1. Mycology
Study of Fungi

2. Characteristics Diverse group of chemoheterotrophs Saprophytes
> 90,000 known species
Saprophytes
Digest dead organic matter
Parasites
Obtain nutrients from tissues of organisms
Molds & mushrooms are multicellular
Yeasts are unicellular

3. Significance Beneficial Decompose dead organisms Recycle nutrients
Mycorrhizae
Association with roots of vascular plants-truffles & oak
Assist in absorption of water & minerals
Control of pests -Gypsy moth
Food & antibiotics

4. Parasitic Fungi Fungal diseases of plants, animals, humans, & bacteria
Irish & potatoes
Dutch elm disease
Death of chestnut trees
Crop damage-wilts, mildews
Spoilage of food- bread, oranges, jams
Athlete’s foot, aspergillosis

5. Nutrition All are chemoheterotrophs
Absorption of nutrients: powerful exoenzymes
Grow at lower pH-5 than bacteria
Grow in high salt and sugar
Metabolize complex CH2O like lignin in wood-wood rot

6. Structure of Fungi
Vegetative structures involved in catabolism and growth
Thallus- in molds and fleshy fungi
Tubular filaments of cells-hyphae
Septate hyphae - cross walls that divide them into unicellullar units
Pores to allow cytoplasm & nuclei to pass
Coenocytic hyphae- no septa, continuous cells with many nuclei

7. Growth Elongate at tips of hyphae
Mycelium- filamentous mass of hyphae visible to eye
Aerial hypha or fruiting body- portion concerned with reproduction
Some mycelium underground
Asexual & sexual spores

8. Yeasts Unicellular fungi Budding yeasts-uneven cell division
Protuberance forms -bud
Nucleus divides & one goes into bud
Cell wall material laid down

9. Pseudohypha Elongated chain of cells Fission yeast
Candida albicans -buds fail to detach
Allows yeast to invade deeper tissues
Fission yeast
Divide evenly like bacteria
Visible growth on medium-colony

10. Dimorphic Fungi Two forms of growth
Grow either as a mold or as a yeast
Dimorphism in pathogenic fungi is temperature dependent
at 37 C yeast like growth
at 25 C it is mold like
Nonpathogenic: CO2 conc
Mucor: on surface yeast, in agar mold

11. Reproduction Filamentous fungi Yeasts
Asexually by fragmentation of hyphae
Asexual and sexual reproduction by spores
Yeasts
Asexually by budding or fission
Sexual reproduction by spores

12. Asexual Spores Produced by aerial hyphae: adapted for dispersal
Progeny genetically identical to parent
Several types
Conidiospores- not enclosed in a sac
produced in a chain at end of a conidiophore
Sporangiospores
Within a sac, sporangium
End of sporangiophore

13. Sexual Spores Three phases of development
Plasmogamy-haploid nucleus of a donor cell (+) penetrates the cytoplasm of a recipient cell (-)
Karyogamy- the 2 nuclei fuse to form a diploid nucleus
Meiosis-diploid nucleus gives rise to haploid nuclei
Sexual spores, some + , some -,some recombinants
Sexual spores used to classify fungi into divisions

14. Classification: Phylum
Zygomycota -saprophytic molds, coenocytic hyphae
Rhizopus - black bread mold
asexual spores are sporangiospores
sexual spores are zygospores -large spore enclosed in a thick wall - fusion of nuclei of 2 cells

15. Ascomycota
Sac fungi includes molds with septate hyphae and some yeasts
Talaromyces
asexual spores are conidiospores
Sexual spores-ascospores
8 produced in sac –ascus
Ascus occurs in fruiting body-ascocarp

16. Basidiomycota Club fungi, mushrooms, toadstools Septate hyphae
Sexual spores- basidiospores produced externally on base pedestal-basidium
4 per basidium
Some produce asexual conidiospores or fragmentation

17. Sexual Reproduction Telomorphs-produce both sexual and asexual spores
Anamorphs- lost ability to reproduce sexually-Penicillium
belonged to Deuteromycota
now classified as anamorphs of other phyla: rRNA & Woese
most are ascomycetes

18. Fungal Diseases Mycosis- fungal infection
< 100 cause human disease
Not highly contagious
Humans acquire from nature
Groups based on degree on tissue involvement and mode of entry
Cutaneous mycoses-dermatophytes
Epidermis, hair & nails
Contagious-direct or indirect contact
Secrete keratinase that degrades keratin

19. Cutaneous Mycoses Tinea( worm) capitis –blisters with scaly ring
Ringworm of the scalp
Spreads circularly forming bald spots
Spread by contact with fomites , cats and dogs
Tinea cruris- ringworm of groin
Tinea pedis - athlete's foot
Live for weeks on shower floor or mat
1992 outbreak among wrestlers
Diagnosis-scrapings; TX–antifungal creams

20. Systemic Mycoses Dimorphic fungi Can spread throughout body
Yeast form is invasive
Can spread throughout body
Usually caused by fungi in soil
Inhalation of spores
Begins in lungs and spread to rest of body
Not contagious person to person

21. Histoplasmosis Histoplasma capsulatum-dimorphic fungi
Filamentous in soil & medium
Yeast like in tissues
Ascomycetes - conidia
Exposure by inhalation of conidia
Found along Ohio River Valley
Moist soil, rich in N: droppings of birds and bats
5% develop clinical disease
Resembles TB
Skin testing-80% in area infected

22. Diagnosis/Treatment Grown in medium that selects for fungal growth
Grow at 25 C and 37 C
KOH preparations of skin biopsies
Dissolves keratin in skin scrapings or biopsies
Leaves only fungal cells
Therapy- amphotericin B or ketoconazole
Toxic to humans

23. Coccidiomycosis ( Valley Fever)
Coccidioides immitis-dimorphic fungi
Asexual spores (conidia) in dry alkaline soil of American SW and S America
Wind carries spores to transmit infection
Driving thru endemic area can cause disease -100,000 infections each year
Spore lodges in lung

24. Disease Influenza like disease Most are asymptomatic
High fever, cough, body aches, chest pain
Most are asymptomatic
Few progress to disseminated infection
Skin test to detect prior infection
Amphotericin B

25. Opportunistic Pathogens
Lack proteins that aid in colonization or invasion
Do not cause disease in healthy persons
Infect susceptible individuals
Aspergillosis-occurs in people with lung diseases or cancer
Inhalation of conidia of Aspergillus turn into mycelium in lungs
Organism is widespread in soil, compost piles, wood, carpets, any dust

26. Disease Hypersensitivity –can be chronic & lead to lung damage
Noninvasive-masses of hyphae in lungs
Invasive pulmonary –pneumonia & necrosis of lung –reportable disease
Construction projects in hospitals
Protect immunosuppressed patients
Erect barriers, negative pressure

27. Candidiasis Candida albicans part of normal flora
Anamorph
Suppressed by bacteria in mucous membranes
If pH changes or on antibiotics, allows yeast to grow and cause infection
Oral thrush or vaginitis-topical creams
AIDS pts often spreads and becomes systemic
May result in death- treat with antifungal

28. Virulence Factors
Exoenzymes attack cells & progressively digest & invade nearby cells
Capsule: some yeasts
Mycotoxins produced by mushrooms
Hallucinogenic
Damage liver
Carcinogens: aflatoxins in grain and peanuts

29. Lichens Classified as fungi, most are ascomycetes
Combination of green alga or cyanobacteria and fungus
Mutualism- each partner benefits from relationship
Fungus obtains nutrients, water and protects partner from desiccation
Partner provides products from photosynthesis-oxygen and sugars

30. Lichens Lichens secrete acids that break down rock
First life to colonize exposed rock
Lichens used as dyes-litmus
Food source for animals
Sensitive to pollution-SO2
3 morphological types