Dumjahn, L.; Wein, P.; Molloy, E. M.; Scherlach, K.; Trottmann, F.; Meisinger, P.; Judd, L. M.; Pidot, S. J.; Stinear, T. P.; Richter, I.; Hertweck, C.

Chromobacterium haemolyticum is an environmental bacterium that can cause severe and fatal opportunistic infections in humans and animals. Although C. haemolyticum is characterized by its strong {beta}-haemolytic activity, the molecular basis of this phenotype has remained elusive over the more than fifteen years since the species was first described. Here, we report the discovery of a family of cyclic lipodepsipeptides that are responsible for the potent haemolytic activity of C. haemolyticum. Comparative genomics of Chromobacterium spp. isolated from different environments revealed a completely conserved gene locus (chl) encoding a non-ribosomal peptide synthetase (NRPS). Metabolic profiling of C. haemolyticum DSM 19808 identified a suite of cyclic lipodepsipeptides as the products of the chl locus, with the three main congeners (jagaricin, chromolysin A and B) being elucidated by a combination of tandem mass spectrometry, chemical derivatization, and NMR spectroscopy. Significantly, a C. haemolyticum chl deletion mutant is devoid of haemolytic activity. Moreover, purified jagaricin, chromolysin A and B are haemolytic at low-micromolar concentrations in an erythrocyte lysis assay. Further bioassays demonstrated that the cyclic lipodepsipeptides are crucial for biofilm-forming and swarming behavior of C. haemolyticum. MALDI mass spectrometry imaging showed that primarily chromolysin A and B are involved in these processes in vitro. Our data shed light on the bioactivities of chromolysin A and B, specialized metabolites that likely contribute to both successful colonization of new niches and virulence potential of C. haemolyticum.