Toxin Production Physiology And Biosynthesis Mechanism In Toxic Dinoflagellate Alexandrium

Alexandrium is a widely spread genus throughout many regions of the world, many species within this genus are able to produce paralytic shellfish toxins (PSTs), a family of potent neurotoxins, which are the causative agents of paralytic shellfish poisoning. This study investigated paralytic shellfish poisoning toxins composition and toxin variability of the genus Alexandrium isolated from the Southeast China Sea, analyzed toxin variability during the cell cycle of the dinoflagellate A. tamarense CI01, detected sulfotransferase activity in Alexandrium strains with various toxin compositions and its characteristics, compared the protein profiles between toxic and none-toxic A. tamarense using proteomic and immunoproteomic approach and toxicity indicator proteins, the main results were as follows:PSP toxin composition profiles of the genus Alexandrium isolated from the Southeast China Sea were investigated and the results showed that six strains of A. affine were non-toxic, while the ten strains of A. tamarense and A. catenella were toxic. These toxic isolates grown in the same culture conditions consistently produced an unusually high proportion of the N-sulfocarbamoyl toxin C1,2 (around 70-80% of total toxins) and medium amounts of gonyautoxin GTX5 (around 20-30% of total) with only trace quantities (<5% of total) of other saxitoxin derivatives (i.e. GTX1, GTX3, GTX4 and neoSTX). The toxin composition of three A. tamarense isolates did not vary with the growth phases, although higher toxin contents (Qt, fmol cell-1) were found in the exponential phase. Variations in temperature, salinity and nutrient levels affected toxin content (Qt) of three A. tamarense isolates but they did not have pronounced effects on the toxin composition (mole %).Toxin content and composition of A. tamarense CI01 varied with the cell cycle, toxin biosynthesis was induced by light, and always occurred during a defined time frame within the G1 phase of the cell cycle. Analyzing toxin biosynthesis time and ratio of C1,2 and GTX2,3 toxin in cells, and combining the function of sulfotransferase in A. tamarense CI01, it was postulated that GTX2,3 was synthesized firstly and then...