Heterologous production of GameXPeptide A (1), as well as of the novel peptide natural products ambactin (2) and xenolindicins A-C (3 a-c), was achieved by using the "overlap extension PCR-yeast homologous recombination" (ExRec) method. ExRec cloning is based on the ability of yeast to assemble overlapping DNA fragments into functional plasmids. Here we used this technique to clone a total of 15 biosynthesis gene clusters from Photorhabdus and Xenorhabdus with sizes of up to 45 kb. The structures of the novel compounds 2 and 3 a, which were produced in Escherichia coli, were elucidated by detailed MS and bioinformatics analysis, and additionally confirmed by their chemical synthesis.

Pyrrolizidine alkaloids (PAs) are widespread plant natural products with potent toxicity and bioactivity. Herein, the identification of bacterial PAs from entomopathogenic bacteria using differential analysis by 2D NMR spectroscopy (DANS) and mass spectrometry is described. Their biosynthesis was elucidated to involve a non-ribosomal peptide synthetase. The occurrence of these biosynthesis gene clusters in Gram-negative and Gram-positive bacteria indicates an important biological function in bacteria.

Pyrrolizidine alkaloids (PAs) are widespread plant natural products with potent toxicity and bioactivity.H erein, the identification of bacterial PAsf rom entomopathogenic bacteria using differential analysis by 2D NMR spectroscopy (DANS) and mass spectrometry is described. Their biosynthesis was elucidated to involve an on-ribosomal peptide synthetase.T he occurrence of these biosynthesis gene clusters in Gram-negative and Gram-positive bacteria indicates an important biological function in bacteria. Figure 3. Proposed biosynthesis of bacterial PA and LCC compounds.S tandard NRPS biochemical pathways (A) might be followed by TE-catalyzed dehydration and cyclization (B) prior to the enzymatic cascade catalyzed by PxaB.