Fluoroacetate Metabolism in Gloeocapsa sp. LB795 and its Relationship to Acetylene Reduction (Nitrogen Fixation)

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Abstract
Sodium fluoroacetate (1 mM) caused an accumulation of citrate and altered the lipid composition in cells of Gloeocapsa sp. LB795. It also inhibited acetylene reduction (N fixation) by the alga, markedly under aerobic conditions, but much less so in the absence of O2. This inhibition is largely the result of the conversion of fluoroacetate to fluorocitrate which, but inhibiting aconitate hydratase (EC 4.2.1.3), interrupts the synthesis of the 2-oxoglutarate required for the assimilation of NH4+. The consequent accumulation of NH4+ within the cells of Gloeocapsa sp. inhibits nitrogenase synthesis and, since O2 rapidly inactivates pre-existing nitrogenase, N fixation by Gloeocapsa sp. decreases under aerobic conditions.