Functional Genomics of the Toxic Dinoflagellate Alexandrium lusitanicum

Claudia Augusto Martins, Ph.D., 2007
Don Anderson, Advisor

Many species in the dinoflagellate genus Alexandrium have been shown to produce saxitoxins, the ethological agent of paralytic shellfish poisoning (PSP). The first case of a toxic Alexandrium that has completely lost the ability to produce saxitoxins is reported here. The loss of toxicity was accompanied by a reduction in growth capability. A subculture of this isolate maintains the ability to produce toxins and to grow at rates previously characteristic of this strain. The differences in the two isolates were demonstrated to be a property of the dinoflagellate and were not dependent on the different bacterial symbionts of each culture.

The pair of subcultures is a novel experimental system to study functional genomics of dinoflagellates related to toxin production and growth. At the metabolome level, compounds were identified that were unique to the non-toxic isolate. Their emergence may be correlated to a disruption of the biosynthetic pathway for PSP toxins, as the compounds share some characteristics with saxitoxins. Difference gel electrophoresis (DIGE) identified proteins differentially expressed between the two subcultures. Proteins down-regulated in the non-toxic subculture are enzymes from the Calvin cycle, which may explain the limited growth of the isolate. Other differentially expressed proteins identified may relate to the loss of toxicity, but their identity remains unresolved.