Figure 2.
(A) Expression of DsrA in response to arabinose. dsrA− cells carrying a rpoS-lacZ fusion in single copy on a λ lysogen (NM22508) were transformed with pNM13 (pBAD-dsrA+) or a vector (pNM12) control grown in LB with ampicillin broth in the presence of the indicated final percentage of arabinose at 32°C. Samples were removed at an OD600 ≈ 1 and assayed for expression of β-galactosidase from the fusion. An isogenic dsrA+ strain (strain NM22507) transformed with the vector (pNM12) was grown without arabinose and assayed under similar conditions (black bar). (B) Stability of DsrA. DsrA and DsrB messages were detected by primer extension and quantitated with a PhosphorImager. Multicopy DsrA was isolated from cells carrying pDDS164.