Cyanobacteria - a potential source of new biologically active substances

Hydrophilic and lipophilic extracts of twelve cyanobacterial strains, isola ted from fresh and brackish water, and two waterblooms, collected during th e summer from the Baltic Sea, were investigated for their antibiotic activi ties against seven microorganisms. No inhibitory effects were found against the three Gram-negative bacteria Escherichia coli, Proteus mirabilis and S erratia marcescens and the yeast Candida maltosa. Of all cyanobacterial sam ples, extracts from seven species inhibited the growth of at least one of t he Gram-positive bacteria Micrococcus flavus, Staphylococcus aureus and Bac illus subtilis. M, flavus proved to be the most sensitive bacterium in the agar diffusion test system. In particular, the hexane and dichlormethane ex tracts showed antimicrobial effects. But only one water extract, prepared f rom material of a natural waterbloom, was found to be active. (C) 1999 Else vier Science B.V. All rights reserved.