Identification and analysis of whole microcystin synthetase genes from two Korean strains of the cyanobacterium Microcystis aeruginosa

Microcystins are cyanobacterial hepatotoxins, and are produced by nonribosomal enzyme complexes, mcy gene cluster. In this study, we report on whole mcy gene clusters from two Korean strains of M. aeruginosa that were blooming in Lake Paldang (FCY-26) and Geum river (FCY-28). Their specific gene locus, amino acid information, and sub-cluster orientation were also characterized in both strains. Both gene clusters are of 55 kb, and also each length, number and the arrangement are identical. Their sequence analysis revealed a cluster of 10 genes (mcyA, B, C, D, E, F, G, H, I, and J) involved in the biosynthesis of microcystin, and mcyABC and mcyDEFGHIJ formed two polycistronic operon structures that are transcribed bidirectionally from a central promoter region between mcyA and mcyD. The analysis of SNPs provided different nucleotide composition and amino acid variations in two Korean strains of M. aeruginosa. This approach is useful to develop genetic indicators identifying toxic cyanobacteria and their cyanotoxins, and helpful for a better understanding of the diversities of mcy gene clusters, the biosynthesis of microcystin, and the mediation of environmental parameters causing algal blooming and HABs.