Characterization of Red Sea Cyanobacteria Aimed for Cell Factory Applications in Saudi Arabia: Synechococcus sp. RSCCF101.

Saudi Arabia is highly accessible to marine water, receives year-round availability of sunlight and generates a high annual carbon dioxide emission, all of which are justifications that merits the deployment of cyanobacterial cell factories. However, industrial cyanobacterial strains capable of thriving in conditions of the Arabian Peninsula are currently lacking. Given the fact that native cyanobacteria from the Red Sea are adapted to the local conditions, they are therefore good cell factory candidates where their inherent attributes can be harnessed. In this dissertation, an isolation and screening pipeline was developed to specifically identify physiologically robust cyanobacterial strains from the central Red Sea. Seventeen unicellular cyanobacterial strains were extensively cataloged through a series of physiological characterization and their evolutionary relationships were ascertained through phylogenetic analyses. Arising from this survey work, a high light, thermo- and halo-tolerant Synechococcus sp. RSCCF101 was selected for metabolic analysis under various growth conditions to assess its suitability as a platform for cell factory development. Significant metabolic changes were observed in cells subjected to different light regimes. High phycocyanin and chlorophyll a content were obtained under the low-light growth (50 μmol photons.m-2.s-1) while high biomass was accumulated, along with an increase external nitrate demand, under the high light growth (200 μmol photons.m-2.s-1). A genomic and transcriptomic approach was undertaken to elucidate the molecular signatures of Synechococcus sp. RSCCF101. Synechococcus sp. RSCCF101 contains a small genome (3 Mbp) that is rich in guanine cytosine content (68%) and harbors genes that encode for compatible solutes biosynthetic pathway and phycobilisome subunits which may account for its halo-tolerant and phycocyanin rich phenotype. Upon high-light treatment, the light harvesting machineries of Synechococcus sp. RSCCF101 was downregulated while the photosystem protection and carbon fixation capacity were upregulated. Taken together, the findings of this research will facilitate in the development of a new model system for industrial applications in high-light, high temperature and high salinity environments in general and Saudi Arabia in particular.