Mycology – Study of fungi – Flashcards
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What is symbiosis?
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Two kinds of organisms living together (ie. microbiota & human host)
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What are 3 types of symbiosis?
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Commensalism, mutualism, and parasitism
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What traits pertain to commensalism?
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*One organism benefits, the other is neither harmed nor benefited. *Eg. normal microbiota, no single species is essential *Saprophytic mycobacteria that inhabit ear and external genitalia *No apparent benefit/harm to host. *ie. cornyebacteria on eye surface
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What is mutualism?
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Where both partners are benefited (ie. cud chewing cows that ferment cellulose via gut bacteria; E. coli synthesizes vitamin B/K in humans)
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What is parasitism?
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Any species that lives at the expense of another- pathogenic bacteria, protozoa, etc.
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Classify 6 different types of parasites
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*Ectoparasites- live on outside of body *Endoparasites- Live inside the host *Obligate parasites- Must have a host (ie. virus) *Permanent parasites- Don't leave once inside *Temp parasites- biting insects, organism living free of host during part of its life cycle *Accidental parasites- Organism desired a different host, not living in usual host.
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Describe 4 different host options for parasites
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*Definitive host- Where the parasite reproduces sexually (sexually mature form of parasite) *Intermediate host- Where juvenile matures or reproduces asexually. An organism that harbors larvae or asexual stage of a parasite *Accidental host- can be humans (ie. Echinococcus granulosus-tapeworm) Human becomes dead-end host *Host specificity- Some parasites are specific about type of host & organ/tissue which they infect. (ie. Rabies virus infects nerve tissue of mammal)
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How many species of fungi are there, and how many are known to be pathogenic?
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100,000; 200 pathogenic
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How are yeasts and molds different, and what class do they fall under?
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Yeasts are unicellular non-filametous organisms (spherical/oval), and molds are multicellular filamentous organisms (long filaments of cells joined together) **Class- fungi
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What is the order of development for molds?
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Cells-> hyphae->Filaments->Mycelium (food fuzz)
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How do hypha grow?
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By elongating at the tips. Each part is capable of growth, so when a fragment breaks off, it can establish on substrate and grow into new hypha
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Describe septate hypha
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Distinct uninucleate cell-like units; most common form; Septum divides hypha into the cell-like units. Can grow to immense size (40 acres, 10 tons)
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Describe Coenocytic hypha
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No septa, just long continuous cells or filaments. Multinucleated
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Which part of hypha obtains nutrients?
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Vegetative hypha. It penetrates the substrate
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When a hypha grows into a filamentous mass, what is it called?
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Mycelium
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What is chitin?
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Found in cell walls of many hypha. Provides rigidity, strength, and resists high osmotic pressures.
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Are hyphae aerobic or anaerobic?
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Aerobic
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How do molds reproduce?
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Asexually by fragmentation of their hyphae, and via fungal reproductive spores
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How are asexual spores formed?
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From the hyphae of one organism (clone via mitosis/ cell division). Spores detach from parent & germinates into new mold.
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Which spores do molds produce less frequently?
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Sexual spores
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Fungal spores are reproductive, whereas what is not?
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Bacterial endospores *A fungal spore is much less tolerant to adverse conditions
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What shape is a yeast?
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Oval or spherical
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How would a nonfilamentous yeast appear on fruit?
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As a white powdery coating
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Yeasts are capable of facultative anaerobic growth, what does this mean?
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It can grow w/ or w/out oxygen, and will use O2 if present. If O2 is unavailable, will use fermentation or anaerobic respiration/glycolysis
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What are the steps of yeast reproduction, and what is the means?
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It uses mitosis; Starts w/ fission- produces 2 daughter cells; Budding- Divides, then divided 1/2 migrates into bud that elongates & breaks off; Pseudohypha- Buds fail to detach after forming allowing invasion of deeper tissues
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What is dimorphic fungi?
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2 forms of growth. Usually in pathogenic species *Mold-like & yeast-like form (Candida albicans)
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What determines whether dimorphic fungi will take a mold-like or yeast-like form?
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Temperature Mold-like @ 80-90degrees F Yeast-like @ 100-105 degrees F
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How do fungi meet their nutritional needs?
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By absorbing dissolved organic matter thru plasma membrane (similar to bacteria) *Note- Fungi are chemoheterotrophs
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What environment conditions suit fungi the best??
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*Acidic w/ pH of 5-6 (bacteria are 6.5-7.5); More resistant to osmotic pressure, so grow well in higher sugar/salt conditions; Less moist (compared to bacteria); Grow well on bathroom wall, leather, newspaper, insulation, toe nail
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What are fungi capable of metabolizing that bacteria can't use for nutrients?
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Complex carbohydrates such as lignan (wood cellulose)
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What is mycosis?
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A fungal infection. Usually not contagious & infrequently spread person to person.
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Which mycoses are restricted to keratin-containing surfaces (dead layers)?
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Cutaneous mycoses
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What are the cutaneous molds, and how do they work?
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Dermatophytes, Tinea, & Ringworm (same entity); Mold colonizes superficial epidermal cells in skin, hair, nails. Vegetative hyphae synthesize/secrete keratinase (enzyme that digests keratin); Partial to heat & moisture, but grows in fridge, crawl space.
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What cell-mediated immune response might a cutaneous mold provoke?
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Damage of living tissue
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What are some characteristics of Tinea capitus, pedis (athlete's foot), unguium, cruris (groin, jock itch)?
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All molds; tend to grow outward in expanding ring-ringworm...this is Tinea of head, feet, nail, groin. Very contagious. Tinea-infected skin is shed and picked up via fomite (hair salon, shower floor, carpeting, bus seats)
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What is Tinea latin for?
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Worm
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What is Candidiasis, and what are 3 types?
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Infection of mucous membranes; Oral candidiasis (thrush), vulvovaginal candidiasis, and balanitis
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What are the signs and symptoms of Candida albicans?
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White (cheesy) tongue is thrush, or oral candidiasis; Thick yellow/white cheesy vaginal coating->irritation->inflamed->severe itch->yeasty odor or none; Penile vesicles-> penile fungal patches-> severe itch/burn
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What would cause Candida albicans?
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Overgrowth of yeast via decreased bacteria, increased pH, antibiotic use. Microbiota of mucous membrane of mouth, intestinal tract, genital/urinary tract that is suppressed to low levels by microbiota competition/antagonism. *Attaches to human epithelial cells by fungal fimbria
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How is Candida albicans transmitted?
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Via saliva, vaginal fluid, STDs, or nosocomial (hospital acquired)
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What percentage of US women have experienced at least 1 episode of Candida albicans?
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75%
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What microbiota suppress Candidiasis, and which ones support?
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Suppress- Lactobilli (create pH of 3.5-4.5) Support- Pregnancy/oral contraceptives-> increased glycogen in vagina; douches/ vaginal deodorants; Uncontrolled diabetes; Antibiotics decrease normal microbiota, so pH increases
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What is an opportunistic mycosis?
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Fungi that exist normally in body w/out adverse effects. Adverseness arises when immune system or normal flora is depressed
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What is immunocompetent?
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Asymptomatic; May clear fungus from body w/ lasting immunity.
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What is Pneumocystis jiroveci?
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An opportunistic mycosis that causes Pneumocystis pneumonia. Proliferates under the immunosuppression of AIDS *AIDS marker. s/s lung inflammation, fever, fluid in lung, dyspnea, non-productive cough
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What is the etiology of sick house syndrome?
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Stachybotrys chartarum. A greenish-black, slimy mold found especially on cellulose products (wood, paper, insulation) that have been wet for several days.
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Why are eukaryotic fungis difficult to treat?
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Fungal drugs can also affect our eukaryotic cells. They can be long-lasting, as they grow very slow. There aren't any vaccines for fungi either. *It is dimorphic
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How is Stachybotrys chartarum (sick house syndrome) transmitted, and what are s/s?
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Respiratory route; Pathogenesis- hypersensitivity/allergy. can produce mycotoxins which can be present in spores and small mold fragments released in air. S/S- cough, wheeze, runny nose. irritates eyes/throat. skin rash/diarrhea
