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Bio@Tech

Earth History. When did life begin? What was the first form of life? When did the first eukaryotes appear? MinuteEarth : The Story of our Planet. Bio@Tech. Campbell & Reece, Fig. 26.10. What role did oxygen play in evolution?. great oxygenation event. Bio@Tech. Bacteria. Eukarya.

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Bio@Tech

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  1. Earth History When did life begin? What was the first form of life? When did the first eukaryotes appear? MinuteEarth: The Story of our Planet Bio@Tech Campbell & Reece, Fig. 26.10

  2. What role did oxygen play in evolution? great oxygenation event Bio@Tech

  3. Bacteria Eukarya Archaea 0 4 Symbiosis of chloroplast ancestor with ancestor of green plants 1 3 Symbiosis of mitochondrial ancestor with ancestor of eukaryotes Billion years ago 4 3 2 2 Possible fusion of bacterium and archaean, yielding ancestor of eukaryotic cells 2 3 1 Last common ancestor of all living things 1 Origin of life 4 “Tree of Life” According to this tree, which group, Bacteria or Archaea, are more closely related to eukaryotes? Bio@Tech Campbell & Reece, Fig. 25.18

  4. unique cell wall structures unique cell membrane lipids DNA replication, transcription & translation machinery similar to eukaryotes How do Bacteria and Archaea differ?

  5. Microfossils Cyanobacteria (Nostocales) from the Bitter Springs Chert, Central Oz, 850 Ma(J.W. Schopf, UCLA http://www.cushmanfoundation.orgt/slides/stromato.html) 2.5-2.7 Ga microfossils (Schopf, 2006. Phil. Trans. R. Soc. B 361: 869-885)

  6. Stromatolites • Stromatolite fossils are structurally indistinguishable from living examples Campbell & Reece, Fig. 26.11

  7. Microbes in the Biosphere From Whitman et al. 1998 PNAS 95:6578-6583: • 4 x 1030 prokaryotic cells on Earth • Subsurface ~3.8 x 1030 • Aquatic ~1 x 1029 • Soils ~2.5 x 1029 • Animals (termites) ~5 x 1024 • Air ~ 5 x 1019 • 350-550 Pg* C = 60-100% of C in plants • 30-50% of C in biosphere • 90% of organic N, P in biosphere *Pg = petagram = 1015 grams Bio@Tech

  8. Microbes R Us • 70 x 1012 prokaryotic cells per person • Mostly in gut: colon has 300 x 109/g • Approx. 30% of solid matter in feces • Gut microbiome > 100 x human genome • Human microbiome project Bio@Tech

  9. Microbes are planetary engineers • Invented all metabolism • Catabolism • Anabolism • Depleted ocean of dissolved iron (Fe2+) • Anoxygenic photosynthesis • 4 Fe2+ + CO2 + 4 H+ 4 Fe3+ + CH2O + H2O • Oxygenic photosynthesis • H2O + CO2 +  CH2O + O2 • 4 Fe2+ + O2 + 4 H+ 4 Fe3+ + 2 H2O • And injected oxygen into atmosphere! Bio@Tech

  10. Banded iron formed by iron oxide precipitates (Image courtesy of Dr. Pamela Gore,Georgia Perimeter College) (Hayes, 2002, Nature 417: 127-128)

  11. oxidation/reduction reactions power cells • Higher-energy molecules are oxidized (lose electrons) • Lower-energy molecules are reduced (gain electrons) • G = -nFE (kJ/mol) • n = # e- transferred • F = Faraday constant • E = redox potential difference

  12. Respiration: electrons from NADHcharge a membrane pH gradient H+ electrochemical gradient H+ Electron transport chain cell membrane NADH O2 or other terminal electron acceptors such as NO3-, SO42-, Fe3+, etc. NAD+ See also: http://www.microbelibrary.org/images/Tterry/anim/ETSbact.html H+ 2e- Electron donors (CH2O and other organic carbon food molecules)

  13. NAD = nicotinamide adenine dinucleotide. NADH + H+ +1/2 O2↔ NAD+ + H2O ΔGo = -52.4 kcal/mol. NAD+/NADH is the cell’s main electron (hydrogen) carrier

  14. Terminal Electron Acceptors • Microbes can use different terminal electron acceptors, but prefer oxygen because it givies the highest energy yield. • O2 ∆G = -479 kJ mol-1 • NO3- ∆G = -453 kJ mol-1 • Mn4+ ∆G = -349 kJ mol-1 • Fe3+ ∆G = -114 kJ mol-1 • SO42- ∆G = -77 kJ mol-1

  15. Periplasmic space Oxidative phosphorylation:F1 ATPase video H+ Stator Rotor http://www.youtube.com/watch?v=PjdPTY1wHdQ stored energy in proton gradient (proton motive force) powers ATP synthesis; analogous to a dam powering a water turbine Internal rod Cata- lytic knob See also: http://www.microbelibrary.org/images/Tterry/anim/ATPsynthbact.html ADP + ATP P i Cytoplasm

  16. Extraction of electrons from carbohydrates to reduce NAD+ H+ electrochemical gradient ETC ADP ATP NADH NADH NADH + FADH2 ATP Pyruvate oxidation Glycolysis Citric acid cycle NAD+ CO2 NAD+ FAD CO2 ADP Glucose, NAD+, ADP

  17. A soil-based microbial fuel cell Bio@Tech

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