GNPS - Targeted and non-targeted mass spectrometry to explore the chemical diversity of the genus Gambierdiscus in the Atlantic Ocean

The 15 strains of Gambierdiscus were cultivated in four separate laboratories. Each laboratory grew their available strains (see sample metadata) in addition to the G. australes strain AUS S080911_1 isolated from Pacific Ocean.

Irradiance (70-100 umol photons m-2 s-1) and light/dark cycle (12h:12h) were standardized between the different laboratories, the other cultivation parameters were defined by each laboratory considering optimal growth parameters and technical requirements.

Samples were extracted twice in methanol 90% from freeze-dried cell pellets (2mL per million of cells). The extraction cycle was as follows: vortex 30 s, ultrasonic bath (25 kHz on ice, 15 min), vortex 30 s and centrifugation (4 000 g, 2 min). The extracts resulting from the two extraction cycles were pooled into an amber glass vial and stored at -80 C (final concentration : 250,000 cells mL-1).

Metabolomic profiles were acquired by Ultra-high-performance Liquid Chromatography-High Resolution Mass Spectrometry (UHPLC-HRMS). The instrumentation consisted of a UHPLC system (1290 Infinity II, Agilent) coupled to a quadrupole-time of flight mass spectrometer (QTOF 6550, Agilent) equipped with a Dual Jet Stream electrospray ionization (ESI) interface. The analytical column was a core-shell Kinetex C18 (100 x 2.1 mm, 1.7 um, Phenomenex) with a suited guard column. Mobile phases consisted of water (A) and acetonitrile/water (95:5, V:V) (B), both containing 2 mM ammonium formate and 50 mM formic acid The flow rate was 0.4 mL min-1 and the injection volume was 5 uL. The following elution gradient was used: 5% B (0-1 min), 5-100% B (1-11 min), 100% B (11-13 min), 5% B (13-18 min).

Mass spectra were recorded in both positive and negative full-scan modes from m/z 100 to 1700 at a mass resolving power of 25 000 full-width at half-maximum (fwhm, m/z = 922.0099) and an acquisition rate of 2 spectra/s.

Auto-MS/MS was performed iteratively: each sample was injected 5 times in ESI+ mode and the ions fragmented were manually excluded from the following analyses