FIG. 3.

Isolation of the promoter for the V. cholerae chromosome 1 parAB locus. (A) Northern blot showing transcripts detected using a parB probe in three separate samples of each strain. The positions of RNA markers and their sizes in kb are depicted to the side of the blot. Arrowheads, transcripts; asterisk, background band from rRNA. (B) Beta-galactosidase activities (in Miller units) assayed in bacteria grown in LB at 37°C to an OD₆₀₀ of 0.4 to 0.6, using the following strains: wild-type parent strain KFV10, KFV10 with a plasmid containing a promoterless lacZ gene (pRKlac290), and KFV10 with pSD19 (pRKlac290 containing the upstream region of parA) (averages of three experiments are shown).