bioenergetics &

•• FINISH UP CHEMOTAXISFINISH UP CHEMOTAXIS

•• THERMODYNAMICS OF GROWTHTHERMODYNAMICS OF GROWTH

•• DIVERISTY IN ENERGY ACQUISITION DIVERISTY IN ENERGY ACQUISITION

Systems MicrobiologyWeds Sept 13 - Ch 5 & Ch 17 (p 533-555)

Bioenergetics & Physiol.Diversity

•• BASIC MODES OF ENERGY GENERATIONBASIC MODES OF ENERGY GENERATION

Filament

Flagellin

Outer Membrane (LPS)

Hook

L Ring

P Ring

MS Ring

C Ring

Rod+ + + +

- - - - - - - -

+ + + +

Peptidoglycan

Periplasm

Basal Body

Mot Protein Fli Proteins(motor switch)

45 nm

Cytoplasmic membrane

14 nm

Figure by MIT OCW.

+++- - -

++ +

+++ +

++-

-- -

--

---

+++- - -

++ +

+++ +

++-

-- -

--

---

Rod

MS Ring

C Ring

Mot Protein

H+

H+H+

Figure by MIT OCW.

Filaments in the bundle are usually normal, i.e., left-handed helices with pitch about 2.5 µm and diameter about 0.5 µm, with the motors turning counterclockwise. During the tumble, one or more motors switch to clockwise, and their filaments leave the bundle and transform to semi-coiled, i.e., right handed helices with pitch about half of normal.

http://www.rowland.harvard.edu/labs/bacteria/projects_filament.html, Howard Berg

Courtesy of Howard C. Berg. Used with permission.

Bundled flagella(Counter-clockwise rotation)

Flagella bundled(Counter-clockwise rotation)

Tumble-flagella pushed apart (Clockwise rotation)

Figure by MIT OCW.

Image removed due to copyright restrictions.See Figure 4-62 in Madigan, Michael, and John Martinko. Brock Biology of Microorganisms. 11th ed.Upper Saddle River, NJ: Pearson Prentice Hall, 2006. ISBN: 0131443291.

Run

Tumble

Attractant

Attractant Present

Figure by MIT OCW.

• CheA is coupled to the receptor through complex with CheW• Ligand free receptors stimulate autophosphorylation of His residue of CheA• Attractant-bound receptors inhibit CheA phosphorylation, repellent increasesthe level of phosphorylation• CheA donates phosphate to CheB and CheY• Phosphorylated CheY interacts with switch proteins in the flagellar motors togenerate CW rotation ( Motors rotate CCW by default) • So the level of phospho-CheY determines the cell's swimming behavior• Mutants that lack CheA or CheY have no mechanism to cause clockwise rotationof flagella and hence swim continually.

ChemotacticSignal transduction

Brock, ch 8.13, pp 226-227

CheYCheP

CheWCheW

+CH2

-CH2

ATPCheA

CheZCheB

Cell wall


Flagellarmotor

Transducer (MCP)

PCheB CheY P

PCheA

Attractants

Figure by MIT OCW.

Methylation – another level of chemotaxis regulation (Adaptation)(Cells can’t sense absolulte concentration - only changes in conc. gradient overtime)

In the presence of attractant – MCP is methylated by CheR(methyltransferase chemotaxis protein), catalyses transfer of methyl group fromS-adenosylmethionine.

The level of methylation of MPC affects receptor sensitivity to attractant ofrepellent

Fully methylated receptor is not able to respond to attractant =>CheA gets autophosphorylated,CheA transfers phosphoryl group to CheBCheB is a demethylase => removesmethyl group from MCPand restores its activity

ChemotacticSignal transduction

CheYCheP

CheWCheW

+CH2

-CH2

ATPCheA

CheZCheB

Cell wall


Flagellarmotor

Transducer (MCP)

PCheB CheY P

PCheA

Attractants

Figure by MIT OCW.

Cartoon interpretation of type IV pilus retraction

Bacterial motility: How do pili pull? Dale Kaiser Current Biology, Volume 10, Issue 21 , 1 November 2000, Pages R777-R780

Figure by MIT OCW.

Grappling hook model for twitching motility• the pilus fiber extends; (2) the fiber binds to a substrate or to another cell;(3) the fiber retracts (the power stroke)

Images removed due to copyright restrictions.See http://www.webcom.com/alexey/moviepage.html.

FOR GROWTH AND BIOSYNTHESIS CELLS NEED :

1. Energy, in the form of ATP - produced from light energy, or byoxidation of energy rich substrates, and proton translocatingATPase.

2. Reducing power, in the form of NADH, produced (mainly)by the oxidation of energy rich substrates and the reduction ofNAD+.

3. Basic macronutrients: C,N,P,S (nmol to mmol in the environment)Mg++, K+, Na+, Ca++

3. Micronutrients - Fe, Mo, Se, W, V, Zn, Ni, etc (also vitamins and other growth factors in some cases)

See Tables 5-2 and 5-3 in Madigan, Michael, and John Martinko. Brock Biology of Microorganisms. 11th ed. Upper Saddle River, NJ: Pearson Prentice Hall, 2006. ISBN: 0131443291.

Tables of micronutrients and vitamins used by living organisms removed due to copyright restrictions.

ALL ORGANISMS

chemotrophs phototrophs

chemolithotrophs chemoorganotrophs

Where do organisms get their energy?

Oxidize inorganiccompounds

Oxidize organiccompounds

Derive energy from light

MICROBIALMICROBIALMETABOLIC METABOLIC DIVERSITYDIVERSITY

Relative VoltageRelative VoltageFUELS (EAT) OXIDANTS (BREATHE)

-10

- 8

- 6

- 4

- 2

0

+ 2

+ 4

+ 6

+ 8

+ 10

+ 12

+ 14

-10

- 8

- 6

- 4

- 2

0

+ 2

+ 4 + 6

+ 8

+ 10 + 12

+ 14

OrganicCarbon

CO2SO4

=

AsO43-

FeOOH

SeO3NO2

-

NO3-

MnO2

NO3-/N2

O2

H2

H2SSo

Fe(II)

NH4+

Mn(II)

A

B

Photoreductants

Microbes can

eat & breathe just

about anything !

FREE ENERGY AND BIOENERGETICS

Gibbs free energy change = Δ G = Gproducts - Greactants = GB - GA

For the chemical reaction : A -> B

A reaction with a negative Δ G releases energy, and is exergonic

A reaction with a positive Δ G releases energy, and is endergonic

‘Good’ electron acceptors

‘Good’ electron donors

Aerobic Respiration :O2 is the terminalelectron acceptor

See Figures 5-9 and 5-19 in Madigan, Michael, and John Martinko. Brock Biology of Microorganisms. 11th ed. Upper Saddle River, NJ: Pearson Prentice Hall, 2006. ISBN: 0131443291.

Images removed due to copyright restrictions.

Electrons are passed from NADH via the electron transport chainto oxygen. Simultaneously, protons are “pumped” outside cell.

The enzyme ATPase can use the energy from the proton gradient to make ATP.

Diagrams of the electron transport chainremoved due to copyright restrictions.

High H+ concentration

Outside cell

Inside cell

Electrons from NADH or chlorophyll

ADP+ Pi

Low H+ concentration

H+ H+

1

2

3

ATP

} Membrane

ATPsynthase

Electron transport chain (includes proton pumps)

Figure by MIT OCW.

See Figures 5-21, 5-22a, and 5-20 in Madigan, Michael, and John Martinko. Brock Biology of Microorganisms. 11th ed. Upper Saddle River, NJ: Pearson Prentice Hall, 2006. ISBN: 0131443291.


METABOLIC DIVERSITY - Defining terms….Modes of Nutrition - Some basic definitionsAn organism needs a source of carbon, plus energy (ATP), plus reducing power (NADH). These may all come from the same source (e.g. glucose provides all three),or they may come from different sources:

• Where does the carbon come from?a) Organic molecules - heterotrophsb) Inorganic - mainly CO2 = autotrophs

• Where does the energy come from?a) Chemical reactions (redox reactions) - chemotrophsb) Light - phototrophs

• What molecule is the electron donor?a) Organic molecules - organotrophsb) Inorganic (e.g., H2O, H2, Sulfur) - lithotrophs

• What molecule is the electron acceptor ?a) O2 = aerobic respirationb) Oxidants other than O2 (SO4, NO3, FeIII) = anaerobic respiration

Heterotrophs“nourished from

others”

Autotrophs“self-

nourishers”

CO2 and H2O O2 + CH2O

energy inputs: solar chemical

Bacterial photosynthesis (anoxygenic)

The original photosynthesizers on Earth likely did not produce oxygen. Theirreactions in the light are slightly different because they use cyclic photosynthesis,and H2S, organic carbon, and other sources for reducing power (not H2O).

Who? bacteria (e.g. Purple or green sulfur bacteria. Also purple and green non-sulfur bacteria)C Source? CO2Energy Source? SunlightElectron Donor? H2S, organics, otherWhere? In anaerobic, light conditions

Use bacteriochlorophyll, not chlorophyll in light reaction.

Light reaction is slightly different, in terms of pigments and electron transfercompounds.

Pigments absorb at slightly different wavelengths – allow these bacteria toabsorb light that algae might not absorb. Absorption max at 890 nm

Write what you think overall reaction is:

2 H2S + CO2 CH2O + 2 S0 + H2O

Phototrophs (Use Light as Energy Source )

Photoautotrophs (Use CO2)

Photoheterotrophs (Use Organic Carbon)

Figure by MIT OCW.

Anoxygenic photoautotrophs utilize cyclicphotophosphorylation

Light

Excited electrons (2 e-)

Electron transport chain

Energy for productionof ATP

Electron carrier

Cyclic Photophosphorylation

Chlorophyll

ATP

Figure by MIT OCW.

LOTS OF DIVERSITY IN BACTERIAL ANOXYGENIC PHOTOTROPHS !

+0.5

+0.25

-0.25E0'(V)

-0.5

-0.75

-1.0

-1.25

0

P870

Purple Bacteria Green Sulfur Bacteria Heliobacteria

Fd

P870

NADH

Reverse electron flow

QCytbc1

Light

Cytc2

BChlBPh

Light Light

Fd

P840

Chl a

QQCyt

bc1Cytc553

Cytc553P840

P798

Chl a-OH

FeS FeS

Cytbc1

P798

Figure by MIT OCW.

See Figures 17-15 and 17-3 in Madigan, Michael, and John Martinko. Brock Biology of Microorganisms. 11th ed. Upper Saddle River, NJ: Pearson Prentice Hall, 2006. ISBN: 0131443291.


Life on Earth Today: TheLife on Earth Today: TheFoundationFoundation

COCO22 + + H H22OOcarbon watercarbon waterdioxidedioxide

CC66HH1212OO66 + + O O22organic oxygenorganic oxygencarboncarbon

Plants Algae,Plants Algae,photosynthetic bacteriaphotosynthetic bacteria

PhotosynthesisPhotosynthesisSolar energySolar energy

AnimalsAnimalsBacteriaBacteria

ChemicalChemicalenergy orenergy or

heatheat

RespirationRespiration

N,P,S,FeN,P,S,Fe……..

The Z scheme = oxygenic photosynthesis = Noncyclic photsynthesis because electrons are not “recycled”

Diagrams of noncyclic photophosphorylation and the Z scheme removed due to copyright restrictions.

+1.0

+0.75 H2O

O2 + 2H12

e-

+0.5

+0.25

0.0

-0.25

-0.5

-0.75

-1.0

-1.25

LightPhotosystem I

Photosystem II

E0(V)

'

LightP680

Cyclic electron flow(generates proton motive force)

Noncyclicelectron flow(generates protonmotive force)

FeS

Pc

QB

Q pool

Chl a0

P680*

NAD(P)HNAD(P)+

P700

Cyt bf

P700*

Fd

Fp

QA

Ph

QA

PSII PSI

The Z Scheme

Figure by MIT OCW.

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