•• 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
Cytoplasmic membrane
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
Cytoplasmic membrane
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.
Images removed due to copyright restrictions.
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.
Images removed due to copyright restrictions.
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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