Synechococcus plasticity under environmental changes

Cyanobacteria are among the oldest photoautotrophic organisms on Earth, and have contributed to shaping the planet's biogeochemistry with their significant biomass and key metabolic activities. Synechococcus, the focus of this review, is one of the prevalent genera in the order Chroococcales, common in oceans and lakes and characterized by a coccoid unicellular or microcolony morphology. The evolution of its phycobilisomes is the key of the adaptation of this tiny photosynthetic cell to different light regimes and environmental conditions. Furthermore, Synechococcus strains are widely distributed from the equator to the poles, showing an extreme adaptability to high and low temperatures. Because of their structural plasticity and ecological adaptability, these cyanobacteria are particularly interesting in the current condition of fast climate change. Moreover, picocyanobacteria of the Synechococcus genus have a potentially vast impact on global cycles thanks to their significant role in the biogeochemical cycles of aquatic ecosystems. As increasing abundances are predicted for this genus worldwide, and in light of the connection between cyanobacteria and global change events, a better characterization of these organisms promises important and timely ecological insights. Here, I will summarize the morphological and genetic characteristics of Synechococcus strains and their distribution in freshwater lakes, also considering its marine counterpart.