Analysis of Toxic and Non-Toxic Alexandrium (Dinophyceae) Species Using RibosomalRNA Gene Sequences

摘要

Sequences of small subunit (Ss) and large subunit (Ls) ribosomal RNA genes (rDNA)from the marine dinoflagellates Alexandrium tamarense, A. catenella, A. fundyense, A. affine, A. minutum, A. lusitanicum and A. andersoni were compared to assess the organisms' relationships. Cultures represent isolates from North America, Western Europe, Thailand, Japan, Australia and the ballast water of several cargo vessels, and include both toxic and non-toxic strains. An emphasis was placed on the A. tamarense/catenella/fundyense species complex, a group of morphotypically-similar organisms found in many regions of the world. Two distinct SsrRNA genes, termed the A gene and the B gene, were found in a toxic A. fundyense isolated from eastern North America. The B gene is considered to be a pseudogene. A restriction fragment length polymorphism (RFLP) assay developed to detect the A and B genes revealed five distinct groups of Alexandrium isolates. Three subdivide the A. tamarense/catenella/fundyense complex, but do not correlate with morphospecies designations. The two remaining groups are associated with cultures that clearly differ morphologically from the A. tamarense/ catenella/fundyense group: the fourth group consists of A. affine isolates, and the fifth group is represented by A. minutum, A. lusitanigum and A. andersoni.