Chapter 9 Fungi - Georgetown ISD



Chapter 9 Fungi

I. Mycology - study of fungi

A. Heterotroph

1. saprophyte - lives off dead organic material

2. parasite - lives off living host

3. mycoses - fungal infections

4. important decomposers

5. secrete digestive enzymes; absorb nutrients

B. Divided into 2 groups

1. Yeast

2. mold

C. Dimorphism - exists in 2 forms (yeast and mold)

D. Unicellular, multicellular, colonial

E. Dermatophytes - cause superficial infections

F. Systemic - affects a number of organs and tissues, or affects the body as a whole.

G. Examples: Rusts, smuts, molds, mildew, yeast, mushrooms, puffballs

H. Eukaryote

1. has same organelles as all other eukaryotes

2. cell wall has chitin

II. Yeast

A. Unicellular

B. Asexual reproduction

1. budding

2. mother cell

3. daughter cell

C. Beneficial

1. bread

2. wine/beer/cider

D. Pathogenic

1. Candida albicans - thrush, vaginal yeast infection (dermatophyte; opportunistic)

-mucous membranes of mouth, throat, vagina

2. Cryptococcus neoformans - cryptococcal meningitis (systemic; opportunistic)

-brain

-skin, lungs

3. dimorphic yeast

a. Histoplasma capsulatum - histoplasmosis (systemic; opportunistic)

-spores in air

-from feces of birds/bats

-infects lungs, lymph glands

-can be fatal

b. Sporothrix schenckii - sporotrichosis (systemic)

-soil

-skin puncture

-lesions, ulcers, abscesses on skin at site of penetration

-lymph system, lungs, joints, rarely the bones

c. Coccidioides immitis - coccidioidomycosis or San Joaquin Valley fever (systemic)

-air

-symptomless except in immunocompromised patients - possibly fatal

III. Mold

A. Multicellular, filamentous fungi

1. hypha - one filament

2. mycelium - woven, intertwining mass of hyphae

3. septa - wall dividing hypha into segments

4. rhizoids - rootlike anchoring structures

B. Reproduction

1. asexual

a. reproductive hyphae

b. sporangia

-sacs at end of reproductive hyphae

-contains spores (sporangiospores)

-sac ruptures - sporangiospores released

c. conidia

-spores - conidiospores

-at end of reproductive

-not enclosed in sac - "free" spores

2. sexual - joining of different genetic material

-zygospores - 2 different strains of hyphae join together

- haploid spores (male/female) from 2 different strains or sexes form and join

together

C. Beneficial

1. food - cheese, soy sauce, cured meats

2. produce antibiotics, organic acids, vitamins

3. decomposers

4. used in genetic studies

D. Pathogenic

1. destroys food and crops

2. allergies

3. dermatophytes

a. athlete's foot

b. ringworm

c. infections of hair, scalp, nails

E. Important molds

1. Penicillium notatum

-antibiotic penicillin

-Sir Alexander Fleming

2. Aspergillus flavus - systemic

- peanuts

-aflatoxin

-neurological complications; liver cancer; possibly fatal

3. Aspergillus fumigatus - systemic

- aspergillosis - lung infection

4. Claviceps purpurea - systemic

-produces ergot from grain

-convulsions, seizures, paralysis, hallucinations

-Salem witch trials

3. Stachybotrys - systemic

-black, toxic mold

4. Rhizopus - black bread mold

5. Neurospora - pink bread mold

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