Mycology I

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Microbiology and Immunology
Microbiology and Immunology 2500A/B

Lecture 9: Mycology I 09/28/2012  Fungi grow really well in the dark  Warm temperatures are inhibitory to fungi, they like cold temperatures  Humans – resistant to fungi due to our body temperature Fungi  Eukaryotes  Plant-like forms but lack defined root or leaf structures and are non-photosynthetic  They are assigned to their own kingdom, Mycota  Saprophytic or parasitic  Unusual metabolic products can be toxic to higher animals Fungal Taxonomy  Speciation was established on microscopic morphology  Yeasts vs. molds vs. dimorphic  Molds: septate vs. aseptate hyphae  Septate hyphae: hyaline vs. demataceous  Many fungi can reproduce both sexually and asexually  Morphological characteristics are different for sexual and asexual stages  Sexual and asexual stages of the same organism may have different genus and species names!  The asexual (anamorphic) stage name is preferred unless there is only a sexual (telomorphic) stage known.  Fungi of which only an anamorphic (asexual) form is known are termed the Fungi imperfecti Clinical Classification 1. Yeasts 2. Mold 3. Dimorphic fungi – can grow as yeast or mold 4. Poisonous mushrooms (homobasidiomycetes)→ mycetism Identification  Yeast – unicellular microorganisms that reproduce by budding primarily  Mold – system of tubules that grow  Identification usually depends upon microscopic examination of the morphology, particularly of sporulating forms  "By their fruits ye shall know them.“  Biochemical tests and other more sophisticated technologies may be employed to identify medically important fungi Yeasts  Single, unconnected vegetative cells  Grow in a manner similar to bacteria but 10X larger  Reproduce by budding  Do not sporulate  Not much of a hazard to laboratory workers  Used for commercial production of alcohol and citric acid Molds  Grow in a complex mass called mycelium composed of tubes called hyphae  When hyphal filaments are packed densely, the mycelium can appear to be cohesive tissue, as in the case of mushrooms (homobasidiomycetes)  Reproduce by the formation of spores Spores  Released in enormous numbers from the mycelium  Ubiquitous (everywhere)  Can become airborne and present a contamination hazard in laboratories working on pathogenic molds  Can be formed asexually (conidia) which is the most common way, or sexually (ascospores) Dimorphic Fungi  Fungi which have both yeast and filamentous phases  Phase usually depends on temperature or other grow
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