Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Brock Biology of Microorganisms Twelfth Edition Madigan / Martinko Dunlap / Clark Metabolic Diversity: Phototrophy, Autotrophy, Chemolithotrophy, and Nitrogen Fixation Chapter 20 Lectures by Buchan & LeCleir

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings I. The Phototrophic Way of Life  20.1 Photosynthesis  20.2 Chlorophylls and Bacteriochlorophylls  20.3 Carotenoids and Phycobilins  20.4 Anoxygenic Photosynthesis  20.5 Oxygenic Photosynthesis

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 20.1 Photosynthesis  Photosynthesis is the most important biological process on Earth  Phototrophs are organisms that carry out photosynthesis  Most phototrophs are also autotrophs  Photosynthesis requires light-sensitive pigments called chlorophyll  Photoautotrophy requires ATP production and CO 2 reduction  Oxidation of H 2 O produces O 2 (oxygenic photosynthesis)  Oxygen not produced (anoxygenic photosynsthesis)

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 20.1 Classification of Phototrophic Organisms

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 20.2 Patterns of Photosynthesis

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 20.2 Patterns of Photosynthesis

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 20.2 Chlorophylls and Bacteriochlorophylls  Organisms must produce some form of chlorophyll (or bacteriochlorophyll) to be photosynthetic  Chlorophyll is a porphyrin  Number of different types of chlorophyll exist  Different chlorophylls have different absorption spectra  Chlorophyll pigments are located within special membranes  In eukaryotes, called thylakoids  In prokaryotes, pigments are integrated into cytoplasmic membrane

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 20.3a Structure and Spectra of Chloro- and Bacteriochlorophyll

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 20.3b Structure and Spectra of Chloro- and Bacteriochlorophyll Absorption Spectrum

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 20.4 Structure of All Known Bacteriochlorophylls

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 20.4 Structure of All Known Bacteriochlorophylls

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 20.4 Structure of All Known Bacteriochlorophylls

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 20.5a Photomicrograph of Algal Cell Showing Chloroplasts

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 20.5b Chloroplast Structure

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 20.2 Chlorophylls and Bacteriochlorophylls  Reaction centers participate directly in the conversion of light energy to ATP  Antenna pigments funnel light energy to reaction centers  Chlorosomes function as massive antenna complexes  Found in green sulfur bacteria

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 20.6 Arrangement of Light-Harvesting Chlorophylls

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 20.7 The Chlorosome of Green Sulfur and Nonsulfur Bacteria Electron Micrograph of Cell of Green Sulfur Bacterium

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 20.7 The Chlorosome of Green Sulfur and Nonsulfur Bacteria Model of Chromosome Structure

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 20.3 Carotenoids and Phycobilins  Phototrophic organisms have accessory pigments in addition to chlorophyll, including carotenoids and phycobiliproteins  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

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 20.8 Structure of  -carotene, a Typical Carotenoid

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 20.9 Structures of Some Common Carotenoids

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 20.9 Structures of Some Common Carotenoids

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 20.3 Carotenoids and Phycobilins  Phycobiliproteins are main antenna pigments of cyanobacteria and red algae  Form into aggregates within the cell called phycobilisomes  Allow cell to capture more light energy than chlorophyll alone

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure Phycobiliproteins and Phycobilisomes

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure Absorption Spectrum with an Accessory Pigment

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 20.4 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 CO 2 fixation comes from reductants present in the environment (i.e., H 2 S, Fe 2+, or NO 2- )  Requires reverse electron transport for NADH production in purple phototrophs

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure Membranes in Anoxygenic Phototrophs Chromatophores Lamellar Membranes in the Purple Bacterium Ectothiorhodospira

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure Structure of Reaction Center in Purple Bacteria Arrangement of Pigment Molecules in Reaction Center

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure Structure of Reaction Center in Purple Bacteria Molecular Model of the Protein Structure of the Reaction Center

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure Example of Electron Flow in Anoxygenic Photosynthesis

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure Arrangement of Protein Complexes in Reaction Center

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure Map of Photosynthetic Gene Cluster in Purple Phototroph

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure Phototrophic Purple and Green Sulfur Bacteria Purple Bacterium, Chromatium okenii Green Bacterium, Chlorobium limicola

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure Electron Flow in Purple, Green, Sulfur and Heliobacteria

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 20.5 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 © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure The “Z scheme” in Oxygenic Photosynthesis

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings II. Autotrophy  20.6 The Calvin Cycle  20.7 Other Autotrophic Pathways in Phototrophs

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 20.6 The Calvin Cycle  The Calvin Cycle  Named for its discoverer Melvin Calvin  Fixes CO 2 into cellular material for autotrophic growth  Requires NADPH, ATP, ribulose bisphophate carboxylase (RubisCO), and phosphoribulokinase  6 molecules of CO 2 are required to make 1 molecule of glucose

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 20.21a Key Reactions of the Calvin Cycle

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 20.21b Key Reactions of the Calvin Cycle

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 20.21c Key Reactions of the Calvin Cycle

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure The Calvin Cycle

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 20.7 Other Autotrophic Pathways in Phototrophs  Green sulfur bacteria use the reverse citric acid cycle to fix CO 2  Green nonsulfur bacteria use the hydroxyproprionate pathway to fix CO 2

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 20.24a Autotrophic Pathways in Phototrophic Green Bacteria

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 20.24b Autotrophic Pathways in Phototrophic Green Bacteria

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings III. Chemolithotrophy  20.8 The Energetics of Chemolithotrophy  20.9 Hydrogen Oxidation  Oxidation of Reduced Sulfur Compounds  Iron Oxidation  Nitrification  Anammox

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 20.8 The Energetics of Chemolithotrophy  Chemolithotrophs are organisms that obtain energy from the oxidation of inorganic compounds  Mixotrophs are chemolithotrophs that require organic carbon as a carbon source  Many sources of reduced molecules exist in the environment  The oxidation of different reduced compounds yields varying amounts of energy

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Energy Yields from Oxidation of Inorganic Electron Donors

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 20.9 Hydrogen Oxidation  Anaerobic H 2 oxidizing Bacteria and Archaea are known  Catalyzed by hydrogenase  In the presence of organic compounds such as glucose, synthesis of Calvin cycle and hydrogenase enzymes is repressed

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure Two Hydrogenases of Aerobic H 2 Bacteria

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Oxidation of Reduced Sulfur Compounds  Many reduced sulfur compounds are used as electron donors  Discovered by Sergei Winogradsky  H 2 S, S 0, S 2 O 3 - are commonly used  One product of sulfur oxidation is H +, which results in a lowering of the pH of its surroundings  Sox system oxidizes reduced sulfur compounds directly to sulfate  Usually aerobic, but some organisms can use nitrate as an electron acceptor

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure Sulfur Bacteria

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 20.27a Oxidation of Reduced Sulfur Compounds Steps in the Oxidation of Different Compounds

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 20.27b Oxidation of Reduced Sulfur Compounds

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Iron Oxidation  Ferrous iron (Fe 2+ ) oxidized to ferric iron (Fe 3+ )  Ferric hydroxide precipitates in water  Many Fe oxidizers can grow at pH <1  Often associated with acidic pollution from coal mining activities  Some anoxygenic phototrophs can oxidize Fe 2+ anaerobically using Fe 2+ as an electron donor for CO 2 reduction

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure Iron-Oxidizing Bacteria Acid Mine Drainage

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure Iron-Oxidizing Bacteria Cultures of A. Ferrooxidans Shown in Dillution Series

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure Iron Bacteria Growing at Neutral pH: Sphaerotilus

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure Electron Flow During Fe 2+ Oxidation

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Fe 2+ Oxidation in Anoxic Tube Cultures Figure Ferrous Iron Oxidation by Anoxygenic Phototrophs

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure Ferrous Iron Oxidation by Anoxygenic Phototrophs Phase-contrast Photomicrograph Of an Iron-Oxidizing Purple Bacterium

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Nitrification  NH 3 and NO 2 - are oxidized by nitrifying bacteria during the process of nitrification  Two groups of bacteria work in concert to fully oxidize ammonia to nitrate  Key enzymes are ammonia monooxygenase, hydroxylamine oxidoreductase, and nitrite oxidoreductase  Only small energy yields from this reaction  Growth of nitrifying bacteria is very slow

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure Oxidation of Ammonia by Ammonia-Oxidizing Bacteria

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure Oxidation of Nitrite to Nitrate by Nitrifying Bacteria

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Anammox  Anammox: anoxic ammonia oxidation  Performed by unusual group of obligate aerobes  Anammoxosome is compartment where anammox reactions occur  Protects cell from reactions occuring during anammox  Hydrazine is an intermediate of anammox  Anammox is very beneficial in the treatment of sewage and wastewater

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 20.34a-b Anammox Phase-contrast Photomicrograph of Brocadia Anammoxidans cells Transmission Electronic Micrograph of a Cell

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 20.34c Reactions in the Anammoxosome

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings IV. Nitrogen Fixation  Nitrogenase and Nitrogen Fixation  Genetics and Regulation of Nitrogen Fixation

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Nitrogenase and Nitrogen Fixation  Only certain prokaryotes can fix nitrogen  Some nitrogen fixers are free living and others are symbiotic  Reaction is catalyzed by nitrogenase  Sensitive to the presence of oxygen  A wide variety of nitrogenases use different metal cofactors  Nitrogenase activity can be assayed using the acetylene reduction assay

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure FeMo-co, the Iron-Molybdenum Cofactor from Nitrogenase

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure Nitrogenase Function

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure Induction of Slime Formation by O 2 in Nitrogen-Fixing Cells

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure Reaction of Nitrogen Fixation in S. thermoautotrophicus

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure The Acetylene Reduction Assay for Nitrogenase Activity

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Genetics and Regulation of Nitrogen Fixation  Highly regulated process because it is such an energy- demanding process  nif regulon coordinates regulation of genes essential to nitrogen fixation  Oxygen and ammonia are the two main regulatory effectors

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure The nif regulon in K. pneumoniae