Assembly and Export of Extracellular Polymeric Substances (EPS) in CyanobacteriaGenomics of Cyanobacteria

Many cyanobacterial strains produce extracellular polymeric substances (EPS), mainly composed of polysaccharides that can remain associated to the cell or be released into the surrounding environment (released polysaccharides (RPS)). The particular characteristics of these EPS, such as the presence of two different uronic acids, sulphate groups and high number of different monosaccharides (up to 13), make them very promising for biotechnological applications. Despite the increasing interest in these polymers, the information about their biosynthetic pathways is still limited. Studies performed in other bacteria revealed that the mechanisms of EPS assembly and export are relatively conserved, generally following the Wzy-dependent or the ABC-dependent pathways, which require the involvement of polysaccharide copolymerase (PCP) and outer membrane polysaccharide export (OPX) proteins. Our previous studies revealed that in cyanobacteria, the genes encoding these proteins occur in multiple copies, scattered throughout the genome, either isolated or in small clusters. However, it is necessary to identify other genes that may be related to this process, understand their genomic distribution, and reconstruct their evolutionary history. The data gathered here provide a first insight on the phylogenetic history of the EPS-related genes, and constitute a robust basis for subsequent studies aiming to optimize EPS production in cyanobacteria.