Mycology - Study of fungi

What environment conditions suit fungi the best??

*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

Describe 4 different host options for parasites

*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)

Classify 6 different types of parasites

*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.

What traits pertain to commensalism?

*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

How many species of fungi are there, and how many are known to be pathogenic?

100,000; 200 pathogenic

What is dimorphic fungi?

2 forms of growth. Usually in pathogenic species *Mold-like & yeast-like form (Candida albicans)

What percentage of US women have experienced at least 1 episode of Candida albicans?

75%

What is mycosis?

A fungal infection. Usually not contagious & infrequently spread person to person.

Are hyphae aerobic or anaerobic?

Aerobic

What are some characteristics of Tinea capitus, pedis (athlete's foot), unguium, cruris (groin, jock itch)?

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)

What is Pneumocystis jiroveci?

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

What is parasitism?

Any species that lives at the expense of another- pathogenic bacteria, protozoa, etc.

How would a nonfilamentous yeast appear on fruit?

As a white powdery coating

How do molds reproduce?

Asexually by fragmentation of their hyphae, and via fungal reproductive spores

What is immunocompetent?

Asymptomatic; May clear fungus from body w/ lasting immunity.

Fungal spores are reproductive, whereas what is not?

Bacterial endospores *A fungal spore is much less tolerant to adverse conditions

How do fungi meet their nutritional needs?

By absorbing dissolved organic matter thru plasma membrane (similar to bacteria) *Note- Fungi are chemoheterotrophs

How do hypha grow?

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

What is the order of development for molds?

Cells-> hyphae->Filaments->Mycelium (food fuzz)

What are 3 types of symbiosis?

Commensalism, mutualism, and parasitism

What are fungi capable of metabolizing that bacteria can't use for nutrients?

Complex carbohydrates such as lignan (wood cellulose)

Which mycoses are restricted to keratin-containing surfaces (dead layers)?

Cutaneous mycoses

What cell-mediated immune response might a cutaneous mold provoke?

Damage of living tissue

What are the cutaneous molds, and how do they work?

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.

Describe septate hypha

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)

What is chitin?

Found in cell walls of many hypha. Provides rigidity, strength, and resists high osmotic pressures.

How are asexual spores formed?

From the hyphae of one organism (clone via mitosis/ cell division). Spores detach from parent & germinates into new mold.

Why are eukaryotic fungis difficult to treat?

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

What is an opportunistic mycosis?

Fungi that exist normally in body w/out adverse effects. Adverseness arises when immune system or normal flora is depressed

What is Candidiasis, and what are 3 types?

Infection of mucous membranes; Oral candidiasis (thrush), vulvovaginal candidiasis, and balanitis

Yeasts are capable of facultative anaerobic growth, what does this mean?

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

What are the steps of yeast reproduction, and what is the means?

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

When a hypha grows into a filamentous mass, what is it called?

Mycelium

Describe Coenocytic hypha

No septa, just long continuous cells or filaments. Multinucleated

What shape is a yeast?

Oval or spherical

What would cause Candida albicans?

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

How is Stachybotrys chartarum (sick house syndrome) transmitted, and what are s/s?

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

Which spores do molds produce less frequently?

Sexual spores

What is the etiology of sick house syndrome?

Stachybotrys chartarum. A greenish-black, slimy mold found especially on cellulose products (wood, paper, insulation) that have been wet for several days.

What microbiota suppress Candidiasis, and which ones support?

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

What determines whether dimorphic fungi will take a mold-like or yeast-like form?

Temperature Mold-like @ 80-90degrees F Yeast-like @ 100-105 degrees F

What is symbiosis?

Two kinds of organisms living together (ie. microbiota & human host)

Which part of hypha obtains nutrients?

Vegetative hypha. It penetrates the substrate

How is Candida albicans transmitted?

Via saliva, vaginal fluid, STDs, or nosocomial (hospital acquired)

What is mutualism?

Where both partners are benefited (ie. cud chewing cows that ferment cellulose via gut bacteria; E. coli synthesizes vitamin B/K in humans)

What are the signs and symptoms of Candida albicans?

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

What is Tinea latin for?

Worm

How are yeasts and molds different, and what class do they fall under?

Yeasts are unicellular non-filametous organisms (spherical/oval), and molds are multicellular filamentous organisms (long filaments of cells joined together) **Class- fungi