TABLE 2.
Peptidoglycan incorporation into side walls near poles of E. coli
| Strain | Treatmenta (protein inhibited) | Avg slopeb (arbitrary units/pixel ± SD) | No. of measurements |
|---|---|---|---|
| MG1655 | Aztreonam (PBP 3) | 4.1 ± 2.4 | 12 |
| MG1655 | SulA (FtsZ) | 3.8 ± 1.7 | 12 |
| AV23-1 | Aztreonam (PBP 3) | 3.7 ± 1.5 | 13 |
| AV23-1 | SulA (FtsZ) | 1.2 ± 0.7c | 9 |
Aztreonam (1 to 2 μg/ml) was added to inhibit the essential septation protein PBP 3 while leaving the function of FtsZ intact. The SulA protein was produced by arabinose induction of the sulA gene on plasmid pFAD38, thereby inhibiting FtsZ.
E. coli sacculi were isolated from strains labeled with d-cysteine and then incubated (chased) in its absence. Peptidoglycan incorporation was quantified by measuring the gray-level profiles of 100 midline pixels along the length of each sacculus, beginning at each pole, moving toward the center of the cell.
The slopes for incorporation of peptidoglycan into E. coli treated with SulA were significantly different (according to Student's t test) between AV23-1 and MG1655 (P < 0.001) and between AV23-1 and AV23-1 treated with aztreonam (P < 0.001).