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Christophe Six
UMR UPMC-CNRS 7144 “Adaptation & Diversité en Milieu Marin"Equipe « Procaryotes Photosynthétiques Marins »
Station Biologique de RoscoffUniversité Pierre et Marie Curie (Paris VI)
Bureau 354, 3ème étage (Bâtiment GT)[email protected]
Unité d’Enseignement : Evolution du Phytoplancton Marin et Biogéochimie
Introduction to Photosynthesis:Evolutionary processes
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What is photosynthesis ?
Sensu lato:
Any synthesis of organic matter that is light dependent
Common Sense:
All processes used by phototrophic organisms using chlorophyll compounds to convert light energy into chemical energy (ATP).
Organic matter
MineralsCofactors
h
. Most of life on Earth is dependent on photosynthesis through food webs. Exception : hydrothermal vents
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Origin of photosynthesis at thescale of Geological times
Millio
ns years
Precambrian
http://www.ipgp.jussieu.fr/files_lib/83_echm-gt.gif
Millio
ns
ye
ars
Millio
ns
ye
ars
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Stromatolites
http://www.cartage.org.lb/en/themes/Sciences/Paleontology/Paleozoology/Precambrian/Precambrian.htm
West of Australiahttp://www.interet-general.info/IMG/Stromatolites-2-3.jpghttp://www.gc.maricopa.edu/earthsci/imagearchive/stromatolite.jpg
Microfossils of filamentouscyanobacteria
The oldest fossils : the Stromatolites
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Microbial coccoid fossil (Eosphaera)
Formation of Gunflint, North Americahttp://gsc.nrcan.gc.ca/paleochron/05_e.php
10 µm
Fossil evidences : the stratified iron formations
Mont Bruce, West of Australiahttp://www.geo.vu.nl/~smit/hamersley/hamersley%20iron.jpg
Iron stratified formations
http://z.about.com/d/geology/1/0/d/-/1/bifslab.jpg
http://www.cartage.org.lb/en/themes/Sciences/Paleontology/Paleozoology/Precambrian/mich03.gif
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Formation couche d’ozone
Radiationcyanobactérienne
Formation couche d’ozone
Formation couche d’ozone
Radiationcyanobactérienne
Bil
lio
n y
ear
s
Diversité (nombre de taxa)Présent
Consequences of the development of oxygenic photosynthesis
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. Sulphurous green bacteria Chlorobium, Prosthecochloris, Pelodictyon, Ancalochloris, Chloroherpeton
. Non-sulphurous green bacteria Chloroflexus, Chloronema, Heliothrix, Roseiflexus
. Non-Sulphurous purple bacteria Rhodospirillum, Rhodobacter, Rhodopseudomonas, Rhodomicrobium
. Sulphurous purple bacteria Chromatium, Thiospirillum, Thiopedia
. Les heliobacteria Heliobacterium
. Photoheterotrophic, anoxygenic, aerobic bacteria Roseobacter, Roseovarius, Erythrobacter
. Cyanobacteria = Oxyphotobacteria Synechococcus, Prochlorococcus, Oscillatoria, Anabaena, Synechocystis, Microcystis, Planktothrix, Trichodesmium, Croccosphaera, etc…
. Photosynthetic (oxygenic) eukaryotes Rhodophyta, Heterokontophyta, Chlorobionta
The photosynthetic organisms on Earth
Lakes & Estuaries
Benthic/Planctonic.Stratified freshwater lakes: Anoxiques zones
Still poorly known; Oceans
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The different groups of photosynthetic organisms on Earth
Photosynthesis
Oxygenic
Anoxygenic
A single type of reaction centre-Typical antenna system (BChl & Carotenoids)
Electron donnors = reduced compounds
Two types of reaction centresAntenna = Phycobilisome or Lhc
Electron donnors = H2O
AnaerobicAerobic(photohétérotrophs)
RC I + RC IICyanobacteria = oxyphotobacteria
(photohétérotrophs & obligatory phototrophs)
Photosynthetic eukaryotes:Eukaryotic phytoplankton, macroalgae,
bryophytes and vascular plants
Aérobic
Purple bacteria(RC II – BChl a ou b – (Calvin cycle)
Sulphurous(obligatory
phototrophs)
Non- sulphurous(photoheterotrophs)
Green bacteria(Chlorosome – no RuBisCO)
Sulphurous(obligatory
phototrophs)RC I
Non- sulphurous(photoheterotrophs)
RC II
Chlorobiaceae Chloroflexaceae
HéliobacteriaRC I
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Anoxygenic photosyntheses
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Reaction centres and bacteriochlorophylls
Bactériochlorophylle a Bactériochlorophylle b
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Sulphurous Green bacteria
Chlorobium tepidumMicrobial mat : Chlorobium
Yellowstone national park, USAMicrobewiki
Chlorobium sp. BS1
Benthic organisms : 1mm beneath the sediment at the bottomof lakes and estuaries
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The antenna complex of Chlorobium spp.
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The reaction centre of Chlorobium spp.
. 3 proteins : 2 proteins A (65 kDa) + 1 small proteine C de 8 kDa
Cofactors linked to these proteins constituting a double, transmembrane, redox chain
. Charge separation: expulsion of an e- from a Bchl a P840,
. Transfer to an acceptor A0 which has a low redox potential, then to A1 = naphtoquinone
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. Electron tranfer to three Iron-Sulphur clusters, named FX, FA et FB
. 2 ferredoxins 2 e- + NAD+ + H+ NADH (universal reductant of metabolic reactions)
=> 2 excitons are necessary to produce one molecule of NADH
Fd soluble
The reaction centre of Chlorobium spp.
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Le centre réactionnel de Chlorobium spp.
. Cytochromic system c553 : complexed (4 hemes) or soluble e- given back to P840
. c553 reduced by flavocytochrome c551 (1 heme + 1 flavin group)
. 2 C551 + S2- C551 + 2 e- + S Sulphur is released in the periplasm
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The electron carrier chain of Chlorobium spp.
Cyclic transport of e-
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Non-sulphurous purple bacteria
http://www.martin-stein.com/images/rhodob.jpg
Rhodobacter sphaeroides
Rhodospirillum rubrum
http://www.de.mpi-magdeburg.mpg.de/research/projects/1010/1014/1020/rhodos.jpg
Rhodopseudomonas sp.
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Rhodobacter sp.
Different types of structures of inner foldings
of the plasmic membrane
Non-sulphurous purple bacteria
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The inner foldings of Rhodobacter sphaeroides (chromatophores)
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The antenna complex of Rhodopseudomonas acidophila
- On pair binds 1 ou 2 BChl 18 BChl perpendicular to the plan per LH2 (= B850 abs max at 850nm)
- LH2 complex : hollow cylinder constituted by 9 motifs = 9 paires de polypeptide et (5-7 kDa)
- The 9 are in periphery, the 9 are inner ; bacteriochlorophylls are located between these two crowns
- The subunits bind an additional molecule of BChl between two -helices, parallel to the plan These 9 BChl = B800 (abs max à 800nm)
- One carotenoid is linked to each
Bleu : PolypeptidesOrange : B800 bacteriochlorophyllsVert : Carotenoids
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Rhodobacter sphaeroides
Rhodopseudomonas viridis
The reaction centre of non-sulphurous purple bacteria
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Photosynthetic apparatus of Rhodobacter sp.
Protein Structure involved in the photosynthetic activity of Rhodobacter sp.(Cross section of the cytoplasmic membrane)
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Cyclic electron transport in Rhodobacter sp.
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Anoxygenic reaction centres
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Oxygenic photosynthesis
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Global reaction : n [CO2 + H2O] [CH2O] n + O2
Location :
Chloroplasts ofvascular plants
Oxygenic photosynthesis
Bryopsis sp. Porphyridium sp. Fucus sp. Synechococcus sp.
Marine chloroplasts
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Photosynthetic membranes : the thylacoids
Stroma/cytosol
Stroma/cytosolLumen
Membranar lipids
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The membranar photosynthetic complexes
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What is a photosystem?
. Two large subunits D1/D2 ; PsaAB)
. A number of small subunits
Photosystem = reaction centre + photosynthetic antenna
. External antenna : the major one
. Inner antenna stuck to the reaction centre : the minor one
. The charge separation : one electron is extracted from a chlorophyll molecule and released in a chain of acceptors
Chl (=P680) chl* (=P680*) + e-
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Photosystem II antennae
. Two major structural groups : intrinsic et extrinsic to the thylacoids
. Large diversity of configuration depending on the taxonomic group
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PS
Intrinsic, major PSII antenna (LHC type)
Intrinsic antennae
LHC type proteins
Th
yla
co
ids
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CP43
D1/D2
CP47
D1/D2
CP47
CP43
Trimères de LHCIIb
Lhcb3 ou 4 ou 5 ou 6
CP43
D1/D2
CP47
D1/D2
CP47
CP43
CP43
D1/D2D1/D2
CP47
D1/D2D1/D2
CP47
CP43
Trimères de LHCIIb
Lhcb3 ou 4 ou 5 ou 6
Trimères de LHCIIb
Lhcb3 ou 4 ou 5 ou 6
Reaction centres
Proteins LHC
Intrinsic antennae
(Top view)
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Pigments associated to intrinsic antennae
Chl aChl b Chl c1
Chl c2
Chl c3
Violaxanthin
Antheraxanthin
Zeaxanthin
Diadinoxanthin
Diatoxanthin
Lutein
Neoxanthin
Prasinoxanthin
19'-hexanoyloxyfucoxanthin
Fucoxanthin
. Chemotaxonomy
. Different roles of the xanthophylls: light harvesting & photoprotection
Peridinin
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Chlorophylls a et b
Pigments associated to intrinsic antennae
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Chl c
Absorption propertiesof chlorophylls
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-carotene (vitamin A)
-carotene
Carotenoids
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Carotenoids: xanthophylls
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-Carotene DiadinoxanthinFucoxanthin
Lutein Zeaxanthin
Carotenoids: absorption properties
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Rhodophyta Cyanophyta
Organisms with extrinsic, photosynthetic antennae
Cryptophyta
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Phycobiliproteins
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. 4 classes of phycobiliproteins :
Allophycocyanin (AP)Phycocyanin (PC)Phycoérythrocyanin (PEC)Phycoérythrin (PE)
Phycobiliproteins
. The classes of phycobiliproteins are differentiatated by:
- The aminoacid sequence of the and chains (between 15 and 20 kDa)
- The composition in phycobilins, and therefore their spectral properties
. 4 classes of phycobilins :
Phycocyanobilin (PCB)Phycobiliviolin (PVB)Phycoérythrobilin (PEB)Phycourobilin (PUB)
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Phycobilins
Phycourobilin
Phycoerythrobilin
Phycyanobilin
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Phycobilin Biosynthesis Glutamyl-ARNt
Glutamate semi aldéhyde
Acide aminolevulinique
Uroporphyrinogène III
Protoporphyrine IX+ Fe
Chlbactériochl
CatalasesCytochromes
Mg
Hème oxygénase
Hème
Biliverdine
Dihydrobiliverdine
Phycobilines
Glutamyl-ARNt
Glutamate semi aldéhyde
Acide aminolevulinique
Uroporphyrinogène III
Protoporphyrine IX+ Fe
Chlbactériochl
CatalasesCytochromes
Mg
Hème oxygénase
Hème
Biliverdine
Dihydrobiliverdine
Phycobilines
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Phycobiliproteins and phycobilins
αPC
βPC
162
17284
84
155
PCB
A
B
C-PC : A=B=PCBPEC : A=PXB, B=PCBR-PCI : A=PCB, B=PEBR-PCII : A=B=PEB
αPC
βPC
162
17284
84
155
PCB
A
B
C-PC : A=B=PCBPEC : A=PXB, B=PCBR-PCI : A=PCB, B=PEBR-PCII : A=B=PEBR-PCIII : A=B=PEBR-PC IV : A = PUB
PVB
αPC
βPC
162
17284
84
155
PCB
A
B
C-PC : A=B=PCBPEC : A=PXB, B=PCBR-PCI : A=PCB, B=PEBR-PCII : A=B=PEB
αPC
βPC
162
17284
84
155
PCB
A
B
C-PC : A=B=PCBPEC : A=PXB, B=PCBR-PCI : A=PCB, B=PEBR-PCII : A=B=PEBR-PCIII : A=B=PEBR-PC IV : A = PUB
αPC
βPC
162
17284
84
155
PCB
A
B
C-PC : A=B=PCBPEC : A=PXB, B=PCBR-PCI : A=PCB, B=PEBR-PCII : A=B=PEB
αPC
βPC
162
17284
84
155
PCB
A
B
C-PC : A=B=PCBPEC : A=PXB, B=PCBR-PCI : A=PCB, B=PEBR-PCII : A=B=PEBR-PCIII : A=B=PEBR-PC IV : A = PUB
PVB
Chromophores donnorvs.
Chromophore acceptor
The phycobilin placed at -84 Is always the acceptor chromophore,
whatever the phycobiliprotein
Phycoerythrins
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757583
83
75
75
83
8375
75
83
83
159140159
140
140
159159
140
-159 159
140
-14
0
250/61
250/61
250
/61
282
282 282
Hexameric PEII diagram
Modified after Wilbanks et al. (1991)
PEII dimer
Synechococcus sp. WH8103
Phycobiliproteins and phycobilins
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Optical properties of phycobiliproteins
Ab
so
rpti
on
Flu
ore
scen
ce
Wavelength (nm)
A
Ab
so
rpti
on
Flu
ore
scen
ce
Ab
so
rpti
on
Ab
so
rpti
on
Flu
ore
scen
ce
Wavelength (nm)
A
D E
C
F
G H
Ab
so
rpti
on
Flu
ore
scen
ce
Wavelength (nm)
A
Ab
so
rpti
on
Flu
ore
scen
ce
Ab
so
rpti
on
Ab
so
rpti
on
Flu
ore
scen
ce
Wavelength (nm)
A
D E
C
F
G H
C-Phycocyanin
Ab
sorb
ance
PCB PEB PEBPUB
Wavelength (nm)
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The phycobilisome
Phycocyanin
Phycoerythrin
Bras
Allophycocyanin
coeur6 nm
11 nm
Hexamer ()6
. Phycobiliprotein hexamers aggregate in macrostructures:
Phycobilisomes of Calothrix sp. PCC 7601
(Sidler, 1994)
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SDS-PAGE (15% acr.) of phycobilisomes fractions Synechococcus sp. PCC7002 (1),
Anabaena sp. PCC7120 (2), Mastigocladus laminosus (3) ;
Weigh markers (4).
LinkersSubunits &
(M. laminosus, Reuter and Nickel-Reuter, 1993)
Phycobilisome linker polypeptides
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Oriented transport of energy in the phycobilisome
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Phycobilisomes constantly diffuse on thylacoids
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Photosystem II structure
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Photosystem II structure
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Photosystem I structure
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How does oxygenic photosynthesis work?
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How does oxygenic photosynthesis work?
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Oxygenic photosynthesis