Factors governing the Toxicity of Cultures containing the Phytoflagellate Prymnesium parvum Carter

Methods for the laboratory maintenance and purification of cultures of Prymnesium parvum are detailed. The upper limit of temperature for the growth of the organism is 30°. Light exerts an augmenting effect on the production of the toxin by Pr. parvum. Rapid and economical procedures for the bioassay of the toxin are based on the use of Gambusia minnows or tadpoles. Cell-free centrifugates of the cultures contain heat-labile toxic material which is non-diffusible through cellophan, sensitive to oxidizing agents, and reversibly inactivated by mild acidity. The toxin is rapidly inactivated by ubiquitous bacterial species (Bacillus subtilis and Proteus vulgaris). Charcoals, clays and calcium sulphate are efficient adsorbents of the toxic material. The concentration levels of toxin in cultures of Prymnesium parvum appear to reflect a dynamic equilibrium between toxin destruction and production; a similar equilibrium may prevail in nature.