Genomic Characteristics of the Toxic Bloom-Forming Cyanobacterium NIES-102.

, a bloom-forming cyanobacterium distributed mainly in freshwater environments, can be divided into at least 12 groups (A-K and X) based on multi-locus phylogenetic analyses. In this study, we characterized the genome of microcystin-producing NIES-102, assigned to group A, isolated from Lake Kasumigaura, Japan. The complete genome sequence of NIES-102 comprised a 5.87-Mbp circular chromosome containing 5,330 coding sequences. The genome was the largest among all sequenced genomes for the species. In a comparison with the genome of NIES-843, which belongs to the same group, the microcystin biosynthetic gene cluster and CRISPR-Cas locus were highly similar. A synteny analysis revealed small-scale rearrangements between the two genomes. Genes encoding transposases were more abundant in these two genomes than in other genomes. Our results improve our understanding of structural genomic changes and adaptation to a changing environment in the species.