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Prokaryotes Bacteria and Archaea Chapter 27 Small Size Two Domains Proteobacteria Universal ancestor Domain Archaea Eukaryotes Nanoarchaeotes Crenarcaeotes Domain Bacteria Euryarchaeotes Korarchaeotes Gram-positive bacteria Cyanobacteria Spirochetes Chlamydias Epsilon Delta Gamma Beta Alpha Phylogeny of Domains Domain Eukarya Bacteria include every mode of nutrition and metabolism Archaea • Single celled microorganisms • Reproduce asexually • Identified as separate Domain in 1977 • First archaea were discovered in extreme conditions. Called extremophiles 6 Halophiles: salt lovers Thermophiles Live at very high temperatures Methanogens • Use CO2 to Oxidize H2 release CH4 • Release methane • O2 is toxic to them • Found in anoxic conditions such as swamps, deep caves, and intestines of animals Bacteria 1 µm Spherical (cocci) 2 µm Rod-shaped (bacilli) 5 µm Spiral Peptidoglycan Cell Walls Lipopolysaccharide Outer membrane Cell wall Pepridoglycan layer Cell wall Pepridoglycan layer Plasma membrane Plasma membrane Protein Protein Grampositive bacteria Gramnegative bacteria 20 µm Gram-positive Gram-negative Movement Internal Membranes Endospores • Dormant tough but not reproductive structures • Ensures survival of bacterium. Resistant to ultraviolet, gamma radiation, temperature fluctuation, household disinfectants... • found in soil, and water Bacterial DNA Bacteria have circular DNA Bacteria Plasmids • Extra-chromosome DNA that is separate from the bacterial chromosomal DNA • Separate self replication • can be transfered to other bacteria and other bacteria species 16 Symbiotic relationships Bioluminescent bacteria 18 Human symbiotic relationships Termites have specialized bacteria that helps them digest cellulose Termites comprise ~50% of the animal biomass in Africa Humans have a long history of using prokaryotes Commercial use of prokaryotes Wastewater Treatment Commercial use of prokaryotes Bioremediation Ecosystem Services Protists Chapter 28 25 Aquatic Producers are often Protists Green Algae Diatoms Diatoms 26 What are ‘Protists’ • They are not plants, animals or fungi • Diverse assortment of eukaryotes • Most are unicellular with complex cells • Found in damp soil, oceans and even human bodies 27 Nutritional Diversity The freshwater ciliate Stentor, a unicellular protozoan (LM) • Autotrophs • Heterotrophs • Mixitrophs 100 µm 100 µm 4 cm Ceratium tripos, a unicellular marine dinoflagellate (LM) Delesseria Sanguinea, a multicellular marine red alga 500 µm Spirogyra, a filamentous freshwater green alga (insert LM) 28 Asexual Reproduction 29 Sexual Reproduction 30 Ciliates Cillated Pellicle 31 Paramecium 32 Diatoms 10,000 species Photosynthetic with golden accessory pigments 33 Diatom Silica in Cell Wall 34 Psuedopod-equipped Protists • Heterotrophic • Psuedopods or axopods • With or without cell walls • Ameoba is a well known psuedopod 35 Slime Molds • Mycetozoans were thought to be fungi • Now understood to be case of evolutionary convergence • Two main branches – Plasmodial slime molds – Cellular slime molds 36 Plasmodial slime mold one super cell 37 Multicellular Brown Algae: Phaeophyta • May grow up to 60 meters • Provide 3 demensional habitats for marine species • Plant like structures, holdfast, stipe, and blades • Pneumatocysts are gasfilled bladders, located at the base of blades provides Boyance 38 Laminaria at low tide 39 Kelp Forest 40 Chlorophyta • Green algae • Autotrophic • Plant-like chloroplasts and pigments • Cellulose cell walls • Red and Green algae are the closest relatives to plants 41 Cladophora form large filamentous mats 42 http://www.youtube.com/watch?v=PoiAKcIls6s&feature=related 43 Fungi and nutrient cycling Chapters 31 and 54 44 Fungi Heterotrophic Decomposers or Symbionts Fungal Characteristics • Heterotrophic – Decomposers Nematod e Hypha e 25 µm – Opportunistic parasites – Many produce mycotoxins as metabolic by-products • Aerobic or facultative anaerobes • Cell wall composed of chitin – more closely related to animals than plants • Grow best in warm, moist environments Hyphae adapted for trapping and killing prey Plant cell wall Fungal hypha Haustori Haustoriu m Plant cell plasma membran e Plant cell 46 Dimorphic • Found in two physical forms: – Unicellular Yeasts – Multicellular Molds and Mushrooms • Hyphae • Mycelium = hyphal mass Reproduction by Spore Formation • Asexual – Haploid spores formed on hyphae – Fragmentation • Broken fragments of hyphae • Sexual – Two mating hyphae types fuse and produce spores Key Heterokaryotic stage Haploid (n) Heterokaryotic (unfused nuclei from different parents) PLASMOGAMY (fusion of cytoplasm) Diploid (2n) KARYOGAMY (fusion of nuclei) Spore-producing structures Zygote Spores ASEXUAL REPRODUCTION Mycelium SEXUAL REPRODUCTION MEIOSIS GERMINATION GERMINATION Spore-producing structures Spores 49 Penicillium (Blue-green Mold) Basidiocarps Fig. 31-20 52 http://www.youtube.com/watch?v=JeF952Xfz4&feature=relmfu 53 Lichens (Fungal-Algal Symbiosis) Lichen Structure Mycorrhizae • Plant roots and symbiotic fungi • Increased nutrient (P) absorption – – – – Greater surface area Enzyme excretions Increased plant bimass may have originally started as parasitism – Most plants have Mycorrhizae infections Mycorrhizae “The Nation that Destroys Its Soil Destroys Itself” – F.D.R. Farmland productivity often suffers from chemical contamination, mineral deficiencies, acidity, salinity, and poor drainage Healthy soils improve plant growth by enhancing plant nutrition 58 Soil is a living, finite resource • Plants obtain most of their water and minerals from the upper layers of soil • Living organisms play an important role in these soil layers • This complex soil ecosystem is fragile • Topsoil contains bacteria, fungi, algae, other protists, insects, earthworms, nematodes, and plant roots • These organisms help to decompose organic material and mix the soil 59 Rocks Contribute Minerals • • • • Weathering Erosion Transportation Sedimentation Grain Size • Sand – 2.1 mm to .05 mm • Silt – Less than .05 mm but greater than .002 mm • Clay – Less than .002 mm Soil Texture • Soil particles are classified by size; from largest to smallest they are called sand, silt, and clay • Soil is stratified into layers called soil horizons • Topsoil consists of mineral particles, living organisms, and humus, the decaying organic material 62 Soil • • • • Minerals Water Air Dead Organic material • Organisms Water and soil interact • Soil particle size influences: – water transport nutrients – soil moisture • Water flows through and evaporates quickly from sandy soils • Clay soils bind water which prevent plants from absorbing Litter and Topsoil • Most plant root biomass • Most nutrient turnover • Most decomposer biomass • Most microbial activity Litter Decomposers 2. Global C sources and sinks (CO2) Net deforestation = 0.9 Atmosphere = 750 +3.2/yr Combustion = 6 GPP = 120 Plant R = 45 Soil R = 75 560 Rivers = .8 92 90 Soils = 1500 Values are 1015 g C, fluxes are annual Schlesinger 1997 Oceans = 38000 3. Nutrient cycling Photosynthetic machinery is nutrient rich (N, P, Ca, etc.) Litterfall Nutrients are lost with leaf senescence Decomposition Nutrient uptake Decomposition processes often mediate nutrient availability for plants Decomposition over Time Litter and Topsoil Organisms Size of Soil Microorganisms Soil Protozoa • Decomposers • Consumers Producers Soil Fungi • Decomposers • Symbionts Soil Actinomycetes • Fungus-like bacteria • Some are symbiotic with plants • Some produce antibiotics Soil Bacteria • Producers • Decomposers • Mineralizers Soil Bacteria and Plant Nutrition • The layer of soil bound to the plant’s roots is the rhizosphere • The rhizosphere has high microbial activity because of sugars, amino acids, and organic acids secreted by roots 78 Rhizobacteria • Free-living rhizobacteria thrive in the rhizosphere, and some can enter roots • Rhizobacteria can play several roles – Produce hormones that stimulate plant growth – Produce antibiotics that protect roots from disease – Absorb toxic metals or make nutrients more available to roots 79 Bacteria in the Nitrogen Cycle • Nitrogen is often an important limiting nutrient for plant growth • The nitrogen cycle transforms nitrogen and nitrogen-containing compounds • Most soil nitrogen comes from actions of soil bacteria 80 Nitrogen-Fixing Bacteria: A Closer Look • N2 is abundant in the atmosphere, but unavailable to plants • Nitrogen fixation is the conversion of nitrogen from N2 to NH3 • Symbiotic relationships with nitrogenfixing bacteria provide some plant species with a built-in source of available N • Most commonly legumes: beans, peas… 81 N2 Atmosphere N2 Atmosphere Soil N2 Nitrogen-fixing bacteria Denitrifying bacteria H+ Nitrate and nitrogenous organic compounds exported in xylem to shoot system (from soil) NH4+ Soil NH3 Ammonifying (ammonia) bacteria NH4+ (ammonium) Nitrifying bacteria NO3– (nitrate) Organic material (humus) Root 82 Nitrogen Cycle Nitrogen Fixation • N2 NH4+ • Nitrogen gas is fixed as ammonium ion. •Photosynthetic •Nitrogen Fixing −Nostoc and Anabaena •Specialized cells: heterocysts Cyanobacteria heterocysts Non-Photosynthetic Nitrogen Fixers • Free-living heterotrophic bacteria – Azotobacter – Azomonas • Symbiotic heterotrophic bacteria – Rhizobium – Mesquite Trees are Facultative N-Fixers Ammonification C2H2O2 + NH4+ Amino acid •Carried out by many heterotrophic microbes. Nitrification • NH4+ -> NO2- -> NO3-2 • Oxidation carried out by aerobic, chemoautotrophic (mineralizing) bacteria Denitrification • NO3-2 NO2N2 • Pseudomonas and Paracoccus • Carried out by anaerobic, heterotrophic microbes • How can we measure denitrification? Nitrogen cycle summary • Nitrogen fixation: • (Gas) N2 NH4 • Ammonification: • (organism) Amino Acid NH4 • Nitrification: • NH4 NO2 NO3 (Mineral) • Denitrification: • (Mineral) NO3 NO2 N2 (Gas) • Carried out by cyanobacteria, Rhizobium, 89 heterotrophs, bacteria, fungi…