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Mycology Clinically Relevant Fungi. ◦ Decompose dead organisms and recycle their nutrients ◦ Form associations with roots of vascular plants, which help.

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Presentation on theme: "Mycology Clinically Relevant Fungi. ◦ Decompose dead organisms and recycle their nutrients ◦ Form associations with roots of vascular plants, which help."— Presentation transcript:

1 Mycology Clinically Relevant Fungi

2 ◦ Decompose dead organisms and recycle their nutrients ◦ Form associations with roots of vascular plants, which help plants absorb water and minerals ◦ Used for food, in religious ceremonies, and in manufacture of foods and beverages ◦ Produce antibiotics ◦ Serve as important research tools ◦ 30% cause diseases of plants, animals, and humans ◦ Can spoil fruit, pickles, jams, and jellies

3 ◦ Acquire nutrients by absorption ◦ Most are saprobes ◦ Some trap and kill microscopic soil-dwelling nematodes ◦ Haustoria allow some to derive nutrients from living plants and animals ◦ Most are aerobic; some are anaerobic; many yeasts are facultative anaerobes

4  Myceteae  Great variety and complexity  Approximately 100,000 species  Majority are unicellular or colonial

5 Can be divided into three groups:  Yeasts  Molds  Macroscopic Fungi

6 Can be divided into three groups:  Yeasts  Round or oval shape  Unique mode of asexual reproduction  Some form pseudohyphae (false filaments)

7 Can be divided into three groups:  Molds  Long, threadlike cells  Filamentous arrangement (hyphae)  Some are dimorphic (yeast-like and filamentous forms exist)

8 Macroscopic fungi  Mushrooms, toad stools  Bracket fungi  Stink horns

9 CHARACTERISTICS  Parasitic or Saprophytic  Eukaryotic  Form Filaments termed hyphae  Hyphae form mycelium septate or aseptate  Cell wall composed of chitin or cellulose  Slow to propagate  Most are aerobic  pH acidic

10 FUNGUS: multicellular, spore bearing, achlorophyllous organism which multiply sexually or asexually and whose usually filamentous somatic structure are septate or aseptate (coenocytic). The nutritional need of a fungus are facilitated by the enzymes cellulase and/or chitinase.

11 *All molds are fungi but all fungi are not molds-- yeasts are fungi but they are unicellular and produce no aerial mycelium molds filamentous fungi that produce aerial mycelium

12  Hyphae: the tubelike filaments that constitute a mycelium.   Mycelia: The somatic hairlike structures of a fungus. A mass of hyphae produced by some fungi. 

13 LOWER FUNGI  Aseptate mycelia  used to be called Phycomycetes  Saprophytic or parasitic  Most primitive fungi  Found mostly in soil, water, leaves  Coenocytic = Aseptate  Produce asexual spore in sporangium

14 Oomycetes   The oomycetes develop biflagellated zoospores with oppositely directed flagella. The mycelia is well developed, branched, aseptate or coenocytic. Sexual reproduction is oogamous. Some species are plant parasites of commerical crops such as grapes and potatoes. Some species are fish parasites. Characteristic of Oomycetes:  water molds  Some portion of life cycle is flagellated  Cause fish disease and disease of commercial crops  Plasmopara  Phytophthora infestations--potato blight  Saplonegia fish infections

15  Differ from fungi in the following ways ◦ Have tubular cristae in their mitochondria ◦ Cell walls are of cellulose instead of chitin ◦ Spores have two flagella – one whiplike and one tinsel- like ◦ Have true diploid thalli

16 Zygomycetes Zygomycetes have well developed mycelia in which the hyphae are usually aseptate; however, septa may form in older portions of the mycelia. Asexual spores are produced in sporangium. Sexual spores are produced after fusion of two gametes formed at hyphal tips. Characteristics of Zygomycetes-  predominantly terrestrial  Breakdown organic molecules and are important in recycling  Some are human pathogens  Life cycle include both sexual and asexual reproduction  characterized by zygospores 

17 Chytridiomycetes responsible for recycling of nutrients in aquatic habitats.

18 Trichomycetes are major parasites of insects.

19 HIGHER FUNGI contain septate mycelia

20 Ascomycetes possess septate hyphae and produce ascospores in sac- like structures known as asci. Karyogamy and meiosis occur in the developing ascus resulting in four haploid cells. These cells become ascospores. Mitosis occurs after meiosis and produces usually eight ascospores per ascus. Produces asexual conidiospores.   Two stages:  1. Sexual or ascospore stage  2. Asexual or conidial stage   Characteristics of Ascomycetes:  Sac fungi also known as Perfect fungi  Mostly plant pathogens  Cell wall composed mostly of chitin  produce sexual (ascospores) and asexual spores (conidiospores)

21 Basidiomycetes The club fungi

22 Basidiomycetes:  Produce basidia, club-like structures in which karyogamy and meiosis occur. At maturity, two or four haploid basidiospores are produced on a basidium. The hyphae are septate and contain clamp connections. Include mushrooms, toadstools, rust, smuts, bracket fungi, puff balls, and birds nest fungi.  Basidiocarp pileus cap stipe stem lamellae gills

23 Deuteromycetes:  Include fungi whose sexual reproductive stages have never been observed. These fungi produce asexual conidia in abundance. The hyphae are septate.  Characteristic of Deuteromycetes  Fungi imperfect: most clinically important  only reproduce asexually by conidiospores  mycelium septate  most pathogenic fungi in this group  either had sexual stage and lost it or it has not been described  all yeast that reproduce only be budding

24 Asexual Spores  Sporangiospores ◦ Formed by successive cleavages within the sporangium ◦ Sporangium attached to the sporangiophore ◦ Released when the sporangium ruptures  Conidiospores ◦ aka conidia ◦ Free spores ◦ Develop either by pinching off the tip of fertile hypha or by segmentation of a vegetative hypha

25 Figure 5.19

26 Histoplasmosis, also known as Darling's disease, is a disease caused by the fungus Histoplasma capsulatum. Symptoms of this infection vary greatly, but the disease primarily affects the lungs.

27 Histoplasmosis Occasionally, other organs are affected; this is called disseminated histoplasmosis, and it can be fatal if untreated. Histoplasmosis is common among AIDS patients because of their lowered immune system. Found in soil and associated with poultry feces and bat guano.

28 Sporothrix schenckii is the causative agent of Sporotrichosis or rose-handler's disease. Sporotrichosis is a subcutaneous infection and it starts following entry of the infecting fungus through the skin via a minor injury and may affect an otherwise healthy individual. Following entry, the infection may spread via the lymphatic route (nodular lymphangitis may develop). Patients infected with Sporothrix schenckii may be misdiagnosed as pyoderma gangrenosum due to the large ulcerations observed during the course of sporotrichosis.

29 Coccidioides immitis is a pathogenic fungust hat resides in the soil in certain parts of the southwestern United States. It can cause a disease called coccidioidomycosis (Valley Fever), and it is a rare cause of meningitis, mostly in Immunocompromised persons. It has been declared a select agent by both the U.S. Department of Health and Human Services and the U.S. Department of Agriculture and is considered a biosafety level 3 pathogen. Infects lungs and skin mainly.

30 Blastomyces s a fungal genus responsible for the medical condition blastomycosis. The most well known species of the genus is Blastomyces dermatitidis. B. dermatitidis is a dimorphic fungal pathogen, found primarily in the Mid-West and Northern United States and Canada. It exists in the soil in a filamentous form that produces spores directly upon the wall of the hyphae, lacking any kind of fruiting body to aid in aerosolization/dissemination of the spores. The natural reservoir of this organism in the environment is not clearly defined, but it seems to be associated with rivers and lakes. Blastomyces is endemic to the Mississippi and Ohio river valleys and the vicinity of the Great Lakes. Outbreaks of blastomycosis are often associated with disruptions of the soil that might lead to the artificial elevation of spore and/or hyphal fragments in the air.

31 These agents infect human and animal hosts when they are inhaled. At the elevated temperature of 37°C in a host, the fungus undergoes a phase transition to the pathogenic yeast form. Yeast form cells multiply in the lung and may cause disease in immuno-competent hosts, sometimes disseminating to the skin, central nervous system and bones.

32 Some fungi exhibit different morphologies--grow as filamentous forms in soil and media, but in a suitable animal host form yeast. May display dimorphism just by changing environment and/or nutritional conditions. Histoplasma capsulatum - mold on media at room temperature, yeast at 37C Candida albicans: yeast at room temperature, pseudohyphae in body  1. Dimorphism is advantageous because it allows them to reproduce more rapidly  2. Fends off immune response (encapsulate)  3. Allow them to obtain nutrition more rapidly

33 Ringworm is a fungal infection of the skin in humans and domestic animals such as sheep and cattle. Those that cause parasitic infection (dermatophytes) feed on keratin, the material found in the outer layer of skin, hair, and nails. These fungi thrive best on skin that is warm and moist.

34 Causative agents of Ringworm Dermatophytes Trichophyton spp Epidermophyton spp Microsporium spp

35 Causative agents of Ringworm Medically dermatophytes are classified as Tinea and the area they are infecting.

36 Tinea capitis Tinea pedis Tinea pubis Tinea corporis

37 Tinea ungumTinea manum Tinea corporis

38 Malassezia furfur aka Tinea versicolor Mottled, discolored skin pigmentation is characteristic of s uperficial skin infection

39 Candida albicans Causes oral and anal thrush Associated with yeast infections of vagina especially after a course of antibiotics.

40 Cryptococcus neoformans Causes infections of brain, meninges, and skin Associated with immunocompromised individuals especially those with AIDS.

41

42 Causative agents Stachybotrysis Cladiosporium Toxins produces by the fungi produce the clinical symptoms.

43 Causative agents Water leaks lead to contamination

44 [INSERT FIGURE 12.27]

45 Fungi are Friends and Foes  Not only involved in infections ◦ Allergies ◦ Poisoning ◦ Agricultural damage  Benefits of fungi ◦ Decomposing organic matter and returning essential minerals to the soil ◦ Mycorrhizae increase the ability of plant roots to absorb water and nutrients ◦ Production of  Antibiotics  Alcohol  Organic acids  Vitamins ◦ Food flavorings


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