Julia Vorholt Lecture 9 - ETH Z

1 Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Brock Biology of Microorganisms, Twelfth Edition Madigan / Martinko / Dunlap / Clark 752-4001-00L Mikrobiologie Julia Vorholt Lecture 9: Phototrophy and autotrophy Global carbon and nitrogen cycles Nov 19, 2012 Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Brock Biology of Microorganisms, Twelfth Edition Madigan / Martinko / Dunlap / Clark 1) Nutrients and microbial growth 2) Introduction to principles of metabolism 3) Chemoorganotrophy 4) Chemolithotrophy 5) Phototrophy 6) Autotrophy, nitrogen fixation 7) Global carbon, nitrogen, sulfur cycles Copyright 2009 Pearson Education Inc.

2 , publishing as Pearson Benjamin Cummings Photophosphorylation and ETP ELQ = h c NA -1 = h v ELQ, Free energy of light quanta h, Planck constant ( 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 PS I and II PS I or II Van Niel, 1930: Photosynthesis CO2 + 2 H2A -> [CH2O] + 2 A + H2O Chap. Fig. Phototrophs Anoxygenic Oxygenic Purple and green bacteria Cyanobacteria, algae, green plants Reducing power Carbon Energy Reducing power Carbon Energy electrons Light Light Copyright 2009 Pearson Education Inc.

3 , publishing as Pearson Benjamin Cummings Groups of Phototrophs GreenNonsulfur-bacteriaGreenSulfur-bacte riaCyanobacteriaHeliobacteriaPurple bacteria (Proteobacteria) Purple Sulfur BacteriaPurple Nonsulfur Bacteria(Gram +)Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Evolutionary Aspects 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, billion years ago. => major consequences in terms of primary biomass production (unlimited availability of H2O) and the presence of O2.

4 Fig. Metabolic highlights O2 level BYA Eon Organisms, events Phanaerozoic Proterozoic Archaean Hadean Cambrian Precambrian Anoxic Extinction of the dinosaurs Early animals Multicellular eukaryotes First eukaryotes with organelles Ozone shield Great oxidation event Cyanobacteria Purple and green bacteria Bacteria/Archaea divergence First cellular life; LUCA Formation of crust and oceans Formation of Earth 0 20% 10% 1% Endosymbiosis? Aerobic respiration Oxygenic photosynthesis (2H2O O2 4H) Sulfate reduction Fe3 reduction Anoxygenic photosynthesis Acetogenesis Methanogenesis Sterile Earth Copyright 2009 Pearson Education Inc.

5 , publishing as Pearson Benjamin Cummings 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 Chap. Fig. Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 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 Chap.

6 Fig. -carotene Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 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 ( , H2S, Fe2+, or NO2-) Chap. Fig. Fig. Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Arrangement of Light-Harvesting Chlorophylls RC, reaction center LH, light harvesting molecules Chap.

7 Fig. Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Structure of Reaction Center in Purple Bacteria Arrangement of Pigment Molecules in Reaction Center Molecular Model of the Protein Structure of the Reaction Center Chap. Fig. 1988, Nobel prize for the structure of the reaction center of Rhodopseudomonas viridis: J. Deisenhofer, H. Michel, and R. Huber Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Electron Flow in Anoxygenic PS in a Purple Bacterium Chap. Fig. Strong electron donor Poor electron donor (V) E0 Cyclic electron flow (generates proton motive force) Red or infrared light External electron donors (H2S, S2O32-, S0, Fe2+) Copyright 2009 Pearson Education Inc.

8 , publishing as Pearson Benjamin Cummings Arrangement of Protein Complexes in Reaction Center Chap. Fig. Photosynthetic membrane Light Out (periplasm) In (cytoplasm) ATPase Quinone pool Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Electron Flow in Purple, Green, Sulfur and Heliobacteria Chap. Fig. PSII PSI PSI Purple bacteria Green sulfur bacteria Heliobacteria Reverse electron flow Light Light Light 0 E0 (V) Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Electron Flow in Oxygenic Photosynthesis Chap.

9 Fig. Photosystem II Photosystem I The Z Scheme: Light Light PSII PSI Cyclic electron flow (generates proton motive force) Noncyclic electron flow (generates proton motive force) E0 (V) Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 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 Chap.

10 Copyright 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 6 different CO2 fixation pathways are known: 1. Calvin-Benson-Bassham cycle 2. Reductive citric acid cycle 3. Reductive acetyl-CoA pathway 4. 3-Hydroxypropionate/malyl-CoA cycle 5. 3-Hydroxypropionate/4-hydroxybutyrate cycle 6. Dicarboxylate/4-hydroxybutyrate cycle CO2 + 4 [H] + n ATP -> (CH2O) + H2O + n ADP + n Pi Chap.