The biosynthetic gene cluster for the β-lactam antibiotic tabtoxin in Pseudomonas syringae

DNA sequence analysis revealed that the biosynthetic genes of the unusual beta-lactam antibiotic tabtoxin reside at the att site adjacent to the lysC tRNA gene in Pseudomonas syringae BR2. ORFs encoded within the region included ones with similarity to beta-lactam synthase and clavaminic acid synthase, as well as amino acid synthesis enzymes. Novel ORFs were present in a portion of the biosynthetic region associated with a toxin hypersensitivity phenotype. Tabtoxin resistance was associated with a fragment containing a major facilitator superfamily (MFS) transporter gene.