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Chapter 5: Microbial Metabolism

Chapter 5: Microbial Metabolism. What is Metabolism?. Metabolism = all chemical reactions that occur in a cell/organism; catabolism + anabolism. Catabolism = breakdown of food molecules to produce energy and molecular subunits (example: amino acids from proteins)

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Chapter 5: Microbial Metabolism

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  1. Chapter 5: Microbial Metabolism

  2. What is Metabolism? Metabolism = all chemical reactions that occur in a cell/organism; catabolism + anabolism. Catabolism = breakdown of food molecules to produce energy and molecular subunits (example: amino acids from proteins) Anabolism = building of macromolecules that the organism needs (proteins from amino acid subunits or DNA from nucleotides)

  3. Metabolic (also called biochemical) pathways http://www.expasy.ch/cgi-bin/show_thumbnails.pl e1 e2 e3 A BCD Feedback inhibition = shutting off of biochemical pathway; product in pathway binds to e1 which changes its shape and stops its work

  4. Enzymes Type of molecule – usually proteins; a few RNA molecules called ribozymes too. Words ending with –ase are enzymes Shape determines function Active site E = enzyme, S = substrate, P = product E + S ES E + P

  5. Enzyme catalyzed reactions

  6. Enzyme-substrate complexes

  7. What affects enzyme activity? •        Temperature •        pH •        Concentration of substrate •        Inhibitors               Ex.  Folic acid pathway  Sulfanilamide competes with PABA; no folic acid made Ex.  Fluoride in drinking water and toothpaste inhibit cavity-causing bacteria

  8. Denaturation of proteins

  9. How temperature, pH, and substrate concentration affect enzyme activity --

  10. How inhibitors work --

  11. Energy molecules in cells ATPADP + Pi NADHNAD+ + H+ + 2e- FADH2FAD + 2H+ + 2e-

  12. Catabolism of Glucose • Aerobic respiration – efficient energy production (1 glucose converted to 38 ATP) • Anaerobic respiration – less efficient (less than 38 ATP); no oxygen • Fermentation – least efficient (2 ATP produced); usually without oxygen

  13. Aerobic Respiration

  14. Anaerobic respiration • Uses parts of all of the aerobic processes (but not all) • Final electron acceptor not oxygen • Possible e- acceptors: Nitrogen compounds NO3- NO2, N2O, N2 Sulfur compounds SO4-2H2S Carbon compounds CO3-2 CH4

  15. Fermentation • Only produces 2 ATP molecules from 1 glucose • Occurs without oxygen (O2) • Detour from glycolysis to a short fermentation pathway • Produces by-products as NAD+ and FAD are regenerated • By-products produced include acids, alcohols, gases, etc.

  16. Practical example: Fact:Clostridiumperfringenscauses gas gangrene Problem: How to cure gas gangrene… Patients affected: Anyone with an anaerobic site of tissue damage; diabetics particularly prone to this disease (Diabetics have poor circulation, nerve damage, lessened pain sensations, lower ability to heal) Diagnosis: Odors, specimen collection and identification of bacteria, X-ray for pockets of gas in tissues Treatment: Essential -- Remove dead tissue (sometimes even amputation of affected limb); Possible -- expose tissues to oxygen through a hyperbaric chamber and/or antibiotic regimen

  17. This photomicrograph reveals Clostridium perfringens grown in Schaedler’s broth using Gram-stain. (Photo by CDC/Don Stalons, 1974.)

  18. Wagner Grade 5 - Unsalvagable Gangrene Gangrene or necrosis to the extent that the foot is beyond salvage and will require a major limb- or life-sparing amputation. http://www.squidoo.com/diabeticfoot

  19. Why do microbes have the ability to switch back and forth between aerobic respiration and an anaerobic process?

  20. What about other food sources besides glucose? What about anabolic reactions?

  21. The End

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