FIG. 3.

The lac promoter of the pSRK vector family is strongly controlled in diverse bacteria. Cultures of A. tumefaciens C58, B. abortus 2308, C. crescentus CB15, P. fluorescens 1855-344, R. leguminosarum 3841, and S. meliloti 1021, each harboring pSRKKm::uidA or pSRKKm(α⁻), were grown in the appropriate medium with (filled bars) or without (open bars) IPTG (1 mM final concentration) as described in Materials and Methods and Results. The cells were harvested and assayed for β-glucuronidase activity, expressed as modified Miller units, as described in Materials and Methods. Error bars show standard deviations.