Nutrition, Growth And Metabolism

Nutrition, Growth and Metabolism

Dr. Alvin Fox

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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

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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+ 2H20 + 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 10

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

COLONY FORMING UNITS

Death

Log

Lag

TIME 15

Growth Curve Stationary

TURBIDITY (cloudiness)

Autolysis

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

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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 19

Glycolysis NAD

Glucose

NADH

Pyruvate

C6

C3 ADP

ATP

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Fermentation NADH

Pyruvate

NAD

Short chain alcohols, fatty acids

(C3)

(C2-C4)

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Anaerobic Respiration = Glycolysis + Fermentation NAD

NADH

ATP NADH

NAD

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Krebs Cycle (C4-C6 intermediate compounds) NAD

Pyruvate (C3)

NADH 3CO2 (C1)

Oxidative phosphorylation NADH

O2 ADP

NAD

H2O

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

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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

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Krebs Cycle - sugar as sole carbon source Krebs -CO2

Pyruvate C3

C

Acetate + Oxalo C2 C4 acetate

X

Pyruvate C3

+ CO2

C

Citrate

-2CO2

BIOSYNTHESIS Oxalo acetate

cycle

ENERGY STORAGE Aspartic acid

Oxaloacetate C4 27

C6

Krebs Cycle – fatty acids as sole carbon source ENERGY

Acetate + Oxalo Fatty acids acetate BIOSYNTHESIS

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

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