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Anaerobic respiration

Anaerobic respiration. Almost the same as aerobic respiration, except replace O 2 with another molecule in electron transport (see Chapter 9 Bact Phy & Meta) Metabolic pathways: Glycolysis or alternatives TCA cycle Electron transport – chain different Example Rxn :

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Anaerobic respiration

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  1. Anaerobic respiration • Almost the same as aerobic respiration, except replace O2 with another molecule in electron transport (see Chapter 9 BactPhy & Meta) Metabolic pathways: • Glycolysis or alternatives • TCA cycle • Electron transport – chain different Example Rxn: C6H12O6 + 6 NO2-,  6 CO2 + 3 N2 + 6 H2O • Can generates up to 36 ATPs/glucose (depends on electron acceptor used)

  2. Anaerobic respiration • Compounds that can serve as electron acceptors Table 6.3 Microbe

  3. Anaerobic respiration Terms Assimilatory – end product incorporated into organic material of cell Dissimilatory – end product not incorporated into organic material of cell (excreted) Complete Oxidizer or oxidizing – fully oxidize carbons in organic molecules to CO2 Incomplete oxidizer – do not fully oxidize carbons in organic molecules to CO2 Chemolithotroph– Energy from chemicals (inorganic) and fix CO2

  4. Anaerobic respiration Fig 17.36 Brock • Denitrification • Reduction of nitrate or nitrite all the way to dinitrogen (N2) gas • Done by some facultative anaerobic chemohetero-trophic bacteria (Pseudomonas, Ralstonia, Paracoccus) if oxygen not present • Reduces nitrogen in soil and wastewater in treatment plants

  5. Anaerobic respiration • Denitrification (17-37c) • Process similar to aerobic respiration • Reduces NADH and pumps protons • Four complexess 17-37a Aerobic respiration Fig 17-37c Denitri-fication

  6. B. Electron Transport Chains Proposed Electron transport chains of Paracoccusdenitrificansfound in soil A Aerobic B. Anaerobic - denitrificaiton

  7. Anaerobic respiration • A few bacteria reduce nitrate to ammonia • Ammonia can be assimilated by incorporation into amino acids • Mentioned in Section 9.1.4 B. Nitrate reduction Fig 12.1 White 3rd

  8. Anaerobic respiration • Sulfate reduction or sulfidogenesis • Electrons reduce sulfate to H2S • Some get electrons from carbon compounds like lactate, ethanol • Other (chemoauto-trophics) get from H2 (hydrogen bacteria) Fig 17.39 Brock

  9. Anaerobic respiration D. Methanogenesis • Reduce organic material (methanol, acetate) or CO2 to methane • Seen in landfills • Done by types of anaerobic archaea • Enzymes use unique coenzymes (See Fig 9.9) Fig 17.44 Brock

  10. Anaerobic respiration D. Methanogenesis • Reduce organic material (methanol, acetate) or CO2 to methane • Seen in landfills • Done by types of anaerobic archaea • Enzymes use unique coenzymes (See Fig 9.9) Fig 9.10 BactPhy & Meta

  11. Anaerobic respiration E. Acetogenesis • Reduce CO2 to acetate • Electron donor usually H2 • Done by some strict anaerobes acting as chemolithotrophs • Fix CO2 via acetyl CoA pathway Fig 17.41 Brock

  12. Anaerobic respiration F. Metal reducers • Uses metals as electron acceptors (Fe, Mn, Co, chromate, etc) • Donors are usually organic molecules (lactate, acetate) • Some can use more than one Fig 17.47 Brock

  13. Anaerobic respiration G. Dehalorespiration • Remove halogen groups (Cl) from chemicals (TCE, PCE, PCP) • Reduction reaction – accept electrons Table 9.9

  14. Phototrophy Pigments capture light energy and use it to excite electrons of reaction centers get electrons from water or other chemicals Use electron transport chain to use energy captured to generate ATP and to generate reduced NAD(P)H Most use captured energy to reduce CO2 molecules to make sugar (carbon fixation) - autotrophy See Chapter 11 BactPhy & Meta

  15. Overview of Phototrophy • 1. Light dependent Capture energy as NADPH and ATP • 2. Light-independent – Carbon fixation – Calvin cycle Calvin cycle

  16. A. Types of Phototrophy Table 5.1 White

  17. A. Types of Phototrophy 1. Oxygenic • Get electrons from water to generate O2 • Done by cyanobacteria and prochlorophytes • Pigments used are chlorophyll a and phycobilins or chlorophyll b • Two light reactions in series (Photosystem I and II) • Two different reaction centers • Reaction 6 CO2 + 6 H2O  C6H12O6 + 6 O2

  18. A. Types of Phototrophy 2. Anoxygenic • Done by purple sulfur, purple non-sulfur, green sulfur bacteria and heliobacteria • Are anaerobic • Get electrons from other reduced substances (H2, H2S, S, alcohols, acids) • One cycle and reaction center involved • Pigments used are different types of bacteriochlorophylls • Reaction 6 CO2 + 6 H2A  C6H12O6 + 6 A2

  19. B. Photosynthetic Pigments Types • Reaction center pigments • Chlorophylls and bacteriochlorophylls • do conversion of light energy to ATP • Light harvesting or Accessory pigments – • Carotenoids, Phycobilins, and chlorophylls • act in light harvesting and photoprotection • pigments are associated with proteins • Most in membrane

  20. B. Photosynthetic Pigments • Absorb light energy of certain wavelengths • The different types of pigments and complexes vary in their absorption spectra • accessory pigments act to expand absoprtion spectra (beyhond reaction center pigment) Fig 17.11 Brock

  21. B. Photosynthetic Pigments • Bacteria differ in their absorption spectra based on their pigments • Plants absorb blue and red light and reflect green light Fig 11.4 BactPhy & Meta

  22. B. Photosynthetic Pigments • Pigment and protein form large complexes in membrane (~300 pigments in array called an antenna) • Only a few pigments in complex act as reaction centers which act directly in converting light energy to ATP (reaction centers) – pair of pigments • Most pigments act to harvest light energy and then funnel energy to a reaction center

  23. Pigments • Chlorophyll and bacteriochlorophylls differ in their absorption spectra Fig 17.3 Brock Green line – chlorophyll a of green alga Red line – bacteriochloro-phyll a of purple non-sulfur bacteria

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