Biosynthesis of the new broad-spectrum lipopeptide antibiotic paenibacterin in Paenibacillus thiaminolyticus OSY-SE.

Paenibacterin is a novel lipopeptide antibiotic with potent activity against Gram-negative and Gram-positive human pathogens. The antibiotic consists of a cyclic 13-residue peptide and an N-terminal C₁₅ fatty acyl chain. To elucidate the biosynthesis of paenibacterin, we determined the whole genome sequence of the producer strain Paenibacillus thiaminolyticus OSY-SE, and the function of the peptide synthetase was confirmed experimentally. The gene cluster of paenibacterin was identified within a 52-kb DNA region, encoding thee non-ribosomal peptide synthetases, PbtA, PbtB and PbtC, and two ABC-transporters, PbtD and PbtE. Both PbtA and PbtB consist of five modules, whereas PbtC comprises three modules. Each of these 13 modules consists of three essential domains (condensation-adenylation-thiolation) and assembles an amino acid into the paenibacterin peptide. Selected adenylation domains in the NRPS were cloned and expressed in Escherichia coli; the substrate specificity of each recombinant A-domain was studied in vitro by protein function analysis. The presence of four epimerization domains in paenibacterin peptide synthetases suggests that Orn₁, Orn₄, Lys₇ and Ser₈ in the paenibacterin molecule have d-configuration; the absolute configuration of two ornithine residues in paenibacterin was confirmed by chiral amino acid analysis using Marfey's reagents. Taken together, the findings enabled us to propose the biosynthetic pathway of paenibacterin.