P126: Biosynthesis, activation and detoxification of anti-bacterial isocoumarins from a marine Bacillus subtilis strain

Amicoumacins are bacterial isocoumarins that exhibit a wide variety of biological effects, including anti-bacterial and anti-tumor activity. Yet, little is known about how these bioactive agents are biosynthesized and activated. Our genome sequence analysis of Bacillus subtilis strain 1779 revealed that the putative amicoumacin biosynthetic gene cluster (ami) encodes a hybrid non-ribosomal peptide synthetase−polyketide synthase enzyme complex, which is organized for the synthesis of fatty acyl-D-glutamine/asparagine derivatives of amicoumacin. UPLC-ESIMS and bioinformatics analyses suggest that fatty acyl-D-Gln/Asn amicoumacin derivatives are first produced as inactive natural “prodrugs” that ultimately get transported and activated via peptide bond hydrolysis to form the active antibiotic amicoumacin A. Deactivation to low self-toxic analogues, including amicoumacin B, appears to arise as an encoded detoxification mechanism. Cloning, sequencing, and mutagenesis of homologous 65 kb amicoumacin biosynthetic gene clusters has afforded the first genetic evidence supporting amicoumacin biosynthesis and reveals the molecular basis for the activation and detoxification mechanisms.