Christophe Six UMR UPMC-CNRS 7144 “Adaptation & Diversité en Milieu Marin" Equipe « Procaryotes...
Transcript of Christophe Six UMR UPMC-CNRS 7144 “Adaptation & Diversité en Milieu Marin" Equipe « Procaryotes...
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
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
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
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
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
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
. 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
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
Anoxygenic photosyntheses
Reaction centres and bacteriochlorophylls
Bactériochlorophylle a Bactériochlorophylle b
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
The antenna complex of Chlorobium spp.
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
. 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.
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
The electron carrier chain of Chlorobium spp.
Cyclic transport of e-
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.
Rhodobacter sp.
Different types of structures of inner foldings
of the plasmic membrane
Non-sulphurous purple bacteria
The inner foldings of Rhodobacter sphaeroides (chromatophores)
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
Rhodobacter sphaeroides
Rhodopseudomonas viridis
The reaction centre of non-sulphurous purple bacteria
Photosynthetic apparatus of Rhodobacter sp.
Protein Structure involved in the photosynthetic activity of Rhodobacter sp.(Cross section of the cytoplasmic membrane)
Cyclic electron transport in Rhodobacter sp.
Anoxygenic reaction centres
Oxygenic photosynthesis
Global reaction : n [CO2 + H2O] [CH2O] n + O2
Location :
Chloroplasts ofvascular plants
Oxygenic photosynthesis
Bryopsis sp. Porphyridium sp. Fucus sp. Synechococcus sp.
Marine chloroplasts
Photosynthetic membranes : the thylacoids
Stroma/cytosol
Stroma/cytosolLumen
Membranar lipids
The membranar photosynthetic complexes
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-
Photosystem II antennae
. Two major structural groups : intrinsic et extrinsic to the thylacoids
. Large diversity of configuration depending on the taxonomic group
PS
Intrinsic, major PSII antenna (LHC type)
Intrinsic antennae
LHC type proteins
Th
yla
co
ids
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)
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
Chlorophylls a et b
Pigments associated to intrinsic antennae
Chl c
Absorption propertiesof chlorophylls
-carotene (vitamin A)
-carotene
Carotenoids
Carotenoids: xanthophylls
-Carotene DiadinoxanthinFucoxanthin
Lutein Zeaxanthin
Carotenoids: absorption properties
Rhodophyta Cyanophyta
Organisms with extrinsic, photosynthetic antennae
Cryptophyta
Phycobiliproteins
. 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)
Phycobilins
Phycourobilin
Phycoerythrobilin
Phycyanobilin
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
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
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
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)
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)
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
Oriented transport of energy in the phycobilisome
Phycobilisomes constantly diffuse on thylacoids
Photosystem II structure
Photosystem II structure
Photosystem I structure
How does oxygenic photosynthesis work?
How does oxygenic photosynthesis work?
Oxygenic photosynthesis