Anatoxin-a biosynthetic gene cluster (CF-9) and produced variants of in PCC 7417. Anatoxin-a pathway identified in the genome of Cylindrospermum sp. PCC 7417 compared to homologous gene clusters from anatoxin-a producing cyanobacteria [8, 26, 27]. Genes with corresponding functions and domain organization are colored the same and connected by grey areas: anaA, proline adenylation, anaB, proline deshydrogenase, anaC, Type II thioesterase; anaD, acyl carrier protein, anaE, anaF and anaG are modular type I polyketide synthase with KS, β-ketoacyl synthase; AT, acyltransferase; KR, ketoacyl reductase; ACP, acyl carrier protein; DH, dehydratase; ER, enoyl reductase and CM, C-methyltransferase. The cyclase, named here anaI, is systematically associated to the anatoxin-a pathway. In addition, the last PKS anaG2 in PCC 7417 lacks the methyltransferase, and an oxidoreductase anaJ was detected. The transposase is present in the surrounding of the cluster only in PCC 6506. The detection of dihydroanatoxin-a from PCC 7417 is presented in Additional file 2: Figure S2.