Temporal and Fluoride Control of Secondary Metabolism Regulates Cellular Organofluorine Biosynthesis

Elucidating mechanisms of natural organofluorine biosynthesis is essential for a basic understanding of fluorine biochemistry in living systems as well as for expanding biological methods for fluorine incorporation into small molecules of interest. To meet this goal we have combined massively parallel sequencing technologies, genetic knockout, and in vitro biochemical approaches to investigate the fluoride response of the only known genetic host of an organofluorine-producing pathway, Streptomyces cattleya. Interestingly, we have discovered that the major mode of S. cattleya's resistance to the fluorinated toxin it produces, fluoroacetate, may be due to temporal control of production rather than the ability of the host's metabolic machinery to discriminate between fluorinated and non-fluorinated molecules. Indeed, neither the acetate kinase/phosphotransacetylase acetate assimilation pathway nor the TCA cycle enzymes (citrate synthase and aconitase) exclude fluorinated substrates based on in vitro biochemical characterization. Furthermore, disruption of the fluoroacetate resistance gene encoding a fluoroacetyl-CoA thioesterase (FlK) does not appear to lead to an observable growth defect related to organofluorine production. By showing that a switch in central metabolism can mediate and control molecular fluorine incorporation, our findings reveal a new potential strategy toward diversifying simple fluorinated building blocks into more complex products.