Abstract
The effect of extracellular metabolites produced by the brown alga Cystoseira barbata growing at different salinities on some bacteria and on the germination of Zea mays was studied. It was found that the alga produces some metabolites which showed an inhibitory effect on the growth of both Escherichia coli and Staphylococcus aureus. At the same time, metabolites promoted the growth of Zea mays seedlings irrespective of the salinity at which the germination was carried out. The production of extracellular metabolites was found to be more when the alga was maintained at 15 ppt salt conc than when it was maintained at 5 ppt or 25 ppt.