PHYTOCHELATIN PRODUCTION IN MARINE-ALGAE .1. AN INTERSPECIES COMPARISON

Phytochelatins are metal-binding peptides produced enzymatically by higher plants, fungi, and algae in response to many metals, particularly Cd. We have studied phytochelatin production in several marine phytoplankton exposed to a range of free Cd ion concentrations. As a result of increased analytical resolution, we have found that all the species contain phytochelatin, even when there is no added Cd, and that elevated phytochelatin concentrations are induced by Cd, even at very low and environmentally relevant concentrations (as low as 10(-12) M free ion concn). In some but not all species, intracellular Cd and phytochelatin concentrations are maintained at a fixed stoichiometric ratio at high Cd concentrations. Phytochelatin production and accumulation appear to be regulated in a manner that varies among phytoplankton species.