Abstract

Anatoxin-producing cyanobacteria pose growing ecological and public health risks, yet the genomic organization of anatoxin biosynthesis remains poorly resolved. Using complete genome assembly of a benthic cyanobacterium of the genus Microcoleus, we show that the entire anatoxin biosynthetic gene cluster is encoded on a small circular plasmid rather than the chromosome. This unexpected localization suggests enhanced mobility of anatoxin biosynthesis and has implications for toxin evolution, release, and environmental surveillance.