The Eukaryotes. Fungi 10/18/2017. Chapter 12 BIO 220

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1 The Eukaryotes Chapter 12 BIO 220 Fig Fungi Mycology = study of fungi Of the more than 100,000 species of fungi, only about 200 are pathogenic to humans and animals Many form mutualistic relationships with other organisms (i.e. mycorrhizae) Decompose dead plant matter (saprophytic), allowing the recycling of elements Humans use fungi for food, to produce foods, and drug production 1

2 Characteristics of molds & fleshy fungi The body or thallus is made of many hyphae Characteristics of molds & fleshy fungi Vegetative hyphae obtain nutrients Aerial hyphae are concerned with reproduction A mycelium can form if conditions are right Grow by elongating at the tips. Fig. 12.2a Fig Yeasts Nonfilamentous, unicellular fungi Can be found as a white powder on fruits and leaves Many reproduce by budding (i.e. S. cerevisiae) Some yeasts form pseudohyphae Fig Fig

3 Yeasts cont. Dimorphic fungi Schizosaccharomyces reproduces by fission Parent cell elongates, its nucleus divides, and two offspring cells are produced Yeasts are facultative anaerobes which allows them to survive in a variety of environments Mold-like forms produce vegetative/aerial hyphae, yeast-like forms reproduce by budding Fig Reproduction of Fungi Filamentous fungi can reproduce asexually by fragmentation of their hyphae Fungi also reproduce by the formation of spores (asexual AND sexual reproduction) Asexual spores Are formed from aerial hyphae Asexual spores are produced through mitosis and subsequent cell division When these spores germinate, they produce organisms that are genetically identical to the parent Two types of asexual spores produce by fungi are conidiospores and sporangiospores 3

4 Conidiospores Spores are unicellular or multicellular and NOT enclosed in a sac ( naked spores) Conidiospores (conidia) are produced at the end of conidiophores Arthroconidia Conidia formed by the fragmentation of a septate hypha into single, slightly thickened cells Coccidioides immitis Fig Fig Blastoconidia Conidia formed from the buds of its parent cell Chlamydoconidia Thick-walled spore formed within a hyphal segment Fig Fig

5 Sporangiospores Spores form within a sac called a sporangium which is at the end of an aerial hypa called a sporangiophore Sexual reproduction is in three phases Plasmogamy Haploid nucleus of donor cell (+) enters cytoplasm of recipient cell (-) Karyogamy Fusion of nuclei, so now have a diploid zygote nucleus Meiosis Haploid nuclei (spores) will be formed, some of which may be genetic recombinants Fig Nutritional requirements Chemoheterotrophs Typically grow best in an environment ph=5 Most molds are aerobic, most yeasts are facultative anaerobes Can grow in relatively high sugar or salt environment Can grow on substances with low moisture content Reduced nitrogen requirement Can metabolize complex carbohydrates Phyla of medically important fungi Zygomycota Microsporidia Ascomycota Basidiomycota 5

6 Zygomycota Saprophytic molds with coenocytic hyphae Microsporidia Obligate intracellular parasites Lack mitochondria, no microtubules Fig i.e. Rhizopusstolonifer Fig i.e. Encephalitozoon cuniculi Ascomycota (sac fungi) Basidiomycota (club fungi) Molds with septate hyphae Yeasts Septate hyphae i.e. Amanita phalloides Fig Fig

7 Anamorphs Fungi that have lost the ability to reproduce sexually Most are members of Ascomycota i.e. Penicillium Mycoses Mycosis = fungal infection Systemic infections deep in body Subcutaneous beneath the skin Cutaneous affect skin, hair, nails Superficial superficial epidermis, hair shafts Opportunistic Coccidioides immitis Etiological agent of coccidioidomycosis (San Joaquin fever) Cryptococcus neoformans Etiological agent of meningitis Widely distributed, especially in areas contaminated by bird feces (esp. pigeons) Transmitted by inhalation of spores in contaminated droppings Most cases occur in people that are severely immunocompromised Amphotericin B & flucytosine Figs , Amphotericin B (polyene antibiotic) injury to plasma membranes (fungicidal) Fig

8 Histoplasma capsulatum Etiological agent of histoplasmosis Humans acquire the disease from airborne conidia, usually found in soil contaminated with large amounts of bird or bat feces Symptoms may range from flu-like symptoms to serious lung infections Dermatomycoses (cutaneous) Dermatophytes colonize the hair, nails, and outer layer of the epidermis Tinea capitis (ringworm), tinea cruris (jock itch), tinea pedis (athlete s foot) Trichophyton (hair, skin, nails) Microsporum (hair, skin) Epidermophyton (skin, nails) Figs , Pneumocystis jirovecii Candidiasis Opportunistic pathogen, which can cause Pneumocystis pneumonia in immunocompromised individuals Fig Fig

9 Claviceps purpurea Etiological agent of ergotism Plant pathogen that grows on grains (rye) Alkaloid toxins contained in sclerotia, causes hallucinations resembling those produced by LSD Constricts blood vessels, potentially causing gangrene of limbs due to inadequate blood flow Benefits of fungi Saccharomyces bread and wine Entomophaga biological pest control Paecilomycesfumosoroseus biological pest control Antibiotic production 9

10 Lichens Lichens Combination of a green alga (or cyanobacterium) and a fungus in a mutualistic relationship Classified based on the fungal partner (usually Ascomycota) Can survive in environments in which the alga or fungus would be unable to survive alone Found on rooftops, trees, newly exposed dirt or rock Fig Protozoa Unicellular Aerobic heterotrophs (mostly) Inhabit soil and water All produce asexually, some sexually as well Fission, budding, or schizogony Conjugation Cells fuse Macronuclei disintegrate Micronuclei exchanged Cells separate Protozoa Trophozoites (feeding and growing form) and cysts (survival) Free-living or parasitic We will discuss based on locomotion Fig

11 Euglena Flagellates Photoautotrophs and chemoheterotrophs! Free-living Does not have a cell wall, rather a protein layer called a pellicle Fig e Giardia intestinalis, G. lamblia, G. duodenalis Etiological agent of giardiasis Fecal-oral transmission Ingestion of cysts in feces-contaminated food or water Excystation results in the release of trophozoites, which attach to intestinal mucosa Become cysts as move towards colon Metronidazole interferes with anaerobic metabolism Trichomonas vaginalis Etiological agent of trichomoniasis Most common transmission route is through sexual contact No cyst stage Fig Fig

12 Trypanosoma brucei Etiological agent of African trypanosomiasis Transmitted by tsetse fly Parasites multiply in the fly gut and continue in the salivary glands Fly takes a blood meal and transfers parasite to human Multiplication in bodily fluids Sexual contact/placenta Trypanosoma cruzi Etiological agent of American trypanosomiasis (aka Chagas disease) Transmitted by reduviid ( kissing ) bug May be asymptomatic or cause symptoms include swelling at site of inoculation, fever and rarely swelling of heart muscle, brain, meninges Some individuals may develop significant heart, esophageal complications Source: MicrobeWiki Fig Paramecium Ciliates Chemoheterotrophs Free-living Cilia used not only for motility but also for food acquisition Fig

13 Balantidium coli Only ciliate that is a human parasite Etiological agent of balantidiasis (balantidial dysentery) Fecal-oral transmission Cysts responsible for infection Trophozoites reproduce in large intestine Mostly asymptomatic, except in immunocompromised Can cause perforation of colon Amebae Use pseudopodia for locomotion Chemoheterotrophs Free-living Amoeba proteus Fig Acanthamoeba Etiological agent of Acanthamoeba keratitis Infection of cornea that can result in permanent impaired vision or blindness Most often seen in contact lens wearers Entamoeba histolytica Chemoheterotroph Etiological agent of amoebiasis (amoebic dysentery) Fecal-oral transmission Cysts Can bore into blood stream Metronidazole Fig

14 Apicomplexa Plasmodium Not motile Obligate internal parasites Complex life cycle Plasmodium etiological agent of malaria Fig Cryptosporidium Etiological agent of cryptosporidiosis Fecal-oral route Most frequent cause of recreational waterborne diarrhea Resistant to most chemical disinfectants, including chlorine Helminthes 14

15 Characteristics of helminthes Multicellular, eukaryotic worms Some are parasitic May lack a digestive system Reduced nervous system Means of locomotion occasionally reduced or lacking Complex life cycle Helminth life cycles Complex, involving a succession of intermediate hosts Some helminthes are dioecious, with male and female worms Reproduction occurs inside host if both male and female worms are present Some helminthes are monoecious or hermaphroditic Hermaphrodites can copulate and simultaneously fertilize each other Platyhelminthes Flatworms (parasitic) Trematodes (flukes) Cestodes (tapeworms) Trematodes Flat, leaf-shaped bodies Suckers hold organism in place Absorb food across cuticle Fig

16 Paragonimus (lung fluke) Schistosoma mansoni (blood fluke) Fig Fig Cestodes Intestinal parasites Suckers and hooks for attachment Absorb food via cuticle Body made of segments called proglottids Each proglottid contains male and female organs Most distal contain eggs Fig Taeniasis Cysticercosis Neurocysticercosis Taenia solium Niclosamide Prevents ATP generation Praziquantel Alters PM permeability 16

17 Nematodes Roundworms Complete digestive system Many are dioecious Intestinal roundworms include whipworms, hookworms and Ascaris Ascaris lumbricoides Dirofilaria immitis Mebendazole, albendazole inhibits absorption of nutrients 17

18 Arthropods as vectors Arthropods are animals having segmented bodies, hard external skeletons, and jointed legs Vectors = arthropods that carry pathogenic microbes Arachnids ticks, spiders Crustaceans crabs, crayfish Insects fleas, flies, mosquitoes 18