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Dr. Alvin Fox

Nutrition, Growth and Metabolism, Lecture 26

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KEY TERMS Obligate aerobeObligate aerobeObligate anaerobeObligate anaerobeAerotolerant anaerobeAerotolerant anaerobeFacultative anaerobeFacultative anaerobeMicroaerophilicMicroaerophilicSiderophoreSiderophoreMesophileMesophileThermophileThermophilePsychrophilePsychrophileGeneration timeGeneration time

Growth curveGrowth curveGlycolysisGlycolysisFermentationFermentationAnaerobic respirationAnaerobic respirationAerobic respirationAerobic respirationTricarboxylic acid (TCA) Tricarboxylic acid (TCA) cycle or Krebs cyclecycle or Krebs cycleOxidative phosphorylationOxidative phosphorylation UbiquinoneUbiquinoneGlyoxylate pathwayGlyoxylate pathway

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Bacterial requirements for growthBacterial requirements for growth

• oxygen (or absence)oxygen (or absence)• energy energy • nutrientsnutrients• optimal temperatureoptimal temperature• optimal pH optimal pH

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Obligate aerobesObligate aerobes

• grow in presence of oxygengrow in presence of oxygen• no fermentationno fermentation• oxidative phosphorylationoxidative phosphorylation

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• 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

Obligate anaerobesObligate anaerobes

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Aerotolerant anaerobesAerotolerant anaerobes

• respire anaerobicallyrespire anaerobically

• not killed by oxygennot killed by oxygen

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Facultative anaerobesFacultative anaerobes

• fermentation fermentation

• aerobic respirationaerobic respiration

• survive in oxygensurvive in oxygen

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Microaerophilic bacteriaMicroaerophilic bacteria

• grow grow – low oxygenlow oxygen

• killed killed – high oxygenhigh oxygen

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Optimal growth temperature Optimal growth temperature

• Mesophiles: Mesophiles:

– human body temperaturehuman body temperature

* pathogens pathogens

* opportunistsopportunists

• pyschrophilepyschrophile– close to freezing close to freezing

• thermophilethermophile– close to boilingclose to boiling

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pH

• Many grow best at neutral pH

• Some can survive/grow

- acid

- alkali

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Nutrient RequirementsNutrient Requirements

• Carbon Carbon • NitrogenNitrogen• PhosphorusPhosphorus• SulfurSulfur• Metal ions (e.g. iron)Metal ions (e.g. iron)

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Siderophores (S)Siderophores (S)

Fe Fe 2+2+//SS

ReceptorReceptor

Fe Fe 2+2+//SS

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Measuring bacterial mass (live + dead) Measuring bacterial mass (live + dead) in liquid culturein liquid culture

TurbidityTurbidity(Cloudiness)(Cloudiness)

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Measuring viable bacteria

colonycolony

Colony forming unitsColony forming units

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Growth Curve

TURBIDITY(cloudiness)

TIME

Lag

Log

Stationary

Autolysis

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Growth Curve

COLONY FORMING UNITS

TIME

Lag

Log

Stationary

Death

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Generation timeGeneration time

• time for bacterial mass to doubletime for bacterial mass to double

• Example Example

100 bacteria present at time 0 100 bacteria present at time 0

If generation time is 2 hrIf generation time is 2 hr

After 8 hr mass = 100 x 2After 8 hr mass = 100 x 244

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SUGAR CATABOLISM

• Glycolysis Glycolysis – Embden Meyerhof Parnas PathwayEmbden Meyerhof Parnas Pathway

– most bacteriamost bacteria

– also animals and plants also animals and plants

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Other pathways for catabolizing sugars

• Pentose phosphate pathway (hexose Pentose phosphate pathway (hexose monophosphate shunt)monophosphate shunt)– generates NADPHgenerates NADPH– common in plants and animalscommon in plants and animals

• Entner Doudoroff Pathway Entner Doudoroff Pathway – a few bacterial speciesa few bacterial species

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•

GlycolysisGlycolysis

NADNAD NADHNADH

GlucoseGlucose PyruvatePyruvateC6C6 C3C3

ADP ADP ATPATP

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FermentationFermentation

PyruvatePyruvate

(C3)(C3)

NADHNADH NADNAD

Short chain alcoholsShort chain alcohols, , fatty acidsfatty acids(C2-C4)(C2-C4)

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Anaerobic Respiration = Anaerobic Respiration = Glycolysis + FermentationGlycolysis + Fermentation

NADNAD NADHNADH

NADHNADH NADNAD

ATPATP

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Krebs Cycle (C4-C6 intermediate compoundsKrebs Cycle (C4-C6 intermediate compounds)

PyruvatePyruvate 3CO3CO22

(C3)(C3)

NADNAD NADHNADH

NADHNADH NADNAD

Oxidative phosphorylationOxidative phosphorylation

OO22 HH22OO

ADPADP ATPATP

(C1)(C1)

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Aerobic Respiration =Aerobic Respiration =Glycolysis + Glycolysis +

Krebs Cycle/oxidative phosphorylationKrebs Cycle/oxidative phosphorylation

• Pyruvate to COPyruvate to CO22

– NADNAD toto NADHNADH

– glycolysis glycolysis

– Krebs cycleKrebs cycle

• Oxidative phosphorylationOxidative phosphorylation

– NADHNADH to to NAD NAD

– ADPADP to to ATP ATP

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Oxidative phosphylationOxidative phosphylation

• converts Oconverts O22 to H to H220 0 (oxidative)(oxidative)

• converts ADP to ATP converts ADP to ATP (phosphorylation)(phosphorylation)

• electron transport chainelectron transport chain

• ubiquinones/cytochrome intermediates ubiquinones/cytochrome intermediates

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The Krebs cycle

Citrate

Isocitrate

Alpha-keto glutarate

Succinate

Fumarate

Malate

OxaloacetatePyruvate

-CO-CO22

Acetate

+-CO-CO2 2 NADHNADH

-CO-CO2 2 NADHNADH

C2

C

C

C4

X

x

C6

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Krebs Cycle - sugar as sole Krebs Cycle - sugar as sole carbon sourcecarbon source

PyruvatePyruvate

AcetateAcetate-CO-CO22

C4C4

PyruvatePyruvate+ CO+ CO22

+Citrate

CCC3C3

Oxaloacetate

Oxaloacetate

-2CO-2CO22

Aspartic acidAspartic acid

Krebs Krebs cyclecycle

ENERGYSTORAGE

BIOSYNTHESISC3C3

CCC2C2

C6C6C4C4

OxaloacetateX

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Krebs Cycle – fatty acids as Krebs Cycle – fatty acids as sole carbon sourcesole carbon source

Fatty acidsFatty acids

AcetateAcetate

+ CitrateOxaloacetate

-2CO-2CO22

Aspartic acidAspartic acid

Krebs Krebs cyclecycle

ENERGY

BIOSYNTHESIS

Isocitrate Succinate Glyoxylate+

AcetateAcetate+

MalateMalate

Oxaloacetatex

C4

C2

C2

C4C6

-2CO-2CO22

Krebs cycle

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The Glyoxylate and Krebs cycles

Citrate

Isocitrate

Alpha-keto glutarate

Succinate

Fumarate

Glyoxylate

++ AcetateMalate

Oxaloacetate

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Krebs cycle only Glyoxylate cycle onlyKrebs and Glyoxylate cycles

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Krebs CycleKrebs Cycle

– biosyntheticbiosynthetic

– energy storage energy storage

• Removal of intermediatesRemoval of intermediates

– must be replenishedmust be replenished

• Unique enzymatic replenishment pathwaysUnique enzymatic replenishment pathways

– sugars sugars

– fatty acidsfatty acids