Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Biochemistry wikipedia , lookup
Nitrogen cycle wikipedia , lookup
Biosequestration wikipedia , lookup
Metalloprotein wikipedia , lookup
Cyanobacteria wikipedia , lookup
Evolution of metal ions in biological systems wikipedia , lookup
Oxidative phosphorylation wikipedia , lookup
Electron transport chain wikipedia , lookup
Light-dependent reactions wikipedia , lookup
Photosynthetic reaction centre wikipedia , lookup
752-4001-00L Mikrobiologie Julia Vorholt Lecture 9: Phototrophy and autotrophy Global carbon and nitrogen cycles Nov 19, 2012 Brock Biology of Microorganisms, Twelfth Edition – Madigan / Martinko / Dunlap / Clark Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 1) 2) 3) 4) 5) 6) 7) Nutrients and microbial growth Introduction to principles of metabolism Chemoorganotrophy Chemolithotrophy Phototrophy Autotrophy, nitrogen fixation Global carbon, nitrogen, sulfur cycles Brock Biology of Microorganisms, Twelfth Edition – Madigan / Martinko / Dunlap / Clark Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Photophosphorylation and ETP ELQ = h c NA -1 = h v ELQ, Free energy of light quanta h, Planck constant (6.6 x 10-34 J s) c, the speed of light (3 x 108 m s-1) NA, Avogadro‘s number (6 x 1023) v, frequency Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Types of Photosynthesis Phototrophs Purple and green bacteria Cyanobacteria, algae, green plants Oxygenic Anoxygenic Reducing power Carbon electrons Energy Reducing power Carbon Light Energy Light PS I and II PS I or II Van Niel, 1930: Photosynthesis CO2 + 2 H2A -> [CH2O] + 2 A + H2O Copyright Chap. 13.1© 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig. 13.2 Groups of Phototrophs Green Sulfurbacteria Green Nonsulfurbacteria Cyanobacteria Heliobacteria (Gram +) Purple bacteria (Proteobacteria) Purple Nonsulfur Bacteria Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Purple Sulfur Bacteria Evolutionary Aspects Eon BYA Organisms, events 0 Sunlight represents the most important energy source on earth. Phototrophs use light as sole energy source. They are the starting point of the food chain. The oxygenic photosynthesis evolved rather early in evolution, 2.7 billion years ago. => major consequences in terms of primary biomass production (unlimited availability of H2O) and the presence of O2. Phanaerozoic O2 level Extinction of the dinosaurs 0.5 Early animals 1.0 Multicellular eukaryotes Metabolic highlights Cambrian Precambrian 20% 10% Proterozoic 1.5 2.0 First eukaryotes with organelles Ozone shield 1% 2.5 Great oxidation event 0.1% Endosymbiosis? Aerobic respiration Oxygenic photosynthesis (2H2O O2 4H) Cyanobacteria 3.0 Archaean Sulfate reduction Fe3 reduction 3.5 Hadean Purple and green bacteria Anoxygenic photosynthesis Anoxic Bacteria/Archaea divergence Acetogenesis 4.0 First cellular life; LUCA Formation of crust and oceans Methanogenesis 4.5 Formation of Earth Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Sterile Earth Fig. 16.6 Chlorophylls and Bacteriochlorophylls Organisms must produce some form of chlorophyll (or bacteriochlorophyll) to be photosynthetic Chlorophyll is a porphyrin They are part of the reaction center (participate directly in the conversion of light energy to ATP) Number of different types of chlorophyll exist with different absorption spectra Copyright Chap. 13.2© 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig. 13.3 Carotenoids and Phycobilins Phototrophic organisms have accessory pigments in addition to chlorophyll, including carotenoids Carotenoids Always found in phototrophic organisms Typically yellow, red, brown, or green Energy absorbed by carotenoids can be transferred to a reaction center Prevent photo-oxidative damage to cells -carotene Copyright Chap. 13.3© 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig. 13.8 Anoxygenic Photosynthesis Anoxygenic photosynthesis is found in at least four phyla of Bacteria Electron transport reactions occur in the reaction center of anoxygenic phototrophs Reducing power for CO2 fixation comes from reductants present in the environment (i.e., H2S, Fe2+, or NO2-) Copyright Chap. 13.4© 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig. 17.2 Fig. 17.6 Arrangement of Light-Harvesting Chlorophylls RC, reaction center LH, light harvesting molecules Copyright Chap. 13.2© 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig. 13.6 Structure of Reaction Center in Purple Bacteria Arrangement of Pigment Molecules in Reaction Center Molecular Model of the Protein Structure of the Reaction Center 1988, Nobel prize for the structure of the reaction center of Rhodopseudomonas viridis: J. Deisenhofer, H. Michel, and R. Huber Copyright Chap. 13.4© 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig. 13.13 Electron Flow in Anoxygenic PS in a Purple Bacterium 1.0 Strong electron donor 0.75 0.5 E0 (V)0.25 Cyclic electron flow (generates proton motive force) 0.0 External electron donors (H2S, S2O32-, S0, Fe2+) 0.25 Poor electron donor 0.5 Red or infrared light Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Chap. 13.4 Fig. 13.14 Arrangement of Protein Complexes in Reaction Center Light Out (periplasm) Quinone pool ATPase Photosynthetic membrane In (cytoplasm) Copyright Chap. 13.4© 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig. 13.15 Electron Flow in Purple, Green, Sulfur and Heliobacteria Purple bacteria Green sulfur bacteria Heliobacteria 1.25 1.0 0.75 0.5 E0 (V) 0.25 0 Reverse electron flow 0.25 0.5 Light Light Light PSII PSI Copyright Chap. 13.4© 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings PSI Fig. 13.17 Electron Flow in Oxygenic Photosynthesis 1.25 The Z Scheme: 1.0 PSII PSI 0.75 Cyclic electron flow (generates proton motive force) 0.5 0.25 E0 0.0 (V) 0.25 Noncyclic electron flow (generates proton motive force) Light 0.5 Photosystem I 0.75 1.0 Photosystem II Light Copyright Chap. 13.5© 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig. 13.18 Oxygenic Photosynthesis Oxygenic phototrophs use light to generate ATP and NADPH The two light reactions are called photosystem I and photosystem II “Z scheme” of photosynthesis Photosystem II transfers energy to photosystem I ATP can also be produced by cyclic photophosphorylation Copyright Chap. 13.5© 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Water blooms in lakes consisting of Cyanobacteria Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Autotrophic CO2-fixation CO2 + 4 [H] + n ATP -> (CH2O) + H2O + n ADP + n Pi 6 different CO2 fixation pathways are known: 1. 2. 3. 4. 5. 6. Calvin-Benson-Bassham cycle Reductive citric acid cycle Reductive acetyl-CoA pathway 3-Hydroxypropionate/malyl-CoA cycle 3-Hydroxypropionate/4-hydroxybutyrate cycle Dicarboxylate/4-hydroxybutyrate cycle Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Chap. 13.12-13 The Calvin Cycle 12 3-PhosphoRubisCO glycerate (36 carbons) 6 Ribulose 1,5-bisphosphate (30 carbons) 12 1,3-Bisphosphoglycerate (36 carbons) Phosphoribulokinase Fixes CO2 into cellular material for autotrophic growth Requires NADPH, ATP, ribulose bisphophate carboxylase (RubisCO), and phosphoribulokinase 6 molecules of CO2 are required to generate one molecule of glucose 12 Glyceraldehyde 3-phosphate (36 carbons) 6 Ribulose 5-phosphate (30 carbons) Sugar rearrangements 10 Glyceraldehyde 3-phosphate (30 carbons) Fructose 6-phosphate (6 carbons) To biosynthesis Overall stoichiometry: 6 CO2 12 NADPH 18 ATP 12 NADP 18 ADP 17 Pi Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Chap. 13.12 C6 H12 O6(PO3 H2) Fig. 13.30 (Oxidized) Nitrogenase and Nitrogen Fixation (Reduced) Only certain prokaryotes can fix nitrogen Some nitrogen fixers are free living and others are symbiotic Products Nitrogenase substrates Reaction is catalyzed by nitrogenase Sensitive to the presence of oxygen A wide variety of nitrogenases use different metal cofactors, usually molybdenum Overall reaction Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Chap. 13.14 Symbiotic Nitrogen Fixation Soy bean Root nodules N2 NH3 with Bradyrhizobium (Alphaproteobacterium) without Copyright Chap. 25.3© 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings (Fig. 25.7) Fig. 25.8 Symbiotic Nitrogen Fixation The mutalistic relationship between leguminous plants and nitrogen-fixing bacteria is one of the most important symbioses known Examples of legumes include soybeans, clover, alfalfa, beans, and peas Rhizobia are the most well-known nitrogen-fixing bacteria engaging in these symbioses Copyright Chap. 25.3© 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Key terms Metabolism - I We need to distinguish between energy sources and carbon sources (both are usually identical for chemoorganotrophic organisms) Chemotrophy (energy from chemical substrates) > Chemoorganotrophy (organic substrates) > Chemolithotrophy (inorganic substrates) Energy sources Phototrophy (energy from light) Autotrophy (CO2 as main carbon source) Heterotrophy (organic compounds as main carbon source) Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Carbon sources Key terms Metabolism - II Aerobic: Growth of an organism using oxygen as electron acceptor Anaerobic: Growth of an organism not using oxygen as electron acceptor Aerotolerant: Anaerobic organism whose growth is not inhibited by oxygen and does not use it as electron acceptor Oxic: Environmental condition where oxygen is present Anoxic: Environmental condition without oxygen Oxygenic: Type of photosynthesis, oxygen is released from water Anoxygenic: Type of photosynthesis, without oxygen release Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings The Carbon Cycle and Major Carbon Reservoirs on Earth CO2 Human activities Respiration Land plants Animals and microorganisms Aquatic CO2 plants and phytoplankton Biological pump Fossil fuels Humus Soil formation Death and mineralization Earth’s crust Aquatic animals CO2 Rock formation Carbon is cycled through all of Earth’s major carbon reservoirs, i.e., atmosphere, land, oceans, sediments, rocks, and biomass Copyright Chap. 24.1© 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig. 24.1 Methane hydrate A methane hydrate is a cage-like lattice of ice, inside of which are trapped molecules of methane. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Pictures by K. Kvenvolden and GEOMAR The Carbon Cycle (CH2O)n Cyanobakterien Pflanzen Oxygene Photosynthese Tiere, verschiedene Mikroorganismen (Paracoccus, E. coli) Aerobe Atmung (Chemolithotrophe) Aerobe Methanoxidation CH4 CO2 Anaerobe Methanoxidation Oxisch Anoxisch Methanogenese Anoxygene Photosynthese Anaerobe Atmung Brock Biology of Microorganisms, Twelfth Edition Purpurbakterien – Madigan / Martinko / Dunlap / Clark (CH O) 2 n Copyright Chap. 24.1© 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings E. coli Paracoccus denitrificans (Fig. 24.2) Assimilation/Baustoffwechsel Anaerober Prozess Aerober Prozess Brock Biology of Microorganisms, Twelfth Edition – Madigan / Martinko / Dunlap / Clark Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Dissimilation/ Energiestoffwechsel The Carbon Cycle Phototrophic organisms are the foundation of the carbon cycle CO2 is fixed primarily by photosynthetic land plants and marine microbes CO2 is returned to the atmosphere by respiration of animals and chemoorganotrophic microbes as well as anthropogenic activities Microbial decomposition is the largest source of CO2 released to the atmosphere The carbon and oxygen cycles are intimately linked Plants dominant phototrophic organisms of terrestrial environments The two major end products of decomposition are CH4 and CO2 Copyright Chap. 24.1© 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings The Nitrogen Carbon Cycle Rhizobien Cyanobakterien N2-Fixierung Org. N (NH2-Gruppen N2 NH3 N2O Ammonifikation E. coli Denitrifikation Pseudomonas Paracoccus NO Nitrifikation Nitrosobakterien (z.B. Nitrosomonas) NO2Brock Biology of Microorganisms, Twelfth Edition – Madigan / Martinko / Dunlap / Clark Nitrobakterien (z.B. Nitrobacter) NO3- Copyright Chap. 24.3© 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings (Fig. 24.7) The Nitrogen Cycle Copyright Chap. 24.3© 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig. 24.7 The Nitrogen Cycle N2 is the most stable form of nitrogen and is a major reservoir The ability to use N2 as a cellular nitrogen source (nitrogen fixation) is limited to only a few prokaryotes Denitrification is the reduction of nitrate to gaseous nitrogen products and is the primary mechanism by which N2 is produced biologically Ammonia produced by nitrogen fixation or ammonification can be assimilated into organic matter or oxidized to nitrate Denitrification and anammox result in losses of nitrogen from the biosphere Copyright Chap. 24.3© 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings The Sulfur Cycle Org. S Chemolithotrophe S-Oxidation H 2S Diss. S0 reduktion Beggiatoa Photolithotrophe Dissimilatorische Sulfatreduktion Assimilatorische Sulfatreduktion Desulfovibrio S0 SchwefelPurpurbakterien SchwefelGrüne Bakterien SO42Brock Biology of Microorganisms, Twelfth Edition – Madigan / Martinko / Dunlap / Clark Copyright Chap. 24.4© 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings (Fig. 24.8) The Sulfur Cycle Hydrogen sulfide is a major volatile sulfur gas that is produced by bacteria via sulfate reduction or emitted from geochemical sources Sulfide is toxic to many plants and animals and reacts with numerous metals Sulfur-oxidizing chemolithotrophs can oxidize sulfide and elemental sulfur at oxic/anoxic interfaces Copyright Chap. 24.4© 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Catabolic Diversity Fermentation Carbon flow Organic compound Carbon flow in respirations Electron transport/ generation of pmf Biosynthesis Aerobic respiration Chemotrophs Electron acceptors Anaerobic respiration Chemoorganotrophy Electron transport/ generation of pmf Electron acceptors Biosynthesis Aerobic respiration Anaerobic respiration Chemolithotrophy Light Phototrophs Photoheterotrophy Organic compound Photoautotrophy Electron transport e donor Generation of pmf and reducing power Biosynthesis Biosynthesis Phototrophy Copyright Chap. 4.12© 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig. 4.22 Chemoorganotrophy Chemoorganotrophy Energy and carbon source: organic compound(s) Fermentation, anaerobic process without external electron acceptors Energy generating process: Substrate-level-phosphorylation (SLP) Example: Lactic acid fermentation Catabolic end product: lactic acid (homofermentative) Chemotrophs Fermentation Carbon flow in respirations Carbon flow Organic compound Electron transport/ generation of pmf Biosynthesis Aerobic respiration Electron acceptors Anaerobic respiration Chemoorganotrophy Anaerobic respiration, alternative electron acceptors (not O2) Energy generating process: Electron transport phosphorylation (and SLP) Catabolic end product: CO2 (exception: methanogenesis -> CH4) Example: Escherichia coli with nitrate Aerobic respiration, O2 as electron acceptor Energy generating process: Electron transport phosphorylation (and SLP) Catabolic end product: CO2 Example 1: Paracoccus Example 2: Escherichia coli Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Chemolithotrophy Energy source: reduced inorganic compound Electron acceptor, mostly O2 Energy generating process: Electron transport phosphorylation Catabolic end product: oxidized inorganic compound Example: Nitrification of Nitro(so)bacteria Carbon source: CO2 (in most bacteria/archaea) Electron transport/ generation of pmf Electron acceptors Biosynthesis Aerobic respiration Anaerobic respiration Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Phototrophy Energy source: Light Energy generating process: Electron transport phosphorylation Carbon source: CO2 (in most bacteria) Light Photoheterotrophy Organic compound Photoautotrophy Electron transport e donor Generation of pmf and reducing power Biosynthesis Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Biosynthesis