Are Pfiesteria species toxicogenic? Evidence against production of ichthyotoxins by Pfiesteriashumwayae

doi:10.1073/pnas.172221699

Are Pfiesteria species toxicogenic? Evidence against production of ichthyotoxins by Pfiesteriashumwayae

^*Department of Chemistry/National Institute of Environmental Health Sciences, Marine and Freshwater Biomedical Science Center, University of Miami, P.O. Box 249118, Coral Gables, FL 33124;^† Virginia Institute of Marine Science, College of William and Mary, Route 1208, Gloucester Point, VA 23062;^‡ Department of Chemistry, Florida International University, 11200 SW 8th Street, Miami, FL 33199; and^§ Center for Marine Science, University of North Carolina, 5600 Marvin K. Moss Lane, Wilmington, NC 28409

Edited by John H. Law, University of Arizona, Tucson, AZ, and approved May 29, 2002 (received for review April 12, 2002)

Abstract

The estuarine genus Pfiesteria has received considerable attention since it was first identified and proposed to be the causative agent of fish kills along the mid-Atlantic coast in 1992. The presumption has been that the mechanism of fish death is by release of one or more toxins by the dinoflagellate. In this report, we challenge the notion that Pfiesteria species produce ichthyotoxins. Specifically, we show that (i) simple centrifugation, with and without ultrasonication, is sufficient to “detoxify” water of actively fish-killing cultures of Pfiesteria shumwayae, (ii) organic extracts of lyophilized cultures are not toxic to fish, (iii) degenerate primers that amplify PKS genes from several polyketide-producing dinoflagellates failed to yield a product with P. shumwayae DNA or cDNA, and (iv) degenerate primers for NRPS genes failed to amplify any NRPS genes but (unexpectedly) yielded a band (among several) that corresponded to known or putative PKSs and fatty acid synthases. We conclude that P. shumwayae is able to kill fish by means other than releasing a toxin into bulk water. Alternative explanations of the effects attributed to Pfiesteria are suggested.

Footnotes

↵ ¶ To whom reprint requests should be addressed. E-mail: rgawley{at}miami.edu.
This paper was submitted directly (Track II) to the PNAS office.
Data deposition: The sequence reported in this paper has been deposited in the GenBank database (accession no. ).
Abbreviations:
1. PKS, polyketide synthase
2. NRPS, nonribosomal peptide synthase
3. CCMP, Center for Culture of Marine Phytoplankton
4. ASW, artificial seawater
5. RT, reverse transcription
6. ITS, internal transcribed spacer