Isolation and identification of the antialgal compound, harmane (1-methyl-β-carboline), produced by the algicidal bacterium, Pseudomonas sp K44-1

Twelve strains of algicidal bacteria were isolated from the surface water of the pond Shinobazu and the moat Ote-bori (Tokyo, Japan). Nine of these strains were considered to be in the Pseudomonas group by analyses of 16S rDNA sequences. The methanol extract of Pseudomonas sp. K44-1 showed marked antialgal activity by the paper disk method. Harmane (1-methyl-beta-carboline) was isolated from the ethyl acetate extract of the whole culture broth of Pseudomonas sp. K44-1 by using silica gel column chromatography and high performance liquid chromatography (HPLC). Harmane showed antagonistic activities against several cyanobacterial strains at a concentration of 30 mug disk(-1).