Assay of fosmidomycin uptake. Uptake of fosmidomycin was measured in mycobacteria and E. coli. Cells were subjected to (A) 1 mg/ml of fosmidomycin for 30 min; (B) 20 μg/ml of fosmidomycin for 60 min. Cell-free extracts (CFE) or culture supernatants (SN) were prepared and serial dilutions were applied to paper disks as described in the methods. For each assay, a standard curve was generated using known concentrations of fosmidomycin. For test samples, zones of inhibition against E. coli were measured and the antibiotic concentration calculated from the standard curve.