The Chlorophyte and the Darkness: a Model System

(work started with Dr. Paul G. Falkowski at Brookhaven National Laboratory, New York)

This is a micrograph of Dunaliella tertiolecta, a common green algae that inhabits tide pools in many parts of the world. This particlar alga is the decendant of a single cell isolated from a Norwegian fjord in 1928. Assuming it has divided just once per week (and it is capable of dividing up to 3 times a day under optimal conditions!), it has survived for over 3000 generations…the equivalent of the time since the end of the last ice age, in human terms. Is this an immortal organism?

Apparently not:


The graphs above show that when placed in darkness for about one week (starting on day 1), there is:

  • a drastic loss of cells
  • a considerable loss of particulate carbon
  • an increase in protease activity (caseinolysis and LAP activity)

The photographs of electrophoretic gels above demonstrate:

  • a considerable change in general cell proteins during this culture decline (A. Total proteins in a silver-stained SDS-PAGE gel)
  • the apperance of a specific protease at the point of decline (B. A casein zymogram showing clear band where there is protease activity)