Nutrition, Growth and Metabolism Lecture 34 Dr. Alvin Fox
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
Bacterial requirements for growth • oxygen (or absence) • energy • nutrients • optimal temperature • optimal pH
Obligate aerobes • grow in presence of oxygen • no fermentation • oxidative phosphorylation
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+ 2H20 + NAD
Aerotolerant anaerobes • respire anaerobically • not killed by oxygen
Facultative anaerobes • fermentation • aerobic respiration • survive in oxygen
Microaerophilic bacteria • grow • low oxygen • killed • high oxygen
Optimal growth temperature • Mesophiles: • human body temperature • pathogens • opportunists • pyschrophile • close to freezing • thermophile • close to boiling
pH • Many grow best at neutral pH • Some can survive/grow • - acid • - alkali
Nutrient Requirements • Carbon • Nitrogen • Phosphorus • Sulfur • Metal ions (e.g. iron)
Siderophores (S) Receptor Fe 2+/S Fe 2+/S
Measuring bacterial mass (live + dead) in liquid culture Turbidity (Cloudiness)
Measuring viable bacteria Colony forming units colony
Growth Curve Stationary COLONY FORMING UNITS Death Log Lag TIME
Growth Curve Stationary TURBIDITY (cloudiness) Autolysis Log Lag TIME
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
SUGAR CATABOLISM • Glycolysis • Embden Meyerhof Parnas Pathway • most bacteria • also animals and plants
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
Glycolysis NAD NADH Glucose Pyruvate C6 C3 ADP ATP
Fermentation NADH NAD Pyruvate Short chain alcohols, fatty acids (C3) (C2-C4)
Anaerobic Respiration = Glycolysis + Fermentation NAD NADH ATP NAD NADH
Krebs Cycle (C4-C6 intermediate compounds) NAD NADH 3CO2 Pyruvate (C3) (C1) Oxidative phosphorylation NADH NAD O2 H2O ADP ATP
Aerobic Respiration =Glycolysis + Krebs Cycle/oxidative phosphorylation • Pyruvate to CO2 • NADtoNADH • glycolysis • Krebs cycle • Oxidative phosphorylation • NADHto NAD • ADPto ATP
Oxidative phosphylation • converts O2 to H20 (oxidative) • converts ADP to ATP (phosphorylation) • electron transport chain • ubiquinones/cytochrome intermediates
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
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
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
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
Krebs Cycle • biosynthetic • energy storage • Removal of intermediates • must be replenished • Unique enzymatic replenishment pathways • sugars • fatty acids
