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Dr. Alvin Fox

Nutrition, Growth and Metabolism, Lecture 26. Dr. Alvin Fox. KEY TERMS. Obligate aerobe Obligate anaerobe Aerotolerant anaerobe Facultative anaerobe Microaerophilic Siderophore Mesophile Thermophile Psychrophile Generation time. Growth curve Glycolysis Fermentation

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Dr. Alvin Fox

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  1. Nutrition, Growth and Metabolism, Lecture 26 Dr. Alvin Fox

  2. KEY TERMS Obligate aerobe Obligate anaerobe Aerotolerant anaerobe Facultative anaerobe Microaerophilic Siderophore Mesophile Thermophile Psychrophile Generation time Growth curve Glycolysis Fermentation Anaerobic respiration Aerobic respiration Tricarboxylic acid (TCA) cycle or Krebs cycle Oxidative phosphorylation Ubiquinone Glyoxylate pathway

  3. Bacterial requirements for growth • oxygen (or absence) • energy • nutrients • optimal temperature • optimal pH

  4. Obligate aerobes • grow in presence of oxygen • no fermentation • oxidative phosphorylation

  5. Obligate anaerobes • no oxidative phosphorylation • fermentation • killed by oxygen • lack certain enzymes: • superoxide dismutase • O2-+2H+ H2O2 • catalase • H2O2 H20 + O2 • peroxidase • H2O2 + NADH + H+ H20 + NAD

  6. Aerotolerant anaerobes • respire anaerobically • not killed by oxygen

  7. Facultative anaerobes • fermentation • aerobic respiration • survive in oxygen

  8. Microaerophilic bacteria • grow • low oxygen • killed • high oxygen

  9. Optimal growth temperature • Mesophiles: • human body temperature • pathogens • opportunists • pyschrophile • close to freezing • thermophile • close to boiling

  10. pH • Many grow best at neutral pH • Some can survive/grow • - acid • - alkali

  11. Nutrient Requirements • Carbon • Nitrogen • Phosphorus • Sulfur • Metal ions (e.g. iron)

  12. Siderophores (S) Receptor Fe 2+/S Fe 2+/S

  13. Measuring bacterial mass (live + dead) in liquid culture Turbidity (Cloudiness)

  14. Measuring viable bacteria Colony forming units colony

  15. Growth Curve Stationary TURBIDITY (cloudiness) Autolysis Log Lag TIME

  16. Growth Curve Stationary COLONY FORMING UNITS Death Log Lag TIME

  17. Generation time • time for bacterial mass to double • Example • 100 bacteria present at time 0 • If generation time is 2 hr • After 8 hr mass = 100 x 24

  18. SUGAR CATABOLISM • Glycolysis • Embden Meyerhof Parnas Pathway • most bacteria • also animals and plants

  19. Other pathways for catabolizing sugars • Pentose phosphate pathway (hexose monophosphate shunt) • generates NADPH • common in plants and animals • Entner Doudoroff Pathway • a few bacterial species

  20. Glycolysis NAD NADH Glucose Pyruvate C6 C3 ADP ATP

  21. Fermentation NADH NAD Pyruvate Short chain alcohols, fatty acids (C3) (C2-C4)

  22. Anaerobic Respiration = Glycolysis + Fermentation NAD NADH ATP NAD NADH

  23. Krebs Cycle (C4-C6 intermediate compounds) NAD NADH 3CO2 Pyruvate (C3) (C1) Oxidative phosphorylation NADH NAD O2 H2O ADP ATP

  24. Aerobic Respiration =Glycolysis + Krebs Cycle/oxidative phosphorylation • Pyruvate to CO2 • NADtoNADH • glycolysis • Krebs cycle • Oxidative phosphorylation • NADHto NAD • ADPto ATP

  25. Oxidative phosphylation • converts O2 to H20 (oxidative) • converts ADP to ATP (phosphorylation) • electron transport chain • ubiquinones/cytochrome intermediates

  26. The Krebs cycle X C Isocitrate C2 Acetate -CO2 NADH C6 Citrate + -CO2 Alpha-keto glutarate C4 Oxaloacetate Pyruvate -CO2 NADH x C Malate Succinate Fumarate

  27. Krebs Cycle - sugar as sole carbon source Acetate Krebs cycle + -CO2 Oxalo acetate Pyruvate C2 Citrate C4 C C6 C3 -2CO2 BIOSYNTHESIS ENERGY STORAGE X Oxalo acetate Aspartic acid + CO2 Oxaloacetate Pyruvate C3 C C4

  28. Krebs Cycle – fatty acids as sole carbon source ENERGY Acetate Krebs cycle + Fatty acids Oxalo acetate Citrate BIOSYNTHESIS x -2CO2 Oxalo acetate Aspartic acid C2 Isocitrate Glyoxylate Succinate + C2 -2CO2 + Acetate Krebs cycle C6 C4 Malate C4

  29. The Glyoxylate and Krebs cycles Isocitrate Citrate 1 Alpha-keto glutarate Glyoxylate Oxaloacetate 2 +Acetate Malate Succinate Fumarate Krebs and Glyoxylate cycles Krebs cycle only Glyoxylate cycle only

  30. Krebs Cycle • biosynthetic • energy storage • Removal of intermediates • must be replenished • Unique enzymatic replenishment pathways • sugars • fatty acids

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