Some cyanobacteria are highly tolerant of salt and grow in media with high osmolarities. Saline and
hypersaline lakes often contain picocyanobacteria, mat-forming species such as Microcoleus chthonoplastes,
bloom-forming, nitrogen-fixing species such as Nodularia spumigena, and the salt-tolerant colonial
species Aphanothece halophytica. Certain taxa are obligate halophiles, and can grow in environments
with salt concentrations of up to 360 g of salt per liter, 10 times the salinity of seawater. Salt-tolerant
cyanobacteria produce a range of osmolytes, that is, solutes that maintain their high internal osmolarity
and turgor pressure without causing toxic effects on proteins and other cellular constituents. The most
important of these are glucosylglycerol (which can account for up to 30% of dry weight in cells grown
in hypersaline media) and glycine betaine.