Joyce Lewin

The Sulfate Requirements of Some Unicellular Marine Algae1

Abstract Nine species of unicellular marine algae were cultured in a synthetic medium in which the sulfate concentration was varied. Final growth in response to sulfate concentration was determined for each species. Sulfate concentrations in the range of 1/100 to 1/200 of that found in natural sea water were sufficient to satisfy the sulfur requirements of seven of the species. Two of the species had somewhat higher requirements, perhaps attributable to additional demands for the accumulation of extracellular sulfated polysaccharides. In the range of limiting concentrations, final growth was proportional to sulfate concentration in most instances. Rapid bleaching of the cells occurred after the sulfate in the medium had become exhausted. A sulfate concentration of 0.2–0.4 g/l, employed in experiments with radioactive sulfur, allowed a high level of incorporation of radioactivity into the algal cells.