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The Role of
Viral Photosynthetic Proteins in
Oceanic Photosynthesis

Acronym: PhotoPhage

Cyanobacteria play a key role in marine photosynthesis, contributing almost 50% of primary production in oligotrophic regions of the ocean, and contribute to the global carbon cycle and the world oxygen supply. Marine cyanophages were recently discovered to carry photosystem II (PSII) genes, and it was suggested that these genes increase phage fitness by helping the phages to maintain photosynthesis in the infected bacterial cells. We recently showed evidence for the presence of photosystem I (PSI) genes in genomes of marine cyanophages [Sharon et al. 2009 Nature 461, 258-262]. Cyanobacterial core PSI gene cassettes, containing psaJFABCDEK, or psaDCAB gene cassettes forms unique clusters in cyanophage genomes, suggestive of selection for a distinct function in virus reproduction. Potentially, the proteins encoded by the viral genes are sufficient for forming intact monomeric PSI complexes. Projection of viral predicted peptides on the cyanobacterial PSI crystal structure suggests that the viral PSI components provide a unique way for funneling reducing power from respiratory and other electron transfer chains to PSI, therefore bypassing the need to rely solely on reducing power from the photosystem electron transfer chain.


The main goals of this proposal are:

(1) To determine how much of oceanic photosynthesis is actually performed with viral proteins.

(2) To establish a model system to understand the role of modified photosynthetic viral proteins in photosynthesis

We hypothesize that viral photosynthetic peptides are integrated into the bacterial photosynthetic membranes in order to maintain photosynthesis in infected cells, that otherwise stop to photosynthesize, and that changes are introduced to the system as a whole.

The proposed research will integrate different OMICS concepts and techniques to explore the interaction of viral PSII and PSI proteins with their host reaction centre complexes, and to examine their influence on global marine photosynthesis production, given the fact that ~5-10% of bacterial cells are infected at any given time. We estimate that this project will bring a significant breakthrough to the photosynthesis field with potential application in both basic and applied sciences. Positive results will enable us to start predicting how much of sun's energy is funneled to the oceans via viral intermediates



A new phage containing both PSII and PSI genes

ERC Team
Oded Beja
(Principal Investigator)

Alon Philosof (Ph.D. student)
Marine microbial metagenomics

Svetlana Fridman
(joint Ph.D. student with Prof. Debbie Lindell)
Viral photosynthesis

Dr. Shay Kirzner (Postdoctoral Fellow)
Viral photosynthesis

Dr. Shirley Larom (Postdoctoral Fellow)
Viral photosynthesis

Dr. Onit Alalouf (Postdoctoral Fellow)
Viral photosynthesis

Gur Hevroni (M.Sc. student)
Viral photosynthesis

Sheila Roitman (M.Sc. student)
Viral photosynthesis

Dr. Ofir Tal (Protein specialist) 


Philosof, A., and Beja, O. A day in a life in the Red Sea: A viral (and phage) perspective. in preparation

Fridman, S. et al. Isolation of a novel myovirus expressing both photosystems- I and II genes during Prochlorococcus infection. in preparation


Roitman*, S., Flores-Uribe*, J., Philosof, A., Knowles, B., Rohwer, F., Ignacio-Espinoza, J.C., Sullivan, M.B., Cornejo-Castillo, F.M., Sanchez, P., Acinas, S.G., Dupont, C.L., and Beja, O. Closing the gaps on the viral photosystem-I psaDCAB gene organization. Environ. Microbiol. accepted
*equal contribution

Hevroni*, G.
Enav*, H., Rohwer, F., and Beja, O. (2015) Diversity of viral photosystem-I psaA genes. ISME J. 9, 1892-1898.
*equal contribution


Researcher's Night September 2014 Line Islands Expedition 2015

Last updated August 2015

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