Identification of a Polyketide Synthase Coding Sequence Specific for Anatoxin-a-Producing <i>Oscillatoria</i> Cyanobacteria

We report the identification of a sequence from the genome of Oscillatoria sp. strain PCC 6506 coding for a polyketide synthase. Using 50 axenic cyanobacteria, we found this sequence only in the genomes of Oscillatoria strains producing anatoxin-a or homoanatoxin-a, indicating its likely involvement in the biosynthesis of these toxins.