Transcript no fungi
“Microbes – The Good, The Bad, and the Globally Powerful” Important Groups of Microbes 1. Bacteria 2. Fungi 3. Protozoa Prokaryotes (“before the nucleus”) • Bacteria – Eubacteria (true bacteria) – E. coli, Cyanobacteria – Archaebacteria (old bacteria) – deep oceans, hot springs Eukaryotes (“true nucleus”) • Fungi -- single cells (e.g., yeasts); mycelia (e.g., mushrooms) • Plants (algae) • Animals (e.g., protozoans, rotifers, nematodes) Important Groups of Microbes 1. Bacteria * Found everywhere * Resting stages * Short generation times * Locomotion • Soils – bacteria = 109 per mL (fungi = 1000-1500 m per mL) • Water (ocean, lakes, streams) – bacteria = 106 per mL (no fungi) Elemental composition of bacteria = Element C % of dry weight 55 O 20 N 10 H 8 P 3 S 1 Bacteria on the head of a pin (~5 μm long) Cholera - intestine thin section Campylobacter - (food poisoning) rotary motor @ 6,000 rpm Proteus - 20 μm Microbial “mat” on the surface of a salt marsh – an ecological community Evolution of Bacteria 1. Two Main Groups = 2. Evolutionary Distance: Eubacteria and Archaebacteria Eubacteria Archaebacteria Plants Animals (a) Eubact -- Archae ------------------- Plant -------- Animal ? - OR - ? (b) Eubact -------------- Archae ------- Plant --------Animal Important Groups of Microbes 2.Fungi * * * * Thin strands called “hyphae” Uncommon in aquatic environments Common in terrestrial environments Secrete enzymes to break down cellulose Soils - fungi = 1000-1500 m/mL Water = no fungi * Fungal hyphae (~15 µm). A network of hyphae = a mycelium. * Picture of “fairy ring” of mushrooms. Ring moves outward as easily digestible organic matter is used up. * One mycelium covered 1290 acres and was thousands of years old (100s of tons). Gall on tree – fungal infection Bread mold Hyphae strands & sporangia Fungus fruiting bodies Root fungus “mycorrhizae” Important Groups of Microbes 3.Protozoa * Single-celled eukaryotes * Important predators on bacteria Protozoan ciliate. Their primary food is bacteria and very small algae. 1. Assimilative versus Dissimilative Processes All cells need ATP and a source of Carbon 2. How do Microbes make a Living? “Production” versus “Respiration” Classification Energy source for generating ATP Source of carbon for the cell Example of organisms Photoautotroph Light CO2 Bacteria, plants Chemoautotroph Inorganic compounds CO2 Bacteria Photoheterotroph Light CO2 Bacteria Organic matter Heterotroph Organic matter Organic matter Bacteria, fungi, animals Respiration requires a reduced organic compound as an electron donor and an oxidized molecule as an electron acceptor (Freeman 2002). Taken together, this is a “Reduction-Oxidation” or “Redox” reaction. Diversity of Dissimilatory Reactions used by Bacteria Electron (e-) Acceptor [Oxidant] Electron (e-) Donor [Reductant] H2 CHO CH4 HS- CHO + + - - CO2 + + - - SO4 2- + + ? - NO3- + + ? + O2 + + + + Reaction name Reductant Oxidant Reaction Stoichiometry Energy Yield (kcal/mol) Aerobic Respiration CHO O2 C6H12O6 + 6O2 6CO2 + 6H2O 686 Nitrate Reduction CHO NO3- CHO + NO3- + H+ CO2 + N2 + H2O 649 Sulfate Reduction CHO SO42- 2CHO + SO42- + 2H+ 2CO2 + HS- + 2H2O 190 H2 CO2 4H2 + CO2 CH4 + 2H2O 8.3 Methanogenesis V. What are the Important Impacts of Microbes on Ecosystems? (1) Generate Oxygen in the Atmosphere (Blue-green algae = Cyanobacteria). (2) Recycle Nutrients Stored in Organic Matter to an Inorganic Form. (3) Fix nitrogen from the Atmosphere into a Useable Form. (4) Allow Herbivores to Consume Poor Quality Food. (5) Give Plant Roots Access to Nutrients in the Soil. (2) Recycle Nutrients Stored in Organic Matter to an Inorganic Form. * Decomposition releases mineral nutrients like Nitrogen and Phosphorus * Fungi are the most important decomposers of structural plant compounds * Decomposition can occur with or without oxygen * Decomposition generates important by-products such as CO2 and CH4 (3) Fix nitrogen from the Atmosphere into a Useable Form. * N-fixation removes N2 from the atmosphere * N-fixation converts N2 into a useable nitrogen form (NH3) * Plants and bacteria form a "symbiotic" relationship: - Plants provide carbon compounds for the bacteria - Bacteria provide nitrogen for the plant Cyanobacteria (blue green algae) and “heterocysts” where the nitrogen fixation occurs. Oxygen poisons N-fixation. Clover Pea Legume roots with nodules that enclose the N-fixing bacteria (4) Allow Herbivores to Consume Poor Quality Food. * Animals lack digestive enzymes for cellulose and lignin * Plants often have "anti-grazing" defenses * Land plant material is poor in nutrients compared to animal tissue * This results in lower consumption of primary productivity by herbivores on land than by herbivores in aquatic systems Plant Community Phytoplankton (open water) Grasslands Kelp beds Salt marshes Mangroves Deciduous forests % of primary production consumed by herbivores 60 - 90 12 - 45 10 7 5 1.5 - 5 (5) Give Plant Roots Access to Nutrients in the Soil. * Plants create zones of nutrient depletion around their roots * Plants form associations with fungi -- "ecto" or "endo" * The plant provides the fungus with organic matter (photosynthate) * The fungi provide the plant with nutrients from decomposition Root fungus – “endotrophic” Summary Be able to answer these questions: • What is the diversity of microbes? • How do the different kinds of microbes function in gaining energy? • What impacts do microbes have on ecosystems and our globe? Take-home points: 1. Microbes can do anything they want, wherever they want, and 2. Without microbes, humans wouldn't be alive.