Influence of spectral wavelength and N:P ratio on the cell cycle of Synechococcusstrain CSIRNIO1 isolated from the central Eastern Arabian Sea

Abstract

The novel phycoerythrin-containing Synechococcus strain CSIRNIO1 belonging to phylogenetic clade II was isolated from the coastal Arabian Sea. Chromophore characteristics of this isolate revealed the presence of phycoerythrin I (PEI), which allows it to utilize green light efficiently. The DNA distribution data indicate a bimodal slow growth model synchronized with the light/dark cycle. The duration of the cell cycle was regulated by spectral wavelength and nutrient concentration. Nitrate and phosphate enrichment shortened G1 phase duration when cells were exposed to equal doses of photosynthetically usable radiation (PUR) of different spectral wavelengths. G2 phase duration was influenced by spectral quality and phosphate concentration. S phase duration was not affected by the spectral wavelength. However, a shorter doubling time corresponding to shortened G1 and S phases was observed under nitrate enrichment. Phosphate enrichment resulted in shortening of all three phases (G1, S and G2). More efficient utilization of green and red light than blue light regulated the duration of the cell cycle as well as the doubling time, suggesting spectral selectivity in this strain. The effects of spectral wavelengths under varying nutrient concentrations will determine the proliferation of Synechococcus and its adaptation to different environmental conditions.