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Dr. Alvin Fox

Nutrition, Growth and Metabolism


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

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


Bacterial requirements for growthBacterial requirements for growth

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


Obligate aerobesObligate aerobes

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


• no oxidative phosphorylation• fermentation• killed by oxygen• lack certain enzymes:

superoxide dismutase O2

-+2H+ H2O2

catalase H2O2 H20 + O2

peroxidase H2O2 H20 /NAD NADH

Obligate anaerobesObligate anaerobes


Aerotolerant anaerobesAerotolerant anaerobes

• respire anaerobicallyrespire anaerobically

• not killed by oxygennot killed by oxygen


Facultative anaerobesFacultative anaerobes

• fermentation fermentation

• aerobic respirationaerobic respiration

• survive in oxygensurvive in oxygen


Microaerophilic bacteriaMicroaerophilic bacteria

• grow grow – low oxygenlow oxygen

• killed killed – high oxygenhigh oxygen


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


pH

• Many grow best at neutral pH

• Some can survive/grow

- acid

- alkali


Nutrient RequirementsNutrient Requirements

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


Siderophores (S)Siderophores (S)

Fe Fe 2+2+//SS

ReceptorReceptor

Fe Fe 2+2+//SS


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

TurbidityTurbidity(Cloudiness)(Cloudiness)


Measuring viable bacteria

colonycolony

Colony forming unitsColony forming units


Growth Curve

COLONY FORMING UNITS

TIME

Lag

Log

Stationary

Death


Growth Curve

TURBIDITY(cloudiness)

TIME

Lag

Log

Stationary

Autolysis


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


SUGAR CATABOLISM

• Glycolysis Glycolysis – Embden Meyerhof Parnas PathwayEmbden Meyerhof Parnas Pathway

– most bacteriamost bacteria

– also animals and plants also animals and plants


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


•

GlycolysisGlycolysis

NADNAD NADHNADH

GlucoseGlucose PyruvatePyruvateC6C6 C3C3

ADP ADP ATPATP


FermentationFermentation

PyruvatePyruvate

(C3)(C3)

NADHNADH NADNAD

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


Anaerobic Respiration = Anaerobic Respiration = Glycolysis + FermentationGlycolysis + Fermentation

NADNAD NADHNADH

NADHNADH NADNAD

ATPATP


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)


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


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


The Krebs cycle

Citrate

Isocitrate

Alpha-keto glutarate

Succinate

Fumarate

Malate

Oxaloacetate

Pyruvate

-CO-CO22

Acetate

+-CO-CO2 2 NADHNADH

-CO-CO2 2 NADHNADH

C2

C

C

C4

X

x

C6


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


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


The Glyoxylate and Krebs cycles

Citrate

Isocitrate

Alpha-keto glutarate

Succinate

Fumarate

Glyoxylate

AcetateMalate

Oxaloacetate

1

2


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

Education

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