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 15N-PSTsinstead of original 14N, 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 15N-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 15N, and the f/2 medium of standard 15N/P concentrationwas the best choice in terms of the species' growth, PST profile, 15N labeling result and experimentcost. After many (>15) generations, the 15N abundance in PSTs extract reached 82.36%, and the 15Natom number introduced into GTX1-4 might be 4⁻6. This paper innovatively provided the initialevidence that 15N isotope application of labeling PSTs in A. minutum is feasible. The 15N-PSTs asbiomarker can be applied and provide further information on PSTs metabolism.
Keywords: 15N stable isotope labeling; Alexandrium minutum; biomarker; dinoflagellate; paralytic shellfish toxins (PSTs).