Biosynthesis and structure elucidation of lapicidamides in Photorhabdus temperata K122

Abstract

Entomopathogenic bacteria of the genus Photorhabdus are prolific producers of various Natural Products (NPs), several of them with novel structures, unusual biosynthetic pathways, and important ecological functions. Many of these NPs are produced by Biosynthetic Gene Clusters (BGCs). In Photorhabdus, many such BGCs encode for mega-enzymes called Non-Ribosomal Peptide Synthetases (NRPSs) and Polyketide Synthases (PKSs). However, a recent analysis of several genomes of Photorhabdus strains has revealed additional BGCs encoding hybrids between NRPS and PKS. The aim of this work is to activate the production of one such NRPS-PKS hybrid BGC – the lapicidamide (lpm) BGC in Photorhabdus temperata K122. An attempt has been made to study the individual biosynthetic steps and decipher the roles of modifying enzymes by generating various desired mutants, followed by analysis using HPLC-MS. Based on the mass spectrometry data, the structure of lapicidamides was predicted, and a putative biosynthetic pathway has been proposed.