Molecular typing of the red-tide dinoflagellate Gonyaulax polyedra in phytoplankton suspensions

Abstract

A group of closely related DNA sequences each approx. 240 base pairs long ('Gp240 family') was detected in the DNA extracted from cultured cells of the red-tide dinoflagellate Gonyaulax polyedra using the polyrnerase chain reaction. While members of the Gp240 family appeared to be present in the DNA of all the isolates of G. polyedra tested, no related sequence could be detected in the DNA of other dinoflagellates, diatoms or marine bacteria In a further set of experiments, the PCR system based on the Gp240 DNA was used to probe phytoplankton samples collected in the Northern Adriatic Sea during a red tide caused by G. polyedra. The results showed that the members of the Gp240 family contain a short simple-sequence stretch givlng nse to length polymorphism. The potential of this molecular identification system to track G polyedra in its natural environment is discussed. Considerations are also made on the evolution of the simple-sequence loci in marine organisms.