Microbe of the WeekMicrobe of the Week

Pseudomonas aeruginosaPseudomonas aeruginosaThe Genus Pseudomonas….The Genus Pseudomonas…. Gram negative obligate free-living Gram negative obligate free-living

aerobic organisms, often in wateraerobic organisms, often in water Can oxidize many organic Can oxidize many organic

compounds to obtain energycompounds to obtain energy Pseudomonas aeruginosaPseudomonas aeruginosa is a is a

human pathogenhuman pathogen

Microbe of the WeekMicrobe of the Week

Pseudomonas aeruginosaPseudomonas aeruginosaAn opportunistic pathogen from the An opportunistic pathogen from the

environment, infecting:environment, infecting: Burn patientsBurn patients Cystic fibrosis patientsCystic fibrosis patients Immuno-compromised patientsImmuno-compromised patients Medically compromised hospitalized patientsMedically compromised hospitalized patients

A naturally antibiotic-resistant organismA naturally antibiotic-resistant organism

Pseudomonas aeruginosaPseudomonas aeruginosaAn opportunistic pathogen from theAn opportunistic pathogen from the

HOT TUB !HOT TUB !

Causing FolliculitsCausing Folliculits

Microbial MetabolismMicrobial MetabolismCellular Respiration and Cellular Respiration and

FermentationFermentation

What happens after glycolysis?What happens after glycolysis?

What happens after glycolysis?What happens after glycolysis? After glucose is broken down to pyruvic After glucose is broken down to pyruvic

acid, pyruvic acid can be channeled into acid, pyruvic acid can be channeled into eithereither Aerobic Respiration Aerobic Respiration OR OR FermentationFermentation

Aerobic respirationAerobic respiration Uses the TCA cycle and electron transport chainUses the TCA cycle and electron transport chain Final electron acceptor is OFinal electron acceptor is O22

Anaerobic respirationAnaerobic respiration Uses the TCA cycle and only PART of the electron Uses the TCA cycle and only PART of the electron

transport chaintransport chain Final electron acceptor is an inorganic molecule other Final electron acceptor is an inorganic molecule other

than Othan O22, like nitrate or sulfate., like nitrate or sulfate.

Aerobic RespirationAerobic Respiration

Tricarboxylic acid (TCA) cycleTricarboxylic acid (TCA) cycle Kreb’s cycle or citric acid cycleKreb’s cycle or citric acid cycle A large amount of potential energy stored in A large amount of potential energy stored in

acetyl CoAacetyl CoA is released by a series of redox is released by a series of redox reactions that transfer electrons to the reactions that transfer electrons to the electron carrier coenzymes (NADelectron carrier coenzymes (NAD++ and FAD) and FAD)

Acetyl CoAAcetyl CoA Where does it come from?Where does it come from? Pyruvic acid, from glycolysis, is converted to Pyruvic acid, from glycolysis, is converted to

a 2-carbon (acetyl group) compound a 2-carbon (acetyl group) compound (decarboxylation)(decarboxylation)

The acetyl group then The acetyl group then combines with combines with Coenzyme A through a Coenzyme A through a high energy bondhigh energy bond

NADNAD++ is reduced to is reduced to NADHNADH

ADP

FADH2

FAD

NADH

NAD+

NADH

NAD+

NAD+

NAD+

Pyruvate

CoA

CoA

CoA

CoA

H2O

CO2

CO2

-ketoglutarate

Succinate

Fumarate

Malate

Oxaloacetate

Isocitrate

NADH

NADH

CO2

Citrate

Acetyl-CoACoA

ATP

PSuccinyl-CoA

CoA

TCA cycleTCA cycle

For every For every molecule of molecule of glucose (2 acetyl glucose (2 acetyl CoA) the TCA CoA) the TCA cycle generatescycle generates 4 CO4 CO22

6 NADH6 NADH 2 FADH2 FADH22

2 ATP2 ATP

Where to now?Where to now?

All the reduced coenzyme electron carriers All the reduced coenzyme electron carriers make their way to the electron transport make their way to the electron transport chainchain 2 NADH from glycolysis2 NADH from glycolysis 2 NADH from pyruvic acid to acetyl CoA 2 NADH from pyruvic acid to acetyl CoA

conversionconversion 6 NADH and 2 FADH6 NADH and 2 FADH22 from the TCA cycle from the TCA cycle

The electron transport chain indirectly The electron transport chain indirectly transfers the energy from these transfers the energy from these coenzymes to ATP coenzymes to ATP

The electron transport chainThe electron transport chain

Sequence of carrier molecules capable of Sequence of carrier molecules capable of oxidation and reductionoxidation and reduction

Electrons are passed down the chain in a Electrons are passed down the chain in a sequential and orderly fashionsequential and orderly fashion

Energy is released from the flow of electrons Energy is released from the flow of electrons down the chaindown the chain

This release of energy is coupled to the This release of energy is coupled to the generation ATP by generation ATP by oxidative phosphorylationoxidative phosphorylation

Membrane location of the ETCMembrane location of the ETC The electron transport chain is located inThe electron transport chain is located in

the inner membrane of the mitochondria of the inner membrane of the mitochondria of eukaryoteseukaryotes

the plasma membrane of prokaryotes the plasma membrane of prokaryotes

The ETC playersThe ETC players Three classes of ETC carrier moleculesThree classes of ETC carrier molecules FlavoproteinsFlavoproteins

Contain a coenzyme derived from riboflavinContain a coenzyme derived from riboflavin Capable of alternating oxidations/reductions Capable of alternating oxidations/reductions Flavin mononucleotide (FMN)Flavin mononucleotide (FMN)

CytochromesCytochromes Have an iron-containing group (heme) which Have an iron-containing group (heme) which

can exist in alternating reduced (Fecan exist in alternating reduced (Fe2+2+) and ) and oxidized (Feoxidized (Fe3+3+) forms) forms

Coenzyme Q (Ubiquinone) Coenzyme Q (Ubiquinone) Small non protein carrier moleculeSmall non protein carrier molecule

Are all ETCs the same?Are all ETCs the same? Bacterial electron transport chains are Bacterial electron transport chains are

diversediverse Particular carriers and their orderParticular carriers and their order

Some bacteria may have several types of Some bacteria may have several types of electron transport chainselectron transport chains

Eukaryotic electron transport chain is more Eukaryotic electron transport chain is more unified and better describedunified and better described

All have the same goal to capture energy All have the same goal to capture energy into ATP into ATP

The mitochondrial ETCThe mitochondrial ETC The enzyme complex NADH dehydrogenase starts the The enzyme complex NADH dehydrogenase starts the

process by dehydrogenating NADH and transferring its process by dehydrogenating NADH and transferring its high energy electrons to its coenzyme FMN high energy electrons to its coenzyme FMN

In turn the electrons are transferred down the chain from In turn the electrons are transferred down the chain from FMN to Q to cytochrome bFMN to Q to cytochrome b

Electrons are then Electrons are then passed from passed from cytochrome b to ccytochrome b to c11

to c to a and ato c to a and a33 with with

each cytochrome each cytochrome reduced as it gains reduced as it gains electrons and electrons and oxidized as it loses oxidized as it loses electronselectrons

OO22, the terminal electron acceptor, the terminal electron acceptor Finally, cytochrome aFinally, cytochrome a33 passes its electrons passes its electrons

to Oto O22 which picks up protons to form H which picks up protons to form H22OO

How is ATP generated?How is ATP generated?

Electron transfer down the chain is accompanied Electron transfer down the chain is accompanied at several points by the active pumping of protons at several points by the active pumping of protons across the inner mitochondrial membraneacross the inner mitochondrial membrane

This transfer of protons is used to generate ATP This transfer of protons is used to generate ATP by by chemiosmosis chemiosmosis as the protons move back as the protons move back across the membraneacross the membrane

The ETC sets up a proton gradientThe ETC sets up a proton gradient As energetic electrons are passed down the ETC some As energetic electrons are passed down the ETC some

carriers (proton pumps) actively pump Hcarriers (proton pumps) actively pump H++ across the across the membrane.membrane.

Proton motive force results from an excess of protons Proton motive force results from an excess of protons on one side of the membraneon one side of the membrane

Generation of ATP by chemiosmosisGeneration of ATP by chemiosmosis Protons can only diffuse back along the gradient Protons can only diffuse back along the gradient

through special protein channels that contain the through special protein channels that contain the enzyme ATP synthase (Fenzyme ATP synthase (Foo).).

ATP synthase (FATP synthase (Foo) uses ) uses the energy released by the energy released by the diffusion of Hthe diffusion of H++ across across the membrane to the membrane to synthesize ATP from synthesize ATP from ADPADP

ETC drives chemiosmosisETC drives chemiosmosis

NADH 3 ATP NADH 3 ATP

FADHFADH22 2 ATP 2 ATP

Aerobic RespirationAerobic Respiration Complete oxidation of 1 Complete oxidation of 1

glucose molecule glucose molecule generates generates 38 ATP38 ATP in in prokaryotesprokaryotes

2 from each of glycolysis 2 from each of glycolysis and 2 from the TCA cycle and 2 from the TCA cycle by substrate level by substrate level phosphorylationphosphorylation

34 from oxidative 34 from oxidative phosphorylation as a phosphorylation as a result of 10 NADH and 2 result of 10 NADH and 2 FADHFADH22 from glycolysis and from glycolysis and the TCA cyclethe TCA cycle

Anaerobic RespirationAnaerobic Respiration Like aerobic respiration, it involves glycolysis, the Like aerobic respiration, it involves glycolysis, the

TCA cycle and an electron transport chain…. but,TCA cycle and an electron transport chain…. but, The final electron acceptor is an inorganic molecule other The final electron acceptor is an inorganic molecule other

than Othan O22

Some bacteria use NOSome bacteria use NO33-- and produce either NO and produce either NO22

--, N, N22O or NO or N2 2

((PseudomonasPseudomonas and and BacillusBacillus)) DesulfovibrioDesulfovibrio use SO use SO44

2- 2- to form Hto form H22SS Methanogens use carbonate to form methaneMethanogens use carbonate to form methane

The amount of ATP generated varies with the pathwayThe amount of ATP generated varies with the pathway Only part of the TCA cycle operates under anaerobic conditionsOnly part of the TCA cycle operates under anaerobic conditions Not all ETC carriers participate in anaerobic respirationNot all ETC carriers participate in anaerobic respiration ATP yield never as high as aerobic respirationATP yield never as high as aerobic respiration

FermentationFermentation Uses Glycolysis but does not use the TCA cycle Uses Glycolysis but does not use the TCA cycle

or Electron Transport Chainor Electron Transport Chain Releases energy from sugars or other organic Releases energy from sugars or other organic

molecules, but only 2 ATP for each glucosemolecules, but only 2 ATP for each glucose Does not use ODoes not use O2 o 2 o or inorganic electron acceptorsor inorganic electron acceptors Uses an organic molecule as the final electron Uses an organic molecule as the final electron

acceptoracceptor Produces only small amounts of ATP and most of Produces only small amounts of ATP and most of

the energy remains in the organic end productthe energy remains in the organic end product

In fermentation, pyruvic acid or its In fermentation, pyruvic acid or its derivatives are reduced by NADH to derivatives are reduced by NADH to fermentation end productsfermentation end products

Ensures recycling of NADEnsures recycling of NAD++ for glycolysis for glycolysis

FermentationFermentation

Why bother with fermentation?Why bother with fermentation? Fermenting bacteria can grow as fast as Fermenting bacteria can grow as fast as

those using aerobic respiration by those using aerobic respiration by markedly increasing the rate of glycolysismarkedly increasing the rate of glycolysis

Fermentation permits independence from Fermentation permits independence from molecular oxygen and allows colonization molecular oxygen and allows colonization of anaerobic environmentsof anaerobic environments

Types of fermentationTypes of fermentation

HomolacticHomolactic Only lactic acidOnly lactic acid StreptococcusStreptococcus and and

LactobacillusLactobacillus

HeterolacticHeterolactic Mixture of lactic acid, Mixture of lactic acid,

acetic acid and COacetic acid and CO22

Can result in food Can result in food spoilagespoilage

Can produceCan produce Yogurt Yogurt Sauerkraut Sauerkraut Pickles Pickles

Acid FermentationAcid Fermentation

Bring on the good stuffBring on the good stuff

Alcohol fermentation by the yeast Alcohol fermentation by the yeast SaccharomycesSaccharomyces is responsible for some of is responsible for some of the better things in lifethe better things in life

COCO22 produced causes bread to rise produced causes bread to rise

Ethanol is used in alcoholic beverages Ethanol is used in alcoholic beverages

End products of fermentationEnd products of fermentation

Metabolic pathways of Energy UseMetabolic pathways of Energy Use

The complete oxidation of glucose to COThe complete oxidation of glucose to CO22

and Hand H22O is considered an efficient processO is considered an efficient process But, 45% of the energy from glucose is But, 45% of the energy from glucose is

lost as heatlost as heat Cells use the remaining energy (in ATP) in Cells use the remaining energy (in ATP) in

a variety of waysa variety of ways E.g., active transport of molecules across E.g., active transport of molecules across

membrane or flagella motionmembrane or flagella motion Most is used for the production of new cellular Most is used for the production of new cellular

componentscomponents

Integration of metabolic pathwaysIntegration of metabolic pathways Carbohydrate catabolic pathways are central to Carbohydrate catabolic pathways are central to

the supply of cellular energy the supply of cellular energy

However, rather than being dead end pathways, However, rather than being dead end pathways, several intermediates in these pathways can be several intermediates in these pathways can be diverted into anabolic pathwaysdiverted into anabolic pathways

This allows the cell to derive maximum benefit This allows the cell to derive maximum benefit from all nutrients and their metabolitesfrom all nutrients and their metabolites

Amphibolic PathwaysAmphibolic Pathways-integration of catabolic -integration of catabolic and anabolic pathways to improve cell efficiencyand anabolic pathways to improve cell efficiency

Amphibolic view of metabolismAmphibolic view of metabolism

GlycolysisGlycolysis

glyceraldehyde-glyceraldehyde-3-phosphate3-phosphate

pyruvatepyruvateTCA cycleTCA cycle

acetyl-CoAacetyl-CoA oxaloacetic acidoxaloacetic acid αα-ketoglutaric -ketoglutaric

acidacid