TABLE 3.
TonB-dependent ferrichrome transport
| Straina | Phenotype | [55Fe]ferrichrome uptakeb |
|---|---|---|
| W3110(pBAD24) | ExbB+ ExbD+ TolQ+ TolR+ | 1,982.5 ± 273 |
| RA1035(pBAD24) | ExbB+ ExbD+ TolQ− TolR− | 1,752.0 ± 33 |
| RA1003(pBAD24) | ExbB− ExbD− TolQ+ TolR+ | 11.3 ± 4.3 |
| RA1045(pRA002) | ExbB+ ExbD− TolQ− pRA002+ | −4.5 ± 2.1 |
| RA1044(pBAD24) | ExbB− ExbD+ TolQ+ TolR− | −6.7 ± 2.9 |
| RA1051(pBAD24) | ExbB− ExbD− TolQ− TolR− | −6.9 ± 6 |
a
Most strains carried plasmid pBAD24; the exception was the strain which carried plasmid pRA002, which encodes TolR. Cells were grown with aeration at 37°C to mid-exponential phase in T-broth supplemented with 100 μg ml−1 ampicillin and then centrifuged and suspended at a concentration of 2 × 108 CFU ml−1 in M9 salts containing 0.1 mM nitrilotriacetate. Transport was initiated by addition of 150 pmol [55Fe]ferrichrome as previously described (34).
b
Uptake is expressed in cpm 55Fe transported per 1 × 109 cells min−1. The values are means ± standard deviations of triplicate assays.