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The Fungi (Eumycota) 1 26 Copyright © McGraw-Hill Global Education Holdings, LLC. Permission required for reproduction or display.

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Presentation on theme: "The Fungi (Eumycota) 1 26 Copyright © McGraw-Hill Global Education Holdings, LLC. Permission required for reproduction or display."— Presentation transcript:

1 The Fungi (Eumycota) 1 26 Copyright © McGraw-Hill Global Education Holdings, LLC. Permission required for reproduction or display.

2 True Fungi: Eumycota Eukaryotic, spore-bearing Chemoorganoheterotrophs with absorptive metabolism Saprophytes –absorb nutrients from dead organic material by releasing degradative enzymes –osmotrophy - absorb soluble products Reproduce sexually and asexually Super Group Opisthokonta 2

3 Terminology Mycology – study of fungi Mycologists – scientists who study fungi Mycoses – diseases caused by fungi Mycotoxicology – study of fungal toxins and their effects 3

4 Taxonomy of Fungi 90,000 fungal species have been described, possible 1.5 million six major fungal groups ChytridiomycotaZygomycota GlomeromycotaAscomycota BasidiomycotaMicrosporidia 4

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6 Fungal Distribution and Importance Primarily terrestrial, few aquatic –global from polar to tropical Primarily terrestrial –few aquatic species Many are pathogenic in plants or animals Some form associations –mycorrhizae – associations with plant roots –lichens associations with algae or cyanobacteria 6

7 Fungal Distribution and Importance… Decomposers –degrade complex organic material in the environment to simple organic compounds and inorganic molecules –carbon, nitrogen, phosphorus, and other critical constituents are recycled for other living organisms 7

8 Fungal Distribution and Importance… Industrial importance –fermentation – yeast used in making bread, wine, beer, cheese, soy sauce –organic acids – citric and gallic acid –certain drugs – ergometrine, cortisone –antibiotics – penicillin, griseofulvin –immunosuppressive agents - cyclosporin 8

9 Fungal Distribution and Importance… Research use –geneticists, cytologists, biochemists, biophysicists, and microbiologists –Saccharomyces cerevisiaea (Bakers/Brewers Yeast yeast model system for cell biology, genetics, and cancer 9

10 Pathogenic Fungi Fungi are eukaryotic saprophytes –~50 produce mycoses in humans –five groups depending on route of infection superficial, cutaneous, subcutaneous are all direct contact systemic infections have disseminated to visceral tissues (most are dimorphic, acquired from inhalation of spores) opportunistic mycoses 10

11 Opportunistic Diseases Opportunistic microorganism – harmless in its normal environment but pathogenic in a compromised host Compromised host – seriously debilitated and has lowered resistance to infection –causes include (but not limited to): malnutrition/alcoholism cancer diabetes another infectious disease trauma from surgery or injury immunosuppression by drugs/hormones genetic deficiencies advanced age 11

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13 Fungal Structure Cell walls composed of chitin polysaccharide Single-celled microscopic fungi = yeasts Body/vegetative structure of a fungus = thallus (pl. thalli) (undifferentiated structure) –multicellular fungi are called molds –thallus consists of long, branched hyphae filaments tangled into a mycelium mass 13

14 Asexual reproduction –Parent cell undergoes mitosis to form daughter cells –May proceed through a spore form 14 Fungal Reproduction

15 Sexual reproduction –Involves fusion of compatible nuclei Homothallic: Sexually-compatible gametes are formed on the same mycelium (self-fertilizing) Heterothallic: Require outcrossing between different, yet compatible mycelia (+ and – mating strains) –A dikaryotic stage can exist temporarily prior to fusion of two haploid nuclei 15

16 Zygomycota Zygomycetes Most are saprophytes –a few are plant and animal parasites Form coenocytic hyphae containing numerous haploid nuclei Some of industrial importance –foods, antibiotics and other drugs, meat tenderizer, and food coloring 16

17 Zygomycota Usually reproduce asexually by spores that develop at the tips of aerial hyphae Sexual reproduction occurs when environmental conditions are not favorable –requires compatible opposite mating types –hormone production causes hyphae to produce gametes –gametes fuse, forming a zygote –zygote becomes zygospore 17

18 Genus Rhizopus R. stolonifer –grows on surface of moist carbohydrate rich foods such as bread –hyphae quickly cover surface as rhizoids, absorb nutrients –stolon hyphae become form new rhizoids 18

19 Importance of Genus Rhizopus Rhizopus-Burkholderia symbiosis –seedling blight in rice bacterium Burkholderia growing within Rhizopus produces toxin Used to produce tempeh from soybeans Used with soybeans to make sufu curd Commercially –used to produce anesthetics, birth control, alcohols, meat tenderizers, yellow coloring in margarine 19

20 Ascomycota Ascomycetes or sac fungi –found in freshwater, marine, and terrestrial habitats –red, brown, and blue-green molds cause food spoilage –some are human and plant pathogens –some yeasts and truffles are edible –some used as research tools 20

21 Ascomycota Yeast Life Cycle Alternates between haploid and diploid –in nutrient rich, mitosis and budding occurs at non-scarred regions –nutrient poor, meiosis and haploid ascus containing ascospores formed haploid cells of opposite mating types fuse tightly regulated by pheromones Many are dimorphic (yeast form and mold form 21

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23 Ascomycota Filamentous Form Life Cycle Asexual reproduction - conidia Sexual reproduction –ascus formation with ascospores –opposite mating types form zygote –ascospores forcefully released from ascocarp, germinate Sclerotia masses of hyphae survive the winter then germinate 23

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25 Genus Aspergillus A. fumigatus –ubiquitous environmental –allergies and significant pathogen (ABPA and Farmer's Lung) A. oryzae –production of fermented foods –important in biotechnology A. flavus –Aflatoxin B 25

26 Aspergillosis Usually caused by Aspergillus fumigatus; also caused by A. flavus Invasive disease results in pulmonary infection –with fever, chest pain and cough that disseminates to brain, kidney –in severely compromised individuals, lungs may fill with mycelia Diagnosis by examination of pathological specimens or by isolation and characterization of fungus Treatment with antifungal drugs; treat underlying disease 26

27 More about Ascomycota Claviceps purpura –parasite on higher plants –ergotism toxic condition from eating infected grain due to lysergic acid diethylamide (LSD) Candida, Blastomyces, Histoplasma –human pathogens Stachybotrys – “sick building syndrome” Aspergillus – aflatoxins and cancer 27

28 Candidiasis Caused by Candida albicans or C. glabrata, dimorphic fungi –members of normal microbiota but numbers kept in check by other microbes disease in healthy individuals occurs as result of disruption of normal microbiota –can also be spread by sexual contact –wide spectrum of disease but most infections involve the skin or mucous membranes 28

29 Nosocomial Candidiasis Important nosocomial pathogens May represent up to 10% of nosocomial bloodstream infections Mortality ~50% when in bloodstream and disseminates to visceral organs 29

30 Candidiasis Oropharyngeal candidiasis (thrush) –common disease of newborns, denture wearers, and those on steroid therapies Paronychia and onychomycosis –associated with Candida infections of the subcutaneous tissues of digits and nails, respectively usually result from continued immersion of hands Intertriginous candidiasis –involves axillae, groin, and skin folds 30

31 Candidiasis Napkin (diaper) candidiasis –found in infants whose diapers are not changed frequently Candidal vaginitis –occurs when lactobacilli are depleted 31

32 Candidiasis Diagnosis of candidiasis is difficult Treatment, control, and prevention –no satisfactory treatment –antifungals used for cutaneous lesions and systemic candidiasis 32

33 Airborne Diseases Blastomycosis –systemic mycosis caused by Blastomyces dermatitidis (dimorphic fungus) –three clinical forms: cutan- eous, pulmonary, and disseminated –after lung inhalation spreads rapidly to skin causing cutaneous ulcers and abscesses –serologic tests for diagnosis –amphotericin B/other anti-fungal drugs for treatment 33

34 Airborne Diseases Coccidioidomycosis –endemic areas Valley fever, San Joaquin fever, or Desert Rheumatism –dimorphic inhale the arthroconidia, converts to large spherule in body Diagnosis –demonstration of spherule Prevention involves avoiding exposure to dust 34

35 Airborne Diseases Cryptococcosis –systemic mycosis caused by yeast Cryptococcus neoformans –source is dried pigeon droppings –inhalation serious disease including meningitis in immunocom- promised (e.g., AIDS); mild or pneumonia-like in others Detecting encapsulated yeast in clinical specimen is diagnostic 35

36 Airborne Diseases Histoplasmosis – common lung disease –caused by Histoplasma capsulatum var. capsulatum (dimorphic) –inhalation of airborne microconidia in bird droppings converts to yeast phase in body; flu-like illness only rarely becomes disseminated –Prevented/controlled by wearing protective clothing in endemic areas and by soil decontamination 36

37 Direct Contact Diseases Superficial mycoses –piedras infections of hair shaft –tineas infections involving outer layers of skin, nails, and hair Trycophyton –most occur in tropics –treatment, prevention, and control removal of skin scales and infected hairs good personal hygiene 37

38 Direct Contact Diseases Cutaneous mycoses –dermatomycoses, ringworms, or tineas different diseases distinguished according to causative agent and area of body affected –most common fungal diseases, occurring worldwide –diagnosis microscopic examination of skin biopsies and culture on Sabouraud’s glucose agar –treatment, prevention, and control topical ointments and antifungal agents 38

39 Direct Contact Diseases Examples of cutaneous mycoses –Tinea capitis – infection of scalp hair –Tinea pedis – athlete’s foot –Tinea unguium – infection of the nailbed –Tinea cruris – jock itch 39

40 Subcutaneous Mycoses Caused by saprophytic inhabitants of soil Introduced in soil-contaminated puncture wounds Clinical manifestations –develops slowly over a period of years –nodules form and ulcerate –organisms spread along lymphatic channels, producing more nodules Diagnosis –culture and examination of fungus from infected tissue Treatment, prevention, and control –antifungal agents and surgical excision 40

41 Subcutaneous Mycoses Chromoblastomycosis –dark brown pigmented nodules Maduromycosis –destroys subcutaneous tissue and produces serious deformities –often called a eumycotic mycetoma Sporotrichosis –when spread throughout body, referred to as extracutaneous sporotrichosis 41

42 Basidiomycota Basidiomycetes (club fungi) –examples include rusts, shelf fungi, puffballs, toadstools, mushrooms –sexual reproduction form basidium basidiospores are released at maturity 42

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44 Human Impact Basidiomycota Decomposers Edible and non-edible mushrooms –toxins are poisons and hallucinogenic Pathogens of humans, other animals, and plants –e.g., Cryptococcus neoformans – cryptococcosis systemic infection, primarily of lungs and central nervous system 44

45 Microsporidia Obligate intracellular fungal parasites that infect insects, fish, and humans –Aquatic birds are common hosts and contribute to large numbers of spores in environment Transitional form is a spore structure capable of surviving outside the host Structurally similar to ‘classic’ fungi –contain chitin, trehalose, and mitosomes –however, lack mitochondria, peroxisomes and centrioles –unique morphology is polar tube essential for host invasion 45

46 Microsporidia Obligate intracellular fungi that belong to phylum Microspora –an emerging infectious disease, found mostly in HIV patients Domestic and feral animals are reservoirs for species that infect humans Produce highly resistant spore 46

47 Microsporidia Infection of host cell occurs when microsporidia extrudes polar tubule from within the spore Symptoms –wide variety including hepatitis, pneumonia, skin lesions, diarrhea, weight loss, and wasting syndrome Diagnosis –based on clinical symptoms and identification of microsporidia in gram or giema-stained specimens –identification can also be made using electron microscopy or PCR Treatment, control, and prevention –some treatment success with antifungal drugs 47

48 Microsporidia Pathogenesis Human infections –Enterocystozoon bieneusi diarrhea pneumonia –Encephalitozoon cuniculi encephalitis nephritis –severe in HIV/AIDS patients 48


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