Publications

The rice seedling blight fungus Rhizopus microsporus harbors endosymbiotic bacteria (Burkholderia rhizoxinica) that produce the virulence factor rhizoxin and control host development. Genome mining … indicated a massive inventory of cryptic non- ribosomal peptide synthetase (NRPS) genes, which have not yet been linked to any natural products. The discovery and full characterization of a novel cyclopeptide from endofungal bac- teria is reported. In silico analysis of an orphan, symbiont-spe- cific NRPS predicted the structure of a nonribosomal peptide, which was targeted by LC-MS/MS profiling of wild-type and engineered null mutants. NMR spectroscopy and chemical deri- vatization elucidated the structure of the bacterial cyclopep- tide. Phylogenetic analyses revealed the relationship of starter C domains for rare N-acetyl-capped peptides. Heptarhizin is produced under symbiotic conditions in geographically con- strained strains from the Pacific clade; this indicates a potential ecological role of the peptide.