THE ANTIBACTERIAL SUBSTANCES OF THE MARINE ALGA STICHOCHRYSIS IMMOBILIS (CHRYSOPHYTA)¹²

Abstract

SUMMARY Two substances with antibacterial activity have been concentrated from the culture medium of Stichochrysis immobilis before senescence occurred, and purified, by a Sephadex G‐25 filtration followed by 2‐dimensional thin‐layer chromatography on Merck F‐254 silica gel plates. One of the substances is obviously a peptide; 11 different amino acids are linked in a 30 amino acid molecule (MW 3400). It was not possible to assign a chemical group to the second substance (MW ≃ 2600); it may be related to “humic acids” (Kalle's gelbstoff). Growth of the most sensitive bacteria was completely inhibited by 20‐fold, or higher, concentrations of substances from the algal culture filtrate (assuming no loss of substances during the concentration processes). The 54 strains of test bacteria were of various origins, though mostly isolated from algal cultures or obtained directly from the marine environment.