TABLE 1.

E. coli strains and plasmids used for this study

Strain or plasmid	Description or genotype	Reference or source
Strains
DH5α	Standard host strain for cloning	17
HNCE1a	marR1 acrB::kan ΔacrD	3
Plasmids
pSportI	High-copy-number cloning and expression vector with amp marker and lac-inducible expression	Gibco BRL
pUCK151A	A 6.5-kb BglII fragment containing the entire acrAB operon cloned into the pUC19 vector	10
pSAcrBHis	acrB gene with His4 tag sequence at its 3′ end cloned into pSportI	This study