Arguments have taken a strange turn over how to isolate toxins from the Pfiesteria microbes accused of killing fish by the millions and threatening human health. Two research teams now say that in the Pfiesteria strain they've examined, there's no toxin to find. Instead, explains one of the teams, the single-celled dinoflagellate alga kills by swarming over a fish and eating away its skin.
A laboratory sample of Pfiesteria shumwayae, one of two named Pfiesteria species, slays fish only by direct contact, says Robert Gawley of the University of Miami in Coral Gables. By centrifuging a solution of