Transcript Non-sulphurous purple bacteria - Station Biologique de Roscoff

Unité d’Enseignement : Evolution du Phytoplancton Marin et Biogéochimie
Introduction to Photosynthesis:
Evolutionary processes
Christophe Six
UMR UPMC-CNRS 7144 “Adaptation & Diversité en Milieu Marin"
Equipe « Procaryotes Photosynthétiques Marins »
Station Biologique de Roscoff
Université Pierre et Marie Curie (Paris VI)
Bureau 354, 3ème étage (Bâtiment GT)
[email protected]
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).
h
Minerals
Cofactors
Organic
matter
. Most of life on Earth is dependent on photosynthesis through food webs.
Exception : hydrothermal vents
Origin of photosynthesis at the
scale of Geological times
Precambrian
Millions years
Millions years
Millions years
http://www.ipgp.jussieu.fr/files_lib/83_echm-gt.gif
The oldest fossils : the Stromatolites
Stromatolites
Microfossils of filamentous
cyanobacteria
West of Australia
http://www.interet-general.info/IMG/Stromatolites-2-3.jpg
http://www.gc.maricopa.edu/earthsci/imagearchive/stromatolite.jpg
http://www.cartage.org.lb/en/themes/Sciences/Paleontology/Paleozoology/Precambrian/Precambrian.htm
Fossil evidences : the stratified iron formations
Iron stratified formations
Microbial coccoid fossil
(Eosphaera)
Mont Bruce, West of Australia
http://www.geo.vu.nl/~smit/hamersley/hamersley%20iron.jpg
10 µm
Formation of Gunflint, North America
http://gsc.nrcan.gc.ca/paleochron/05_e.php
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
Consequences of the development of oxygenic photosynthesis
Diversité (nombre de taxa)
Billion years
Présent
The photosynthetic organisms on Earth
. 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
Lakes & Estuaries
Benthic/Planctonic.
Stratified freshwater lakes:
Anoxiques zones
. Les heliobacteria
Heliobacterium
. Photoheterotrophic, anoxygenic, aerobic bacteria
Roseobacter, Roseovarius, Erythrobacter
Still poorly known; Oceans
. Cyanobacteria = Oxyphotobacteria
Synechococcus, Prochlorococcus, Oscillatoria, Anabaena, Synechocystis, Microcystis, Planktothrix,
Trichodesmium, Croccosphaera, etc…
. Photosynthetic (oxygenic) eukaryotes
Rhodophyta, Heterokontophyta, Chlorobionta
The different groups of photosynthetic organisms on Earth
Photosynthesis
Oxygenic
Two types of reaction centres
Antenna = Phycobilisome or Lhc
Electron donnors = H2O
Anoxygenic
A single type of reaction centre
-Typical antenna system (BChl & Carotenoids)
Electron donnors = reduced compounds
Aérobic
RC I + RC II
Cyanobacteria = oxyphotobacteria
(photohétérotrophs & obligatory phototrophs)
Aerobic
Anaerobic
Photosynthetic eukaryotes:
Eukaryotic phytoplankton, macroalgae,
bryophytes and vascular plants
(photohétérotrophs)
Purple bacteria
(RC II – BChl a ou b – (Calvin cycle)
Sulphurous
(obligatory
phototrophs)
Non- sulphurous
(photoheterotrophs)
Green bacteria
Héliobacteria
(Chlorosome – no RuBisCO)
RC I
Sulphurous
(obligatory
phototrophs)
RC I
Chlorobiaceae
Non- sulphurous
(photoheterotrophs)
RC II
Chloroflexaceae
Anoxygenic photosyntheses
Reaction centres and bacteriochlorophylls
Bactériochlorophylle a
Bactériochlorophylle b
Sulphurous Green bacteria
Microbial mat : Chlorobium
Chlorobium sp. BS1
Chlorobium tepidum
Yellowstone national park, USA
Microbewiki
Benthic organisms : 1mm beneath the sediment at the bottom
of 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
The reaction centre of Chlorobium spp.
. 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
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
Rhodospirillum rubrum
Rhodobacter sphaeroides
http://www.de.mpi-magdeburg.mpg.de/research/projects/1010/1014/1020/rhodos.jpg
http://www.martin-stein.com/images/rhodob.jpg
Rhodopseudomonas sp.
Non-sulphurous purple bacteria
Rhodobacter sp.
Different types of structures
of inner foldings
of the plasmic membrane
The inner foldings of Rhodobacter sphaeroides (chromatophores)
The antenna complex of Rhodopseudomonas acidophila
- 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
- On pair  binds 1 ou 2 BChl  18 BChl perpendicular to the plan per LH2 (= B850 abs max at 850nm)
- 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 : Polypeptides
Orange : B800 bacteriochlorophylls
Vert : Carotenoids
The reaction centre of non-sulphurous purple bacteria
Rhodobacter sphaeroides
Rhodopseudomonas viridis
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
Oxygenic photosynthesis
Global reaction : n [CO2 + H2O]
[CH2O] n + O2
Location :
Chloroplasts of
vascular plants
Marine
chloroplasts
Bryopsis sp.
Porphyridium sp.
Fucus sp. Synechococcus sp.
Photosynthetic membranes : the thylacoids
Stroma/cytosol
Lumen
Stroma/cytosol
Membranar lipids
The membranar photosynthetic complexes
What is a photosystem?
Photosystem = reaction centre
+ photosynthetic antenna
. Two large subunits
D1/D2 ; PsaAB)
. A number of small subunits
. 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
. Large diversity of configuration  depending on the taxonomic group
. Two major structural groups : intrinsic et extrinsic to the thylacoids
Intrinsic antennae
Intrinsic, major PSII antenna (LHC type)
Thylacoids
PS
LHC type proteins
Intrinsic antennae
CP43
D1/D2
CP47
CP43
Proteins LHC
D1/D2
CP47
Reaction centres
Lhcb3 ou 4 ou 5 ou 6
Trimères de LHCIIb
(Top view)
Pigments associated to intrinsic antennae
. Chemotaxonomy
Chl a
19'-hexanoyloxyfucoxanthin
Chl b
Chl c1
Lutein
Chl c2
Neoxanthin
Chl c3
Prasinoxanthin
Fucoxanthin
Peridinin
. Different roles of the xanthophylls: light harvesting & photoprotection
Violaxanthin
Antheraxanthin
Zeaxanthin
Diadinoxanthin
Diatoxanthin
Pigments associated to intrinsic antennae
Chlorophylls a et b
Absorption properties
of chlorophylls
Chl c
Carotenoids
-carotene (vitamin A)
-carotene
Carotenoids: xanthophylls
Carotenoids: absorption properties
-Carotene
Fucoxanthin
Lutein
Zeaxanthin
Diadinoxanthin
Organisms with extrinsic, photosynthetic antennae
Rhodophyta
Cyanophyta
Cryptophyta
Phycobiliproteins
Phycobiliproteins
. 4 classes of phycobiliproteins :
Allophycocyanin (AP)
Phycocyanin (PC)
Phycoérythrocyanin (PEC)
Phycoérythrin (PE)
. 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
Hème
oxygénase
Hème
Biliverdine
Dihydrobiliverdine
Phycobilines
Mg
Chl
bactériochl
Catalases
Cytochromes
Phycobiliproteins and phycobilins
αPC
A
84
βPC
162
PCB
B
84
155
C-PC : A=B=PCB
PVB B=PCB
PEC : A=PXB,
R-PCI : A=PCB, B=PEB
R-PCII : A=B=PEB
R-PCIII : A=B=PEB
R-PC IV : A = PUB
Phycoerythrins
172
Chromophores donnor
vs.
Chromophore acceptor
The phycobilin placed at -84
Is always the acceptor chromophore,
whatever the phycobiliprotein
Phycobiliproteins and phycobilins
250/61
282
140
282
 PEII dimer
282
Hexameric PEII diagram
Modified after Wilbanks et al. (1991)
Synechococcus sp. WH8103
Optical properties of phycobiliproteins
Absorbance
Absorption
Fluorescence
PCB
PEB
C
A
Wavelength (nm)
Wavelength (nm)
C-Phycocyanin
C
D
PUB PEB
D
E
E
F
The phycobilisome
. Phycobiliprotein hexamers aggregate in macrostructures:
Allophycocyanin
Phycoerythrin
Phycocyanin
11 nm
6 nm
coeur Bras
Hexamer ()6
Phycobilisomes of
Calothrix sp. PCC 7601
(Sidler, 1994)
Phycobilisome linker polypeptides
Subunits  & 
SDS-PAGE (15% acr.) of phycobilisomes fractions
Synechococcus sp. PCC7002 (1),
Anabaena sp. PCC7120 (2),
Mastigocladus laminosus (3) ;
Weigh markers (4).
Linkers
(M. laminosus, Reuter and Nickel-Reuter, 1993)
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