THE MECHANISMS OF FLUORIDE TOXICITY AND FLUORIDE RESISTANCE IN SYNECHOCOCCUS LEOPOLIENSIS (CYANOPHYCEAE)

Fluoride was supplied as dissolved NaF at concentrations ranging from 0.26 to 7.9 mM (5-150 ppm) to three freshwater microalgae: Synechococcus leopoliensis (Racib.) Komarek (Cyanophyta), Oscillatoria limnetica Lemmermann (Cyanophyta) and Chlorella pyrenoidosa Chick (Chlorophyta). Growth of C. pyrenoidosa was unaffected by fluoride, and uptake of fluoride by this organism was not detectable. It is suggested that fluoride enters sensitive cells of S. leopoliensis principally as undissociated HF; that its major inhibitory effect in these cells is the reduction in cellular ATP; and that fluoride-resistant cells accumulate less fluoride by developing increased permeability to the fluoride anion.