Title: Microbial Metabolism Title: What is the title of ...c141).pdfthe Embden-Meyerhof Pathway –Alternate Pathway •Pentose Phosphate Pathway •Entner-Doudoroff Pathway •Biologists

Title: What is the title of this lecture?

Speaker: Amit Dhingra

Created by: (remove if same as speaker)

online.wsu.edu

Title: Microbial Metabolism

Instructor: Consetta Helmick

Microbial Metabolism

• Microbial Metabolism

– Aerobic Cellular Respiration or in bacteria called the Embden-Meyerhof Pathway

– Alternate Pathway

• Pentose Phosphate Pathway

• Entner-Doudoroff Pathway

• Biologists had noticed that in vats of grape juice, alcohol and CO2 are produced while yeast cells increase in number– In 1850s, Louis Pasteur set out to prove

• Simplified setup: clear solution of sugar, ammonia, mineral salts, trace elements

• Added a few yeast cells—as they grew, sugar decreased, alcohol level increased

• Strongly supported idea, but Pasteur failed to extract something from inside the cells that would convert sugar

– In 1897, Eduard Buchner, a German chemist, showed that crushed yeast cells could convert sugar to ethanol and CO2; awarded Nobel Prize in 1907

A Glimpse of History

• All cells need to accomplish two fundamental tasks

– Synthesize new parts

• Cell walls, membranes, ribosomes, nucleic acids

– Harvest energy to power reactions

– Sum total of these is called metabolism

– Human implications

• Used to make biofuels

• Used to produce food

• Important in laboratory

• Invaluable models for study

• Unique pathways potentialdrug targets

Microbial Metabolism

• Can separate metabolism into two parts– Catabolism

• Processes that degrade compounds to release energy

• Cells capture to make ATP

– Anabolism• Biosynthetic processes

• Assemble subunits of macromolecules

• Use ATP to drive reactions

– Processes intimately linked

Principles of Metabolism

Macromolecules

(proteins, nucleic acids,

polysaccharides, lipids)

Subunits

(amino acids,

nucleotides, sugars,

fatty acids)

Catabolic processes harvest

the energy released during the

breakdown of compounds and

use it to make ATP. The

processes also produce

precursor metabolites used in

biosynthesis.

Anabolic processes (biosynthesis)

synthesize and assemble subunits

of macromolecules that make up

the cell structures. The processes

use the ATP and precursor

metabolites produced in

catabolism.

ANABOLISMCATABOLISM

Energy source

(glucose)

(source of nitrogen,

sulfur, etc.)

(acids, carbon

dioxide)

Waste products Nutrients

Energy

Precursor

metabolites

Cell structures

(cell wall, membrane,

ribosomes, surface

structures)

Energy

Energy

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

• Energy is the capacity to do work

• Two types of energy

– Potential: stored energy (e.g., chemical bonds, rock on hill, water behind dam)

– Kinetic: energy of movement (e.g., moving water)

– Energy in universe cannot becreated or destroyed, but it canbe converted between forms

Energy

• Photosynthetic organisms harvest energy in sunlight– Power synthesis of organic

compounds from CO2

– Convert kinetic energy of photons to potential energy of chemical bonds

• Chemoorganotrophs obtain energy from organic compounds– Depend on activities of

photosynthetic organisms

Harvesting Energy

Radiant energy

(sunlight)Photosynthetic organisms harvest the energy

of sunlight and use it to power the synthesis

of organic compounds from CO2. This

converts radiant energy to chemical energy.

Chemoorganotrophs degrade organic

compounds, harvesting chemical energy.Chemical energy

(organic compounds)

(top): © Photodisc Vol. Series 74, photo by Robert Glusie;

(bottom): © Digital Vision/PunchStock


• Metabolic pathways

– Series of chemical reactions that convert starting compound end product

• May be linear, branched, cyclical

Components of Metabolic Pathways

Starting compound Intermediatea Intermediateb End product

End product1

End product2

Intermediateb

(c) Cyclical metabolic pathway

End product

Intermediated

Starting compound

Intermediatec

Intermediatea

(a) Linear metabolic pathway

(b) Branched metabolic pathway

Intermediatea

Intermediateb2

Intermediateb1

Starting compound


Three types of Glucose metabolism

• Aerobic Respiration Cellular Respiration

• Anaerobic Respiration

• Fermentation

Overview of Metabolism in Bacteria

• Central metabolic pathways

– Glycolysis

– Pentose phosphate pathway

– Tricarboxylic acid cycle

• Key outcomes

– ATP

– Reducing power

– Precursor metabolites~ ~

~ ~

+

+

21

5

4

GLUCOSE

Pentose phosphate

pathway

Starts the oxidation of glucose

Glycolysis

Oxidizes glucose to pyruvateReducing

power

ATP

by substrate-level

phosphorylation

Fermentation

Reduces pyruvate

or a derivative

Biosynthesis

Transition step

Acetyl-

CoAAcetyl-

CoA

Respiration

Uses the electron transport

chain to convert reducing

power to proton motive force

ATP

by oxidative

phosphorylation

ATP

by substrate-level

phosphorylation

Reducing

power

TCA cycle

Incorporates an acetyl

group and releases CO2

(TCA cycles twice)

CO2 CO2

3a

X 2CO2

CO2

3b

Yields

Yields

Yields

Yields

Yields Reducing

power

Reducing

power

~ ~

Acids, alcohols, and gasesPyruvate Pyruvate


• Role of Enzymes

– Biological catalysts: accelerate conversion of substrate into product by lowering activation energy

• Highly specific: one at each step

• Reactions would occur without, but extremely slowly

Components of Metabolic PathwaysR

ela

tive e

nerg

y

Activation

energy

without an

enzyme

End productEnzyme cEnzyme b

IntermediatebIntermediatea

Enzyme a

(b)

Starting compound

(a)

Energy of

products

Activation

energy

with an

enzyme

Energy of

reactants

Progress of reaction


• Adenosine triphosphate (ATP)

– Energy currency of cell

– Three negatively charged phosphate groups repel

• Bonds inherently unstable, easily broken

• Releases energy to drive cellular processes

• High energy phosphate bonds denoted by ~

• ATP ADP + Pi

Energy Molecule

O

O

O–

PO O

O

O–

P

O

OO–

PO–

N

N N

N

Adenosine

Phosphate groups

High-energy

bonds

Ribose

OHOH

Adenine

CH2

NH2


• Role of ATP– Adenosine triphospate (ATP) is energy currency

• Composed of ribose, adenine, three phosphate groups• Adenosine diphospate (ADP) acceptor of free energy• Cells produce ATP by adding Pi to ADP using energy• Release energy from ATP to yield ADP and Pi

• Three processes to generate ATP– Substrate-level phosphorylation

• Exergonic reaction powers

– Oxidative phosphorylation• Proton motive force drives

– Photophosphorylation• Sunlight used to create proton

motive force to drive

PPP

PP

~

~

~

Unstable (high-energy) bonds

Energy used

The energy comes

from catabolic

reactions.

Energy released

The energy drives

anabolic reactions.

ADP

PiPi

ATP


• Role of Electron Carriers

– Energy harvested in stepwise process

• Electrons transferred to electron carriers, which represent reducing power (easily transfer electrons to molecules)– Raise energy level of recipient molecule

• NAD+/NADH, NADP+/NADPH, and FAD/FADH2

– Serve as carbon skeletons for building macromolecules

Aerobic cellular respiration Bacteria produce Precursor Metabolites

Overview of Metabolism in Bacteria

• Central metabolic pathways

– Glycolysis

– Pentose phosphate pathway

– Tricarboxylic acid cycle

• Key outcomes

– ATP

– Reducing power

– Precursor metabolites~ ~

~ ~

+

+

21

5

4

GLUCOSE

Pentose phosphate

pathway


Glycolysis


power

ATP

by substrate-level

phosphorylation

Fermentation

Reduces pyruvate

or a derivative

Biosynthesis

Transition step

Acetyl-

CoAAcetyl-

CoA

Respiration




ATP

by oxidative

phosphorylation

ATP

by substrate-level

phosphorylation

Reducing

power

TCA cycle



(TCA cycles twice)

CO2 CO2

3a

X 2CO2

CO2

3b

Yields

Yields

Yields

Yields

Yields Reducing

power

Reducing

power

~ ~

Acids, alcohols, and gasesPyruvate Pyruvate


Aerobic Cellular Respiration or Embden-Meyerhof Pathway in bacteria

• Requires oxygen as the final electron acceptor

• Produces 38 ATP’s in Bacterial and 36 ATP’s in Eukaryotic cells

• Prokaryotic cells produce precursor metabolites which become cellular components or macromolecules

• Glycolysis

– Converts 1 glucose to 2 pyruvates; yields net 2 ATP, 2 NADH

– Investment phase:

• 2 phosphate groups added

• Glucose split to two 3-carbon molecules

– Pay-off phase:

• 3-carbon molecules converted to pyruvate

• Generates 4 ATP, 2 NADH total

~ ~

~

~ ~

~

~

~ ~

~

~ ~

~

~ ~

~

~ ~

+

+

x2

PPP

PPP

PPP2

1

5

4

3b

~ ~

~ ~

~

GLUCOSE

Yields

Fermentation

Reduces pyruvate

or a derivative

PyruvatePyruvate

Reducing

power

Yields

Biosynthesis

Transition step3a

YieldsReducing

power

CO2

CO2

CO2CO2

TCA cycle



(TCA cycles twice)

ATP

by substrate-level

phosphorylation

Reducing

power

Respiration


Chain to convert reducing


Yields

ATP

by oxidative

phosphorylation

~

1

2

3

8

4

5

6

9

7

H2O

ATP is expended to add a phosphate group.

A chemical rearrangement occurs.

ATP is expended to add a phosphate group.

The 6-carbon molecule is split into two 3-carbon

molecules.

A chemical rearrangement of one of the

molecules occurs.

The addition of a phosphate

group is coupled to a redox

reaction, generating NADH and

a high-energy phosphate bond.

ATP is produced by

substrate-level

phosphorylation.

A chemical rearrangement occurs.

Water is removed, causing the

phosphate bond to become

high-energy.

ATP is produced by

substrate-level

phosphorylation.

Pyruvate

ATP

ADP

Phospho-

enolpyruvate

2-phospho-

glycerate

3-phospho-

glycerate

ATP

ADP

1,3-bisphospho-

glycerate

Glyceraldehyde

3-phosphate

Dihydroxyacetone

phosphate

Fructose

1,6-bisphosphate

ADP

ATP

Fructose

6-phosphate

Glucose

6-phosphate

10

H2O

NADH + H+

NAD+

Glucose

ATP

ADP

NADH + H+

NAD+

Pentose phosphate

pathway


Glycolysis


power

ATP

by substrate-level

phosphorylation

Acids, alcohols, and gases

Yields

~ ~


Bacterial Alternative Pathway

Pentose Phosphate Pathway– Also breaks down glucose– Important in biosynthesis of precursor metabolites

• Ribose 5-phosphate, erythrose 4-phosphate

– Also generates reducing power: NADPH

• Precursor metabolites– Glucose molecules can have

different fates– Can be completely oxidized

to CO2 for maximum ATP– Can be siphoned off as

precursor metabolite foruse in biosynthesis

6.10. Anabolic Pathways—Synthesizing Subunits from Precursor Molecules


Pentose phosphate

pathway

Ribose 5-phosphate

Erythrose 5-phosphate

Nucleotides

amino acids

(histidine)

Amino acids

(phenylalanine,

tryptophan,

tyrosine)

Lipids

(glycerol

component)

Amino acids

(cysteine,

glycine, serine)

Amino acids

(phenylalanine,

tryptophan, tyrosine)

Amino acids

(aspartate, asparagine,

isoleucine, lysine,

methionine, threonine)

TCA cycle

Amino acids

(arginine, glutamate,

glutamine, proline)

Lipids

(fatty acids)

Amino acids

(alanine,

leucine, valine)

Peptidoglycan

Lipopolysaccharide

(polysaccharide)

Glucose 6-phosphate

Fructose 6-phosphate

Dihydroxyacetone

phosphate

3-phosphoglycerate

Phosphoenolpyruvate

Pyruvate

Acetyl-CoAAcetyl-CoA

Pyruvate

Oxaloacetate

- ketoglutarate

Glycolysis

X 2

• Transition Step

– CO2 is removedfrom pyruvate

– Electrons reduce NAD+

toNADH + H+

– 2-carbon acetyl group joined to coenzyme A to form acetyl-CoA

– Takes place in mitochondria in eukaryotes


~~ ~ + Pi

H2O

1

2

8

7

6

5

3

4

A redox reaction

generates NADH.

Water is added.

A redox reaction

generates FADH2-

The energy released

during CoA removal is

harvested to produce ATP.ADPATP

CoA

A redox reaction

generates NADH,

CO2 is removed,

and coenzyme A

is added.

A redox reaction

generates NADH

and CO2 is

removed.

A chemical

rearrangement occurs.

The acetyl group is transferred

to oxaloacetate to start a new

round of the cycle.

Transition step:

CO2 is removed, a redox reaction generates

NADH, and coenzyme A is added.

NADH + H+

Acetyl-CoA

CoA

CoA

NADH + H+ Oxaloacetate

NAD+

Malate

Fumarate

FADH2

FAD Succinate Succinyl-CoA

CoA

CoA

CO2

NAD+

-ketoglutarate

Isocitrate

Citrate

CoA

NAD+

CO2

Pyruvate

NAD+

CO2

NADH + H+

NADH + H+

+

+

x 2

21

5

4

~ ~

~ ~

~ ~

GLUCOSE

Respiration




ATP

by oxidative

phosphorylation

Yields

ATP

by substrate-level

phosphorylation

Reducing

power

Yields

CO2

CO2

Pyruvate Pyruvate

3a Transition step

YieldsReducing

power

Acetyl-

CoA

Acetyl-

CoA

Biosynthesis

YieldsReducing

power

Pentose phosphate

pathway


Glycolysis

Oxidizes glucose to pyruvate

YieldsReducing

power

ATP

by substrate-level

phosphorylation


CO2CO2

Fermentation

Reduces pyruvate

or a derivative

TCA cycle



(TCA cycles twice)

3b

• Tricarboxylic Acid (TCA) Cycle– Completes

oxidation of glucose

• Produces– 2 CO2

– 2 ATP– 6 NADH– 2 FADH2

– Precursor metabolites


~~ ~ + Pi

H2O

1

2

8

7

6

5

3

4

A redox reaction

generates NADH.

Water is added.

A redox reaction

generates FADH2-

The energy released

during CoA removal is

harvested to produce ATP.ADPATP

CoA

A redox reaction

generates NADH,

CO2 is removed,

and coenzyme A

is added.

A redox reaction

generates NADH

and CO2 is

removed.

A chemical

rearrangement occurs.

The acetyl group is transferred

to oxaloacetate to start a new

round of the cycle.

Transition step:

CO2 is removed, a redox reaction generates

NADH, and coenzyme A is added.

NADH + H+

Acetyl-CoA

CoA

CoA

NADH + H+ Oxaloacetate

NAD+

Malate

Fumarate

FADH2

FAD Succinate Succinyl-CoA

CoA

CoA

CO2

NAD+

-ketoglutarate

Isocitrate

Citrate

CoA

NAD+

CO2

Pyruvate

NAD+

CO2

NADH + H+

NADH + H+

+

+

x 2

21

5

4

~ ~

~ ~

~ ~

GLUCOSE

Respiration




ATP

by oxidative

phosphorylation

Yields

ATP

by substrate-level

phosphorylation

Reducing

power

Yields

CO2

CO2

Pyruvate Pyruvate

3a Transition step

YieldsReducing

power

Acetyl-

CoA

Acetyl-

CoA

Biosynthesis

YieldsReducing

power

Pentose phosphate

pathway


Glycolysis


YieldsReducing

power

ATP

by substrate-level

phosphorylation


CO2CO2

Fermentation

Reduces pyruvate

or a derivative

TCA cycle



(TCA cycles twice)

3b

ETC located in MitochondriaCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

21

5

4

Pentose phosphate

pathway


GLUCOSE

Glycolysis


YieldsReducing

power

ATP

by substrate-level

phosphorylation

Fermentation

Reduces pyruvate

or a derivative

Acids, alcohols, and gasesPyruvatePyruvate

Reducing

power

Yields

Biosynthesis

Transition step3a

YieldsReducing

power

CO2CO2

Acetyl-

CoA

Acetyl-

CoA

CO2

CO2

TCA cycle



(TCA cycles twice)

Yields

ATP

by substrate-level

phosphorylation

Reducing

power

Respiration




Yields

ATP

by oxidative

phosphorylation

x 2

3b

+PPP ~ ~

PPP

+

4 4 2 H+ 10 H+

+ 3 Pi

H2O

O22

e–

Eukaryotic cell

Inner

mitochondrial

membrane

Electron Transport Chain

Complex I

Ubiquinone

Complex III

NADHComplex II

3 ADP

3 ATP

Mitochondrial

matrix

Intermembrane

space

Use of Proton Motive Force

ATP synthase

(ATP synthesis)Complex IV

Proton motive force

is used to drive:

Terminal

electron acceptor

Cytochrome c

NAD+

H+H+

H+

H+ 1/2

Path of

electrons

2

The Electron Transport Chain—


ve forcerive:

+

H+ H+

Terminal

electron acceptor

–

O2

Prokaryotic cell

Cytoplasmic

membrane

Electron Transport Chain

NADH dehydrogenase

H+ (0 or 4)

Uses of Proton Motive Force

Rotation of a flagella

Outside of

cytoplasmic

membrane

Transported

molecule

NADH

Cytoplasm

3 ADP

3 ATP

+ 3 Pi

NAD+

H+

Succinate

dehydrogenase

Path of

electrons

Ubiquinone

Active transport

(one mechanism)

ATP synthase

(ATP synthesis)Ubiquinol oxidase

H+ (2 or 4) 10 H+

H2O

2 H+

Proton motive force

is used to drive:

2 e–

1/2

The Electron Transport Chain• Electron transport chain is membrane-embedded

electron carriers– Pass electrons sequentially, eject protons in process

– Prokaryotes: in cytoplasmic membrane

– Eukaryotes: in inner mitochondrial membrane

– Energy gradually released

– Release coupled to ejection

of protons

– Creates electrochemicalgradient

– Used to synthesize ATP

– Prokaryotes can also powertransporters, flagella

2

1/2

e–

O22 H+

Energy released is

used to generate a

proton motive force.

Electrons from the

energy source

High energy

Low energy Electrons donated

to the terminal

electron acceptor.

H2O


The Electron Transport Chain

• ATP Yield of Aerobic Respiration in Prokaryotes

– Substrate-level phosphorylation:

• 2 ATP (from glycolysis; net gain)

• 2 ATP (from the TCA cycle)

• 4 ATP (total)

– Oxidative phosphorylation:

• 6 ATP (from reducing power gained in glycolysis)

• 6 ATP (from reducing power gained in transition step)

• 22 ATP (from reducing power gained in TCA cycle)

• 34 (total)

– Total ATP gain (theoretical maximum) = 38

ATP Yield of Aerobic Respiration in ProkaryotesCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

~ ~

~ ~

~ ~

~ ~

~ ~

~ ~

~ ~

~ ~

Substrate-level

phosphorylation2 ATP

4 ATP

18 ATP

6 ATPOxidative

phosphorylation

Oxidative

phosphorylation

Oxidative

phosphorylation

2 NADH

6 NADH

2 FADH2

2 ATP

6 ATP

Substrate-level

phosphorylation

Oxidative

phosphorylation

2 NADH

2 ATP

net gain = 0

2 ATP

GLUCOSE

Glycolysis


x 2 CO2

CO2

TCA cycle



(TCA cycles twice)

21

5

4

Pentose phosphate

pathway


GLUCOSE

Glycolysis


Yields

Reducing

power

ATP

by substrate-level

phosphorylation

Fermentation

Reduces pyruvate

or a derivative

Acids, alcohols, and gasesPyruvatePyruvate

Reducing

power

Yields

Biosynthesis

Transition step3a

YieldReducing

power

CO2CO2

Acetyl-

CoAAcetyl-

CoA

CO2

CO2

TCA cycle



(TCA cycles twice)

Yields

ATP

by substrate-level

phosphorylation

Reducing

power

Respiration




Yields

ATP

by oxidative

phosphorylation

x 2

3b

Pyruvate Pyruvate

Acetyl-

CoA

Acetyl-

CoA

Anaerobic environments

• Prokaryotes unique in ability to use reduced inorganic compounds as sources of energy

– E.g., hydrogen sulfide (H2S), ammonia (NH3)

• Produced by anaerobic respiration from inorganic molecules (sulfate, nitrate) serving as terminal electron acceptors

• Important example of nutrient cycling

• Four general groups

The Electron Transport Chain

– Anaerobic respiration in E. coli

• Harvests less energy than aerobic respiration– Lower electron affinities of terminal electron acceptors

• Some components different

• Can synthesize terminal oxidoreductase that uses nitrate as terminal electron acceptor – Produces nitrite

– E. coli converts to less toxic ammonia

– Sulfate-reducers use sulfate (SO42–) as terminal

electron acceptor

• Produce hydrogen sulfide as end product

Fermentation• Fermentation end products varied; helpful in

identification, commercially useful– Ethanol

– Butyric acid

– Propionic acid

• 2,3-Butanediol

• Mixed acids

H2

Fermentation

pathway

Microorganisms

Lactic acid

Streptococcus

Lactobacillus

Ethanol Butyric acid Propionic acid Mixed acids 2,3-Butanediol

EnterobacterE. coliPropionibacteriumSaccharomyces

End products Lactic acid Ethanol

CO2

Butyric acid

Butanol

Acetone

IsopropanolCO2

CO2

Propionic acid

Acetic acid

Acetic acid

Lactic acid

Succinic acid

EthanolCO2

H2

CO2H2

Clostridium

Pyruvate


(yogurt, dairy, pickle), b (wine, beer), (acetone): © Brian Moeskau/McGraw- Hill; (cheese): © Photodisc/McGraw-Hill; (Voges-Proskauer Test), (Methyl-Red Test): © The McGraw-Hill Companies, Inc./Auburn University Photographic Services

Aerobic Cellular Respiration (ACR) in Bacteria summary

Glycolysis Glucose to pyruvateProduces: 2 NADH, 2ATP’s and 6 precursor metabolites

Acetyl Co A or Transitional stepProduces: 2 NADH, 2 CO2 and 1 precursor metabolite

TCA or Krebs cycleProduces: 6 NADH, 2 FADH, 2 ATP’s, 4 CO2, and 2 precursor metabolites

Electron Transport ChainProduces: 38 ATP’s

Oxygen requiredExamples of Bacteria: E. Coil and Staph species

Summary

• Aerobic Cellular Respiration (ACR)

– Or Embden-Meyerhoff Pathway in bacteria

• Pentose Phosphate Pathway

• Entener-Doudoroff Pathway

Pentose Phosphate Pathway Summary

• Glucose to pyruvate

– Produces:

• 5 carbon sugar to intermediate products

• Nucleic acids, nucleotides and amino acids

• 1 ATP

• 2 NADPH (Calvin cycle) Photosynthetic bacteria

• Products go ACR, Anaerobic respiration and Fermentation

• Example of bacteria are E. Coli and Bacillus Sp.

Entner-Doudoroff Pathway summary

• Glucose – pyruvate

• Produces:– 1 ATP

– 1 NADH

– 1 NADPH (Calvin cycle)

– Products can go to ACR, Anaerobic respiration or Fermentation

– Can process Glucose independent• EX Pseudomonas Sp, E. Coli, Bacteroides Sp.

• Only Gram negative can use

Documents

Title: Microbial Metabolism Title: What is the title of ...c141).pdfthe Embden-Meyerhof Pathway –Alternate Pathway •Pentose Phosphate Pathway •Entner-Doudoroff Pathway •Biologists