Table 3.
Sensitivity of low activity ExbB substitutions to TonB-dependent colicins and phage ϕ80
| Mutations or substitution(s)a | Ara (%)b | Sensitivityc |
||||
|---|---|---|---|---|---|---|
| Col B | Col D | Col Ia | Col M | ϕ80 | ||
| None (WT) | NA | 8,8,8 | 6,6,6 | 7,7,7 | 6,6,6 | 8,8,8 |
| ΔexbBD ΔtolQRA | NA | T,T,T | T,T,T | T,T,T | T,T,T | T,T,T |
| pExbBD | 0.00005 | 7,7,7 | 4,4,4 | 7,7,7 | 6,6,6 | 7,7,7 |
| S34A | 0 | T,T,T | T,T,T | T,T,T | T,T,T | T,T,T |
| S34C | 0.00005 | T,T,T | T,T,T | 2,2,2 | 3,3,3 | 3,3,3 |
| S34T | 0 | T,T,T | T,T,T | U,U,U | T,T,T | 1,1,1 |
| T135A | 0.00005 | 3,3,3 | T,T,T | 4,4,4 | 3,3,3 | 3,3,3 |
| T148A | 0.00005 | 7,7,7 | 2,2,2 | 7,7,7 | 4,4,5 | 3,3,3 |
| T148C | 0.0001 | 3,3,3 | T,T,T | 4,4,4 | T,T,T | T,T,T |
| T148V | 0.00005 | T,T,T | T,T,T | T,T,T | T,T,T | T,T,T |
| T181A | 0.00005 | 7,7,7 | 3,3,3 | 7,7,7 | 6,6,6 | 8,8,8 |
| T181C | 0.0001 | 7,7,7 | 3,3,3 | 7,7,7 | 6,6,6 | 8,8,8 |
| T181V | 0.00005 | 7,7,7 | 3,3,3 | 7,7,7 | 3,3,3 | 7,7,7 |
| T148A T181A | 0.00005 | T,T,T | T,T,T | T,T,T | T,T,T | T,T,T |
| T148C T181C | 0.0001 | 3,3,3 | T,T,T | 4,4,4 | T,T,T | 4,4,4 |
| T148V T181V | 0.00005 | T,T,T | T,T,T | T,T,T | T,T,T | T,T,T |
a
WT indicates strain W3110, and ΔexbBD ΔtolRQA indicates strain RA1017. Both contained the empty vector control from which all plasmids were expressed, pBAD24. All mutants were expressed near chromosomal levels in strain RA1017. The corresponding plasmid names are listed in Table 1.
b
Percentage of l-arabinose added to growth medium and plates to achieve near chromosomal expression levels. NA, not applicable.
c
Colicins (Col) and phage ϕ80 were spotted in 5-fold and 10-fold dilutions, respectively. Results are presented as the reciprocal of the highest dilution that provided clearing (8, 5−8, or 10−8 dilution). U, undiluted; T, tolerant (insensitive).