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Cyanobacterin LU-1, produced by Nostoc linckia CALU 892, inhibits the growth of many cyanobacteria and eukaryotic algae. The minimum effective dose of a crude preparation to Synechococcus sp. R-2 is ca 1 g ml-1. The antibiotic hinders cell division and light-dependent oxygen evolution in Synechococcus sp. R-2 (PCC 7942) cells. It is not active against heterotrophic bacteria and fungi, and is non-toxic to mice.Purified cyanobacterin LU-1 contains a nitrous heterocycle with sugar and phenolic substituents. Cyanobacterin LU-1 accumulates in the medium during the course of growth, although not in direct proportion to cell density. Productivity of the culture depends on temperature.

Biologically active compounds were detected in water blooms on Lake Ladoga for the first time. Screening for cytotoxicity and for trypsin and acetylcholinesterase inhibitors revealed a degree of inhibitory activity by the water bloom biomass, which indicates the presence of cyanobacterial toxins in Lake Ladoga. High performance liquid chromatography (HPLC) of extracts of selected samples from the lake demonstrated a rather high diversity of bioactive compounds including hepatotoxic cyclic peptides (microcystins), enzyme inhibitors (cytotoxins), and a series of unidentified substances. Thirteen toxins and protease inhibitors were identified by the HPLC. The toxins were most diverse in the most eutrophic southern part of the lake (up to 12 bioactive compounds). Chromatograms showed that planktopeptin BL dominated in most of the samples investigated, except those from Svir Bay, where mcyst-LR prevailed. The results obtained indicate anthropogenic eutrophication of Lake Ladoga and a decrease in water quality. This lake is used as the only source of drinking water for the city of St. Petersburg.

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