Imaging Mass Spectrometry and Genome Mining Reveal Antimicrobial Peptides of Novel CCFM18.

The mechanism of metabolites produced by lactic acid bacteria in mediating microbial interactions has been difficult to ascertain. This study comparatively evaluated the antimicrobial effect of the novel bacterium CCFM18 and explored the global chemical view of its interactions with indicator bacteria. CCFM18 had sufficiently strong antimicrobial activity to effectively inhibit the growth of the indicator bacteria and enhance their intracellular reactive oxygen species (ROS) level. The emerging technique of matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) imaging mass spectrometry indicated that CCFM18 increased the production of pediocin PA-1 and the penocin A profile during its interaction with the indicator bacteria, thus differing from CCFM28 (a commonly used laboratory strain). Strikingly, the production of coagulin A was triggered only by signaling molecules made by the competing strain , suggesting an idiosyncratic response from CCFM18. Bioinformatic mining of the CCFM18 draft genome sequence revealed gene loci that code for the complex secondary metabolites analyzed via MSI. Taken together, these results illustrate that chemical interactions between CCFM18 and indicator bacteria exhibit high complexity and specificity and can drive CCFM18 to produce different secondary metabolites.