TITLE Metabolomics data on extracellular metabolites from Alexandrium minutum, Prymnesium parvum, Tisochrysis lutea in the context of microalgae-bacteria interactions ABSTRACT raw data (.mzXML, + and -MS, HRMS and HRMS/MS) of extracellular metabolites found in the exudates of the three microalgae, and in axenic versus xenic conditions for Alexandrium minutum and Prymnesium parvum. DESCRIPTION Exudates were extracted by Solid Phase Extraction. The C18 cartridge (LRC Bond Elut, Agilent, 200 mg, 6 mL) was conditioned with 3 mL of methanol and 3 mL of L1 medium. The 60 mL samples were loaded using reservoirs (50 mL, Agilent). The cartridges were rinsed with 6 mL of milli-Q water, dried for 5 min and then eluted with 3 mL of methanol. The eluates were evaporated to dryness under a flux of nitrogen at 40°C and resuspended in 300 µL of methanol. A blank sample (L1 medium) was processed as samples. All extracts were stored at -80 °C until analysis. Metabolomic profiles were acquired by liquid chromatography coupled to high resolution mass spectrometry (LC-HRMS) as in (Gémin et al., 2021). Briefly, the system was a UHPLC (1290 Infinity II, Agilent technologies, Santa Clara, CA, USA) coupled to a quadrupole-time of flight mass spectrometer (QTOF 6550, Agilent technologies, Santa Clara, CA, USA) equipped with a Dual Jet Stream ESI interface. Both positive and negative full scan modes were used over a mass-to-charge ratio (m/z) ranging from 100 to 1700. The injection volume was 5 µL. The batch was prepared as recommended by (Broadhurst et al., 2018), by using a mix of 10 phycotoxins as the Standard Reference Material and a mixture of all samples for the qualitative control (QC) samples. The injection order was randomized and QCs were injected every 5 samples. LC-HRMS raw data (.d) were converted to .mzXML format using MS-Convert (ProteoWizard 3.0) (Chambers et al., 2012).