Cyanobacterial protease inhibitor microviridin J causes a lethal molting disruption in Daphnia pulicaria.

Laboratory experiments identified microviridin J as the source of a fatal molting disruption in Daphnia species organisms feeding on Microcystis cells. The molting disruption was presumably linked to the inhibitory effect of microviridin J on daphnid proteases, suggesting that hundreds of further cyanobacterial protease inhibitors must be considered potentially toxic to zooplankton.

Isolation, characterization, and quantitative analysis of Microviridin J, a new Microcystis metabolite toxic to Daphnia.

This paper describes the purification and characterization of microviridin J. a newly discovered metabolite of Microcystis that causes a lethal molting disruption in Daphnia spp., upon ingestion of living cyanobacterial cells.

Multiple alternate transcripts direct the biosynthesis of microcystin, a cyanobacterial nonribosomal peptide.

The mcyABCDEFGHIJ gene cluster of Microcystis aeruginosa encodes the mixed polyketide synthase/nonribosomal peptide synthetase (microcystin synthetase) which is responsible for biosynthesis of the potent liver toxin microcystin. The sequence and orientation of the mcy genes have previously been reported, but no transcriptional analysis had been performed prior to this study. The mcyABCDEFGHIJ genes are transcribed as two polycistronic operons, mcyABC and mcyDEFGHIJ, from a central bidirectional promoter between mcyA and mcyD.