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Chapter 12 The Eukaryotes: Fungi, Algae, Protozoa, and Helminths Part 1.

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Presentation on theme: "Chapter 12 The Eukaryotes: Fungi, Algae, Protozoa, and Helminths Part 1."— Presentation transcript:

1 Chapter 12 The Eukaryotes: Fungi, Algae, Protozoa, and Helminths Part 1

2 Fungi, Algae, Protozoa, and Helminths

3 Fungi Mycology: the study of fungi –rRNA sequencing causing many reclassification Eukaryotic (unicellular, filamentious, fleshy) Aerobic or facultatively anaerobic Chemoheterotrophic Most are decomposers (important in the food chain); absorb nutrients instead of ingestion –decompose dead plant matter (organic molecules to inorganic molecules) & recycle vital elements

4 Fungi Few are plant and human pathogens Incidence of serious fungal infections have been rising –Nosocomial infections and in people who are immunocompromised Beneficial –Recycling of nutrients in the environment –Symbiotic fungi (mycorrhizae) help plants roots absorb minerals and water from the soil –Serve as food; used to produce foods and drugs for humans

5 Fungi Table 12.2

6 Characteristics of Fungi Fungal structures are used for identification in a clinical laboratory –Yeast identification based on biochemical tests –Multicellular fungi based on physical appearance: 1) colony characteristics, 2) type of hyphae, and 3) reproductive spores (asexual spores for clinical ID & sexual spores for phyla) Fungal colonies (vegetative structures) are composed of the cells involved in catabolism and growth

7 Molds and fleshy fungi Fig The fungal thallus (body) consists of hyphae; a mass of hyphae is a mycelium. –Hypha (pl. hyphae): a long filament of cells in fungi –Septate hyphae: hyphae with cross-walls (septa) –Coenocytic hyphae: hyphae with no septa

8 –Vegetative hypha: the portion of a hypha that obtains nutrients –Reproductive (aerial) hypha: the portion of a hypha concerned with reproduction –Aerial hyphae bear reproductive spores Molds and fleshy fungi Figure 12.2

9 Yeasts Unicellular fungi; usually spherical or oval shape; usually reproduce by budding Capable of facultative anaerobic growth –Fermentation used in brewing, wine-making, and baking Pseudohypha: A short chain of fungal cells that results from the lack of separation of daughter cells after budding Yeast cells grown on a solid medium resemble bacterial colonies

10 Fission yeasts divide symmetrically (e.g. Saccharomyces) Budding yeasts divide asymmetrically Yeasts Figure 12.3

11 Pathogenic dimorphic fungi are yeastlike at 37°C and moldlike at 25°C –Moldlike form produce aerial and vegetative hyphae –Yeastlike form reproduce by budding Dimorphic fungi Figure 12.4

12 Life cycle Fig Filamentous fungi can reproduce asexually by fragmentation of their hyphae Sexual and asexual reproduction through formation of spores (formed from aerial hyphae)

13 Life cycle Asexual spores: formed by the hyphae of one organism through mitosis –Gives rise to a new mold that is genetically identical to the parent Sexual spores: result from the fusion of nuclei from 2 opposite mating strains of the same species of fungus –Gives rise to a new mold that has genetic characteristics of both parental strains –Usually produced in response to changes in environment

14 Sporangiosphore –form within a sac called sporangium at the end of a sporangiophore (aerial hypha), e.g. Rhizopus Chlamydospore –a thick-walled spore formed by rounding and enlargement within a hyphal segment e.g. Candina albicans (yeast) Asexual spores Figure 12.5

15 Asexual spores Conidiospore (conidium) –a unicellular or multicellular spore that is not enclosed in a sac; produced in a chain at the end of a conidiophore (aerial hypha), e.g. Aspergillus –Arthrospore: formed by the fragmentation of a septate hypha into single, slightly thickened cells, e.g. Coccidioides immitis –Blastoconidium: buds coming off the parent cell, e.g. C. albicans (yeast) and Cryptotoccus

16 Conidiospores Figure 12.5

17 Results from sexual reproduction Three phases –PlasmogamyHaploid donor cell nucleus (+) penetrates cytoplasm of recipient cell (–) –Karyogamy+ and – nuclei fuse –MeiosisDiploid nucleus produces haploid nuclei (sexual spores) In laboratory setting, most fungi exhibit only asexual spores (used for clinical identification) Sexual spores

18 ZygosporeFusion of haploid cells produces one zygospore e.g. Rhizopus Sexual spores Figure 12.6

19 AscosporeFormed in a sac (ascus), e.g. Penicillium Sexual spores Figure 12.7

20 BasidiosporeFormed externally on a pedestal (basidium), e.g. mushrooms Sexual spores Figure 12.8

21 Nutritional adaptations Fungi adapted to environments that would be hostile to bacteria –Usually grow better in acidic environment (pH of about 5) & require less nitrogen for growth –Aerobic (molds) or facultative anaerobes (yeasts) –More resistant to osmotic pressure (can grow in relatively high sugar or salt concentration) –Can grow on a very low moisture surface –Capable of metabolizing complex carbohydrates (e.g. lignin)

22 Medically Important Phyla of Fungi Not all fungi cause disease –many are found as contaminants in foods and in as contaminants on bacterial cultures (laboratory) Four phyla: Zygomycota, Ascomycota, & Basidiomycota (these are telomorphs); and Anamorphs (Deuteromycota) –Telomorphs: produce both sexual and asexual spores; the sexual stage in the life cycle of a fungus –anamorphs: Ascomycete fungi that have lost the ability to reproduce sexually; the asexual stage of a fungus (asexual spores only)

23 Medically Important Phyla of Fungi Zygomycota (conjugation fungi) –Saprophytic (obtain nutrients from dead organic matter) molds with coenocytic hyphae –Asexual spore = sporangiospores; sexual spores = zygospores –e.g. Rhizopus & Mucor (Opportunistic, systemic mycoses) Rhizopus nigricans (common bread mold)

24 Zygomycete Life Cycle Figure 12.6

25 Medically Important Phyla of Fungi Ascomycota (sac fungi) –molds with septate hyphae and some yeasts –Sexual spores = ascospore; and frequently asexual spores = conidiospores –e.g. Aspergillus (opportunistic, systemic mycosis) Blastomyces dermatitidis, Histoplasma capsulatum (systemic mycoses) Microsporum, Trichophyton (cutaneous mycoses)

26 Ascomycete Life Cycle Figure 12.7

27 Basidiomycota (club fungi, mushrooms) –Molds with septate hyphae –Sexual spores = basidiospores; and sometimes asexual spores = conidiospores –Cryptococcus neoformans (systematic mycosis) Medically Important Phyla of Fungi

28 Basidiomycete Life Cycle Figure 12.8

29 Anamorphs Anamorphic fungi: –Produce asexual spores only; historically fungi whose sexual cycle had not been observed were called Deuteromycota –rRNA sequencing places most in Ascomycota, a few are Basidiomycota – e.g. Penicillium Sporothrix (subcutaneous mycosis) Stachybotrys, Coccidioides, Pneumocystis (systemic mycoses) Candida albicans (Cutaneous mycoses)

30 Tend to be chronic (long-lasting) infections due to slow growth of fungi & hard to treat –Drugs that will affect fungal cells (eukaryotes) also affect animal cells (also eukaryotes) Systemic mycoses: deep within body –Usually caused by fungi living in soil Subcutaneous mycoses: beneath the skin –Usually caused by saprophytic fungi living in soil and on vegetation Fungal Diseases (mycoses)

31 Cutaneous mycoses: affect hair, skin, nails –Usually caused by fungi living in soil, on animals or humans (can be transmitted from human to human or from animal to human) Superficial mycoses: localized, e.g., hair shafts, and surface epidermal cells –Prevalent in tropical climates

32 Fungal Diseases (mycoses) Opportunistic mycoses: caused by normal microbiota or fungi that are normally harmless –infect immunocompromised host; patients on broad-spectrum antibiotics; or people who is seriously debilitated or traumatized

33 Gypsy moth controlEntomorphaga Ceratocystis ulm (Dutch elm disease) Taxol productionTaxomyces Cryphonectria parasitica (chestnut blight) Cellulose used for juices and fabric Trichoderma Food spoilage Negative Effects Bread, wine, beerSaccharomyces Positive EffectsFungi Economic Effects of Fungi Used in biotechnology, biological pest controls vs. undesirable effects

34 Mutualistic combination of an alga (or cyanobacterium) & fungus –Classified according to the fungal partner (most often an ascomycete) –Mutualism: a type of symbiosis in which both organisms or populations are benefited Alga produces and secretes carbohydrates (via photosynthesis), fungus provides holdfast (enclose alga) Some of the slowest growing organisms on Earth Lichens

35 Figure 12.10

36 Lichens Often the first life forms to colonize newly exposed soil or rock –Colonize habitats that are unsuitable for either the alga or the fungus alone Grouped into 3 morphologic categories –Crustose, foliose, and fruiticose Used as dyes for clothing, an antimicrobial agent, the dye in litmus paper; cause allergic contact dermatitis


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