The genus contains only two species, both unable to produce microcystins: and .

Spirulina is the commercial name for edible cyanobacteria of the genus . The taxonomy of this genus is confusing with four species distributed in two lineages. Furthermore, the species has been cited as toxic by potentially producing microcystins. Taxonomic ambiguity combined with suspected health concerns constitute a major issue for spirulina producers. In a collection of six cultivars and one ecotype, we identified strains of the two lineages through metagenetic and morphological analyses. We demonstrated that the genus only comprises two distinct species according to genomic comparisons of three genomes obtained in this study and 19 reference genomes. We showed that the V3-V4 region of the 16S rRNA gene is sufficient to identify the genus and to distinguish the two species. Toxinogenesis investigations on eleven genomes from each species revealed no genes involved in cyanotoxin synthesis, reflecting the inability of this genus to produce microcystins.