TABLE 2.
Roles of PspB and PspD in the phage shock responsea
| Strain | β-Galactosidase assay result (Miller units) | Alkaline phosphatase assay result (U/h) |
|---|---|---|
| DH5α(vector) | 57.2 ± 0.05 | 6 ± 0.05 |
| DH5α(vector + pspD) | 1968 ± 26 | 7 ± 0.02 |
| DH5α(vector + pspB) | 686 ± 8 | 7 ± 0.02 |
| MG1655(pSJ1, pGZ119EH, NI) | 183.4 ± 6.4 | |
| MG1655(pSJ1, pGZ119EH, I) | 242.9 ± 6.4 | |
| MG1655(pSJ1, pPMR129, NI) | 196 ± 6.6 | |
| MG1655(pSJ1, pPMR129, I) | 657.2 ± 9.3 | |
| MG1655 ΔpspD(pSJ1, pGZ119EH, NI) | 191.0 ± 3.3 | |
| MG1655 ΔpspD(pSJ1, pGZ119EH, I) | 197.24 ± 2.2 | |
| MG1655 ΔpspD(pSJ1, pPMR129, NI) | 199.6 ± 4.0 | |
| MG1655 ΔpspD(pSJ1, pPMR129, I) | 700.6 ± 18.6 |
E. coli strain DH5α was the host for gene fusion constructs. This strain lacks endogenous β-galactosidase activity and has minimal alkaline phosphatase activity. The vector was pLKC480 for fusions made to lacZ (34), and pspB and pspD were amplified with primers and clones containing appropriate restriction sites (verified by sequencing; primers are available on request). The vector was pBAF for fusions made to phoA (13a), and cloning sites and primers were as described above for fusions to lacZ. Assays were in triplicate using bacteria grown in LB supplemented with the appropriate antibiotic (ampicillin at 100 μg/ml), and results are means ± standard errors. The pGZ119EH vector is described in the work of Lessel et al. (18). Strains were grown with no induction (NI) in LB supplemented with the appropriate antibiotics. For strains grown with induction (I), IPTG at a concentration of 1 mM was used throughout growth to induce the expression of pIV (encoding the secretin) from pPMR129. pPMR129 is vector pGZ119EH containing the pIV gene from phage f1 under lac promoter control (10).