Ambigol A is an antibiotic against Serratia sp. ATCC 39006 (S39006) strain. The terrestrial cyanobacterium Fischerella ambigua 108b produces the three polychlorinated triphenyls ambigol A–C that exhibit interesting antimicrobial, antiviral and cytotoxic activities. They are structurally related to polybrominated diphenylethers synthesized by diverse marine bacteria that are known to be highly toxic and are bioaccumulating in natural food webs. All ambigols display unusual connectivities: Ambigols A and B exhibit chlorination and ambigol C biaryl-ether bonds in the relative meta position at the central phenol unit, which is flanked by two 2,4-dichlorophenol units in all three compounds. Here we report on the identification of the biosynthetic gene cluster (BGC) reponsible for ambigol production in F. ambigua.
