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

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

2 2 KEY TERMS Obligate aerobe Obligate anaerobe Aerotolerant anaerobe Facultative anaerobe MicroaerophilicSiderophoreMesophileThermophilePsychrophile Generation time Growth curve GlycolysisFermentation Anaerobic respiration Aerobic respiration Tricarboxylic acid (TCA) cycle or Krebs cycle Oxidative phosphorylation Ubiquinone Glyoxylate pathway

3 3 Bacterial requirements for growth oxygen (or absence)oxygen (or absence) energyenergy nutrientsnutrients optimal temperatureoptimal temperature optimal pHoptimal pH

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

5 5 no oxidative phosphorylation fermentation killed by oxygen lack certain enzymes: superoxide dismutase O H + H 2 O 2 catalase H 2 O 2 H O 2 peroxidase H 2 O 2 + NADH + H + H NAD Obligate anaerobes

6 6 Aerotolerant anaerobes respire anaerobicallyrespire anaerobically not killed by oxygennot killed by oxygen

7 7 Facultative anaerobes fermentationfermentation aerobic respirationaerobic respiration survive in oxygensurvive in oxygen

8 8 Microaerophilic bacteria growgrow –low oxygen killedkilled –high oxygen

9 9 Optimal growth temperature Mesophiles:Mesophiles: –human body temperature * pathogens * opportunists pyschrophilepyschrophile –close to freezing thermophilethermophile –close to boiling

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

11 11 Nutrient Requirements CarbonCarbon NitrogenNitrogen PhosphorusPhosphorus SulfurSulfur Metal ions (e.g. iron)Metal ions (e.g. iron)

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

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

14 14 Measuring viable bacteria colony Colony forming units

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

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

17 17 Generation time time for bacterial mass to doubletime for bacterial mass to double ExampleExample 100 bacteria present at time bacteria present at time 0 If generation time is 2 hr If generation time is 2 hr After 8 hr mass = 100 x 2 4 After 8 hr mass = 100 x 2 4

18 18 SUGAR CATABOLISM GlycolysisGlycolysis –Embden Meyerhof Parnas Pathway –most bacteria –also animals and plants

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

20 20 Glycolysis Glycolysis NADNADH Glucose Pyruvate C6C3 ADPATP

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

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

23 23 Krebs Cycle (C4-C6 intermediate compounds Krebs Cycle (C4-C6 intermediate compounds ) Pyruvate Pyruvate 3CO 2 (C3) NADNADH NADH NAD Oxidative phosphorylation O2 O2O2 O2 H2OH2OH2OH2O ADP ATP (C1)

24 24 Aerobic Respiration = Glycolysis + Krebs Cycle/oxidative phosphorylation Pyruvate to CO 2Pyruvate to CO 2 –NAD to NADH –glycolysis –Krebs cycle Oxidative phosphorylationOxidative phosphorylation – NADH to NAD –ADP to ATP

25 25 Oxidative phosphylation converts O 2 to H 2 0 (oxidative) converts O 2 to H 2 0 (oxidative) converts ADP to ATP (phosphorylation) converts ADP to ATP (phosphorylation) electron transport chain electron transport chain ubiquinones/cytochrome intermediates ubiquinones/cytochrome intermediates

26 26 The Krebs cycle Citrate Isocitrate Alpha-keto glutarate Succinate Fumarate Malate Oxaloacetate Pyruvate -CO 2 Acetate + -CO 2 NADH C2 C C C4 X x C6

27 27 Krebs Cycle - sugar as sole carbon source Pyruvate Acetate -CO 2 C4 Pyruvate + CO 2 + Citrate CC3 Oxalo acetate Oxaloacetate -2CO 2 Aspartic acid Krebscycle ENERGY STORAGE BIOSYNTHESIS C3 C C2 C6 C4 Oxalo acetate X

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

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

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


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