The role of monic acid A in pseudomonic acid A biosynthesis in Pseudomonas fluorescens

The putative role of monic acid A as a biosynthetic intermediate of the antibiotic pseudomonic acid A, providing a C17 moiety requiring only esterification with a C9 fatty acid, has been tested by administration of [14C]monic acid A early in the pseudomonic acid A idiophase of a Pseudomonas fluorescens fermentation. [14C]Monic acid A was not taken up by the cells and the pseudomonic acid A subsequently accumulated was not radiolabelled. Experimental demonstration of the biosynthetic role of monic acid A and the potential use of monate analogues in biotransformations will require unexpectedly elaborate strategies to ensure the uptake of these compounds into bacterial protoplasts. The impermeability to monic acid A explains for the first time why it is not an antibiotic.