Table 4.
E. coli CFT073 and K-12 DCS sensitivity when grown on MOPs glycerol medium in the presence of increasing concentrations of d-alanine or glycine
| A.A./DCS ratioa | Avg. zone of inhibitionb (mm) for: |
|||
|---|---|---|---|---|
| CFT073 |
K-12 |
|||
| d-Alanine | Glycine | d-Alanine | Glycine | |
| 0:1 | 18.9 (±0.4) | 21.5 (±1.6) | 32.7 (±1.1) | 32.4 (±1.1) |
| 1:1 | 15.3 (±0.3) | 19.8 (±1.9) | 31.4 (±0.3) | 32.9 (±1.7) |
| 10:1 | Resistant | Resistant | 29.1 (±0.4) | 33.5 (±0.4) |
| 100:1 | Resistant | Resistant | Resistant | Resistant |
A.A./DCS ratio, amino acid/d-cycloserine ratio. A 10-μl aliquot from a 24.5 mM solution of DCS was added to each disk. For the amino acid competition assays, d-alanine or glycine solutions of the appropriate concentrations were added to each disk in a 10-μl aliquot. For the 0:1 A.A./DCS experiment, in addition to DCS a 10-μl aliquot of H2O was added to the disk.
DCS sensitivity was determined by antibiotic disk diffusion assay on a MOPS glycerol plate containing no antibiotics or amino acids. Each data point represents the average zone of growth inhibition and the resulting standard deviations from three experimental replicates.