FIG. 2.

Northern blot analysis of afrA expression in the presence and absence of afrR and afrS. Total RNA was separated by formaldehyde agarose gel electrophoresis and transferred to a nylon membrane. The blotted RNA was hybridized to a single-stranded RNA probe corresponding to the antisense sequence of a KpnI fragment internal to afrA. Size standards were visualized by UV illumination of the ethidium bromide-stained gel. The mobilities of the size standards, expressed in kilobases, are shown on the left. Lane 1, DH5α(pRKB19); lane 2, DH5α(pRKB19,p507); lane 3, DH5α(pRKB19,p598); lane 4, DH5α(pRKB19,p501).