Lipopeptides and antibiotics from a marine Bacillus pumilus mediate a potential “catch and kill” effect on pathogenetic Vibrio parahaemolyticus

ABSTRACT Bacteria produce a diverse range of specialized metabolites that influence the health and behavior of neighboring cells and, therefore, have potential applications in treating diseases. Deciphering the intended ecological functions of specialized metabolites is challenging due to the small scales at which these interactions occur and the complexity of unraveling simultaneous responses to multiple signals. In this study, we investigated the chemical interactions between two marine bacterial colonies, Vibrio parahaemolyticus PSU5429 and Bacillus pumilus YP001. When the two bacteria were grown in proximity on agar, V. parahaemolyticus exhibited swarming motility toward B. pumilus , but close approach to the B. pumilus colony was impeded by a zone of inhibition. Matrix-assisted laser desorption/ionization time-of-flight imaging mass spectrometry (MALDI-TOF IMS) suggested that lipopeptides produced by Bacillus induced swarming motility, a finding corroborated by genomic and chemical analyses of YP001. Based on activity and metabolomics guidance, the antibiotic amicoumacin B was found to be responsible for the observed antibiosis, while swarming motility by V. parahaemolyticus was induced by lipopeptides and two lipoamides. In this scenario, lipopeptide production by the Bacillus colony induces the Vibrio colony to swarm toward a lysis zone, resulting in a possible “catch and kill” effect. These results demonstrate the complexity of behaviors and outcomes exhibited by microbes under the simultaneous influence of different allelochemicals, suggesting possible interplays between antibiotics and compounds that induce motility. IMPORTANCE Microbes communicate and compete using small molecules, yet linking specific metabolites to visible behaviors is difficult. We combine imaging mass spectrometry, genomics, analytical chemistry, and bioassays to decode an interaction between a marine Bacillus and the pathogen Vibrio parahaemolyticus . Surfactin-like lipopeptides act at a distance to stimulate Vibrio swarming and draw cells toward the colony. Amicoumacin B accumulates at the interface and halts growth, yielding a simple “catch and kill” outcome. This study shows that the spatial localization of natural products shapes microbial behavior on surfaces and provides a general, scalable workflow that maps chemistry to phenotype. Beyond this case, the approach can be applied broadly to understand and, ultimately, tune microbial interactions relevant to marine ecosystems, aquaculture health, and microbiome engineering.