FIG. 1.

algD TnlacZ reporter activity in B728a mutants. Six individual β-galactosidase assays were performed (FluorReporter lacZ/Galactosidase Quantitation Kit F-2905; Molecular Probes) with each culture of strains grown in MGY (17) for 16 h at ambient temperature with aeration. Shown is the mean β-galactosidase activity as fluorescence units (FU)/microgram of total cellular protein for the mean of two repetitions of the experiment. The error bars represent the standard errors of the means. (A) Expression of the reporter in algD in various genetic backgrounds without (black column) or with (gray column) 0.6 M sorbitol added to the MGY medium. The β-galactosidase activity from BGAC1.313 was 322 (±21) FU without or 566 (±23) FU with sorbitol in the medium. The independent exchange mutant BGAC2.313 gave 310 (±27) FU and 563 (±23) FU, respectively (data not shown). (B) Restoration of algD expression by wild-type gacA on a plasmid (pSyrgac23). Strains were grown in MGY containing 0.6 M sorbitol and 10 μg of tetracycline per ml. The β-galactosidase activity from BGAC1.313(pLAFR3) was 677 (±99) FU. The cosmid pLAFR3 was used as the vector control for pSyrgac23.