Transcript Nutrition
Nutrition, Growth and Metabolism, Lecture 26 Dr. Alvin Fox 1 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 2 Bacterial requirements for growth • • • • • oxygen (or absence) energy nutrients optimal temperature optimal pH 3 Obligate aerobes • grow in presence of oxygen • no fermentation • oxidative phosphorylation 4 • • • • 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 5 Aerotolerant anaerobes • respire anaerobically • not killed by oxygen 6 Facultative anaerobes • fermentation • aerobic respiration • survive in oxygen 7 Microaerophilic bacteria • grow – low oxygen • killed – high oxygen 8 Optimal growth temperature • Mesophiles: – human body temperature * pathogens * opportunists • pyschrophile – close to freezing • thermophile – close to boiling 9 pH • Many grow best at neutral pH • Some can survive/grow - acid - alkali 10 Nutrient Requirements • • • • • Carbon Nitrogen Phosphorus Sulfur Metal ions (e.g. iron) 11 Siderophores (S) Receptor Fe 2+/S Fe 2+/S 12 Measuring bacterial mass (live + dead) in liquid culture Turbidity (Cloudiness) 13 Measuring viable bacteria Colony forming units colony 14 Growth Curve Stationary TURBIDITY (cloudiness) Autolysis Log Lag TIME 15 Growth Curve Stationary COLONY FORMING UNITS Death Log Lag TIME 16 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 17 SUGAR CATABOLISM • Glycolysis – Embden Meyerhof Parnas Pathway – most bacteria – also animals and plants 18 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 19 Glycolysis NAD NADH Glucose Pyruvate C6 C3 ADP ATP 20 Fermentation NADH Pyruvate NAD Short chain alcohols, fatty acids (C3) (C2-C4) 21 Anaerobic Respiration = Glycolysis + Fermentation NAD NADH ATP NADH NAD 22 Krebs Cycle (C4-C6 intermediate compounds) NAD Pyruvate NADH 3CO2 (C3) (C1) Oxidative phosphorylation NADH NAD O2 H2O ADP ATP 23 Aerobic Respiration = Glycolysis + Krebs Cycle/oxidative phosphorylation • Pyruvate to CO2 – NAD to NADH – glycolysis – Krebs cycle • Oxidative phosphorylation – NADH to NAD – ADP to ATP 24 Oxidative phosphylation • converts O2 to H20 (oxidative) • converts ADP to ATP (phosphorylation) • electron transport chain • ubiquinones/cytochrome intermediates 25 The Krebs cycle -CO2 C2 Acetate Citrate Isocitrate C6 + C X -CO2 NADH Alpha-keto glutarate Oxaloacetate C4 -CO2 NADH Pyruvate x Succinate C Malate Fumarate 26 Krebs Cycle - sugar as sole carbon source -CO2 Pyruvate C3 C Acetate + Oxalo C2 C4 acetate X + CO2 Pyruvate C3 C Citrate C6 -2CO2 BIOSYNTHESIS Oxalo acetate Krebs cycle ENERGY STORAGE Aspartic acid Oxaloacetate C4 27 Krebs Cycle – fatty acids as sole carbon source ENERGY Acetate + Oxalo acetate BIOSYNTHESIS Fatty acids x Oxalo acetate Krebs cycle Citrate -2CO2 Aspartic acid C2 Isocitrate Succinate + Glyoxylate -2CO2 C6 Krebs cycle C2 + Acetate C4 Malate 28 C4 The Glyoxylate and Krebs cycles Isocitrate Citrate Oxaloacetate Malate 1 Glyoxylate 2 + Acetate Alpha-keto glutarate Succinate Fumarate Krebs and Glyoxylate cycles Krebs cycle only Glyoxylate cycle only 29 Krebs Cycle – biosynthetic – energy storage • Removal of intermediates – must be replenished • Unique enzymatic replenishment pathways – sugars – fatty acids 30