Microbe of the Week Microbe of the Week Pseudomonas aeruginosa The Genus Pseudomonas…. Gram negative obligate free-living aerobic organisms, often in water Gram negative obligate free-living aerobic organisms, often in water Can oxidize many organic compounds to obtain energy Can oxidize many organic compounds to obtain energy Pseudomonas aeruginosa is a human pathogen Pseudomonas aeruginosa is a human pathogen

Microbe of the Week Microbe of the Week Pseudomonas aeruginosa An opportunistic pathogen from the environment, infecting: Burn patients Burn patients Cystic fibrosis patients Cystic fibrosis patients Immuno-compromised patients Immuno-compromised patients Medically compromised hospitalized patients Medically compromised hospitalized patients A naturally antibiotic-resistant organism

Pseudomonas aeruginosa An opportunistic pathogen from the HOT TUB ! Causing Folliculits

Microbial Metabolism Cellular Respiration and Fermentation

What happens after glycolysis?

After glucose is broken down to pyruvic acid, pyruvic acid can be channeled into either After glucose is broken down to pyruvic acid, pyruvic acid can be channeled into either Aerobic Respiration OR Fermentation Aerobic Respiration OR Fermentation Aerobic respiration Aerobic respiration Uses the TCA cycle and electron transport chain Uses the TCA cycle and electron transport chain Final electron acceptor is O 2 Final electron acceptor is O 2 Anaerobic respiration Anaerobic respiration Uses the TCA cycle and only PART of the electron transport chain Uses the TCA cycle and only PART of the electron transport chain Final electron acceptor is an inorganic molecule other than O 2, like nitrate or sulfate. Final electron acceptor is an inorganic molecule other than O 2, like nitrate or sulfate.

Aerobic Respiration Tricarboxylic acid (TCA) cycle Tricarboxylic acid (TCA) cycle Kreb’s cycle or citric acid cycle Kreb’s cycle or citric acid cycle A large amount of potential energy stored in acetyl CoA is released by a series of redox reactions that transfer electrons to the electron carrier coenzymes (NAD + and FAD) A large amount of potential energy stored in acetyl CoA is released by a series of redox reactions that transfer electrons to the electron carrier coenzymes (NAD + and FAD)

Acetyl CoA Where does it come from? Where does it come from? Pyruvic acid, from glycolysis, is converted to a 2-carbon (acetyl group) compound (decarboxylation) Pyruvic acid, from glycolysis, is converted to a 2-carbon (acetyl group) compound (decarboxylation) The acetyl group then combines with Coenzyme A through a high energy bond The acetyl group then combines with Coenzyme A through a high energy bond NAD + is reduced to NADH NAD + is reduced to NADH

ADP FADH 2 FAD NADH NAD + NADH NAD + Pyruvate CoA H2OH2O CO 2 CO 2  -ketoglutarate Succinate Fumarate Malate Oxaloacetate Isocitrate NADH CO 2 Citrate Acetyl-CoA CoA ATP P Succinyl-CoA CoA TCA cycle For every molecule of glucose (2 acetyl CoA) the TCA cycle generates For every molecule of glucose (2 acetyl CoA) the TCA cycle generates 4 CO 2 4 CO 2 6 NADH 6 NADH 2 FADH 2 2 FADH 2 2 ATP 2 ATP

Where to now? All the reduced coenzyme electron carriers make their way to the electron transport chain All the reduced coenzyme electron carriers make their way to the electron transport chain 2 NADH from glycolysis 2 NADH from glycolysis 2 NADH from pyruvic acid to acetyl CoA conversion 2 NADH from pyruvic acid to acetyl CoA conversion 6 NADH and 2 FADH 2 from the TCA cycle 6 NADH and 2 FADH 2 from the TCA cycle The electron transport chain indirectly transfers the energy from these coenzymes to ATP The electron transport chain indirectly transfers the energy from these coenzymes to ATP

The electron transport chain Sequence of carrier molecules capable of oxidation and reduction Sequence of carrier molecules capable of oxidation and reduction Electrons are passed down the chain in a sequential and orderly fashion Electrons are passed down the chain in a sequential and orderly fashion Energy is released from the flow of electrons down the chain Energy is released from the flow of electrons down the chain This release of energy is coupled to the generation ATP by oxidative phosphorylation This release of energy is coupled to the generation ATP by oxidative phosphorylation

Membrane location of the ETC The electron transport chain is located in The electron transport chain is located in the inner membrane of the mitochondria of eukaryotes the inner membrane of the mitochondria of eukaryotes the plasma membrane of prokaryotes the plasma membrane of prokaryotes

The ETC players Three classes of ETC carrier molecules Three classes of ETC carrier molecules Flavoproteins Flavoproteins Contain a coenzyme derived from riboflavin Contain a coenzyme derived from riboflavin Capable of alternating oxidations/reductions Capable of alternating oxidations/reductions Flavin mononucleotide (FMN) Flavin mononucleotide (FMN) Cytochromes Cytochromes Have an iron-containing group (heme) which can exist in alternating reduced (Fe 2+ ) and oxidized (Fe 3+ ) forms Have an iron-containing group (heme) which can exist in alternating reduced (Fe 2+ ) and oxidized (Fe 3+ ) forms Coenzyme Q (Ubiquinone) Coenzyme Q (Ubiquinone) Small non protein carrier molecule Small non protein carrier molecule

Are all ETCs the same? Bacterial electron transport chains are diverse Bacterial electron transport chains are diverse Particular carriers and their order Particular carriers and their order Some bacteria may have several types of electron transport chains Some bacteria may have several types of electron transport chains Eukaryotic electron transport chain is more unified and better described Eukaryotic electron transport chain is more unified and better described All have the same goal to capture energy into ATP All have the same goal to capture energy into ATP

The mitochondrial ETC The enzyme complex NADH dehydrogenase starts the process by dehydrogenating NADH and transferring its high energy electrons to its coenzyme FMN The enzyme complex NADH dehydrogenase starts the process by dehydrogenating NADH and transferring its high energy electrons to its coenzyme FMN In turn the electrons are transferred down the chain from FMN to Q to cytochrome b In turn the electrons are transferred down the chain from FMN to Q to cytochrome b Electrons are then passed from cytochrome b to c 1 to c to a and a 3 with each cytochrome reduced as it gains electrons and oxidized as it loses electrons Electrons are then passed from cytochrome b to c 1 to c to a and a 3 with each cytochrome reduced as it gains electrons and oxidized as it loses electrons

O 2, the terminal electron acceptor Finally, cytochrome a 3 passes its electrons to O 2 which picks up protons to form H 2 O Finally, cytochrome a 3 passes its electrons to O 2 which picks up protons to form H 2 O

How is ATP generated? Electron transfer down the chain is accompanied at several points by the active pumping of protons across the inner mitochondrial membrane Electron transfer down the chain is accompanied at several points by the active pumping of protons across the inner mitochondrial membrane This transfer of protons is used to generate ATP by chemiosmosis as the protons move back across the membrane This transfer of protons is used to generate ATP by chemiosmosis as the protons move back across the membrane

The ETC sets up a proton gradient As energetic electrons are passed down the ETC some carriers (proton pumps) actively pump H + across the membrane. As energetic electrons are passed down the ETC some carriers (proton pumps) actively pump H + across the membrane. Proton motive force results from an excess of protons on one side of the membrane Proton motive force results from an excess of protons on one side of the membrane

Generation of ATP by chemiosmosis Protons can only diffuse back along the gradient through special protein channels that contain the enzyme ATP synthase (F o ). Protons can only diffuse back along the gradient through special protein channels that contain the enzyme ATP synthase (F o ). ATP synthase (F o ) uses the energy released by the diffusion of H + across the membrane to synthesize ATP from ADP ATP synthase (F o ) uses the energy released by the diffusion of H + across the membrane to synthesize ATP from ADP

ETC drives chemiosmosis NADH 3 ATP FADH 2 2 ATP

Aerobic Respiration Complete oxidation of 1 glucose molecule generates 38 ATP in prokaryotes Complete oxidation of 1 glucose molecule generates 38 ATP in prokaryotes 2 from each of glycolysis and 2 from the TCA cycle by substrate level phosphorylation 2 from each of glycolysis and 2 from the TCA cycle by substrate level phosphorylation 34 from oxidative phosphorylation as a result of 10 NADH and 2 FADH 2 from glycolysis and the TCA cycle 34 from oxidative phosphorylation as a result of 10 NADH and 2 FADH 2 from glycolysis and the TCA cycle

Anaerobic Respiration Like aerobic respiration, it involves glycolysis, the TCA cycle and an electron transport chain…. but, Like aerobic respiration, it involves glycolysis, the TCA cycle and an electron transport chain…. but, The final electron acceptor is an inorganic molecule other than O 2 The final electron acceptor is an inorganic molecule other than O 2 Some bacteria use NO 3 - and produce either NO 2 -, N 2 O or N 2 (Pseudomonas and Bacillus) Some bacteria use NO 3 - and produce either NO 2 -, N 2 O or N 2 (Pseudomonas and Bacillus) Desulfovibrio use SO 4 2- to form H 2 S Desulfovibrio use SO 4 2- to form H 2 S Methanogens use carbonate to form methane Methanogens use carbonate to form methane The amount of ATP generated varies with the pathway The amount of ATP generated varies with the pathway Only part of the TCA cycle operates under anaerobic conditions Only part of the TCA cycle operates under anaerobic conditions Not all ETC carriers participate in anaerobic respiration Not all ETC carriers participate in anaerobic respiration ATP yield never as high as aerobic respiration ATP yield never as high as aerobic respiration

Fermentation Uses Glycolysis but does not use the TCA cycle or Electron Transport Chain Uses Glycolysis but does not use the TCA cycle or Electron Transport Chain Releases energy from sugars or other organic molecules, but only 2 ATP for each glucose Releases energy from sugars or other organic molecules, but only 2 ATP for each glucose Does not use O 2 o or inorganic electron acceptors Does not use O 2 o or inorganic electron acceptors Uses an organic molecule as the final electron acceptor Uses an organic molecule as the final electron acceptor Produces only small amounts of ATP and most of the energy remains in the organic end product Produces only small amounts of ATP and most of the energy remains in the organic end product

In fermentation, pyruvic acid or its derivatives are reduced by NADH to fermentation end products In fermentation, pyruvic acid or its derivatives are reduced by NADH to fermentation end products Ensures recycling of NAD + for glycolysis Ensures recycling of NAD + for glycolysis Fermentation

Why bother with fermentation? Fermenting bacteria can grow as fast as those using aerobic respiration by markedly increasing the rate of glycolysis Fermenting bacteria can grow as fast as those using aerobic respiration by markedly increasing the rate of glycolysis Fermentation permits independence from molecular oxygen and allows colonization of anaerobic environments Fermentation permits independence from molecular oxygen and allows colonization of anaerobic environments

Types of fermentation Homolactic Only lactic acid Only lactic acid Streptococcus and Lactobacillus Streptococcus and LactobacillusHeterolactic Mixture of lactic acid, acetic acid and CO 2 Mixture of lactic acid, acetic acid and CO 2 Can result in food spoilage Can result in food spoilage Can produce Can produce Yogurt Yogurt Sauerkraut Sauerkraut Pickles Pickles Acid Fermentation

Bring on the good stuff Alcohol fermentation by the yeast Saccharomyces is responsible for some of the better things in life Alcohol fermentation by the yeast Saccharomyces is responsible for some of the better things in life CO 2 produced causes bread to rise CO 2 produced causes bread to rise Ethanol is used in alcoholic beverages Ethanol is used in alcoholic beverages

End products of fermentation

Metabolic pathways of Energy Use The complete oxidation of glucose to CO 2 and H 2 O is considered an efficient process The complete oxidation of glucose to CO 2 and H 2 O is considered an efficient process But, 45% of the energy from glucose is lost as heat But, 45% of the energy from glucose is lost as heat Cells use the remaining energy (in ATP) in a variety of ways Cells use the remaining energy (in ATP) in a variety of ways E.g., active transport of molecules across membrane or flagella motion E.g., active transport of molecules across membrane or flagella motion Most is used for the production of new cellular components Most is used for the production of new cellular components

Integration of metabolic pathways Carbohydrate catabolic pathways are central to the supply of cellular energy Carbohydrate catabolic pathways are central to the supply of cellular energy However, rather than being dead end pathways, several intermediates in these pathways can be diverted into anabolic pathways However, rather than being dead end pathways, several intermediates in these pathways can be diverted into anabolic pathways This allows the cell to derive maximum benefit from all nutrients and their metabolites This allows the cell to derive maximum benefit from all nutrients and their metabolites Amphibolic Pathways-integration of catabolic and anabolic pathways to improve cell efficiency Amphibolic Pathways-integration of catabolic and anabolic pathways to improve cell efficiency

Amphibolic view of metabolism Glycolysis glyceraldehyde- 3-phosphate glyceraldehyde- 3-phosphate pyruvate pyruvate TCA cycle acetyl-CoA acetyl-CoA oxaloacetic acid oxaloacetic acid α-ketoglutaric acid α-ketoglutaric acid