ystems Microbiology eds Sept 20 - Ch 5 & Ch 17 (p ) ioenergetics & Metab.Diversity BASIC MODES OF ENERGY GENERATION

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1 ystems Microbiology eds Sept 20 - Ch 5 & Ch 17 (p ) ioenergetics & Metab.Diversity BASIC MODES OF ENERGY GENERATION THERMODYNAMICS OF GROWTH -cont d APPLICATIONS of MICROBIAL CHEMOLITHOTROPHY & ANAEROBIC RESP.

2 Phototrophs (Use Light as Energy Source ) Photoautotrophs (Use CO 2 ) Photoheterotrophs (Use Organic Carbon) Figure by MIT OCW.

3 Cyclic Photophosphorylation Excited electrons (2 e - ) Electron transport chain Energy for production of ATP ATP Light Chlorophyll Electron carrier Figure by MIT OCW. Anoxygenic photoautotrophs utilize cyclic photophosphorylation

4 LOTS OF DIVERSITY IN BACTERIAL ANOXYGENIC PHOTOTROPHS! E 0 ' (V) Purple Bacteria Green Sulfur Bacteria Heliobacteria P798 P840 Chl a-oh Chl a P870 BChl BPh FeS FeS P870 Cyt c 2 Q Cyt bc 1 Light NADH Reverse electron flow P840 Cyt c 553 Light Cyt bc 1 Q Fd P798 Cyt c 553 Cyt bc 1 Light Q Fd Figure by MIT OCW.

5 E ' 0 (V) P680* Ph Q A Q B Q pool Cyt bf Noncyclic electron flow (generates proton motive force) Cyclic electron flow (generates proton motive force) Pc P700* Chl a 0 Q A P700 Photosystem I FeS Fd NAD(P) + Fp NAD(P)H Light P680 e - Photosystem II H 2 O 1 O 2 + 2H 2 Light The Z Scheme PSII PSI Figure by MIT OCW.

6 HALOARCHAEA Live in hypersaline habitats Aerial photograph of haloarchaea changing the colors of their saltwater habitats removed due to copyright restrictions.

7 H + Asp-96 Asp-85 Arg-82 Glu-204 Retinal Glu-194 H + Figure by MIT OCW.

8 Microbial rhodopsins fall into two main functional classes Light-driven ion pumps Sensory rhodopsins Rhodopsin Functional Diversity H + BR HR SRl Htrl SRll Htrll Bacteriorhodpsin Cl - Cytoplasm His-kinase Methylation helices His-kinase Regulator P Regulator P Regulator Flagellar motor Figure by MIT OCW.

9 Cell interior Bacteriorhodopsin and proteorhodospin Light driven proton pumps H + Asp-96 2 High H + concentration H + H + Outside cell Electron transport chain (includes proton pumps) } Membrane Asp-85 Arg-82 Glu-204 H + Retinal Glu Inside cell ADP+ Pi Electrons from NADH or chlorophyll ATP synthase ATP 3 Cell exterior Figure by MIT OCW. Low H + concentration Figure by MIT OCW.

10 Images and diagrams of various rhodopsins removed due to copyright restrictions. See Science 289 (September 15, 2000).

11 Venter et al., Environmental Genome Shotgun Sequencing of the Sargasso Sea, Science 394:66-74 (2004) Diagram removed due to copyright restrictions. Many new bacterial proteorhodopsins discovered in environmetnal shotgun sequencing

12 Images of a hybrid automobile, hydrocarbons, and electricity removed due to copyright restrictions.

13 Where do organisms get their energy? ALL ORGANISMS chemotrophs phototrophs Derive energy from light chemolithotrophs xidize inorganic compounds chemoorganotrophs Oxidize organic compounds

14 ICROBIAL ETABOLIC IVERSITY Microbes can eat & breathe just about anything! Relative Voltage REDUCTANTS (EAT) Organic Carbon Photoreductants H 2 H 2 S S o Fe(II) A B CO 2 SO 4 = AsO 4 3- FeOOH Relative Voltage OXIDANTS (BREATHE) NH 4 + Mn(II) SeO 3 NO 2 - NO 3 - MnO 2 NO 3- /N O

15 Diagrams removed due to copyright restrictions. See Figures 5-22a, 5-20, and 5-23 in Madigan, Michael, and John Martinko. Brock Biology of Microorganisms. 11th ed. Upper Saddle River, NJ: Pearson Prentice Hall, ISBN:

16 METABOLIC DIVERSITY - Continued. hemolithoautotroph (chemo [chemical], litho [rock], auto[self], troph [feeding]) nergy source: inorganic substrates (H2, NH3, NO2-, H2S, Fe2+) arbon source: CO 2 - acceptor: O 2 (aerobes), or S(some anaerobes), Fe 3+, NO 3, SO 4 hemolithoautotrophs can be grouped according to the inorganic ompounds that they oxidize for energy: itrifiers - Oxidize reduced Nitrogen compounds such as NH4+ ulfur Oxidizers- Oxidize reduced Sulfur compounds such as H2S, S0, and S2Oron Oxidizers- Oxidize reduced Iron-Fe2+ (ferrous iron) ydrogen Oxidizers-Oxidize Hydrogen gas-h2

17 Table of energy yields from the oxidation of various inorganic electron donors removed due to copyright restrictions. See Table 17-1 in Madigan, Michael, and John Martinko. Brock Biology of Microorganisms. 11th ed. Upper Saddle River, NJ: Pearson Prentice Hall, ISBN:

18 METABOLIC DIVERSITY CHEMOLITHOAUTOTROPHS - Examples

19 CHEMOLITHOTROPHIC AMMONIA OXIDATION - AEROBIC NH /2O 2 --> NO H 2 O + 2H + AMO O NH 2 OH N + 5H+ + H 2 O O- Oxidation of hydroxylamine HAO 4e- 2e- Cyt c Cyt c 2e- 2e- Q 2e- Cyt aa 3 Periplasm 2H + H + NH 2 OH+ H 2 O Oxidation of ammonia 1 2 NH + O 2 + 2H + 3 O 2 + 4H + H 2 O Reduction of oxygen ADP ATP + Pi H + Figure by MIT OCW.

20 HEMOLITHOTROPHIC MMONIA OXIDATION - ANAEROBIC Anammox means "anaerobic ammonium oxidation". Anammox is both a new low-cost method of N-removal in wastewater treatment, and a spectacular microbial way of life - woo - woo! Courtesy of the Department of Microbiology at Radboud University Nijmegen. Used with permission.

21 2NH 4+ /N 2 half reaction (6e-) Eo = V 2NO 2- /N 2 half reaction (6e-) Eo = V ΔE o = E o (electron acceptor) - E o (electron donor) = 1233 mv ΔG o =-nf ΔE o = -(3) (96.5 kj/vmol)(1.233v) = kj/mol roda predicted, based solely on the thermodynamics, that such icroorganisms should exist. (And also the fact that if a ioenergetically favorable niche exists, a microbe will evolve o fill it!). bout a decade later, the bugs were discovered in bioreactors tarted from waste water treatment plants.

22

23 Diagram removed due to copyright restrictions.

24 Compared to conventional nitrification/denitrification, this method saves 100% of the carbon source, & 50% of the required oxygen. This leads to a reduction of operational costs of 90%, a decrease in CO 2 emissions of more than 100% (the process actually consumes CO 2 ), and a decrease in energy demand. Photograph removed due to copyright restrictions

25 Anaerobic ammonium oxidation by anammox bacteria in the Black Sea Marcel M. M. Kuypers, A. Olav Sliekers, Gaute Lavik, Markus Schmid, Bo Barker Jørgensen, J. Gijs Kuenen, Jaap S. Sinninghe Damsté, Marc Strous and Mike S. M. Jetten. Nature 422, (10 April 2003) Graphs removed due to copyright restrictions.

26 ANAEROBIC RESPIRATION = Dumping your electrons on something other than oxygen

27 Denitrification = Use of NO 3 - as terminal electron acceptor, that results in complete conversion to N 2 gas. Diagrams removed due to copyright restrictions. See Figures and in Madigan, Michael, and John Martinko. Brock Biology of Microorganisms. 11th ed. Upper Saddle River, NJ: Pearson Prentice Hall, ISBN:

28 Geobacter growing on iron oxides Anaerobic respiration CH 3 COO - Fe 3+ Image of geobacter growing on iron oxides removed due to copyright restrictions. e - CO 2 Fe 2+

29 Complex Organic Matter Hydrolysis Fermentable Substrates Fermentation H 2 Acetate Other low molecular weight organic acids } Microbial Competition for Substrates } NO 3 - reducers Mn(IV) reducers Fe(III) reducers SO 4 2- reducers Methanogens Organic Matter Degradation In Anaerobic Environments Figure by MIT OCW.

30 Diagram removed due to copyright restrictions.

31 Energetic explains order: not all e- acceptors are equal! 25 E- acceptor ΔG o (using glucose) Oxygen kj/mol NO Mn (IV) Fe(III) Sulfate -380 CO2-350 From Nealson and Saffarini 1994

32 Complex Assemblage of Organic Matter Hydrolysis into Constituents Fermentable Sugars and Amino Acids Fermentation by a Fermentative Microbial Consortium Long-Chain Fatty Acid Acetate and Minor Products Aromatic Compounds Fe 3+ Oxide Fe 2+ Geobacter spp. CO 2 Generalized pathway for the anaerobic oxidation of organic matter to carbon dioxide with Fe 3+ oxide serving as an electron acceptor in temperate, freshwater and sedimentary environments. The process is mediated by a consortium of fermentative microorganisms and Geobacter species. Figure by MIT OCW.

33 High organics Source Low O 2 Methanogenic 2 SO 4 reduction Fe(III) reduction Mn(IV) reduction - NO 3 (IV) reduction Aerobic Groundwater flow High O 2 Figure by MIT OCW. The distribution of terminal electron-accepting processes (TEAPs) observed within anaerobic portions of aquifers contaminated with organic compounds.

34 Images removed due to copyright restrictions. See Lovley, D. R., E. J. P. Phillips, Y. A. Gorby, and E. R. Landa. "Microbial Reduction of Uranium." Nature 350 (1991):

35 naerobic respiration to clean up of uranium pollution Soluble= mobile Insoluble, immobile cetate + U (VI) U (IV) s + CO 2 Photograph removed due to copyright restrictions. H 3 C U(VI) U (IV) s + 2HCO H+ Carried out by Geobacter Example of bioremediation ovley DR, Phillips EJP, Gorby YA, Landa ER. Microbial Reduction of Uranium, 1991, Nature. 50(6317):

36 Diagram removed due to copyright restrictions.

37 Diagram removed due to copyright restrictions. See Bond, Holmes, Tender, and Lovley. Science 295 (2002):

38 Diagram and photograph of a sediment microbial fuel cell removed due to copyright restrictions.

39 V=IR Atomic force microscope stage Correspondence between pilus current and applied voltage demonstrating the linear, ohmic, response characteristic of a true conductor. Schematic of the electronic connection of the AFM tip in a conducting probe atomic force microscope (CP-AFM). HOPG, highly oriented pyrolytic graphite. Extracellular electron transfer via microbial nanowires. Nature Jun 23;435(7045):

40 Good electron acceptors Good electron donors

41 Photograph removed due to copyright restrictions

42 SO 4 2- Seawater Sea Floor Sulfate Reduction Zone DNS A B SO 4 2- Diffusion C DNS METHANE FLUX Figure by MIT OCW.

43 ANAEROBIC METHANE OXIDATION Geochemical Observations: CH 4 + SO 4 2- HCO HS - + H 2 O Microbiologically??? CH 4 + 2H 2 O CO 2 + 4H 2 Reverse Methanogenesis ΔG o = +131 kj/mol HSO H 2 HS - + 4H 2 O Sulfate reduction ΔG o = -156 kj/mol CH 4 + HSO 4 2- CO 2 + HS - + 2H 2 O ΔG o = -25 kj/mol

44 SO 4-2 CH 4 H 2 HS - CO 2

45 World maps showing global methane distribution removed due to copyright restrictions. See D Hondt et al. Science 295 (2002): 2067.