High-resolution Mass Spectrometry Analysis of E. chevalieri

High-resolution tandem mass spectrometry (HR-MS/MS) was carried out using a Finnigan LTQ Orbitrap coupled to a Surveyor Plus HPLC pump and autosampler (Thermo Fisher, Bremen, Germany) in positive ionization mode using an MS range of m/z 100–2000, an MS2 range of m/z 200–1500, and an MSn range of m/z 0–1000, with 30,000 resolution. LC-MS data were acquired using Xcalibur version 2.2. HR-MS/MS raw data files were converted from .RAW to .mzXML format using the Trans-Proteomic pipeline (Institute for Systems biology, Seattle) [29 (link)], and clustered with MS-Cluster using Global Natural Products Social Molecular Networking (GNPS-https://gnps.ucsd.edu) [30 (link)]. A molecular network was created using the online workflow at GNPS. The following settings were used for generation of the network: minimum pairs cos 0.6; parent mass tolerance, 1.0 Da; ion tolerance, 0.2; network topK, 10; minimum matched peaks, 6; minimum cluster size, 2. Data were visualized and analyzed using Cytoscape 3.6.0.
The compounds common to both liquid and solid growth conditions of E. chevalieri MUT 2316 were highlighted, as well as the compounds unique to each condition.