Growth-stimulating Effects of Algal Excreted Substances on Bacteria Isolated from Algal Blade Surface of the Brown Alga Eisenia bicyclis.

Growth of bacteria isolated from a new blade surface of the brown alga E. bicyclis was stimulated by algal excreted organic matter (EOM). The bacteria utilized some major algal components such as mannitol, fucoidan and alginate, but failed to utilize laminaran. Two fractions of EOM were obtained by elution on an activated charcoal column. The effect of these two fractions on growth was different. The first fraction caused bacterial cell density to increase linearly with concentration, whereas the second fraction stimulated bacterial growth at low concentration, yet increasing concentrations did not cause an increase in cell density. From the result of 1H-NMR, the second fraction seemed to consist of some sugars and phenolic substances.