Plasmid-mediated microcystin production in Fischerella CENA161

The strain Fischerella sp. CENA161 is a microcystin producing cyanobacterium isolated from spring water in Brazil. The complete biosynthetic mcy gene cluster and potential microcystin congeners were published in 2018. In this work, bioinformatic analysis of whole-genome sequence and hybrid assembled data from Fischerella sp. CENA161 was performed. For detection of putative plasmids in this strain, the plasmid assembly mode in SPAdes was used on reads sequenced with the MiSeq and PacBio plataforms, followed by annotation of resulting contigs using PlasmidFinder. The complete genome size of CENA161 is 5.9 Mb and three plasmids were annotated with sizes of 728, 242 and 192 kb. The complete mcy gene cluster was found in the larger plasmid. Genome mining of available microcystin-producing cyanobacteria was also carried out to detect the partitioning of microcystin biosynthetic pathways in chromosomes and plasmids, and will be presented. Plasmid-mediated microcystin production is a significant public health concern given its potential to easily spread among aquatic cyanobacteria.