1. Increasing Absorption Range for Photosynthesis

2. Goals Express different photosynthetic pigments in cyanobacteria
Increase the wavelengths that can absorb light energy and transfer to photosynthetic machinery
Potentially increase efficiency?

3. Photosynthetic Pigments
Chlorophylls
Phycobilins
Β carotene
Carotenoids

4. How do the Photo-Pigs work?
Chlorophylls
Transfers electrons around → reaction center
Incorporated into photosystem protein complexes
Carotenoids
Membrane bound
Transfers electrons to chlorophyll
Phycobilins
Water soluble, in cytoplasm
Also transfers electrons to chlorophyll

5. Model Organism: Cyanobacteria
Synechococcus, Synechocystis sp. PCC6803
Chlorophyll a, Phycobilins (phycocyanin, allophycocyanin, allophycocyanin B, phytoerythrin)
Genetically tractable

6. What has been done before?
Expressed chlorophyll b in Synechocystis sp. PCC6803
Demonstrated that it is incorporated into P700 chlorophyll-protein complex
Satoh et al., Journal of Biological Chemistry, (6)

7. What can we do?

8. Idea 1: BioBrick: Bba_K152005
Four enzymes required for beta-carotene synthesis:
geranylgeranyl diphosphate synthase (CrtE - BbaK152001)
phytoene synthase (CrtB - BbaK152002)
phytoene dehydrogenase (CrtI - BbaK18003)
lycopene beta-cyclase (CrtY - BbaK152003)

9. Carotenoid Biosynthesis in Synechococcus

10. Questions to ask / Things to do
When overexpressed is beta-carotene incorporated into a photosystem?
What does beta-carotene normally do in cyanobacteria?
How/Why was this biobrick made? What did they feed the E. coli?
Can E. coli constructs be used in cyanobacteria?

11. Idea 2: Express Chlorophyll d
Spectrum is red shifted
Can act as reaction center?
Need to find protein that can do this reaction.
Larkum and Kuhl, Trends in Plant Science (2005) 10 (8).