*4.5. Mass Spectral Data Acquisition*

LC–MS/MS was performed using a Thermo Scientific Accela LC system coupled to a Thermo Finnigan LTQ Orbitrap mass spectrometer with an ESI source. Bacterial metabolite extracts and control media extracts (no bacteria) were prepared at 1 mg/mL in ACN and were injected onto an ACE 5 (Hichrom) C18 column (5 μm, 75 × 3.0 mm) using the following gradient: 1–5 min (5% ACN in H2O), 5–25 min (5–100% ACN), 25–30 min (100% ACN). Mass data were collected in positive ion mode using ESI and mass range 150–1500 *m*/*z* (15,000 resolution). Data-dependent MS2 scans were obtained using collision-induced dissociation (CID) with an energy of 35 eV and activation time of 30,000 ms for the first, second, and third most intense peaks.

#### *4.6. Mass Spectral Data Processing*

Mass spectral data were processed using MZmine v2.38 freeware (http://mzmine. sourceforge.net/ (accessed on 9 November 2020)) for peak detection, deconvolution, deisotoping, filtering, alignment and gap filling to make multiple data files comparable. Throughout the data processing, the *m*/*z* tolerance used was 0.01, peaks were detected above 3.00E3 and the minimum time span and tR tolerance was 0.1 min. Mass detection was performed using a centroid mass detector with a noise level set at 2.00 × 103.
