N Stable Isotope Labeling PSTs in for Application of PSTs as Biomarker.

The dinoflagellate Alexandrium minutum (A. minutum) which can produce paralyticshellfish toxins (PSTs) is often used as a model to study the migration, biotransformation,accumulation, and removal of PSTs. However, the mechanism is still unclear. To provide a new toolfor related studies, we tried to label PSTs metabolically with 15N stable isotope to obtain N-PSTsinstead of original N, which could be treated as biomarker on PSTs metabolism. We then culturedthe A. minutum AGY-H46 which produces toxins GTX1-4 in f/2 medium of different 15N/Pconcentrations. The N-PSTs' toxicity and toxin profile were detected. Meanwhile, the 15N labelingabundance and 15N atom number of 15N-PSTs were identified. The 14N of PSTs produced by A.minutum can be successfully replaced by N, and the f/2 medium of standard N/P concentrationwas the best choice in terms of the species' growth, PST profile, 15N labeling result and experimentcost. After many (>15) generations, the N abundance in PSTs extract reached 82.36%, and the Natom number introduced into GTX1-4 might be 4⁻6. This paper innovatively provided the initialevidence that N isotope application of labeling PSTs in A. minutum is feasible. The N-PSTs asbiomarker can be applied and provide further information on PSTs metabolism.