Role of associated bacteria in growth and toxicity of cultured benthic dinoflagellates.

Clonal cultures of the toxic benthic dinoflagellate Ostreopsis lenticularis isolated from the coastal waters of southwest of Puerto Rico show peak toxicities during the stationary phase of growth, correlated with significant increases in bacteria directly associated with these cells. The specific toxicity (MU/mg) of dinoflagellate extracts in control cultures increased 340% during the static phase of culture growth, while those cultures treated with antibiotics that inhibit prokaryote protein synthesis showed no significant increase in toxicity during this phase of culture growth. There was a significant decrease in the diversity of dinoflagellate associated bacterial strains in antibiotic treated cultures. These data indicate that associated bacteria play a role in toxin production by dinoflagellate-bacteria consortia when grown in laboratory culture.