A halophile is an organism adapted to growth in high-salt environments, with its preferred or required salt conditions depending on the species. The term describes a way of living, rather than one clade. For example, Haloferax volcanii is a member of Archaea, whereas Dunaliella parva belongs to the algae. A halophile must sustain cellular function despite the effects of external salinity on water movement and proteins.[ref]
A concrete mechanism was tested by Ami Ben-Amotz and Mordhay Avron in 1973. They measured intracellular glycerol in Dunaliella parva and estimated its concentration using cellular volume. Changing external sodium chloride caused corresponding changes in intracellular glycerol, with a new balance through osmoregulation reached after about 90 minutes. Their leakage measurements supported metabolic production and breakdown of glycerol as the explanation, rather than simple escape of the solute. This connects environmental change to measurable osmoregulation.[ref]
The experiment illustrates why a growth habitat alone does not identify a mechanism. Two halophiles can inhabit salty surroundings while controlling intracellular solutes differently. A useful comparison specifies the organism, external salt concentration, cellular response and time after the salt change.
New to topics? Read the docs here!