TABLE 2.
MICs of β-lactams and specific activities of BlaA in wild-type S. oneidensis and its derivative strains
| Straina | MIC (μg/ml)b |
Mean β-lactamase activityc ± SD |
|||
|---|---|---|---|---|---|
| AMP | CTX | IPM | No inducer | Inducer | |
| WT | 4 | 0.02 | 0.5 | 12 ± 0.8 | 125 ± 7 |
| ΔmrcA | 128 | 0.08 | 4 | 258 ± 22 | 228 ± 21 |
| ΔlpoA | 32 | 0.04 | 2 | 71 ± 11 | 241 ± 23 |
| ΔmrcB | 4 | 0.02 | 0.5 | 13 ± 0.8 | 116 ± 7.9 |
| ΔlpoB | 4 | 0.02 | 0.5 | 13 ± 1.2 | 128 ± 13 |
| ΔampG | 128 | 0.08 | 2 | 29 ± 4 | 238 ± 5.1 |
| ΔblaA | <0.5 | <0.005 | <0.06 | 2 ± 1 | 0 |
| ΔmrcA/mrcA | 128 | 0.08 | 4 | − | − |
| ΔmrcA/mrcA + Ara | 32 | 0.04 | 1 | 44 ± 2.3 | 227 ± 7.1 |
| ΔlpoA/lpoA | 32 | 0.04 | 2 | − | − |
| ΔlpoA/lpoA + Ara | 8 | 0.02 | 0.5 | 19 ± 0.1 | 174 ± 17 |
| ΔmrcA ΔblaA | <0.5 | <0.005 | <0.06 | 3 ± 0.5 | 0 |
| ΔlpoA ΔblaA | <0.5 | <0.005 | <0.06 | 3 ± 0.8 | 0 |
| ΔmrcA ΔampG | 128 | 0.08 | 2 | 216 ± 35 | 236 ± 18 |
a
ΔmrcA/mrcA and ΔlpoA/lpoA represent the ΔmrcA and ΔlpoA strains, respectively, complemented with pHGC02 harboring a copy of the corresponding S. oneidensis genes in trans. Ara, arabinose.
b
AMP, ampicillin; CTX, cefotaxime; IPM, imipenem.
c
Nanomoles of nitrocefin hydrolyzed per minute per milligram of protein. Induction was carried out with 200 μg/ml ampicillin for 2 h. −, not tested.