The Eukaryotic Members of the Microbial World Chapter 12 notes A Glimpse of History Irish Potato Famine 1845 1847 Water mold Phytophthora infestans decimated crop Estimated 1 5 million people died during famine More than 1 million emigrated to U S Canada Population of Ireland dropped by 25 Showed danger of relying on a single crop Potatoes brought to Europe 200 years earlier from South America Easy to grow convenient nearly complete food source Potato blight results in nearly 10 billion year in losses In 2009 genomes of potato and P infestans sequenced Informal groups of microscopic eukaryotes simple autotrophs photosynthesizers heterotrophic organisms chitin in cell wall Algae Fungi Protozoa Protists Chapter 12 includes multicellular worms certain insects since implicated in human disease often transmitted or carried in microscopic forms microscopic heterotrophs that are not fungi eukaryotes that are not fungi plants animals Nucleus membrane bound organelles no peptidoglycan usually well developed cytoskeleton Microscopic Eukaryotes Eukaryotics differ from prokaryotes May be haploid and or diploid Asexual reproduction via mitosis Sexual reproduction via meiosis Diploid cells produce haploid cells Can develop into haploid organisms or gametes Fusion of 2 gametes yields diploid cell recombination of genetic material Fungi Fungi molds yeasts mushrooms Refers to morphological forms not classification Yeasts Molds Mushrooms Mycology single celled fungi filamentous fungi is study of mushrooms reproductive structures of certain fungi Fungi cell wall contains chitin Fungal membranes typically have ergosterol Fungi excrete enzymes to degrade larger molecules Along with bacteria principle decomposers Can degrade cellulose and lignin wood Releases CO2 nitrogen compounds into soils nutrients from dead or decaying matter Saprophytic Some act as parasites of living tissue few infect humans but plant infections common Some fungi form symbiotic relationships e g lichens Classification of fungi in state of flux 80 000 recognized species likely over 1 million total Chapter 12 considers only 4 major groups Chytrids usually live in water some in mammalian gut Some parasitic B dendrobatidis infects frogs Only fungi with motile forms reproductive cells Zygomycetes Ascomycetes truffles lichens Basidiomycetes Structure of Fungi include black bread mold Rhizopus reproductive structures called sporangia sac fungi include 75 of known fungi Penicillium pathogens morels and club fungi include mushrooms plant parasites smuts rusts Most fungi multicellular composed of hyphae Visible mass of hyphae termed mycelium Tips of hyphae grow rapidly in direction of food source grow throughout food openings remain between cells allowing movement along hypha High surface to volume ratio aids nutrient absorption Fungi most successful in moist environments Some have specialized hyphae Parasitic fungi haustoria protrude into host cells Saprophytic fungi rhizoids may anchor to substrate Dimorphic fungi can grow as single yeast cells or multicellular mycelia E g Histoplasma capsulatum mold in soil Reproductive spores easily airborne develop into yeast form when inhaled cause disease Fungal Habitats mostly terrestrial Found in nearly every habitat on earth including thermal pools volcanic craters high salt environments Some widespread others specialize on a single plant Fungi found that can degrade leather cork hair wax ink jet fuel carpet drywall even some plastics Often responsible for food spoilage since may grow in concentrations of salts sugars acids that kill most bacteria including pH range from 2 2 to 9 6 Most prefer 20 C to 35 C but easily survive lower temperatures some grow below freezing Most aerobic some yeasts facultative anaerobes Some obligate anaerobes live in rumen of cows Symbiotic Relationships Lichens are association of fungus and photosynthesizer alga or cyanobacterium Fungus protects absorbs water and nutrients Allows growth in ecosystems where neither could alone could survive e g sub Arctic tundra bare rock Mychorrhizas beneficial association with plant roots High surface area of hyphae supplies plant with water minerals nitrogen phosphorous Plant supplies fungi with organic compounds Estimated 80 of vascular plants have mychorrhizas Plants grow better with some e g orchids require Reproduction in Fungi Certain insects depend on fungi E g leaf cutting ants farm fungal gardens Ants cannot eat often poisonous tropical vegetation Instead chop plants into pieces add mycelium Fungi grow digest plant material produce reproductive structures eaten by ant Structures important in identification Spore reproductive cells formed sexually or asexually Asexual spores called conidia or sporangiospores in zygomycetes Housed in structures sporangia zygomycetes or asci ascomycetes or in basidiomycetes beneath mushroom or puffball Reproduction results from fusion of hyphae from two different mating types termed Yields dikaryon two nuclei Nuclei fuse undergo meiosis form haploid spores Yeast may reproduce by mitosis or budding Molds may reproduce by fragmentation Spores carried by wind water germinate grow hyphae Economic Importance of Fungi Medical Importance of Fungi Antimicrobial medicines e g penicillin griseofulvin Useful tools for study of eukaryotic cells Yeasts genetically engineered to produce important molecules including human insulin hepatitis B vaccine Saccharomyces cerevisiae brewer s or baker s yeast used in production of wine beer bread Other species used in cheese making Also greatest spoilers of food tons of food discarded annually Crop diseases impose billions of dollars in costs Relatively few species infect humans but many produce important antimicrobials net impact likely positive Some common athlete s foot jock itch serious diseases rare e g cryptococcal meningitis Human illnesses 3 routes Allergic reaction Fungus grows on in body causes mycosis disease Fungus produces toxins Fungal spores everywhere on earth up to altitudes of more than 7 miles air may contain 10 000 cells m3 Mycoses often named after causative agent e g Candida albicans causes candidiasis May refer to affected body part e g cutaneous mycoses of skin invading molds called dermatophytes Toxins include aflatoxins produced by Aspergillus species found in grains peanuts carcinogenic Rye mold Claviceps purpurea ergot produces hallucinogenic toxin active chemical purified to yield drug ergotamine Some e g Amanita produce toxins fatal