• Saxitoxins: role of prokaryotes

      Baker, Tracie Renee (2001-05)
      Saxitoxins, the toxins associated with paralytic shellfish poisoning (PSP), are synthesized by dinoflagellates, cyanobacteria, and possibly bacteria. The specific objectives of this study were to determine growth conditions that promote high and low levels of toxin accumulation in Aphanizomenon flos-aquae (cyanobacterium) and Pseudomonas stutzeri (bacterium). Putative saxitoxins of P. stutzeri identified by HPLC-FLD in this study, and previously by other laboratories, were determined to be 'imposters' based on their chemical and physical properties, suggesting that this bacterium may not synthesize PSP toxins. In the cyanobacterium, toxin production was enhanced under higher light intensities and temperatures. Toxin accumulation reached maximal levels when cellular nitrogen was from either (NO₃-+NH₄)-N or N₂-N, while urea-N drastically reduced toxin levels. These data will be used in future studies aimed at identifying the genes involved in saxitoxin synthesis via molecular technologies that rely upon expression of the 'saxitoxin genes' under different growth conditions.