogen for energy and use maltose and glucose for energy metabolism 8. Most are aerobic; yeasts fermentative and grow both aerobically and anaerobically 9. Cell wall prevents osmotic lysis and protects against mechanical injury and entrance by harmful macromolecules   Two principal kinds of fungi are molds and yeasts  Main element of vegetative or growing form of mold is hypha, a branching tubular structure, 2-10 um in diameter  Hyphae become intertwined to form a mycelium MOLDS  Vegetative mycelium consists of surface hyphae, whereas hyphae that arise above surface are known as aerial or reproductive mycelium  Hyphae of aerial mycelium produce reproductive cells or spores collectively referred to as fruiting bodies  Hyphae of fungi are divided by cross- walls called septa  Some aerial hyphae produce stalk-like structures referred to as conidiospores or sporangiophores which give rise to asexual spores called conidiospores or sporangiospores   Oval or spherical cells ranging in diameter from 3 to 5 um  Some yeasts or yeast-like fungi produce chains of irregular yeast cells YEASTS referred to as pseudohyphae  Some fungi exist in mycelial form at room temperature but convert to yeast form at 37’C or when in tissues of animals ; called dimorphic  Two independent classification systems for fungi 1. Anamorphs – asexual structures 2. Teleomorphs – sexual structures  Sexual reproduction takes place by fusion of haploid nuclei (karyogamy) followed by CLASSIFICATIO meiotic division of diploid nucleus N SYSTEMS  Two hyphal protoplasts may unite (plasmogamy) then followed immediately by karyogamy Asexual reproduction 1. Sporulation followed by germination ex. Aspergillus and Penicillium 2. Fragmentation of hyphae ex. 3. Budding of yeast ex. Candida and Cryptococcus  Sexual or perfect stage of dermatophytic (ringworm) fungi Microsporum nanum is called Nannizzia obtusa (ascomycetes); only asexual stage found on skin  Sexual stage of Cryptococcus neoformans was called Filobasidiella neoformans   Fungal cells larger than most bacteria and are eukaryotic  They possess all cytoplasmic organelles except chloroplasts and consequently are not photosynthetic CELLULAR  Medically important structures of a fungus: STRUCTURE 1. Capsule S OF FUNGI 2. Cell wall 3. Cytoplasmic membrane Capsule  Some have external coating of slime or a compact capsule  Capsule or slime layer composed of amorphous polysaccharide that may cause cells to adhere or  clump together  Fungal capsule maybe antigenic and antiphagocytic Cell Wall  Major structure of fungus  Determines shape and process of fungal morphogenesis such as sporulation and yeast-mold dimorphism  Lies immediately external to cytoplasmic membrane  Most of fungal cell a thatch of polysaccharide (chitin, glucan, mannan, cellulose) called microfibrils; rest is protein and glycoprotein which cross-link the polysaccharide chain  Wide variety of fungi share same polysaccharide, hence common surface antigen  Many unique antigenic determinants resulting from different branching patterns of polysaccharide  Antigens useful for classification  Detection of species-specific surface antigens provides sensitive means of identification of slow- growing or poorly sporulating pathogenic fungi or both Cell Membrane  Bilayered membrane similar in structure and composition to cell membrane of higher eukaryotes  Unlike bacterial membrane but similar to other eukaryotes which fungal membrane contains sterols  Principal fungal sterols are ergosterol and zymosterol (mammalian cell membrane possesses cholesterol)  In 1969, Whittaker separated bacteria into Kingdom Prokaryotae or Monera and classified living organisms into 5 kingdoms based on cellular organization and nutritional pattern 1. Procaryotae or Monera - prokaryotic, unicellular, variable nutrition patterns – bacteria. Kingdom 2. Protista- eukaryotic, unicellular or colonial, heterotrophic – protozoa, slime molds, some algae. Myceteae 3. Myceteae or Fungi - eukaryotic, unicellular or multicellular, heterotrophic or absorptive – molds, yeasts, mushrooms. 4. Plantae - eukaryotic, multicellular or colonial, autotrophic – plants, some algae, mosses, ferns. 5. Animalia - eukaryotic, multicellular, heterotrophic or ingestive – animals.  1. Chytridiomycota – Chytrids 2. Zygomycota – conjugated fungi Kingdom 3. Ascomycota – sac fungi Fungi 4. Basidiomycota – club fugi 5. Glomeromycota 1. Chytridiomycota: Chytrids  Simplest and most primitive Eumycota or true fungi 2. Zygomycota  Bread mold, Rhizopus stolonifera  Sexual and asexual life cycle 3. Ascomycota: Sac fungi  Formation of ascus 4. Basidiomycota  Mushrooms 5. Glomeromycota  Closely associated with roots of trees  Arbuscular mycorrhizae: hyphae interact with root cells  Deuteromycota: Fungi imperfecti   Except dermatophytes, rarely cause disease in healthy, immunocompetent animals 1. Pathogenic fungi: cause ringworm and more common mycoses such as blastomycosis and histoplasmosis 2. Opportunistic fungi: seldom cause disease; disease associated with FUNGAL immunocompromised individuals, numerous INFECTIONS and widespread in nature  Penicillium, Aspergillus, Mucor, Absidia, Rhizopus  Introduced to tissues as result of abrasion or trauma Systemic Fungal Infections 1. Prolonged administration of antibiotics 2. Radiation, steroid therapy, folic acid antagonists, etc 4. Immunosuppressive therapy 5. Cytotoxic drugs 6. Immune deficiency 7. Endocrine disorders  HAVE A PLEASANT DAY!