The Basic Research In Growth And Toxigenic Gene Of Alexandrium

Marine Alexandrium is an important red algae and distributed in the coast of North America, Europe, and Asian extensively. Half species of genus Alexandrium can produce paralytic shellfish poisoning. Red tides produced by toxic Alexandrium had caused worldwide aquaculture loss and human poisoning. Once the harmful red tide bread out, it endanger enormously, so great request is proposed on the growth, identification and toxin producing mechanism of Alexandrium.Alexandrium is small in size and similar in morphylogy between different species, and effective identifying characteristic is lacked at present. Utilizing molecular biology method can get reliable, accurate and sensitive characters. Combing the molecular biology data with the knowledge of morphylogy, more reliable and objective results can be drawn. Three newly isolated strains from Chinese waters are named Alexandrium sp. qd1, Alexandrium sp. qd2 and Alexandrium sp. gz by morphological describing. The 5.8S ribosomal DNA gene and flanking internal transcribed spacer 1 and spacer 2 (ITS1 and ITS2) from 3 isolates are amplified, sequenced, and subjected to phylogenetic analysis. Alexandrium sp. gz and Alexandrium sp. qdl groupe to toxic A. catenella (from South Korea and Japan) and two unidentified Alexandrium strains (AC03 and AN01) which suggested to be catenalla in a previous study with high bootstrap value. Alexandrium sp. gz and Alexandrium sp. qdl were identified as A. catenella. Then, A. catenella is broadly distributed in Chinese waters, and has a few geographical and genotype strains. Alexandrium sp. qd2 differed greatly with the genus Alexandrium, but cluster with Symbiodinium californium, Symbiodinium sp. G15 and Gymnodinium sp. Zhao 01 with 100% bootstrap value. Alexandrium sp. qd2 is affiliated to Symbiodinium, and probably belongs to a free-living stain.