When Simple Is Not So Simple/Unique Single-Cell Organisms

The Dunaliella cells are ovoid, or egg-shaped, and very small-about ten microns long. Placed end to end, it would take about 2,500 of them to make one inch.  Each cell has two whip-like flagella at one end, which allow it to swim.  Similar to  plants, Dunaliella cells use photosynthesis to provide energy.  They produce food from carbon dioxide, minerals, and other nutrients absorbed into the cell, and they reproduce by cell division.

Dunaliella can live even in a saturated salt solution. It is one of the very few organisms of any kind that can live and propagate in the Dead Sea, which has a salt concentration about eight times that of seawater.  This so-called simple organism can also survive changes in the salt concentration of its environment.

Consider, for instance, Dunaliella bardawill, found in  shallow salt marshes in the Sinai desert.  The water in these marshes can be diluted quickly during a thunderstorm or can reach saturated salt concentration when the extreme desert heat evaporates  the water.  Thanks in part to its ability to produce and accumulate glycerol in just the right amount, this tiny alga can tolerate such extreme changes.  Dunaliella bardawil is able to synthesize glycerol very rapidly, starting within minutes of a change in salt concentration, either producing or eliminating glycerol as needed in order to adapt.  this is important because in some habitats the salt concentration can change considerably within a matter of hours. 

Next time: When Simple Is Not So Simple/ Conclusion of Unique Single-Cell Organisms

From the Awake! magazine