Synechococcus

Competition of photosynthetic organisms for light has triggered the development of an amazing variety of pigments and chromophorylated proteins during evolution. This diversity is stunning in the ubiquitous marine cyanobacterium Synechococcus, one of the two most abundant oxygenic phototrophs on Earth. Six distinct pigment types or subtypes have been described thus far in this genus, with the most sophisticated one being able to change its pigmentation according to the ambient light colour (green or blue). This large range of pigmentation likely plays a crucial role in the Synechococcus community structure. It arises from differences in the composition of the light-harvesting complexes (‘phycobilisomes’ or PBSs), which comprise various combinations of ‘phycobiliproteins’, each binding one to three different types of chromophores (or ‘phycobilins’). Most genes involved in the synthesis and regulation of PBS ‘rods’ (the most variable part of PBSs) are gathered into a specialized genomic region ranging in size from 9 to 28.5 kbp.

In the METASYN project, we propose a large scale study of PBS gene diversity :

• in culture, by sequencing 20 to 25 new cultured Synechococcus strains (in addition to the 11 genomes currently available)
• in the field, by sequencing fosmids containing the main PBS region from natural Synechococcus populations collected in different trophic regimes in the Mediterranean sea.

The main outcomes of this project will be :

• to gain new insights into the relative abundance of the different Synechococcus pigment types in the field along natural physico-chemical gradients.
• to improve our understanding of the evolution and mechanisms of lateral transfer of phycobilisome genes between Synechococcus lineages.
• to discover new pigment types and novel phycobiliproteins of potential commercial interest.