The relative rates of oxidation of lipovitellin and of its lipid constituent

Axenic culture of the heterotrophic dinoflagellate Pfiesteria shumwayae in a semi-defined medium

A semi-defined, biphasic culture medium was developed that supported the axenic growth of three strains of the heterotrophic dinoflagellate Pfiesteria shumwayae. Maximum cell yields and division rates in the semi-defined medium ranged from 0.1 x 10(5) to 4.0 x 10(5) cells/ml and 0.5 to 1.7 divisions/day, respectively, and depended on the concentration of the major components in the medium as well as the P. shumwayae strain. The medium contained high concentrations of certain dissolved and particulate organic compounds, including amino acids and lipids. Pfiesteria shumwayae flagellated cells were attracted to insoluble lipids present in the medium and appeared to feed on the lipid particles, suggesting that phagocytosis may be required for growth in axenic culture. Development of a semi-defined medium represents significant progress toward a completely defined axenic culture medium and subsequent determination of the biochemical requirements of P. shumwayae, needed to advance understanding of the nutritional ecology of this species. Further, this medium provides an economical, simplified method for generating high cell densities of P. shumwayae in axenic culture that will facilitate controlled investigations on the physiology and biochemistry of this heterotrophic dinoflagellate.

AXENIC CULTIVATION OF THE HETEROTROPHIC DINOFLAGELLATE PFIESTERIA SHUMWAYAE AND OBSERVATIONS ON FEEDING BEHAVIOR(1)

Pfiesteria shumwayae Glasgow et J. M. Burkh. [=Pseudopfiesteria shumwayae (Glasgow et J. M. Burkh.) Litaker, Steid., P. L. Mason, Shields et P. A. Tester] is a heterotrophic dinoflagellate commonly found in temperate, estuarine waters. P. shumwayae can feed on other protists, fish, and invertebrates, but research on the biochemical requirements of this species has been restricted by the lack of axenic cultures. An undefined, biphasic culture medium was formulated that supported the axenic growth of two of three strains of P. shumwayae. The medium contained chicken egg yolk as a major component. Successful growth depended on the method used to sterilize the medium, and maximum cell yields (10(4)  · mL(-1) ) were similar to those attained in previous research when P. shumwayae was cultured with living fish or microalgae. Additionally, P. shumwayae flagellate cells ingested particles present in the biphasic medium, allowing detailed observations of feeding behavior. This research is an initial step toward a chemically defined axenic culture medium and determination of P. shumwayae metabolic requirements.