Julia Vorholt Lecture 7:

Size: px

Start display at page:

Download "Julia Vorholt Lecture 7:"

Julianna Kelly
5 years ago
Views:

1 L Mikrobiologie Julia Vorholt Lecture 7: Chemoorganotrophy Nov 5, 2012 Brock Biology of Microorganisms, Twelfth Edition Madigan / Martinko / Dunlap / Clark Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings

2 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 Brock Biology of Microorganisms, Twelfth Edition Madigan / Martinko / Dunlap / Clark Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings

3 Introduction into Principles of Metabolism Catabolism/ Dissimilation Anabolism/ Assimilation Free energy of chemical reactions Chemotrophy > Organotrophy > Lithotrophy Free energy of light Phototrophy ATP ADP + P i Heat Maintenance energy Biomass Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings

4 Energy Conservation Substrate-level phosphorylation (SLP) Electron-transport-coupled phosphorylation (ETP) Intermediates Energy-rich intermediates Energized membrane Less energized membrane ATP directly synthesized from an energy-rich intermediate ATP produced from proton motive force formed by transport of electrons from organic or inorganic electron donors Chap. Copyright Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig. 4.13

5 Chemoorganotrophy Two mechanisms for catabolism of organic compounds: Fermentation No external electron acceptor ATP directly synthesized from an energy-rich intermediate, relatively little energy yield Respiration Exogenous electron acceptors are present to accept electrons generated from the oxidation of electron donors ATP produced from proton motive force formed by transport of electrons from organic or inorganic electron donors Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings

Substrate-level phosphorylation within glycolysis Glucose Pyruvate 2 lactate Intermediates Glucose 6-P Fructose 6-P Fructose 1,6-P 2 Pyruvate Dihydroxyacetone-P Glyceraldehyde-3-P Energetics Yeast

6 Substrate-level phosphorylation within glycolysis Glucose Pyruvate 2 lactate Intermediates Glucose 6-P Fructose 6-P Fructose 1,6-P 2 Pyruvate Dihydroxyacetone-P Glyceraldehyde-3-P Energetics Yeast Lactic acid bacteria 1,3-Bisphosphoglycerate 3-P-Glycerate 2-P-Glycerate Phosphoenolpyruvate Enzymes Hexokinase Isomerase Phosphofructokinase Aldolase Triosephosphate isomerase Glyceraldehyde-3-P dehydrogenase Phosphoglycerokinase Phosphoglyceromutase Enolase Pyruvate kinase Glucose + 2 ADP + 2 NAD -> 2 pyruvate + 2 ATP + 2 NADH Chap. Copyright Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig. 4.14

7 The Essentials of Fermentation Uptake Excretion Organic compound Fermentation product Energy-rich compound Substrate-levelphosphorylation Oxidized compound Chap. Copyright Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig. 14.1

8 Fermentations: Energetic and Redox Considerations Fermentation is a form of anaerobic redox process that occurs if no external electron acceptor for the oxidation of organic substrates is available. Energy conservation in form of ATP is usually achieved through the oxidation of substrates via substrate-level phosphorylation. The reducing equivalents formed in this process are used to reduce an oxidized intermediate or second organic molecule. Chap. Copyright Pearson Education Inc., publishing as Pearson Benjamin Cummings

9 Common Bacterial Fermentations Fermentations are classified by either the substrate fermented or the products formed Chap. Copyright Pearson Education Inc., publishing as Pearson Benjamin Cummings

11 Lactic acid Bacteria Gram positive rods or cocci Important for food production (Lactococcus, Lactobacillus), as human pathogens and commensals (Streptococcus, Lactobacillus) Produce lactate as a main product of fermentation Aerotolerant Do not need Fe Auxotroph (need vitamines) Chap. Copyright Pearson Education Inc., publishing as Pearson Benjamin Cummings

12 Lactic acid Bacteria Homofermentative: Streptococcus Enterococcus Lactococcus some Lactobacillus Main product: Lactate Sugar degradation: Embden-Meyerhof pathway (glycolysis) Heterofermentative: Leuconostoc some Lactobacillus Main products: Lactate, carbon dioxide, ethanol, acetate Sugar degradation: modified (no aldolase of EMP pathway) Phosphoketolase pathway or Bifidobacterium bifidum pathway Chap. Copyright Pearson Education Inc., publishing as Pearson Benjamin Cummings

Lactic acid Fermentation - homofermentative Glucose Fructose 1,6 -bisphosphate Aldolase 2 Glyceraldehyde 3-phosphate (G3-P) Dihydroxyacetone phosphate 2 1,3-Bisphosphoglyceric acid 2 Pyruvate 2

13 Lactic acid Fermentation - homofermentative Glucose Fructose 1,6 -bisphosphate Aldolase 2 Glyceraldehyde 3-phosphate (G3-P) Dihydroxyacetone phosphate 2 1,3-Bisphosphoglyceric acid 2 Pyruvate 2 Lactate Glucose 2 lactate 2H + G kj (C 6 H 12 O 6 ) 2(C 3 H 5 O 3 ) (2 ATP) 2 ATP/glucose Chap. Copyright Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig. 14.3a

14 Lactic acid Fermentation - heterofermentative Ethanol Acetaldehyde Glucose Glucose 6-phosphate 6-Phosphogluconic acid Ribulose 5-phosphate CO 2 Xylulose 5-phosphate Phosphoketolase Acetyl phosphate Glyceraldehyde 3-P 1,3-Bisphosphoglyceric acid Pyruvate - Lactate Glucose lactate ethanol CO 2 H + G kj (C 6 H 12 O 6 ) (C 3 H 5 O 3 ) (C 2 H 5 OH) (1 ATP) 1 ATP/glucose Chap. Copyright Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig. 14.3b

15 Ethanol Fermentation Saccharomyces cerevisae Embden- Meyerhof pathway 2 2 CO ATP/glucose 2 Chap. Copyright Pearson Education Inc., publishing as Pearson Benjamin Cummings

16 Mixed acid Fermentation (e.g. E. coli) Embden- Meyerhof pathway 2 Pyruvate:Formate lyase Acetyl - CoA + 2 Formate Phospho transacetylase Acetate kinase Acetyl - P 2-3 ATP/glucose Acetate Chap. Copyright Pearson Education Inc., publishing as Pearson Benjamin Cummings

18 Energy Conservation Electron-transport-coupled phosphorylation (ETP) Energized membrane Less energized membrane ATP produced from proton motive force formed by transport of electrons from organic or inorganic electron donors Chap. Copyright Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig. 5.14

19 Electron-transport-coupled phosphorylation Membrane associated Mediates transfer of electrons from primary donor to terminal acceptor Conserves some of the energy released during transfer, ATP synthesis via ATP synthase Many oxidation-reduction enzymes are involved in electron transport (e.g., NADH dehydrogenases, flavoproteins, iron-sulfur proteins, cytochromes) Results in generation of ph gradient and an electrochemical potential across the membrane (the proton motive force) n H + H + 3 H + Electron transport chain ATP synthase Dred + Aox Dox + Ared ADP + P i ATP ATP produced at the expense of the proton motive force which is generated by electron transport If A is oxygen => aerobic respiration!!! Chap. Copyright Pearson Education Inc., publishing as Pearson Benjamin Cummings

Principles of Electron Transport Systems Electron transport system oriented in cytoplasmic membrane so that as electrons are transported, protons are separated Carriers in electron transport chain

20 Principles of Electron Transport Systems Electron transport system oriented in cytoplasmic membrane so that as electrons are transported, protons are separated Carriers in electron transport chain arranged in membrane in order of their increasingly positive reduction potential The final carrier in the chain donates the electrons and protons to the terminal electron acceptor NAD(P) + /NAD(P)H E = V 1.13 V 218 kj/mol G = - n F E (kj/mol) Oxygen E = V Chap. Copyright Pearson Education Inc., publishing as Pearson Benjamin Cummings

21 Redox systems Hydrogen transfer Isoalloxazine ring R Ribitol Oxidized form FAD (FMN) Oxidized Quinone, oxidized R Reduced form FADH 2 (FMNH 2 ) Quinone, oxidized Reduced Quinonol, reduced Flavines: (e.g. FMN, FAD) Prosthetic group of enzymes Accepts 2 electrons and 2 protons Quinones Hydrophobic non-protein-containing molecules that participate in electron transport Accept electrons and protons but only pass on electrons Chap. Copyright Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig. 4.15, 5.18

Redox systems Electron transfer Cysteine Cysteine Cysteine Cysteine Iron sulfur proteins; Fe 2 S 2

cytochrome c Iron-Sulfur Proteins Contain clusters of iron and sulfur (e.g.

electrons only Cytochromes Proteins that contain heme prosthetic groups Accept and donate a single

22 Redox systems Electron transfer Cysteine Cysteine Cysteine Cysteine Iron sulfur proteins; Fe 2 S 2 cluster Cysteine Cysteine Cysteine Cysteine Iron sulfur proteins; Fe 4 S 4 cluster Heme of cytochrome c Iron-Sulfur Proteins Contain clusters of iron and sulfur (e.g., ferredoxin) Reduction potentials vary depending on number and position of Fe and S atoms Carry electrons only Cytochromes Proteins that contain heme prosthetic groups Accept and donate a single electron via the iron atom in heme Chap. Copyright Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig. 4.16, 4.17

23 Aerobic Respiration E 0 (V) Electron transport process in the membrane of Paracoccus denitrificans 0.22 Resembles the one from Mitochondria Complex I (NADH:quinone oxidoreductase) NADH donates e - to FMN FMN donates e - to quinone Complex II (succinate dehydrogenase complex) Bypasses Complex I Feeds e - and H + from FADH directly to quinone pool ENVIRONMENT Q cycle Complex II Succinate Fumarate CYTOPLASM Complex III (cytochrome bc 1 complex) Transfers e - from quinones to cytochrome c Cytochrome c shuttles e - to cytochromes a and a Complex IV (cytochromes a and a 3 ) Terminal oxidase; reduces O 2 to H 2 O 0.39 E 0 (V) Chap. Copyright Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig. 4.19

24 Substrate-level phosphorylation within glycolysis Glucose Substrate-levelphosphorylation Pyruvate Acetyl-CoA C 2 C 4 2 lactate Electron transport-coupled phosphorylation C 5 2 Pyruvate C 6 Oxalacetate 2 Citrate 3 Aconitate 3 Malate 2 Isocitrate 3 Fumarate 2 Succinate 2 Succinyl-CoA -Ketoglutarate 2 Electron transportcoupled phosphorylation Chap. Copyright Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig. 4.14

25 Energetics Balance for Aerobic Respiration Chap. Copyright Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig. 4.21b

26 Aerobic Respiration Electron transport process in the membrane of Escherichia coli Chap. Copyright Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig a

27 Anaerobic Respiration The use of electron acceptors other than oxygen Examples include nitrate (NO 3- ), ferric iron (Fe 3+ ), sulfate (SO 4 2- ), carbonate (CO 3 2- ), certain organic compounds Less energy released compared to aerobic respiration Energy released from redox reactions can be determined by comparing reduction potentials of each electron acceptor Dependent on electron transport, generation of a proton motive force, and ATPase activity Chap. Copyright 4.12, Pearson Education Inc., publishing as Pearson Benjamin Cummings

Major Forms of Anaerobic Respiration 0.42 0.3 Anoxic Proton reduction; Pyrococcus furiosus, obligate anaerobe Carbonate respiration; acetogenic bacteria, obligate anaerobes 0.27 0.

22 E 0 (V) 0 Sulfate respiration (sulfate reduction); obligate anaerobes (SO 4 2- SO 3 2-, E 0 0.52) Fumarate respiration; facultative aerobes 0.

28 Major Forms of Anaerobic Respiration Anoxic Proton reduction; Pyrococcus furiosus, obligate anaerobe Carbonate respiration; acetogenic bacteria, obligate anaerobes Sulfur respiration; facultative aerobes and obligate anaerobes Carbonate respiration; methanogenic Archaea; obligate anaerobes 0.22 E 0 (V) 0 Sulfate respiration (sulfate reduction); obligate anaerobes (SO 4 2- SO 3 2-, E ) Fumarate respiration; facultative aerobes 0.2 Iron respiration; facultative aerobes and obligate anaerobes Thermodynamic hierarchy of electron acceptors Oxic (oxygen present) Reductive dechlorination; facultative aerobes and obligate anaerobes Nitrate respiration; facultative aerobes (some reduce NO 3- to NH 4 ) Denitrification; facultative aerobes Manganese reduction; facultative aerobes Aerobic respiration; obligate and facultative aerobes Organisms: Enterobacteria, e.g. E. coli Organisms: (many) Pseudomonas Paracoccus Chap. Copyright Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig

Gases Nitrous oxide N 2 O Nitrous oxide reductase Dinitrogen N 2 -> Denitrification is a biological source of

29 Dissimilative Reduction of Nitrate Nitrate Nitrite NO 3 Nitrate reductase NO 2 Nitrate reduction (Escherichia coli) NH 4 + Nitrite reductase Nitric oxide NO Nitric oxide reductase Denitrification (Pseudomonas stutzeri) Gases Nitrous oxide N 2 O Nitrous oxide reductase Dinitrogen N 2 -> Denitrification is a biological source of gaseous N 2 Chap. Copyright Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig

Respiration and Anaerobic Respiration Periplasm Periplasm Nitrate reductase complex Q cycle Q cycle Nitrate reductase Cytoplasm Cytoplasm Aerobic respiration Nitrate reduction Periplasm Nitrate

30 Respiration and Anaerobic Respiration Periplasm Periplasm Nitrate reductase complex Q cycle Q cycle Nitrate reductase Cytoplasm Cytoplasm Aerobic respiration Nitrate reduction Periplasm Nitrate reductase complex NO 2 reductase N 2 O reductase Q cycle Nitrate reductase Nitric oxide reductase Cytoplasm Denitrification Chap. Copyright Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig

Julia Vorholt Lecture 8:

752-4001-00L Mikrobiologie Julia Vorholt Lecture 8: Nov 12, 2012 Brock Biology of Microorganisms, Twelfth Edition Madigan / Martinko / Dunlap / Clark 1) Nutrients and microbial growth 2) Introduction to