Genomics of Salt Acclimation

During their long evolution, cyanobacteria were able to inhabit all light-exposed ecosystems. One of the main environmental factors determining cyanobacterial distribution is the salinity of the surrounding medium. Among cyanobacterial strains, three main salt-tolerance groups can be distinguished: low- and moderate-halotolerant cyanobacteria as well as hypersaline strains. Regardless of the final salt resistance, all cyanobacteria apply two basic strategies for a successful acclimation to enhanced salt concentrations: accumulation of compatible solutes combined with active export of toxic ions, particularly Na+ and Cl−. During the years 1991–2010, the molecular basis of these mechanisms has been elucidated. Today, many complete genome sequences appear in databases of cyanobacterial strains, which are often difficult to cultivate in the laboratory. These data were used here to screen the genomes of more than 60 cyanobacteria regarding their compatible solute accumulation capacities. Hence, the existing knowledge about cyanobacterial salt acclimation was used to annotate basic salt-resistance mechanisms on the basis of genome information. Understanding the basic salt acclimation among cyanobacteria will also be useful for their future biotechnological application, which will be performed preferentially in saline waters.