Dr. Alvin Fox

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Nutrition, Growth and Metabolism, Lecture 26
Dr. Alvin Fox
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KEY TERMS
Obligate aerobe Obligate anaerobe Aerotolerant
anaerobe Facultative anaerobe Microaerophilic Side
rophore Mesophile Thermophile Psychrophile Generat
ion time
Growth curve Glycolysis Fermentation Anaerobic
respiration Aerobic respiration Tricarboxylic
acid (TCA) cycle or Krebs cycle Oxidative
phosphorylation Ubiquinone Glyoxylate pathway

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Bacterial requirements for growth

• oxygen (or absence)
• energy
• nutrients
• optimal temperature
• optimal pH

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Obligate aerobes

• grow in presence of oxygen
• no fermentation
• oxidative phosphorylation

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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

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Aerotolerant anaerobes

• respire anaerobically
• not killed by oxygen

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Facultative anaerobes

• fermentation
• aerobic respiration
• survive in oxygen

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Microaerophilic bacteria

• grow
• low oxygen
• killed
• high oxygen

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Optimal growth temperature

• Mesophiles
• human body temperature
• pathogens
• opportunists
• pyschrophile
• close to freezing
• thermophile
• close to boiling

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pH

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

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Nutrient Requirements

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

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Siderophores (S)
Receptor
Fe 2/S
Fe 2/S
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Measuring bacterial mass (live dead) in liquid
culture
Turbidity (Cloudiness)
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Measuring viable bacteria
Colony forming units
colony
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Growth Curve
Stationary
TURBIDITY (cloudiness)
Autolysis
Log
Lag
TIME
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Growth Curve
Stationary
COLONY FORMING UNITS
Death
Log
Lag
TIME
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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

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SUGAR CATABOLISM

• Glycolysis
• Embden Meyerhof Parnas Pathway
• most bacteria
• also animals and plants

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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

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Glycolysis
NAD
NADH
Glucose
Pyruvate
C6
C3
ADP
ATP

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Fermentation

NADH
NAD
Pyruvate
Short chain alcohols, fatty acids
(C3)
(C2-C4)
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Anaerobic Respiration Glycolysis Fermentation
NAD
NADH
ATP
NAD
NADH
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Krebs Cycle (C4-C6 intermediate compounds)
NAD
NADH
3CO2
Pyruvate
(C3)
(C1)
Oxidative phosphorylation
NADH
NAD
O2
H2O
ADP
ATP
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Aerobic Respiration Glycolysis Krebs
Cycle/oxidative phosphorylation

• Pyruvate to CO2
  
  
• NAD to NADH
• glycolysis
• Krebs cycle
• Oxidative phosphorylation
• NADH to NAD
• ADP to ATP

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Oxidative phosphylation

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

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The Krebs cycle
X
C
Isocitrate
C2
Acetate
-CO2 NADH
C6
Citrate

-CO2
Alpha-keto glutarate
C4
Oxaloacetate
Pyruvate
-CO2 NADH
x
C
Succinate
Malate
Fumarate
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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
C4
C
C3
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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
C4
C6
Malate
C4
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The Glyoxylate and Krebs cycles
Isocitrate
Citrate
1
Alpha-keto glutarate
Glyoxylate
Oxaloacetate
2
Acetate
Succinate
Malate
Fumarate
Krebs and Glyoxylate cycles
Krebs cycle only
Glyoxylate cycle only
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• Krebs Cycle
• biosynthetic
• energy storage
• Removal of intermediates
• must be replenished
• Unique enzymatic replenishment pathways
• sugars
• fatty acids